In-ear earphone device with active noise control

Abstract

An in-ear earphone device for insertion into a person's ear canal is disclosed. The in-ear earphone device comprises a noise microphone, a loudspeaker and a signal processor arranged to provide an active noise control signal based on a recorded audio signal from the noise microphone, wherein the loudspeaker is arranged to reproduce the active noise control signal in the ear canal. In addition, the device comprises a damped vent comprising one or more vent elements and one or more dampening elements, the damped vent being arranged to couple the ear canal to an external acoustic environment. The damped vent is characterized by an inward vent transfer function H VI from the external acoustic environment to the ear canal. The damped vent is arranged to dampen an acoustic resonance of the one or more vent elements such that the inward vent transfer function H VI has a resonance amplitude ratio in a resonance frequency range from 100 Hz to 2 kHz of at most 3 dB. The damped vent is arranged to provide a reference amplitude in a reference frequency range from 20 Hz to 100 Hz of at most 3 dB larger than the inward vent transfer function H VI .

Description

Technical Field

[0001] The present invention relates to an in-ear headphone device arranged to provide active noise control. Background Technology

[0002] The field of in-ear headphone devices is rapidly developing, particularly due to the ever-increasing capabilities of digital electronics. A key prospect for headphone devices is the ability to provide active noise control, a process in which a microphone records sound and a speaker cancels out this feedback by utilizing the principle of destructive interference. Therefore, unwanted noise, such as that from a noisy external environment, can be significantly reduced in the ear canal of a user with such a device.

[0003] However, in-ear headphone devices (especially those configured to provide active noise control) suffer from several problems that impair device functionality. One example is dynamic acoustic leakage that occurs during user activity (most notably during jaw movement), where small air channels extend from the external environment into the ear canal, disrupting the normally tight separation of the ear canal. This leakage can allow increased unwanted noise to enter, and cause severe distortion of active noise control and sound reproduction performed by the speakers.

[0004] Despite the provision of computing power through modern electronic devices, the rapidly changing conditions provided by dynamic acoustic leakage cannot be properly managed within the scope of digital signal processing without causing significant distortion to the user. Summary of the Invention

[0005] The inventors have identified the aforementioned problems and challenges related to active noise control in in-ear headphones, and subsequently proposed the invention described below, which reduces some of the disadvantages of known technologies.

[0006] This invention relates to an in-ear headphone device for insertion into a human ear canal, the in-ear headphone device comprising: a noise microphone, a speaker, and a signal processor arranged to provide an active noise control signal based on a recorded audio signal from the noise microphone, wherein the speaker is arranged to reproduce the active noise control signal in the ear canal; and a damping vent comprising one or more venting elements and one or more suppressing elements, the damping vent being arranged to couple the ear canal to an external acoustic environment; wherein the damping vent is characterized by an inward venting transfer function H from the external acoustic environment to the ear canal. VI ; and wherein the damping vent is arranged to suppress acoustic resonance of the one or more venting elements, such that the inward venting transfer function H of the damping vent is VI The resonance amplitude in the resonant frequency range from 100 Hz to 2 kHz is greater than the inward ventilation transfer function H.VI The reference amplitude is at most 3 dB larger in a reference frequency range from 20 Hz to 100 Hz.

[0007] An in-ear earphone device can be understood as an earphone device arranged to be worn by a user by fitting the device in the user’s outer ear, such as in the ear canal, close to the ear canal. The in-ear earphone device can also extend at least partly into the user’s ear canal. The in-ear earphone device can typically be shaped to fit at least partly within the outer ear and / or ear canal, thereby ensuring the fit of the device with the user’s ear. The in-ear earphone device can also be understood as an in-ear earphone, an earplug, an in-canal earphone, an ear muff, or a hearable device.

[0008] For example, an in-ear earphone can allow a user to listen to an audio source with a minimum of sound disturbing the surrounding environment. Thus, applications of in-ear earphones can for example be listening to media, performing telecommunication, performing a hearing aid, voice intelligibility enhancement, and active noise control.

[0009] The in-ear earphone device according to the present invention comprises a noise microphone, a loudspeaker, and a signal processor arranged to provide active noise control in combination with the loudspeaker based on sound recorded by the noise microphone.

[0010] Sound can be understood as an audible pressure wave. A loudspeaker can generate sound by receiving a drive signal (e.g. an alternating current) which can generate a back-and-forth movement of a part of the loudspeaker (e.g. a diaphragm) to push air and thus reproduce the received drive signal as sound. And in the opposite way, a microphone can convert sound into an electrical signal based on a voltage and / or a current when a pressure wave makes a movable part of the microphone move back and forth to generate an electrical signal.

[0011] Active noise control can be understood as a method for reducing unwanted sound by adding an active noise control sound which has an opposite sound pressure compared to the unwanted sound. Active noise control can also be referred to as active noise reduction or active noise cancellation and can be considered a type of feedback.

[0012] To provide active noise control, an estimate or a representation of the unwanted sound is needed to produce the opposite sound. For this purpose, a noise microphone comprising one or more microphones is provided to record a representation of the unwanted sound. The noise microphone can be positioned to mainly record sound from the user’s ear canal, i.e. to more or less directly measure the unwanted sound as the user will perceive it, or to mainly record sound from the environment surrounding the user, i.e. the external acoustic environment, which is indirectly representing the unwanted sound as the user will perceive it through the in-ear earphone device’s inward transfer function H TI The noise microphone can be positioned to mainly record sound from the user’s ear canal, i.e. to more or less directly measure the unwanted sound as the user will perceive it, or to mainly record sound from the environment surrounding the user, i.e. the external acoustic environment, which is indirectly representing the unwanted sound as the user will perceive it through the in-ear earphone device’s inward transfer function H

[0013] Based on the recorded sound from the noise microphone, an active noise control signal can be generated, which is preferably designed to cancel the unwanted sound inside the user's ear by destructive interference when reproduced by the loudspeaker. Preferably, the signal is the additive inverse of the unwanted sound and can thus be derived from the unwanted sound, e.g. by inverse phase, inverse polarity or taking the additive inverse. Furthermore, the active noise control signal is preferably also adapted to take into account non-ideal frequency responses of the actual microphones, loudspeakers and signal processing etc. such that the reproduced sound will in practice be as close as possible to the inverse of the unwanted sound. Furthermore, in practice, the active noise control can preferably be limited to certain frequency bands, e.g. audible frequencies below 1 kHz.

[0014] The active noise control signal can be reproduced by the loudspeaker of the earphone to generate active noise control sound and thus cancel the unwanted sound inside the user's ear. The same loudspeaker can simultaneously emit another audio signal (e.g. music or speech), which can preferably be substantially unaffected by the active noise control. The audio signal (e.g. music or speech) emitted by the loudspeaker that is not emitted for the purpose of active noise control can be referred to as the desired audio signal.

[0015] Active noise control is typically combined with passive noise control, which can typically be understood as sound reduction by insulating noise material. An in-ear earphone device without substantial passive noise control can typically not be able to generate sufficient active noise control sound to properly cancel the unwanted sound. Therefore, an in-ear earphone device arranged to provide active noise control is typically arranged to provide an approximately air-tight separation between the ear canal and the external environment. This can for example be achieved by a flexible tip arranged to provide an acoustic seal.

[0016] In practice, due to the irregular geometry of the ear, and especially during mandibular movements, an air-tight separation cannot be achieved in an in-ear earphone device etc. Even with a tip that is as flexible as practically possible (also taking into account durability, cost etc.), there will almost always be a leakage sound that passes and through the earphone device into the ear canal. This dynamic nature of the noise transfer function requires that the active noise control continuously adapts the algorithm that produces the active noise control signal to fit the changing inward total transfer function H TI During changes in leakage, this continuous adaptation can further require a large number of changes in the filter coefficients that are updated for each filter, resulting in frequent mismatch of the active noise control signal compared to the actual noise, which results in audible artefacts.

[0017] The transformation experienced by a sound of different frequencies when propagating from one point to another can be described by a transfer function H(s). The transfer function can describe both the propagation efficiency, e.g. by the magnitude or absolute value G of the transfer function, and the phase shift φ that the sound experiences. The phase shift can be related to a group delay τ g , which is the negative of the derivative of the phase shift φ with respect to frequency, describes the change in time delay between different frequencies during propagation.

[0018] In the context of an in-ear headphone device, the transfer function describing how a sound is affected when propagating from the external environment to the ear canal can be described by an inward total transfer function H TI . Preferably, the active noise control of the in-ear headphone device is designed to act according to this inward total transfer function H TI , e.g. by the device requiring a larger amplitude of the active noise control signal in the user's ear canal for frequencies that are efficiently transmitted, than for frequencies that are inefficiently transmitted.

[0019] Furthermore, the inward total transfer function H TI has an associated phase shift / group delay, which describes to what extent a frequency is delayed when transmitted from the external environment to the ear canal. Preferably, the active noise control is designed to act according to this group delay, e.g. if a frequency is transmitted with a large group delay, the corresponding active noise control signal should be delayed accordingly.

[0020] As mentioned above, the active noise control relies on the signal recorded by the noise microphone to generate the active noise control signal. However, the noise microphone can also record any sound of the desired audio signal that leaks through the headphone device and / or escapes from the ear canal through the headphone device itself. This can lead to an undesired feedback effect, which can be referred to as loudspeaker feedback. Based on the fact that the processor at least approximately knows what sound the loudspeaker is generating, loudspeaker feedback can be addressed and removed by performing signal processing accordingly. For this, a properly characterized transfer function is needed that describes the efficiency of sound transmission from the ear canal to the external environment, in particular to the one or more microphones. This transfer function can be referred to as the outward total transfer function H TO .

[0021] The present inventors have identified a number of problems and challenges that have a substantially negative impact on the performance in some or all use cases of a typical in-ear headphone device that is arranged to provide active noise control. These prominent problems are now addressed in detail. After this, an intuitive but simple solution to these problems is presented that was conceived and developed by the present inventors.

[0022] A common problem with in-ear earphone devices having acoustic seals is the occlusion effect, which occurs when the ear canal is blocked and is most noticeable when the user is speaking. The user's own voice can be carried in the form of vibrations by the bone and tissue, which in turn can vibrate the ear canal and generate a sound pressure within the ear canal. Especially at low frequencies, this sound pressure is greatly increased when the ear canal is occluded by the earphone device. Thus, when speaking and wearing an occluding device, the user will experience a deep, hollow, rumbling, echoing or distorted reproduction of the user's own voice.

[0023] The occlusion effect of in-ear earphone devices can be suppressed by a vent, i.e. a channel or duct, arranged to couple the ear canal to the outside environment. It should however be noted that this is not a logical element to incorporate into an in-ear earphone device arranged to provide active noise control for several reasons. In particular, such devices rely on passive noise control, and a vent can typically impair the passive noise control as it allows noise to propagate much more easily through the earphone to the ear canal.

[0024] Furthermore, the addition of a vent can cause a Helmholtz resonance when the device is worn. A Helmholtz resonance is a resonance phenomenon that can occur when a cavity, e.g. an ear canal, is acoustically coupled to the ambient environment through a neck or neck, e.g. a vent. If any air or air mass in the neck is set in motion, the pressure within the cavity will be affected and act as a restoring force on the air mass in the neck. Thus, when set in motion, the air mass in the neck can oscillate at an inherent frequency, which can then be understood as the characteristic frequency of the Helmholtz resonance of the system.

[0025] Thus, an in-ear device with a vent can introduce a Helmholtz resonance in the user's ear canal with a characteristic frequency when the device is worn, which is typically at a very inconvenient frequency in the audible range, e.g. around 1 kHz. Thus, the user will experience an unwanted amplification of sound at this characteristic frequency. An in-ear earphone device arranged to provide active noise control can not be able to properly provide active noise control at this characteristic frequency.

[0026] Furthermore, the acoustic reproduction of a desired audio signal, e.g. music or telecommunication, can be substantially distorted by the presence of an acoustic Helmholtz resonance at a frequency close to the characteristic frequency of the Helmholtz resonance.

[0027] In addition, a vent arranged to reduce the occlusion effect by letting low frequency noise escape from the ear canal will also allow sound in the low frequency range of a desired audio signal, e.g. music, to leave the ear canal. Thus, the acoustic reproduction of a desired audio signal in the low frequency range will be degraded. Typically, the low frequency reproduction capabilities of a miniature loudspeaker available in an in-ear earphone device are already far below the ideal low frequency reproduction capabilities, and are not able to reproduce the low frequencies at a level of amplification to counteract the low frequency degradation effect of the vent.

[0028] Other issues of in-ear earphone devices are associated with different shapes and sizes of different outer ears of different users. For example, one user’s ear canal can have a different volume than another user’s ear canal. Furthermore, each time an in-ear earphone device is inserted into a user’s ear, it can not be inserted into exactly the same position. These different conditions can be referred to as user variability and can for example affect the performance of the in-ear earphone device in the low frequency range.

[0029] User variability affects the in-ear total transfer function H TI Since active noise control depends on the magnitude of this transfer function, it is challenging to provide active noise control that is optimally perceived for any user each time the in-ear earphone device is worn. Active noise control further relies on the phase of the in-ear total transfer function H TI which can also be affected by user variability leading to further distortions. An adaptive filter is used, but if the in-ear total transfer function H TI changes rapidly or significantly, the adaptive filter can not be able to follow the changes without producing audible artifacts.

[0030] Similar variations can occur for the inverse transfer function, the out-ear total transfer function H TO which can vary between users and each time the in-ear earphone device is worn. It is therefore challenging to properly handle the loudspeaker feedback since the efficiency of the sound from the loudspeaker to reach the microphone is unpredictable due to user variability.

[0031] Furthermore, due to user variability, the acoustic reproduction of the desired audio signal in the low frequency range is deteriorated.

[0032] Other issues of in-ear earphone devices are associated with dynamic acoustic leakage. These can specifically occur during user jaw movements, which can typically disturb the near- airtight separation or acoustic seal between the ear canal and the external environment. For example, when the user speaks or chews, the small air passage between the earphone tip and the ear canal, also referred to as leakage, can continuously open and close or at least change the sound propagation properties of the flexible tip.

[0033] Dynamic acoustic leakage is particularly problematic for in-ear earphone devices that are arranged to provide active noise control. First, dynamic acoustic leakage can suddenly introduce undesired noise. Second, dynamic acoustic leakage can change the magnitude related to the in-ear total transfer function H TI which can typically distort the active noise control since it relies on this transfer function. Similarly, the out-ear total transfer function H TOby dynamic acoustic leakage, and thus, any loudspeaker feedback can also change, resulting in undesired distortion of the active noise control signal. Furthermore, the acoustic leakage can strongly influence the in-ear total transfer function H TI related group delay, which further distorts the active noise control.

[0034] Furthermore, since the dynamic acoustic leakage influences the transfer efficiency from the ear canal to the external acoustic environment, and thus, from the loudspeaker to the user's eardrum, the reproduction of the desired audio signal (e.g. music) perceived by the user can also be distorted.

[0035] Hence, it can be summarized that there are problems in the field of in-ear earphone devices arranged to provide active noise control:

[0036] - the occlusion effect cannot be suppressed without degrading the active noise control due to the introduction of the Helmholtz resonance;

[0037] - the occlusion effect cannot be suppressed without degrading the audio reproduction due to the introduction of the Helmholtz resonance;

[0038] - the occlusion effect cannot be suppressed without degrading the loudspeaker sound reproduction due to the sound leaving the device, especially in the low audio frequency range;

[0039] - user differences can influence the amplitude of the in-ear total transfer function H TI , distorting the active noise control;

[0040] - user differences can influence the phase of the in-ear total transfer function H TI , distorting the active noise control;

[0041] - user differences can influence the out-ear total transfer function H TO , distorting the loudspeaker feedback;

[0042] - user differences can influence the out-ear total transfer function H TO , distorting the reproduction of the desired audio signal, especially in the low audio frequency range;

[0043] - dynamic acoustic leakage can suddenly let noise in, which the active noise control cannot suppress;

[0044] - dynamic acoustic leakage can influence the amplitude of the in-ear total transfer function H TI , distorting the active noise control;

[0045] - dynamic acoustic leakage can influence the phase of the in-ear total transfer function H TI , distorting the active noise control;

[0046] - the dynamic acoustic leakage can affect the total outward transfer function H TO - thereby distorting the reproduction of the desired audio signal, in particular in the low audio frequency range.

[0047] - the dynamic acoustic leakage can affect the total outward transfer function H TO - thereby distorting the reproduction of the desired audio signal, in particular in the low audio frequency range.

[0048] For the above-mentioned problems, the inventors have conceived a novel and inventive solution which relates to the field of in-ear earphone devices, in particular to in-ear earphone devices arranged to provide active noise control. A comprehensive model and extensive simulations of a worn in-ear earphone device show the feasibility of embodiments of the invention to overcome or reduce one or more of the described problems, preferably the feasibility to simultaneously overcome or reduce several of them in the same device.

[0049] The in-ear earphone device according to the invention comprises a damped vent comprising one or more venting elements and one or more dampening elements. For example, the damped vent can be a vent with a dampening mesh located at one or both ends of the vent, or a vent configured with an integrated dampening effect. According to the invention, the damped vent is arranged to couple an ear canal to an external acoustic environment.

[0050] According to embodiments, the damped vent is arranged to dampen an acoustic resonance of the one or more venting elements, such that the inward venting transfer function H VI The resonance amplitude ratio of the inward venting transfer function H VI The reference amplitude in the reference frequency range from 20 Hz to 100 Hz is at most 3 dB. In other words, the damped vent is arranged to dampen a resonance peak occurring in the frequency range from 100 Hz to 2 kHz.

[0051] As mentioned above, a vent without dampening in combination with the closed cavity of an ear canal will typically cause a Helmholtz resonance somewhere in this frequency range (if the vent is tuned for audio purposes, e.g. for reducing occlusion effect). At lower frequencies, the amplitude of such an acoustic resonance will typically be higher than a substantially flat amplitude (e.g. 6 dB).

[0052] The damped vent according to the present invention allows a maximum of 3 dB peak in the typical resonance band, instead of the natural e.g. 6 dB, thereby halving the sound pressure level at the peak of the Helmholtz resonance. In a preferred embodiment, the damped vent is critically damped, thereby suppressing the peak to a reference level, leaving a substantially flat frequency response between 20 Hz and the cut-off frequency (e.g. somewhere between 400 Hz and 2 kHz, e.g. 800 or 1 kHz). In embodiments, the damped vent can even be over-damped, i.e. suppress the peak further, thereby below the reference amplitude.

[0053] The skilled person in the field of acoustics is able to design a damped vent based on the properties provided herein, by choosing an appropriate damping cloth or other damping material to provide inside the vent or at one or both of its ends, and / or providing geometrical features in the vent design (e.g. slits) that are designed to achieve a damping effect. The model of the simulation described below and in connection with the figures also provides examples of vent sizes and suppression elements.

[0054] The damped vent aspect of the present invention is particularly inventive, as coupling the ear canal to the external acoustic environment in an in-ear headphone device arranged to provide noise control is highly counter-intuitive. The vent itself can passively suppress the occlusion effect, but would reduce the effect of passive noise control and introduce a Helmholtz resonance. However, by in addition including a suppression element and performing a clever choice of design parameters, the performance of the in-ear headphone device can be significantly improved, contrary to what would be expected.

[0055] To further introduce the present invention, it is advantageous to introduce some further concepts. The damped vent can be characterized by an inward vent transfer function H VI from the external acoustic environment to the ear canal, and an outward vent transfer function H VO from the ear canal to the external acoustic environment. The dynamic acoustic leakage can be characterized by an inward leakage transfer function H LI from the external acoustic environment to the ear canal, and an outward leakage transfer function H LO .

[0056] Furthermore, if a noise microphone is arranged to mainly record sound from the external acoustic environment, the in-ear headphone device can comprise an electro-acoustic path, e.g. comprising the noise microphone, a signal processor and a loudspeaker. The electro-acoustic path can be characterized by an inward electro-acoustic transfer function H EI from the external acoustic environment to the ear canal.

[0057] The inward total transfer function H TI may e.g. comprise the inward vent transfer function H VI and the inward leakage transfer function H LIcombination of the outward venting transfer function H TO may comprise the combination of the outward venting transfer function H VO and the outward leakage transfer function H LO .

[0058] In the following, arguments are presented that explain why a damped vent can not be a disadvantage for an in-ear earphone device, but can actually lead to many improvements of such a device.

[0059] A problem associated with adding a damped vent to an in-ear earphone device that is arranged to provide active noise control can be that the damped vent can let additional noise into the ear canal of the user. However, since the inward venting transfer function H VI is typically well defined and well known, this additional noise is directly suppressed by the active noise control.

[0060] Adding an undamped vent to an in-ear earphone device can suppress the occlusion effect when wearing the device, but leads to a Helmholtz resonance. By further adding a suppression element to the vent, the Helmholtz resonance and the related distortion it can generate can be removed.

[0061] Thus, due to the presence of the Helmholtz resonance, the occlusion effect can be suppressed without degrading the active noise control and the audio reproduction. Furthermore, since sound leaves the device, especially in the low audio frequency range, adding a vent can typically degrade the reproduction of sound. However, the suppression element will reduce this effect and provide an improved sound reproduction, especially in the low audio frequency range, compared to a device without the suppression element.

[0062] By implementing a damped vent, several problems associated with user variability can also be solved.

[0063] Active noise control can typically be arranged to suppress audible frequencies up to about 1 kHz. At these frequencies, user variability can significantly influence the total inward transfer function H TI , both for an in-ear earphone device without a vent and for a device with an undamped vent. In a device with a damped vent, the influence of user variability on the total inward transfer function H TI is significantly reduced at the relevant frequencies.

[0064] In a similar way, the outward total transfer function H TO is less influenced by user variability in an in-ear earphone device with a damped vent, and loudspeaker feedback can thus generate less distortion. The outward total transfer function H TO also influences the reproduction of the desired audio signal in the ear canal, especially in the low audio frequency range, and the damped vent improves the audio reproduction in this frequency range.

[0065] The damping vent is particularly effective in addressing issues related to dynamic leakage. In a typical in-ear headphone device without a damping vent, the user can hear very noticeably any sound that suddenly enters the ear canal through the dynamic acoustic leakage that occurs. In contrast, in a typical embodiment of the invention, noise can enter through both the damping vent and the dynamic acoustic leakage. Since the damping vent has a predictable inward vent transfer function H VI , it is easy to suppress the noise that enters through the damping vent. Importantly, any sound that enters the ear canal through the dynamic acoustic leakage can again exit through the damping vent. Thus, according to embodiments of the invention, the user hears much less noticeably the sound of the dynamic acoustic leakage compared to the sound that leaks into the ear canal without being able to exit through the vent.

[0066] For an in-ear headphone device with active noise control without a vent, the dynamic acoustic leakage can strongly alter the inward total transfer function H TI , because in this case the leakage transfer function is a major part of the total transfer function. This relates to both the magnitude and the phase of the inward total transfer function H TI . Thus, the dynamic acoustic leakage can continuously alter the inward total transfer function H TI , generating distortion of the active noise control, resulting in audible artifacts. For a typical embodiment according to the invention, the damping vent ensures that the inward total transfer function H TI varies much less in occurrence of dynamic acoustic leakage, because the inward vent transfer function H VI forms a typical major part of the inward total transfer function H TI , resulting in a significantly reduced amount of variation, thereby reducing audible artifacts due to adaptation mismatch.

[0067] In a similar way, the outward total transfer function H TO is less affected by dynamic acoustic leakage in an in-ear headphone device with a damping vent, and loudspeaker feedback can thus generate further less distortion. The outward total transfer function H TO affects additionally the reproduction of the desired audio signal in the ear canal, particularly in the low audio frequency range, and the damping vent improves the audio reproduction in this frequency range.

[0068] To summarize the proposed advantages and solutions, the inventors have identified and solved a number of problems in the field of in-ear earphone devices arranged to provide active noise control according to the present invention. Solving these problems is generally based on the inventive creation of a novel damped vent that is carefully tailored to both allow substantial acoustic coupling between the ear canal and the ambient environment, while at the same time eliminating undesirable resonance effects, such as Helmholtz resonance. Thus, in-ear earphone devices according to embodiments of the present invention can:

[0069] - suppress occlusion effect without degrading active noise control due to the introduction of a time-varying Helmholtz resonance;

[0070] - suppress occlusion effect without degrading audio reproduction due to the introduction of a time-varying Helmholtz resonance;

[0071] - suppress occlusion effect while minimizing degradation of loudspeaker sound reproduction due to sound leaving the device, especially in the low audio frequency range;

[0072] - reduce distortion due to user variability affecting the magnitude of the in-ear total transfer function H TI ;

[0073] - reduce distortion due to user variability affecting the phase of the in-ear total transfer function H TI ;

[0074] - reduce distortion from loudspeaker feedback due to user variability affecting the out-ear total transfer function H TO ;

[0075] - improve loudspeaker sound reproduction, especially in the low audio frequency range, due to reduced user variability affecting the transfer function from loudspeaker to eardrum involved in the out-ear total transfer function H TO ;

[0076] - reduce the impact of sound entering the ear canal via dynamic acoustic leakage by allowing sound to leave through the damped vent;

[0077] - reduce distortion due to dynamic acoustic leakage affecting the magnitude of the in-ear total transfer function H TI ;

[0078] - reduce distortion due to dynamic acoustic leakage affecting the phase of the in-ear total transfer function H TI ;

[0079] - reduce distortion from loudspeaker feedback due to dynamic acoustic leakage affecting the out-ear total transfer function H TO ; and / or

[0080] - improve loudspeaker sound reproduction, especially in the low audio frequency range, due to dynamic acoustic leakage affecting the transfer function from loudspeaker to eardrum involved in the out-ear total transfer function HTO the transfer function from the loudspeaker to the eardrum is reduced, thus improving the loudspeaker sound reproduction, especially in the low frequency range.

[0081] Compared to both the closed design and the design with undamped vent, in the embodiments of the invention with damped vent, the active noise control filter arranged to model the inward and outward transfer functions can have smoother amplitude and phase characteristics and can change less when algorithms such as LMS are used to adapt to changes in leakage or ear canal placement.

[0082] Compared to acoustic designs where the loudspeaker and vent share a common volume before reaching the ear canal, the disclosed arrangement has the advantage that less of the sound from the loudspeaker is transmitted to the outward facing microphone, especially at frequencies above the vent cutoff.

[0083] In embodiments, when said in-ear earphone device is inserted into said person's ear canal, said inward vent transfer function H VI and said acoustic resonance are properties of said damped vent.

[0084] The acoustic properties of an in-ear earphone device change depending on the environment in which it is evaluated. In the present disclosure, the acoustic properties are considered for an inserted device, i.e. when the loudspeaker and one end of the damped vent are coupled to a closed ear canal cavity, and the other end of the damped vent is open to the external acoustic environment, in particular the outer ear. Thereby, the acoustic resonance is for example considered a result of the interaction between the tube coupling the closed cavity to the open space.

[0085] In embodiments, said loudspeaker and said damped vent are acoustically separated within said in-ear earphone device.

[0086] In some embodiments, the loudspeaker and the damped vent are preferably not directly to a common chamber or duct or the like, thereby not having a common outlet from the earphone device to the ear canal.

[0087] In embodiments, said loudspeaker and said damped vent are acoustically separated within said in-ear earphone device by a dampening element.

[0088] In some embodiments, the loudspeaker and the damped vent are acoustically separated or partitioned by a dampening element.

[0089] In embodiments, said loudspeaker and said damped vent are coupled to said ear canal through separate ducts.

[0090] Thereby, compared to embodiments where the loudspeaker and vent are combined inside the device through a common duct to the ear canal, the loudspeaker sound is mainly delivered to the ear canal, with more sound leaving through the vent to the external environment than reaching the eardrum.

[0091] In embodiments, the damping vent is arranged with a cross-sectional area corresponding to a cylinder with a diameter in the range from 1.5 mm to 3.5 mm, such as from 2.0 mm to 3.0 mm, e.g. 2.3 mm or 2.5 mm.

[0092] The preferred cross-sectional area of the damping vent may, for example, be in the range from 1.8 mm 2 to 9.6 mm 2 , such as from 3.1 mm 2 to 7.1 mm 2 , e.g. 4.2 mm 2 or 4.9 mm 2 . The damping vent can have various cross-sectional shapes, such as circular, rectangular, semi-circular, etc., and can have a varying cross-sectional area along its length, or be combined by two or more vents, split vents, etc., but preferably can be designed with dimensions corresponding to the above-mentioned dimensions of a cylindrical vent.

[0093] In embodiments, the damping vent is arranged with a length corresponding to a cylinder with a length in the range from 2.5 mm to 10 mm, such as from 3.5 mm to 9 mm, such as from 4.5 mm to 8 mm, e.g. 5 mm or 7 mm.

[0094] The damping vent can have various shapes along its length, and can be straight / curved or bent, etc., and can be combined by two or more vents, split vents, etc., but preferably can be designed with dimensions corresponding to the above-mentioned dimensions of a cylindrical vent.

[0095] In embodiments, the vent can be characterized by an acoustic mass based on the cross-sectional area and the length of the damping vent, wherein the combination of the acoustic mass and a typical effective volume of the ear canal can be characterized by a vent cutoff frequency selected from the range from 500 Hz to 2000 Hz, such as from 650 Hz to 1600 Hz, such as from 700 Hz to 1200 Hz, e.g. 800 Hz, 900 Hz, or 1000 Hz.

[0096] The acoustic mass can also be understood as an acoustic inertia and can describe the extent to which a body of air resists changing its velocity. For example, in embodiments of the present invention, a body of air in the damping vent can have an acoustic mass determined by the length and the cross-sectional area of the damping vent. The acoustic mass in combination with a typical effective volume of the ear canal can be characterized by a vent cutoff frequency. For example, the typical effective volume of the ear canal can be understood as the remaining volume of the ear canal when the device is inserted into the ear canal of an average or typical user.

[0097] In an embodiment, the noise microphone is arranged to mainly record sound from the outer acoustic environment.

[0098] The advantage of recording sound from the outer acoustic environment for acoustic noise control is that the noise can be measured with minimal influence of the sound present in the ear canal, which can include desired sound reproduced by the earphone device, such as music playback or a phone conversation. Feedback from the inner loudspeaker to the outer directional microphone can be measured and taken into account in the processing. Furthermore, the outer directional noise microphone can advantageously be used for the dual purpose of recording noise to be cancelled as well as desired environmental sound (e.g. speech conversation, announcements or desired warning sounds) not to be cancelled (or even to be enhanced). A certain degree of directionality for e.g. speech conversation can be achieved by mounting the microphone accordingly, or by using several microphones or microphone ports at different locations on the earphone device. The distinction between sound to be cancelled and sound not to be cancelled (possibly even to be enhanced) can be based on a simple crossover filter with a crossover frequency at e.g. about 800-1000 Hz, or on a more advanced algorithm, e.g. a signal content distinction technique, e.g. detecting and preserving or enhancing speech features in the recorded sound and creating an active noise control signal based on the rest of the recorded signal. The dual purpose noise microphone can also be used to record the user's own speech, e.g. for telecommunication or digital assistant purposes.

[0099] In an embodiment, the noise microphone is arranged to mainly record sound from the ear canal.

[0100] By using the sound in the ear canal as input for the active noise control, i.e. by recording with a noise microphone pointing into the ear canal, the active noise control algorithm receives direct feedback about the performance of the active noise control signal actually reproduced in the ear canal. Thereby, the adjustment of the active noise control signal can be faster and / or more accurate. Desired sound reproduced by the earphone device itself, e.g. music playback or a phone conversation, can be subtracted from the feedback signal before applying it as an error signal to the active noise control algorithm. Desired environmental sound, such as speech conversation, announcements etc. can also be preserved to a certain range by a crossover filter or other signal content distinction technique, e.g. speech feature extraction.

[0101] In an embodiment, the in-ear earphone device comprises an auxiliary microphone.

[0102] Various embodiments can utilize several microphones for various purposes. Auxiliary microphones positioned opposite to the noise microphone (i.e. pointing into the ear canal when the noise microphone is arranged to mainly record ambient sound, or pointing to the environment when the noise microphone is arranged to mainly record ear canal sound) can assist the signal processor in tasks where the noise microphone is less advantageous. For example, an auxiliary microphone pointing into the ear canal can provide an error signal for an active noise control algorithm based on the ambient directional noise microphone, and vice versa. Furthermore, auxiliary microphones can be used to record the user's voice for telecommunication and digital assistant purposes. The combination of noise and auxiliary microphones can further be used to measure the transfer function between the environment and the ear canal, and vice versa. Furthermore, several ambient directional microphones located at different positions around the headphone device can improve the directivity of sound recording, e.g. for improved discrimination between dialog speech and background noise.

[0103] In an embodiment, the microphone arranged to mainly record sound from the ear canal is coupled to the ear canal via a separate microphone tube.

[0104] A microphone pointing into the ear canal (whether it is a noise microphone or an auxiliary microphone) can preferably be coupled to the ear canal via a separate microphone tube, whereby the microphone occupies less space in the ear canal and is not directly coupled to the cavity or tube of the loudspeaker or the damping vent. Through the microphone tube, the microphone receives a mix of the sound present in the ear canal, only influenced by the predictable transfer function of the microphone tube.

[0105] In an embodiment, the microphone is acoustically coupled to the ear canal via the damping vent.

[0106] In some embodiments of the invention, a microphone (e.g. a noise microphone) can directly record sound from the damping vent. Depending on the positioning of one or more dampening elements, the microphone can then mainly record sound from the external environment, from the ear canal, or record a balanced mix of sound from the external environment and the ear canal.

[0107] In an embodiment, the signal processor is based on an estimated inward total transfer function H TI The active noise control signal is provided.

[0108] Basically, the active noise control algorithm is arranged to reproduce sound opposite to the noise that is still present after propagating from the environment to the ear canal through the damping vent, dynamic acoustic leakage, electro-acoustic path (if present), etc., i.e. as represented by the inward total transfer function H TI . It is therefore advantageous, especially for an environment-facing noise microphone, to base the active noise control signal on an estimate of this transfer function. The inward total transfer function H TIThe in-ear total transfer function H TI can be estimated at design or manufacturing time and stored in the earphone device as a pre-defined function and used as a starting point. However, the earphone device is preferably arranged to update the transfer function to accommodate different dynamic acoustic leakage, different user ear canal characteristics, etc. Some of the possibilities of estimating (i.e. adapting) the in-ear total transfer function H TI during use are described above.

[0109] In an embodiment, the estimated in-ear total transfer function H VI is based on an estimate of the in-ear vent transfer function H VI .

[0110] As described above, the in-ear vent transfer function H VI forms a major and fairly predictable part of the in-ear total transfer function H TI . Since the in-ear vent transfer function H VI can be estimated based on a model of a substantially fixed damping vent or measurements made by the designer or manufacturer, a qualified estimate of the in-ear total transfer function H TI can be based on the estimate of the in-ear vent transfer function H VI , possibly taking into account an average or guessed model of the in-ear leakage transfer function H LI of the dynamic acoustic leakage.

[0111] In an embodiment, the estimated in-ear total transfer function H TI is based on a difference between sound recordings of the external acoustic environment and the ear canal, respectively.

[0112] When microphones can record both primarily for the ambient sound and primarily for the ear canal sound, e.g. by arranging a noise microphone towards the environment and an auxiliary error microphone towards the ear canal, or by arranging a noise microphone towards the ear canal and an auxiliary microphone for telecommunication, digital assistance and / or enhanced dialogue speech towards the environment, a comparison of their recorded sound can be used to determine an estimate of the in-ear total transfer function H TI .

[0113] In an embodiment, the estimated in-ear total transfer function H TI is based on an estimated out-ear total transfer function H TO .

[0114] When the out-ear total transfer function H TO is known or estimated, this function can be transformed (e.g. its poles and zeros) to find an estimate of the in-ear total transfer function H TI (i.e. the opposite direction), which can be used to improve active noise control.

[0115] In an embodiment, the estimated out-ear total transfer function H TObased on a difference between the sound reproduced by the loudspeaker and the sound recorded by the noise microphone.

[0116] When the noise microphone or the auxiliary microphone is positioned to mainly record external environmental noise, it will also record feedback of sound escaping from the loudspeaker through the vent, leakage and earphone. By comparing the loudspeaker output with the external microphone input, an estimate of the outwards total transfer function H TO This is advantageous in itself, as it allows the signal processor to control the undesired loudspeaker to microphone feedback to avoid in worst case scenarios, e.g. blowing a whistle or screaming. Furthermore, the measured or estimated outwards total transfer function H TO can be used to determine the inwards total transfer function H TI for improved active noise control as described above. Thus, the estimate or measurement of the outwards total transfer function H TO can be used in both active noise control as well as active feedback control.

[0117] In an embodiment, the signal processor is arranged with an active noise control algorithm, e.g. of the LMS algorithm type, such as filter-x LMS or directional search LMS, and characterized by a step size.

[0118] The skilled person in the field of earphone devices with active noise control can use various suitable active noise control algorithms. In principle, the active noise control algorithm comprises an adaptive filter that is continuously updated to generate sound as opposite to the undesired noise as possible. Since active noise control is typically not applied to higher frequencies, a typical sampling rate of the recorded noise signal can be e.g. 2 kHz, thereby allowing active noise control for noise below 1 kHz. Other frequency ranges for active noise control are available to the skilled person, with appropriate adjustments accordingly, e.g. tuning of the vented earphone characteristic frequency, etc.

[0119] A relevant parameter of different active noise control algorithms is the step size, which determines the degree to which the adaptive filter is changed by each algorithm iteration. A smaller step size allows for a more accurate adaptation to the measured noise, while a larger step size allows for keeping track of large and fast changes in the undesired noise. If the step size is chosen too small by targeting improved accuracy, the adaptive noise filter in an earphone without a vent, where leakage is the inwards total transfer function H TIThe most important part of the process (the filter) will be unable to track large changes in noise characteristics caused by variations in dynamic acoustic leakage, such as when a user chews or speaks. This can lead to audible artifacts whenever the noise characteristics or transfer function change significantly. On the other hand, if the step size is chosen to be too large in order to quickly adapt to significant changes in the transfer function, the adaptive filter will tend to exceed each correction and oscillate around the optimal filter setting. This can lead to audible artifacts or less noise suppression during steady-state conditions where the noise and transfer function change smoothly only over time. For some active noise control algorithms, the frequency of algorithm iteration can be increased to allow for smaller step sizes while still finding the optimal filter setting as quickly as with larger step sizes. In the example, doubling the processing frequency allows for half a step size without reducing the algorithm's response to significant changes. However, increasing the processing frequency requires more expensive processors and auxiliary components and consumes more battery power. In other words, there is a trade-off between filter adaptation performance, processing speed, cost, and battery consumption.

[0120] Through embodiments of the present invention, the inward total transfer function H can be improved. TI Its stability is due to its large dependence on the inward ventilation transfer function H. VI The inward ventilation transfer function H VI It is essentially fixed and fairly predictable over time (unlike the unpredictable and dynamic inward leakage transfer function H). LI (Compared to) headphones without damping vents, through a more stable inward total transfer function H TI The degree of adaptation required for active noise control algorithms and adaptive filters is reduced. This benefit can be used for various purposes depending on different interests. An advantageous embodiment utilizes improved transfer function stability to reduce the step size, thereby achieving more accurate noise control during steady-state conditions without compromising tracking performance under dynamic conditions, since dynamic conditions are less dynamic due to the less dynamic steady-state transfer function caused by the damping vent. Another advantageous embodiment utilizes improved transfer function stability to reduce processing requirements, such as using cheaper components and / or slower processing frequencies, without again compromising tracking performance under dynamic conditions, since dynamic conditions are less dynamic due to the less dynamic steady-state transfer function caused by the damping vent. Other combinations of the parameters in the above trade-offs are also suitable and advantageous embodiments of the invention.

[0121] Active noise control can typically be causal or non-causal. In causal active noise control, the microphone is usually located closer to the noise source than the speaker, allowing the acoustic segments recorded at the noise microphone to be processed in time so that the speaker can reproduce the active noise control signal, which is configured to eliminate the recorded acoustic segments in the ear canal.

[0122] In non-causal active noise control, it can not be possible to process a sound wave segment recorded at the noise microphone in time to cancel the same sound wave segment in the ear canal. Instead, non-causal active noise control relies on the recorded sound to predict future noise in the ear canal. Even in embodiments where causal active noise control is possible, in some embodiments, active noise control can benefit from a component that includes a prediction of future noise (i.e., how the received sound will develop) in order to pre-adjust the algorithm in the right direction.

[0123] In embodiments where the noise microphone is arranged to mainly record sound from the ear canal, active noise control can generally be non-causal active noise control. Thus, active occlusion control can generally be a type of non-causal active noise control.

[0124] Non-causal and causal active noise control require different signal processing procedures. Signal processing for non-causal active noise control can generally rely on a larger degree of prediction as it relies on predicting future noise.

[0125] Embodiments of the invention are generally characterized by having better predictability than devices without a damped vent. For example, the overall inward transfer function is less susceptible to dynamic acoustic leakage. Embodiments of the invention can thus also provide for improved non-causal active noise control, or a combination of causal and non-causal active noise control.

[0126] In embodiments, the in-ear earpiece device is arranged with a crossover frequency, a voice extraction function, or other separating means between sound that is desired to experience active noise control and sound that is desired to be heard unaffected or even enhanced.

[0127] For some applications of in-ear earpiece devices, it can not be desirable to have active noise control or full adoption of active noise control. This can for example be in embodiments where the user can sometimes desire to hear ambient sound (e.g., for conversation, announcements, orientation in traffic, etc.). Adoption of a suitable crossover frequency (e.g., at about 800Hz-1 kHz) or voice extraction function or other separating means can allow for different handling of sound that is desired to experience active noise control, such as noise, and sound that is desired to be heard unaffected or even enhanced, such as speech. The separating means can advantageously be user configurable and / or capable of being switched on or off as needed.

[0128] In embodiments, the in-ear earpiece device is arranged with options for switching on or off the active noise control signal, adjusting its frequency range or the noise pattern it is controlled for.

[0129] In some embodiments, it can be desirable to provide a user-selectable active noise control, such that the user can turn it off when it is not relevant or even unwanted, e.g. in some of the above-mentioned situations. In embodiments, the settings of the active noise control algorithm can be user-configurable, directly or indirectly, by allowing the user to select the frequency range of the noise control, the degree of noise suppression, select between large or small step sizes for fast tracking or accurate stable conditions, etc., or by allowing the user to select a noise control mode, e.g. between quiet or noisy environment, stable or dynamic use, requirement or desire to hear ambient speech simultaneously with the noise control, etc.

[0130] In embodiments, the estimated inward total transfer function H TI comprises a time-varying inward transfer function component comprising an inward leakage transfer function H LI , and a static inward transfer function component comprising the inward venting transfer function H VI .

[0131] As mentioned above, the inward total transfer function H TI in a headphone device comprising both a damped vent and an unavoidable dynamic acoustic leakage comprises at least a dominant, substantially stable and predictable contribution from the damped vent, and a subordinate, time-varying and unstable contribution from the dynamic acoustic leakage. Accordingly, advantageous embodiments comprise an estimated inward total transfer function H TI having at least these two components. In some embodiments, the components are measured, estimated or modelled separately and can thus be distinguished and adjusted separately in the inward total transfer function H TI . In other embodiments, the inward total transfer function H TI is measured, estimated or modelled in a way that does not allow to distinguish the two components, however comprising both components (albeit inseparably).

[0132] In embodiments, the signal processor is arranged to update the representation of the estimated inward total transfer function H TI preferably recursively, cyclically or continuously, e.g. at an active noise control sampling rate or algorithm iteration rate, e.g. in the range from 800 to 4000 times per second, e.g. from 1200 to 3000 times per second, such as 2000 times per second.

[0133] As acknowledged by the skilled person, the representation of the inward total transfer function H TIThe adaptive active noise control filter is preferably continuously updated to track smooth and major changes in the noise characteristics or transfer functions. However, in embodiments of the invention, the algorithm step size (e.g. step size of the LMS algorithm) can be reduced compared to headphone devices without a damped vent without increasing the algorithm iteration rate or otherwise increasing the processing requirements.

[0134] In embodiments, the signal processor is arranged to update the estimated inward total transfer function H TI in the representation.

[0135] The adaptive active noise control filter is preferably updated in steps determined by a predetermined but configurable step size, which is chosen to achieve a suitable trade-off between accurate tracking and fast tracking of the noise characteristics and transfer functions with as little audible artifacts as possible. However, in embodiments of the invention, the algorithm step size (e.g. step size of the LMS algorithm) can be reduced compared to headphone devices without a damped vent without increasing the tracking time or audible artifacts.

[0136] In embodiments, the signal processor is arranged to provide an active occlusion control signal, and the loudspeaker is arranged to reproduce the active occlusion control signal in the ear canal.

[0137] In embodiments, the active occlusion control signal is based on a signal recorded from a microphone arranged to predominantly record sound from the ear canal, e.g. the noise microphone arranged to predominantly record sound from the ear canal.

[0138] Embodiments of the invention are preferably arranged to suppress the occlusion effect, but can not completely eliminate the occlusion effect. Thus, some embodiments of the invention are arranged to provide active occlusion control. Here, a microphone can typically record sound from the ear canal (e.g. occlusion), and based on this recording, a processor can generate an active occlusion control signal, which a loudspeaker can reproduce in the ear canal to further suppress the occlusion effect.

[0139] The overall procedure for active occlusion control is similar to the procedure for active noise control, in particular if the noise microphone is arranged to predominantly record sound from the ear canal. In some embodiments of the invention, the active noise control signal can also be interpreted as an active occlusion control signal.

[0140] In embodiments where the noise microphone is arranged to primarily record sound from the ear canal, the active noise control can typically be non-causal active noise control. Thus, active occlusion control can typically be a type of non-causal active noise control and thereby require a greater degree of predictability as it relies on predicting future noise. Since embodiments of the invention with a damped vent are typically characterized by a better predictability than devices without a damped vent, the total inward transfer function is less susceptible to dynamic acoustic leaks. Embodiments of the invention can thus also provide improved non-causal active noise control, such as improved active occlusion control.

[0141] In embodiments, the resonance amplitude is the inward vent transfer function H VI Any amplitude in the range from 100 Hz to 2 kHz.

[0142] The damped vent of the invention is preferably arranged to not allow an amplitude higher than 3 dB than a reference amplitude in the 100 Hz - 2 kHz frequency band, regardless of the origin of the amplitude. In other words, amplitude peaks occurring in the absence of a damped vent in the above frequency range are within the scope of the invention, whether they are direct, indirect or not caused by a resonance phenomenon. In a preferred embodiment, a damped vent is provided for which the inward vent transfer function H VI is essentially flat, i.e. without peaks above 3 dB than a reference amplitude, preferably from 20 Hz all the way up to 2 kHz, but at least from 100 Hz to 2 kHz. The reference amplitude of the transfer function is typically 0 dB. In some embodiments, the suppressive element is further arranged to provide a nominal attenuation of the reference frequency band, for example in the range from 2 dB to 10 dB, such as from 2 dB to 6 dB, for example from 3 dB to 4 dB. In such embodiments, the damped vent is arranged to not allow an amplitude higher than 3 dB than the nominal attenuation in the frequency range from 100 Hz to 2 kHz.

[0143] In embodiments, the resonance amplitude is the inward vent transfer function H VI The amplitude at 800 Hz.

[0144] A damped vent that realizes a damping of a resonance to reduce the resonance amplitude to an amplitude at 800 Hz that is not more than 3 dB larger than a reference amplitude between 20 Hz and 100 Hz is highly advantageous since the frequency range around 800 Hz is particularly relevant in headphone and active noise control applications.

[0145] In embodiments, the resonance amplitude is at most 2 dB, such as at most 1 dB, for example at most 0 dB, larger than the reference amplitude.

[0146] In a preferred embodiment, the resonance amplitude is reduced as much as possible towards 0 dB with respect to the reference amplitude. In embodiments, the damped vent can even be over-damped, i.e. further suppress the peak, so lower than the reference amplitude.

[0147] In embodiments, the reference amplitude is based on the inward vent transfer function H VI The average amplitude in the range from 20 Hz to 100 Hz, such as from 20 Hz to 60 Hz or from 60 Hz to 100 Hz.

[0148] The inward vent transfer function H VI The frequency response is generally substantially flat in these frequency ranges, with an average amplitude generally about 0 dB. In some embodiments, the suppression element is further arranged to provide a nominal attenuation of the reference frequency band, for example in the range from 2 dB to 10 dB, such as from 2 dB to 6 dB, for example from 3 dB to 4 dB. In such embodiments, the damped vent is arranged to not allow an amplitude higher than 3 dB above the nominal attenuation in the frequency range from 100 Hz to 2 kHz.

[0149] In embodiments, the suppression element is arranged to provide a nominal attenuation in the frequency band from 50 Hz to 500 Hz, for example at 500 Hz in the range from 2 dB to 10 dB, such as from 2 dB to 6 dB, for example from 3 dB to 4 dB.

[0150] The nominal attenuation is preferably a wideband attenuation, reducing the reference amplitude by for example 3-4 dB. In such embodiments, the damped vent is preferably arranged to suppress the acoustic resonance amplitude to no more than 3 dB above the nominal attenuation reference amplitude. For example, in embodiments, the damped vent nominally attenuates all audible frequencies by about 3-4 dB, but further attenuates a resonance peak that is originally 6 dB above the reference value by at least 3 dB, thus achieving a generally flat response in the passband between -3 dB and -4 dB, for example, with the resonance peak no more than 0 dB, and more preferably attenuated to a critically suppressed state.

[0151] By embodiments of the invention, the resulting sound pressure level (SPL) in the ear canal is optimized to improve speech intelligibility. When speech is presented at very low levels, it is difficult to understand because important speech cues are inaudible, which makes it difficult to distinguish phonemes. As the level is increased, speech discrimination increases until at some point discrimination starts to deteriorate with increasing level. This phenomenon is commonly referred to as the “flip-over effect”. In a cocktail party scenario, the overall environmental SPL is typically above the flip-over point. According to embodiments, the damped vent of the acoustic attenuation applies a nominal attenuation, thereby increasing intelligibility of speech in loud speech or noisy environments.

[0152] An advantageous feature of embodiments of the invention is the passive handling of bass, whereby frequencies below the low-pass cutoff frequency are acoustically attenuated. Many conventional noise suppression algorithms, including adaptive microphone direction patterns, exhibit considerable gain in SNR. However, they often fail to deliver better speech intelligibility scores in practical tests, because these algorithms are prone to produce "glitches" or unnatural sounds that attract the user's attention, thereby reducing the focus on the speech to be discriminated or even masking the speech. This is avoided by including the nominal attenuation of the present embodiments.

[0153] Embodiments of the invention can be advantageous in that by applying a slight general or nominal attenuation, long stays in noisy or otherwise disruptive environments are facilitated. For example, a general attenuation of 3 dB can reduce the noise exposure by 50%, or alternatively can allow the wearer to stay twice as long with the ear subjected to the same noise exposure as without the system.

[0154] To further increase the protection from exposure to loud sounds, embodiments can advantageously include means for limiting the peak SPL delivered to the ear canal. This can be done acoustically in the damping vent, for example by a narrow slot in the vent.

[0155] In embodiments, the inward vent transfer function H VI is characterized by having a low-pass characteristic, wherein the inward vent transfer function H VI is at least 3 dB lower than the reference amplitude for any amplitude from the low-pass cutoff frequency to 10 kHz.

[0156] The cutoff frequency is generally defined as the frequency at which the amplitude drops below 3 dB of the amplitude in the passband, here referred to as the reference amplitude. Designing a damping vent with a low-pass characteristic from the environment to the ear canal, i.e. the inward vent transfer function H VI , limits the bandwidth of the above-mentioned characteristics of the damping vent to frequencies below the cutoff frequency. An advantage of the limited damping vent bandwidth can be, for example, attenuation of feedback from the internal loudspeaker to the external microphone at frequencies above the cutoff frequency. For this purpose, the cutoff frequency can advantageously be chosen as a trade-off between allowing the most dominant noise, i.e. bass frequencies, to escape the ear canal through the vent and at the same time attenuating the exit of important speech frequencies for improved speech intelligibility and feedback reduction. Another advantage can be to coordinate the bandwidth of the active noise control algorithm with the low-pass characteristic of the damping vent, because in preferred embodiments the active noise control algorithm is most effective or can only be applied to lower frequencies, e.g. up to 1 kHz.

[0157] Furthermore, for users with noise-induced hearing loss, this is typically most prominent at about 3 kHz due to the resonance of the open ear canal. It is therefore particularly advantageous to include a gain reduction mechanism that limits the power transmitted to the ear at about 3 kHz.

[0158] Furthermore, for embodiments implementing an electro-acoustic path with high-pass characteristics as described below, the low-pass characteristics of the damped vent reduce the acoustic masking of the high frequency band, thereby improving the degree of control and possible SNR that can be achieved by the electro-acoustic path. In embodiments, the low-pass cut-off frequency and the high-pass cut-off frequency establish a cross-over frequency between the damped vent and the electro-acoustic path.

[0159] Furthermore, if the electro-acoustic path is implemented by any kind of directional microphone assembly (i.e. one or more directional microphones, or microphones mounted at such positions so as to effectively function as directional microphones), the directivity is particularly important for speech intelligibility. By implementing a limited bandwidth of the damped vent passband (e.g. up to 800 Hz or 1 kHz), the amount of omnidirectional sound received through the damped vent is reduced, thereby minimizing the masking of directional sound received by the microphone. This can be highly advantageous, since the electro-acoustic path cannot attenuate the acoustically omnidirectional sound received by the damped vent, but rather more or less fully controls the gain and filters of the electro-acoustic path. In particular, the directivity is important for the intelligibility of consonants (i.e. the higher end of the speech spectrum), whereby above the preferred cut-off frequency.

[0160] In embodiments, the low-pass cut-off frequency is in the range from 400 Hz to 2000 Hz, such as from 500 Hz to 1600 Hz, such as from 600 Hz to 1200 Hz, such as 800 Hz.

[0161] In embodiments, the device further comprises an electro-acoustic path comprising a microphone that primarily records ambient sound, e.g. the noise microphone, a variable gain, and the loudspeaker, wherein the electro-acoustic path is arranged to couple the external acoustic environment to the ear canal.

[0162] By the electro-acoustic path from the environment to the ear canal, the environmental sound can be electronically processed (e.g. digitally processed) and reproduced in the ear canal. In embodiments, the variable gain is an analog filter and a digital side chain with a gain controller implemented to control the analog filter. In another embodiment, the variable gain is also digital. In different embodiments, the processing can have various purposes with different advantages, e.g. amplifying certain frequency bands and attenuating other frequency bands, or filtering certain sound features and attenuating other sound features, e.g. for providing a focus in the ear canal to certain sound content (e.g. speech), e.g. to improve speech intelligibility. Furthermore, according to embodiments, the electro-acoustic path can also apply a negative gain to improve the intelligibility of speech. The electro-acoustic path can also implement a peak limiting (e.g. electro-mechanical), such as using a thin membrane with limited movement in the loudspeaker and microphone, thereby reducing the electrical gain when loud sounds are detected and / or by emitting a phase inverted copy of the sound to be attenuated via the loudspeaker.

[0163] In embodiments, the electro-acoustic path is characterized by an inward electro-transfer function H EI with a high-pass characteristic having a high-pass cut-off frequency, preferably based on the low-pass cut-off frequency, such as in the range from 400 Hz to 2000 Hz, such as from 500 Hz to 1600 Hz, such as from 600 Hz to 1200 Hz, such as 800 Hz.

[0164] Preferably, the high-pass characteristic of the electro-acoustic path is substantially flat from the cut-off frequency to at least 5 kHz (such as 7 kHz). In embodiments, the low-pass cut-off frequency and the high-pass cut-off frequency establish a cross-over frequency between the damping vent and the electro-acoustic path.

[0165] By the combination of the transfer function of the electro-acoustic path and the transfer function of the damping vent, embodiments with two types of paths (i.e. the acoustically damping vent and the electro-acoustic path) facilitate establishing a hybrid transfer function. An advantageous effect of the combined transfer function is that the control algorithm of the system can focus on controlling frequencies above the cross-over frequency only.

[0166] In embodiments, the electro-acoustic path is arranged to apply a high-pass gain for frequencies above the high-pass cut-off frequency, preferably applying the high-pass gain in the range from -30 dB to 20 dB at 3 kHz, such as in the range from -25 dB to 15 dB at 3 kHz, such as in the range from -20 dB to 10 dB at 3 kHz.

[0167] In embodiments, the arrangement of the damping vent for suppressing the acoustic resonance is obtained by the suppressing element.

[0168] In other words, preferably the dampening of the acoustic resonance by the dampening vent's dampening element reduces the resonance amplitude to not more than the reference amplitude by more than a few dB, as mentioned above.

[0169] In embodiments, the one or more vent elements comprise one or more of the one or more dampening elements.

[0170] In some embodiments of the invention, any of the one or more dampening elements can be built into the one or more vent elements.

[0171] In embodiments, the one or more dampening elements comprise a dampening cloth, a dampening mesh, a dampening foam and / or a dampening slit.

[0172] The dampening element can have any form or material as long as it somehow manages to oppose the acoustic flow to some extent. The dampening element can be characterized by an acoustic impedance, which measures the opposition the dampening element exerts on the acoustic flow. Thus, the dampening element and its acoustic impedance are analogous to a resistor and the resistance of a resistor in an electrical circuit.

[0173] In embodiments, the one or more dampening elements are characterized by an acoustic impedance, wherein the acoustic impedance is in the range from 20 acoustical ohms to 500 acoustical ohms, such as from 50 acoustical ohms to 400 acoustical ohms, e.g. 180 acoustical ohms or 200 acoustical ohms.

[0174] Acoustical ohm is in CGS units, i.e. 1 acoustical ohm = 1 dyne-s / cm 5 wherein dyne is a derived unit of force in the CGS unit system.

[0175] In embodiments, the in-ear earphone device is battery powered, such as by a rechargeable battery.

[0176] In embodiments, the in-ear earphone device is arranged to receive an external audio signal, e.g. by an audio signal interface, wherein the loudspeaker is arranged to reproduce the external audio signal.

[0177] In many embodiments, it can be preferred to allow an external audio signal to be provided to the in-ear earphone device, which can be emitted as sound by the loudspeaker. The external audio signal can be provided from an external unit, such as an audio source, which is arranged to output an electrical audio signal and has connection means for delivering the audio signal to the in-ear earphone device. Examples of connection means are wired connections, such as cable connections, and wireless connections, such as Bluetooth connections, e.g. Bluetooth A2DP or Bluetooth aptX, or Wi-Fi connections.

[0178] In some embodiments, the external audio signal can be processed before being reproduced by the loudspeaker.

[0179] In embodiments, the in-ear earpiece device is configured as a truly wireless earpiece.

[0180] Hereby, the in-ear earpiece does not require a cable, neither to an audio source, nor to the two in-ear earpieces of a set of earpieces.

[0181] In embodiments, the in-ear earpiece device is arranged to transmit a signal recorded by a microphone, such as the noise microphone or the auxiliary microphone.

[0182] In some embodiments of the invention, it can be advantageous that a microphone records sound, which can then be transmitted, e.g. for telecommunication purposes. Preferably, the recording can be performed by a microphone arranged to mainly record sound from the external environment.

[0183] The present invention further relates to a set of in-ear earpiece devices comprising a first in-ear earpiece device and a second in-ear earpiece device according to any of the above, wherein the first in-ear earpiece device is arranged to fit into a first concha of a user, and wherein the second in-ear earpiece device is arranged to fit into a second concha of the user.

[0184] Many embodiments of the present invention comprise a set of two in-ear earpiece devices. These can for example be worn by a user in the left and right concha, respectively. Hence, the housings of the two devices of the set can typically be mirror images.

[0185] This can ensure noise control to both ears of a user. Furthermore, it allows the user to listen to a desired audio signal in stereo.

[0186] In embodiments of the present invention, the first in-ear earpiece device and the second in-ear earpiece device can have different processing, e.g. one of the devices can be a master device, while the other device is a slave device, wherein the master device controls the slave device and acts as a communication hub.

[0187] In embodiments of the present invention, the two in-ear earpiece devices are configured to communicate with each other, directly or indirectly, e.g. via a common controller, in order to coordinate settings, or to provide improved directional sound processing or active noise control. BRIEF DESCRIPTION OF DRAWINGS

[0188] Various embodiments and advantages of the present invention will be described below with reference to the accompanying drawings, in which

[0189] Figure 1 An in-ear earpiece device according to embodiments of the present invention is shown,

[0190] Figure 2 An exemplary inward vent transfer function according to the present invention is shown,

[0191] Figures 3a to 3c various in-ear earphone devices with different microphone layouts are shown,

[0192] Figure 4 in-ear earphone devices with dynamic acoustic leakage are shown,

[0193] Figures 5a to 5h various layouts of damping vents are shown according to embodiments of the application,

[0194] Figures 6a to 6c effects of using dampening elements with various acoustic impedances are shown according to some embodiments of the application,

[0195] Figures 7a to 7b one advantageous effect of damping vents in relation to dynamic acoustic leakage according to preferred embodiments of the application is shown,

[0196] Figures 8a to 8g various simulated in-ear earphone devices under the influence of dynamic acoustic leakage in relation to inward noise are shown,

[0197] Figures 9a to 9g various simulated in-ear earphone devices under the influence of dynamic acoustic leakage in relation to audio reproduction are shown, and

[0198] Figures 10a to 10c the influence of user differences in different scenarios is shown. DETAILED DESCRIPTION

[0199] Figure 1 An in-ear earphone device 101 according to embodiments of the application is shown. Figure 1 The illustration of Fig. 1 shows an in-ear earphone device 101 when inserted in an ear canal 110 of a user wearing the device. The in-ear earphone device 101 is preferably resting in the user's concha 111 and is provided with a flexible ear tip 112 for providing an acoustic seal in the ear canal 110 of different users.

[0200] The in-ear earphone device 101 comprises a damping vent 105 acoustically coupling the ear canal 110 with an external acoustic environment 109 outside the ear canal 110. Ideally, the in-ear earphone device 101 has an outer shape blocking the ear canal 110 of the user, however small leakage paths (not shown in the figures) can naturally occur at the interface between the flexible ear tip 112 and the ear canal 110, and these leakages can dynamically change as the user moves around and e.g. when the user is talking or chewing.

[0201] The damping vent 105 of this embodiment comprises a vent element 106, which is preferably formed as a circular or semi-circular conduit, although other vent element designs are conceivable. The purpose of the damping vent is to facilitate the transmission of acoustic sound between the external acoustic environment 109 and the ear canal 110, however at a reduced sound pressure level (SPL). The dampening properties of the damping vent 105 are provided by a dampening cloth 107, which in this embodiment is located at one end of the damping vent 105. In another embodiment of the invention, the dampening properties of the damping vent 105 are provided by dampening cloth at both ends of the damping vent 105, and in yet another embodiment of the invention, the dampening properties of the damping vent 105 are provided by slits or openings in the vent element 106.

[0202] The in-ear earphone device 101 comprises a noise microphone 102 arranged to mainly record acoustic sound from the external acoustic environment 109 and to provide a recorded audio signal RAS. In the figure of this embodiment, the noise microphone 102 is shown arranged at the end of the in-ear earphone device 101 facing the external acoustic environment, however in other embodiments of the invention, the noise microphone 102 can be further arranged within the in-ear earphone device 101 and acoustically coupled to the external acoustic environment 109 by a microphone duct (not shown in the figure). The in-ear earphone device 101 further comprises a signal processor 103 configured to receive the recorded audio signal RAS and to provide an active noise control signal ANCS based on the received recorded audio signal RAS. A loudspeaker 104 of the in-ear earphone device 101 is arranged to reproduce the provided active noise control signal ANCS in the ear canal 110 of a user of the in-ear earphone device 101. In the figure of this embodiment, the loudspeaker 104 is shown contained within the in-ear earphone device 101, and the acoustic sound emitted by the loudspeaker is transmitted to the ear canal 110 via a loudspeaker duct 108. However, in other embodiments of the invention, the loudspeaker duct 108 can be omitted, and the loudspeaker 104 can be arranged closer to the ear canal facing end of the in-ear earphone device 101. In other embodiments of the invention, the loudspeaker duct 108 and the damping vent 105 can be formed as two acoustically divided sub-portions of a combined acoustic port.

[0203] Since the in-ear earphone device 101 according to the invention is arranged to reproduce an active noise control signal, it is able to perform a method known as active noise control or active noise cancellation. Unwanted sound from the external acoustic environment 109 is recorded by the noise microphone 102, and based on the recorded audio signal RAS, the signal processor 104 provides an active noise control signal ANCS, which is designed to cancel the unwanted sound within the ear canal 110 of a user by destructive interference when reproduced by the loudspeaker 104.

[0204] Figure 2 An exemplary in-ventilation transfer function H VI may be understood as a transfer function from the outer environment to the ear canal without substantial influence from dynamic acoustic leakage or a loudspeaker. Three representations of the in-ventilation transfer function H VI are shown as curves S1-S3. According to the present application, one or more dampening elements are arranged to dampen an acoustic resonance of the in-ventilation transfer function H VI .

[0205] The graph shows a reference frequency range 403 from 20 Hz to 100 Hz. Based on the reference frequency range 403, a reference amplitude 400 can be determined, for example as an average sound pressure level of the in-ventilation transfer function H VI over the range. Based on the reference amplitude 400, a resonance amplitude threshold 401 can be determined, for example, the resonance amplitude threshold 401 can be 3 dB larger than the reference amplitude 400.

[0206] The curve S1 can be an in-ventilation transfer function H VI of an in-ear headphone device with a vent having no substantial damping. Thus, the curve S1 has a resonance amplitude 405 exceeding the resonance amplitude threshold 401. A device according to the curve S1 can not contain the advantages of the present application and is not disclosed by the claims.

[0207] The curve S2 can be an in-ventilation transfer function H VI of an in-ear headphone device with a damped vent. The curve S2 has a resonance amplitude 405 according to the present application within the resonance amplitude threshold 401.

[0208] The curve S3 can be an in-ventilation transfer function H VI of an in-ear headphone device with a damped vent. The resonance amplitude 405 of the curve S3 is approximately equal to the reference amplitude 400. For example, the acoustic resonance of the damped vent can be approximately critically damped. Thus, the resonance amplitude 405 of the curve S3 is within the resonance amplitude threshold 401.

[0209] Figures 3a to 3c Various in-ear headphone devices 101 with different microphone layouts according to embodiments of the present application are shown.

[0210] Figure 3a An in-ear headphone device 101 according to a preferred embodiment of the present application is shown also when inserted into an ear canal 110 of a user. Figure 1The in-ear headphone device 101, when in use, is arranged to at least provide the reproduction of an active noise control signal ANCS, and this reproduced signal (in the form of acoustic sound waves) is combined in the ear canal 110 with a sound originating from an unwanted sound source, such as the engine of an airplane or the rumbling wheels of a train or bus (if the user of the in-ear headphone device 101 commutes by airplane, train, or bus, respectively). Since the active noise control signal ANCS is designed to eliminate (e.g., cancel) the unwanted sound, the combined sound picked up by the user's eardrum 201 is effectively perceived as an acoustic void signal.

[0211] With this arrangement of the noise microphone 102, the noise microphone 102 primarily records sounds from the external acoustic environment surrounding the user, which indirectly represent unwanted sounds that the user will perceive through the headphone device.

[0212] Figure 3b An alternative embodiment of the invention is shown, wherein a noise microphone 102 is arranged in an in-ear headphone device 101 such that it can record sound within the ear canal 110 of a user wearing the in-ear headphone device. With this arrangement, the noise microphone 102 primarily records sound from within the user's ear canal, i.e., more or less directly measures unwanted sound when the user perceives it.

[0213] Figure 3c Another alternative embodiment of the invention is shown, wherein the noise microphone 102 is used in conjunction with... Figure 3b The noise microphone 102 shown in the embodiment is arranged in a similar manner. In this embodiment of the invention, the in-ear headphone device 101 further includes an auxiliary microphone 202, which is similar to... Figure 3a The noise microphone 102 of the illustrated embodiment is similarly positioned in the in-ear headphone device 101.

[0214] Figure 4 It shows the same as Figure 3aearphone device 101 and the user's ear. The acoustic leak 203 can take on any size and geometry depending on the shape of the user's ear and how the in-ear earphone device 101 is inserted into the ear canal 110. In addition, there can also be additional leak paths (not shown) and these can also take on any size and geometry. For convenience, any arrangement of leak(s) in the seal between the in-ear earphone device 101 and the user's ear is referred to as the leak path 203, which can thus be an effective leak path. The acoustic leak 203 can also change dynamically (i.e., over time) as the user moves around, such as when the user is walking or jogging, and also when the user is using his / her jaw, such as when the user is talking.

[0215] The dynamically changing acoustic leak 203 presents an entry for unwanted sound from the external acoustic environment 109 to enter the user's ear canal 110. As will be appreciated with reference to the embodiments shown previously, the in-ear earphone device 101 according to any of the previously shown embodiments can also exhibit an acoustic leak 203 when inserted into the user's ear due to, for example, improper fit of the in-ear earphone device 101. Figure 4

[0216] In addition to the acoustic leak 203, the damping vent 105 also presents an entry for unwanted sound from the external acoustic environment 109 to enter the user's ear canal 110. However, the unwanted sound from the external acoustic environment 109 that enters through the acoustic leak 203 can exit through the damping vent 105. In this way, the damping vent serves a dual purpose in that sound can enter from the external acoustic environment 109 and into the ear canal 110, and sound that passes through the acoustic leak 203 can exit through the damping vent 105 and back into the external acoustic environment 109.

[0217] Figures 5a to 5h Various layouts of the damping vent 105 according to embodiments of the present application are shown.

[0218] Figure 5a A side view of the damping vent 105 according to embodiments of the present application is shown. The damping vent 105 includes a vent element 106 in the form of a cylinder and a dampening element 107 in the form of a damping cloth. Although in this embodiment the vent element 106 is shown as a cylindrical element, other geometrical shapes are also contemplated. ​

[0219] The dampening element 107 in the form of a damping cloth is shown positioned at one end of the venting element 106, however it can be positioned in any end of the venting element 106, and in another embodiment of the present invention the dampening vent 105 comprises dampening elements 107 positioned in both ends of the dampening vent 105. The dampening element 107 of the present embodiment is positioned within the opening of the venting element 106, however, in another embodiment of the present invention the dampening element 107 can be positioned in such a way that it covers the opening of the venting element 106.

[0220] Figure 5b A side view of a dampening vent 105 according to an embodiment of the present invention is shown. Several venting elements 106 form a branched dampening vent 105, which further comprises a dampening element 107 in the form of a damping cloth. The dampening element 107 of the present embodiment is positioned within the opening of the venting element 106, however, in another embodiment of the present invention the dampening element 107 can be positioned in such a way that it covers the opening of the venting element 106. Furthermore, in other embodiments of the present invention the branched dampening vent can comprise any number of dampening elements 107, such as a dampening element 107 covering all openings of the venting elements 106.

[0221] Figures 5c to 5d Two side views of a dampening vent 105 according to an embodiment of the present invention are shown. Figure 5c A dampening vent 105 is shown constructed with a speaker duct 108, which the loudspeaker 103 can be acoustically coupled to. In this embodiment of the present invention the speaker duct 108 and the dampening vent 105 constitute a cylindrical acoustic tube, i.e. each of the two has a semi-cylindrical geometry. In other embodiments of the present invention the speaker duct 108 and the dampening vent 105 can constitute a combined acoustic tube having any geometry. In Figure 5c In the middle a dashed line c-c is shown representing the plane c. In Figure 5d In the middle a view of the embodiment is shown as seen from the plane c, which shows the longitudinal geometry of the combined speaker duct 108 and dampening vent 105.

[0222] Figure 5e An embodiment of the present invention is shown, where the in-ear earphone device 101 (not shown in the figure) comprises two separate dampening vents 105. Each dampening vent 105 is similar to the dampening vent 101 shown with respect to the embodiment of Figure 5a In the middle a view of the embodiment is shown as seen from the plane c, which shows the longitudinal geometry of the combined speaker duct 108 and dampening vent 105. Figure 5e The configuration of the dampening vent 105 in the middle comprises a venting element 106 and a dampening element 107. The dampening element 107 of the present embodiment is a damping cloth present in the opening of the venting element 106, however, other configurations of the dampening element are conceivable.

[0223] Figure 5f Embodiments of the present application are shown, in which the dampening vent 105's dampening properties are facilitated by a dampening element 107 in the form of a slit. In another embodiment, the dampening element 107 is integrated into the vent element 106, for example to interfere with the air flow or to facilitate air leakage.

[0224] Figure 5g Embodiments of the present application are shown, in which a microphone (for example the noise microphone 102) is arranged to mainly record sound from the dampening vent 105. Thus, the microphone can be considered to be acoustically coupled to the vent element 106 of the dampening vent 105 within the in-ear earphone device 101. In other embodiments, the in-ear earphone device 101 comprises several vent elements 106, and the microphone and / or the loudspeaker can be coupled to any of these vent elements 106 according to embodiments of the present application. In Figure 5g In the shown embodiment, the dampening vent 105 has a single dampening element 107 at one side. In such embodiments, the microphone can thus mainly record sound from the external environment, or mainly record sound from the ear canal, depending on the precise positioning of the dampening element 107 and the microphone.

[0225] Figure 5h Embodiments of the present application are shown, in which the loudspeaker duct 108 and the dampening vent are partly coupled by a dampening element 107. The dampening vent 105 further comprises dampening elements 107 at both ends of the vent element 106. The loudspeaker duct 108 and the dampening vent 105 can feature any type of separation according to embodiments of the present application. The loudspeaker 103 can for example be acoustically coupled to the dampening vent 105 within the in-ear earphone device 101, acoustically decoupled from the dampening vent 105 within the in-ear earphone device 101 (see for example Figure 5c ), or partly coupled to the dampening vent 105 within the in-ear earphone device 101 as Figure 5h shown.

[0226] In the above described embodiments of the present application, various configurations of the dampening vent 105 are demonstrated. However, the present application is not limited to any particular configuration and thus various other embodiments are available to the skilled person. The dampening vent configuration can be achieved by any combination of the above described embodiments; thus the dampening vent configuration can comprise one or more dampening vents 105, the individual dampening vent can comprise any number of vent elements 106 and dampening elements 107, the microphone and / or the loudspeaker can be acoustically coupled to the vent element or can have a separate duct, and the vent and the duct can have any geometry.

[0227] Figures 6a to 6cThe effect of using a dampening element with various acoustic impedances according to some embodiments of the present application is shown in comparison to an open ear. The presented data was obtained by performing a simulation of the system using the equivalent electronic device diagram as shown in Figure 6a which can be reproduced by a person skilled in the art.

[0228] Figure 6a The simulation shown corresponds to a typical embodiment of the present application. The 60 dB signal simulation source 300 corresponds to noise from the external environment, and the top ear simulation microphone 301 corresponds to the sound heard in the ear. In this simulation, sound can enter the ear canal via two different paths: the vent path 302 and the leak path 304. The vent path 302 is split so that the first part of the vent path is composed of two vent elements, which are combined into a single vent element. The leak path 304 has a large acoustic impedance in this particular simulation, which corresponds to no substantial dynamic acoustic leakage.

[0229] The vent path 302 includes an impedance Rv, which corresponds to a dampening element according to the present application. For Figures 6b to 6c the value of the impedance is varied to simulate the effect of using dampening elements with different acoustic impedances.

[0230] In Figure 6b the simulation curve S4 shows the signal corresponding to an open ear. The curve has a characteristic resonance at about 3 kHz.

[0231] The simulation curves S5-S9 correspond to acoustic impedances Rv of 0 acoustic ohms, 45 acoustic ohms, 90 acoustic ohms, 180 acoustic ohms, and 360 acoustic ohms, respectively, where all the values provided are in acoustic ohms in CGS. It is evident from the simulation that when the acoustic impedance is low, a resonance is clearly present at about 900 Hz. However, as the acoustic impedance is increased, the resonance is damped, and for a sufficiently large acoustic impedance, no resonance peak characteristic is seen. If a very large acoustic impedance is chosen, a wide range of frequencies is damped, and not only the resonance. Thus, for this simulation embodiment, the preferred acoustic impedance is about 180 acoustic ohms, as the resonance characteristic has been removed, but in addition thereto, sounds below the desired cut-off frequency are essentially not damped.

[0232] The preferred acoustic impedance of the dampening element can vary for different embodiments of the present application. For example, the acoustic impedance can depend on the composition of the vent element, the cross-sectional area of the vent element, the length of the vent element, and the remaining volume of the ear canal when the insertion device is inserted. The main purpose of the dampening element is typically to remove the Helmholtz resonance characteristic, without unnecessarily damping additional sounds, and thus the acoustic impedance should be chosen accordingly.

[0233] Some embodiments of the invention can also comprise several dampening elements, and preferably the combined effect thereof should be to dampen the Helmholtz resonance that would occur without the dampening elements when the device is inserted.

[0234] Figure 6b It is additionally shown how the damped vent can reduce the sound pressure in the ear at frequencies above the desired cut-off. The attenuation can reach 20 dB or more in the open ear canal resonance region compared to an open ear. At higher frequency resonances, which can vary significantly between ears, it can also be attenuated by the damped vent in combination with other acoustic elements such as a damped inlet to a cavity such as a loudspeaker front volume. In the exemplary illustration of this figure, the difference in amplitude of the sound pressure level between the peaks of the curves S5-S9 and the two resonance features of the curve S4 at about 8 kHz and about 9 kHz, respectively, is 9 dB. This dampening effect at relatively high frequencies can be preferred in some embodiments of the invention.

[0235] Figure 6c The same curves as in Figure 6b are shown, but now relative to the simulated curves associated with an open ear S4. Thus, Figure 6c The curves shown can be interpreted as the passive insertion gain, i.e. the change in gain experienced by the user when wearing the inactive device. It should be noted that the simulated data has been truncated at about 6.5 kHz for simplicity. The insertion gain data in this frequency region is visually dominated by Figure 6b the resonance features at 8-9 kHz shown, but the detailed variations of these features do not significantly affect the overall perception of sound through the common signal under normal conditions.

[0236] Figures 7a to 7b One advantageous effect of the damped vent 105 according to preferred embodiments of the invention is shown. The presented data is obtained by performing a simulation of the system using an equivalent electronic circuit diagram as Figure 7a shown, which can be reproduced by a person skilled in the art.

[0237] Figure 7a The simulation shown in the top part of corresponds to a typical embodiment of the invention with a damped vent, whereas the bottom part corresponds to an in-ear headphone device without a damped vent. The 60 dB SPL signal simulation source 300 corresponds to noise from the external environment at the entrance to the outer ear, and the ear simulation microphone 301 corresponds to the sound heard in the ear for both simulated devices. In the simulation of a typical embodiment of the invention, the signal can enter the ear canal via three different paths: the vent path 302, the electro-acoustic path 303, and the leakage path 304. However, in Figures 7a to 7bIn the illustrated simulation, the signal simulation source 300 is connected to the ear simulation microphone 301 only via the leakage plot path 304. This simulation thus involves sound entering the ear through dynamic acoustic leakage. Signals that have entered through the leakage plot path 304 can exit through the vent plot path 302, and the signal recorded by the ear simulation microphone 301 is thus reduced.

[0238] Figure 7a The leakage plot path 304 of both simulation devices of Fig. 2 comprises a plot element having a leakage diameter Dlk / DLK corresponding to the diameter of the dynamic acoustic leakage. In each plot, this leakage diameter is varied to show the influence that the dynamic acoustic leakage can exert on the signal reaching the ear simulation microphone 301.

[0239] Figure 7b The signal reaching the ear simulation microphone is shown for various simulation in-ear headphone devices, wherein the curves S16-S20 correspond to simulation in-ear headphone devices having a damped vent, and the curves S21-S25 correspond to simulation devices without a damped vent. The curves S16-S20 and S21-S25 correspond to a leakage having a combined cross-sectional area corresponding to a circular cross-section having a diameter of 0.035 cm, 0.05 cm, 0.07 cm, 0.08 cm and 0.1 cm, respectively.

[0240] For the simulation curves S21-S25, any signal that has entered the region of the ear simulation microphone 301 will tend to stay at the ear simulation microphone 301, and will thus be recorded as a large signal. In contrast, for the simulation curves S16-S25, the sound pressure level recorded by the ear simulation microphone 301 is significantly lower, because the signal in the region of the ear simulation microphone 301 can exit this region through the vent plot path 302. For example, for a leakage diameter of 0.05 cm, as shown by the curves S17 and S22, the difference in sound pressure level of the leakage contribution at 200 Hz between the simulation devices is about 12 dB.

[0241] Thus, as Figures 7a to 7b The simulation and its results as shown serve as a proof that embodiments of the present invention can reduce the influence of dynamic acoustic leakage in the ear canal by allowing sound to exit through a damped vent.

[0242] Figures 8a to 8g Various simulation in-ear headphone devices are shown under the influence of dynamic acoustic leakage, which devices have no vent, have an open, undamped vent, or have a damped vent.

[0243] The presented data are obtained by performing simulations of the system using an equivalent electronic device plot as shown in Fig. 3, which can be reproduced by a person skilled in the art. Figure 8a

[0244] ​Figure 8a The illustrated simulations correspond to an in-ear earphone device. The 60 dB SPL constant pressure signal simulation source 300 corresponds to the noise from the external environment at the entrance to the outer ear, and the ear simulation microphone 301 corresponds to the sound heard in the ear. The signal can reach the ear simulation microphone 301 via three different paths: the vented graph path 302, the electroacoustic graph path 303, and the leakage graph path 304. However, in the simulations related to Figures 8a to 8g the electroacoustic graph path 303 does not carry a signal.

[0245] The vented graph path 302 is split so that the first part of the vented graph path is composed of two vent elements that are merged into a single vent element in which the impedance Rv is positioned. For Figures 8b to 8c , Figures 8d to 8e and Figures 8f to 8g various figures, the value of the impedance is changed to simulate respectively a device without vent (large impedance), a device with an open undamped vent (small impedance), and a device with a damped vent (medium impedance).

[0246] The leakage graph path 304 has a leakage diameter Dlk / DLK corresponding to the equivalent diameter of the dynamic acoustic leakage. In each graph, this leakage diameter is changed to show the impact that the dynamic acoustic leakage can impose on the signal reaching the ear simulation microphone 301.

[0247] Figures 8b to 8c The signal reaching the ear simulation microphone 301 is shown for a device without vent, i.e. with Rv = 1 M ohm (acoustic) in CGS units, where Figure 8b the amplitude of the sound pressure level of the transmitted signal is shown, and Figure 8c the phase of the transmitted signal is shown. Both of these entities are relevant to active noise control. The curves S26-S28 and S29-S31 correspond respectively to a leakage diameter of 0.05 cm, 0.07 cm and 0.1 cm.

[0248] Figure 8b It is clearly shown how the dynamic leakage can affect the signal amplitude, for example the amplitude of the inward total transfer function H TI In particular in the range of 400 Hz and above, the difference in sound pressure level is 10 dB to 15 dB.

[0249] In addition, Figure 8c it is shown how the dynamic leakage can additionally affect the signal phase, in particular in the range from 100 Hz to 700 Hz.

[0250] These simulations thus show the huge effect that the dynamic acoustic leakage can have on an in-ear earphone device without vent.

[0251] Figures 8d to 8e The signal to the ear canal simulation microphone 301 for a device with an open undamped vent is shown, i.e. Rv = 0, where Figure 8d The amplitude in sound pressure level of the transmitted signal is shown, and Figure 8e The phase of the transmitted signal is shown. Both of these entities are relevant for active noise control. The curves S32-S35 and S36-S39 correspond to a leakage diameter of 0 cm, 0.05 cm, 0.07 cm and 0.1 cm, respectively.

[0252] Figure 8d How an in-ear headphone device with an open vent can suffer from the presence of a Helmholtz resonance is shown. The addition of dynamic acoustic leakage can shift the location of this resonance to a different frequency, which can be difficult to handle continuously for a device arranged to provide active noise control.

[0253] Figure 8e The signal phase in a device with an undamped vent is shown, and how dynamic acoustic leakage affects the signal phase. Below 500 Hz, the phase behaves relatively well, regardless of any dynamic acoustic leakage. However, from just below 1 kHz, the phase has a sharp downward tendency. In general, this sharp transition is detrimental for active noise control purposes. Dynamic acoustic leakage can shift this sharp transition around, which further makes this phase behaviour problematic.

[0254] Thus, these simulations show how a device with an undamped vent can have serious problems in providing optimal active noise control.

[0255] Figures 8f to 8g The signal to the ear canal simulation microphone 301 for a device with a damped vent is shown, i.e. Rv = 180 acoustic ohms in CGS units, where Figure 8f The amplitude in sound pressure level of the transmitted signal is shown, and Figure 8g The phase of the transmitted signal is shown. Both of these entities are relevant for active noise control. The curves S40-S43 and S44-S47 correspond to a leakage diameter of 0 cm, 0.05 cm, 0.07 cm and 0.1 cm, respectively.

[0256] Figure 8f How dynamic leakage can affect the signal amplitude is shown. Compared to the simulation for a device without a vent (S1-S3), the effect of the leakage is significantly smaller. For example, at 1 kHz, the difference in sound pressure level between a leakage diameter of 0.05 cm and 0.1 cm is about 3 dB with a damped vent, whereas the difference is about 15 dB without a vent. Compared to the simulation for a device with an undamped vent (S32-S35), the effect of the leakage is also significantly smaller. For example, at 1 kHz, the difference in sound pressure level between a leakage diameter of 0.05 cm and 0.1 cm is about 3 dB with a damped vent, whereas the difference is about 15 dB without a vent. Figures 8b to 8c Figures 8d to 8e ​) show no Helmholtz resonance in contrast. For larger leaks, a similar resonance feature does occur, but this feature behaves better than Figure 8d the Helmholtz resonance shown in Figure 3, which shifts in frequency with changes in the size of the leak.

[0257] Figure 8g The signal phase in the device with the damped vent is shown, as well as how dynamic acoustic leakage affects this signal phase. The phase behaves well for all of the simulated dynamic acoustic leakage throughout the range relevant for active noise control, i.e. up to frequencies of about 1 kHz.

[0258] Thus, Figures 8a to 8g The simulations of Figure 4 are a proof that, in the context of dynamic acoustic leakage, an in-ear headphone device with a damped vent is superior to a device without a vent and to a device with an undamped vent for the purpose of active noise control. Specifically, it has been shown that the changes due to the dynamic acoustic leakage affecting the magnitude of the in-to-out total transfer function H TI can be reduced, and the distortion due to the dynamic acoustic leakage affecting the phase of the in-to-out total transfer function H TI can be reduced. These improvements can be obtained by controlling and suppressing the Helmholtz resonance established by the ear canal and the acoustic path to the environment.

[0259] Figures 9a to 9g Various simulated in-ear headphone devices are shown under the influence of dynamic acoustic leakage, either without a vent, with an open undamped vent, or with a damped vent. Specifically, the electro-acoustic graph path includes a simulated loudspeaker that generates a signal, which is transmitted to an ear simulated microphone 301.

[0260] The presented data is obtained by performing simulations of the system using the equivalent electronic graph as shown in Figure 5, which can be reproduced by a person skilled in the art. Figure 9a

[0261] Figure 9a The simulated graph shown in Figure 4 corresponds to an in-ear headphone device. For illustrative purposes, a simple loudspeaker model consisting of a constant volume velocity source and a pre-volume is established. The simulated loudspeaker delivers a signal through the graph path 303 to the ear canal. The amplitude of the constant volume velocity source is adjusted to produce a signal of about 60 dB SPL at low frequencies in the ear simulated microphone. The behavior of this signal at the ear simulated microphone 301 is relevant for active noise control and the reproduction of a desired audio signal. The signal can generally partially reach the ear simulated microphone 301 and partially leave the simulated ear canal region through the vent graph path 302 and the leakage graph path 304.

[0262] ​The vented graph path 302 is split so that the first part of the vented graph path is composed of two vent elements that merge into a single vent element with the impedance Rv positioned therein. For Figures 9b to 9c 、 Figures 9d to 9e and Figures 9f to 9g For the various figures, the value of the impedance is changed to simulate respectively a device without vent (large impedance), a device with an open undamped vent (small impedance) and a device with a damped vent (medium impedance).

[0263] The leak graph path 304 has a leak diameter Dlk / DLK corresponding to the cross section of the dynamic acoustic leak. In each graph, this leak diameter is changed to show the impact that the dynamic acoustic leak can impose on the signal reaching the ear analog microphone 301.

[0264] Figures 9b to 9c The signal reaching the ear analog microphone 301 is shown for a device without vent, i.e. Rv = 1 Mega Ohm (acoustic) in CGS units, where Figure 9b The sound pressure level amplitude of the signal is shown, and Figure 9c The sound pressure level amplitude of the signal relative to a reference signal without dynamic acoustic leak is shown. Curves S48-S53 and S54-S59 correspond respectively to a leak diameter of 0 cm, 0.03 cm, 0.05 cm, 0.07 cm, 0.08 cm and 0.1 cm.

[0265] Figures 9b to 9c It is clearly shown how the dynamic leak can affect the amplitude of the signal from the loudspeaker reaching the ear in an in-ear device without vent, which is related to the transfer function from the loudspeaker to the ear drum, but also to the total transfer function H TO outward. Especially at low frequencies, the impact of the leak is huge, for example at 150 Hz, the difference in sound pressure level between the curves shown is more than 25 dB. Also, up to over 1 kHz, the difference in sound pressure level is significant.

[0266] Therefore, these simulations show the huge impact that the dynamic acoustic leak can have on an in-ear headphone device without vent.

[0267] Figures 9d to 9e The signal reaching the ear analog microphone 301 is shown for a device with an open undamped vent, i.e. Rv = 0, where Figure 9b The sound pressure level amplitude of the signal is shown, and Figure 9c The sound pressure level amplitude of the signal relative to a reference signal without dynamic acoustic leak is shown. Curves S60-S64 and S65-S69 correspond respectively to a leak diameter of 0 cm, 0.03 cm, 0.05 cm, 0.07 cm and 0.1 cm.

[0268] Figure 9d It is clear how an in-ear earphone device with open undamped vent can suffer from a large amount of sound loss, which is related to the impedance of the outward sound path. Especially in the low frequency range, the signal recorded by the ear simulator microphone 301 is 20-30 dB lower than the signal emitted from the analog speaker of 60 dB.

[0269] Therefore, these simulations show that a device with undamped vent is not suitable for audio reproduction.

[0270] Figures 9f to 9g It is shown that the signal reaching the ear simulator microphone 301 for a device with damped vent, i.e. in CGS units, Rv= 180 acoustical Ohm, where Figure 9f The sound pressure level amplitude of the signal is shown, and Figure 9g The sound pressure level amplitude of the signal relative to a reference signal without dynamic acoustic leakage is shown. The curves S70-S75 and S76-S80 correspond to a leakage diameter of 0 cm, 0.03 cm, 0.05 cm, 0.07 cm, 0.08 cm and 0.1 cm, respectively.

[0271] In comparison, Figures 9b to 9c The simulated curves of Figures 9f to 9g show a large reduction of the amplitude difference between the curves of different simulated leakage diameters. Furthermore, Figure 9d and Figure 9f The comparison between

[0272] Therefore, Figures 9a to 9g The simulations of TO are a proof that in the context of dynamic acoustic leakage, an in-ear earphone device with damped vent is superior to a device without vent and to a device with undamped vent for active noise control purposes and for sound reproduction. An in-ear earphone device with damped vent can provide a low amplitude of the outward total transfer function H TO with a favorable balance between the change of the outward total transfer function H TO due to dynamic acoustic leakage, especially at low frequencies, and the reduction of the sound pressure from the loudspeaker at the ear drum due to sound leaving via the vent. It has been shown that the distortion due to the influence of dynamic acoustic leakage on the outward total transfer function H TO for loudspeaker feedback and active noise control can be reduced and at the same time the reduction of the sound pressure from the loudspeaker at the ear drum due to sound leaving via the vent is limited.

[0273] Figures 10a to 10c The influence of user variability, e.g. different ear canal sizes and different insertion positions between users, in different scenarios (open ear, in-ear device with open vent and in-ear earphone device with damped vent) is shown.

[0274] Figure 10a The illustrated simulation plots correspond to (from top to bottom) an in-ear earphone device with a damped vent, an in-canal device, an open ear, and a reference open ear. The 60 dB signal simulation source 300 corresponds to noise from the external environment, and the various ear simulation microphones 301 correspond to the sound heard in the ear in different scenarios.

[0275] The graphical elements of the simulation ear canal are positioned before the ear simulation microphones 301. In the simulation, the simulation ear canal depends on the parameter vLcnl / CLCNL, which corresponds to the size of a portion of the ear canal, and this parameter is varied to study the impact of user differences. The graphical elements after the reference open ear plot path 307 of the simulation ear canal do not change, and the simulation signals recorded by the corresponding ear simulation microphones are used for reference.

[0276] Figure 10b The signals reaching the various ear simulation microphones are shown, where the curves S81-S83 correspond to the simulated in-ear earphone device with a damped vent, the curves S84-S86 correspond to the simulated in-canal device, and the curves S87-S89 correspond to the open ear. Within each scenario, the simulated size of the portion of the ear canal is -0.2 cm, 0 cm, and 0.2 cm.

[0277] In general, above 6-7 kHz, all curves are dominated by sharp resonance features. At these frequencies, these features are typical for an ear. Inserting an in-ear earphone device can change these features, but the resonance behavior will typically persist in some form.

[0278] In addition, the open ear curves S87-S89 all show the well-known natural resonance of the ear at about 3 kHz, and the in-canal curves S84-S86 show the Helmholtz resonance at about 1 kHz. In contrast, the damped vent curves S81-S83 show no resonance features below 6-7 kHz.

[0279] Active noise control is typically implemented at frequencies up to 1 kHz. Within this range, the in-canal curves S84-S86 are mainly affected by user differences. In contrast, the damped vent curves S81-S83 are minimally affected.

[0280] Figure 10c The same curves as in Figure 10b are shown, but now relative to the curves obtained by the reference open ear plot path 307. Thus, Figure 10c The illustrated curves can be interpreted as passive insertion gain, i.e., the change in gain experienced by a user when wearing an inactivity device.

[0281] Figures 10a to 10cThe simulation is a proof that in-ear headphone devices with damped vents are an improvement compared to in-ear devices with open vents in the context of user variance. Specifically, according to embodiments of the invention, the simulation shows that distortions due to user variance affecting the magnitude of the inward total transfer function H TI may be reduced.

[0282] List of reference signs:

[0283] 101 in-ear headphone device

[0284] 102 noise microphone

[0285] 103 signal processor

[0286] 104 loudspeaker

[0287] 105 damped vent

[0288] 106 venting element

[0289] 107 dampening element

[0290] 108 loudspeaker duct

[0291] 109 external acoustic environment

[0292] 110 ear canal

[0293] 111 pinna (outer ear)

[0294] 112 flexible earplug

[0295] 201 eardrum (ear drum)

[0296] 202 auxiliary microphone

[0297] 203 acoustic leakage

[0298] 300 signal simulation source

[0299] 301 ear simulation microphone

[0300] 302 venting graph path

[0301] 303 electroacoustic graph path

[0302] 304 leakage graph path

[0303] 305 open ear graph path

[0304] 306 in-ear graph path

[0305] 307 reference open ear graph path

[0306] 400 reference magnitude

[0307] 401 Resonance magnitude threshold

[0308] 402 Magnitude threshold distance

[0309] 403 Reference frequency range

[0310] 404 Resonance frequency range

[0311] 405 Resonance magnitude

[0312] S1-S97 Simulated signal curves

[0313] RAS Recorded audio signal

[0314] ANCS Active noise control signal

[0315] H VI , H VO Inward vent transfer function, outward vent transfer function

[0316] H LI , H LO Inward leak transfer function, outward leak transfer function

[0317] H TI , H TO Inward total transfer function, outward total transfer function

[0318] H EI Inward electroacoustic transfer function

Claims

1. An in-ear earphone device for insertion into a person's ear canal, the in-ear earphone device comprising: a noise microphone, a loudspeaker and a signal processor arranged to provide an active noise control signal based on a recorded audio signal from the noise microphone, wherein the loudspeaker is arranged to reproduce the active noise control signal in the ear canal; and a damped vent comprising one or more vent elements and one or more dampening elements, the damped vent being arranged to couple the ear canal to an external acoustic environment; 3. The in-ear earphone device according to claim 1, wherein the loudspeaker and the damped vent are acoustically separated within the in-ear earphone device. wherein said damping vent is characterized by an inward vent transfer function H from said external acoustic environment to said ear canal VI ; and wherein the damping vent is arranged to dampen acoustic resonance of the one or more venting elements, such that the inward vent transfer function H VI a resonance amplitude ratio in a resonance frequency range from 100 Hz to 2 kHz of the inward vent transfer function H VI a reference amplitude ratio in a reference frequency range from 20 Hz to 100 Hz of the inward vent transfer function H 2. The in-ear earphone device of claim 1, wherein the inward vent transfer function H VI and the acoustic resonance is a property of the damping vent.

4. The in-ear earphone device according to claim 1, wherein the loudspeaker and the damped vent are acoustically separated within the in-ear earphone device by a dampening element.

5. The in-ear earphone device according to claim 1, wherein the loudspeaker and the damped vent are coupled to the ear canal by separate ducts.

6. The in-ear earphone device according to claim 1, wherein the damped vent is arranged with a cross-sectional area equivalent to a cylinder with a diameter in the range from 1.5 mm to 3.5 mm.

7. The in-ear earphone device according to claim 1, wherein the damped vent is arranged with a cross-sectional area equivalent to a cylinder with a diameter in the range from 2.0 mm to 3.0 mm.

8. The in-ear earphone device according to claim 1, wherein the damped vent is arranged with a length equivalent to a cylinder with a length in the range from 2.5 mm to 10 mm.

9. The in-ear earphone device according to claim 1, wherein the damped vent is arranged with a length equivalent to a cylinder with a length in the range from 3.5 mm to 9 mm.

10. The in-ear earphone device according to claim 1, wherein the damped vent is arranged with a length equivalent to a cylinder with a length in the range from 4.5 mm to 8 mm.

11. The in-ear earphone device according to any of claims 1 to 10, wherein the vent is characterized by an acoustic mass based on the cross-sectional area and length of the damped vent, wherein the combination of the acoustic mass and the typical effective volume of the ear canal is characterized by a vent cut-off frequency selected from the range from 500 Hz to 2000 Hz.

12. The in-ear earphone device according to any of claims 1 to 10, wherein the vent is characterized by an acoustic mass based on the cross-sectional area and length of the damped vent, wherein the combination of the acoustic mass and the typical effective volume of the ear canal is characterized by a vent cut-off frequency selected from the range from 650 Hz to 1600 Hz. ​ 13. The in-ear earphone device according to any one of claims 1 to 10, wherein the vent is characterized by an acoustic mass based on the cross-sectional area and length of the damping vent, wherein the combination of the acoustic mass and the typical effective volume of the ear canal is characterized by a vent cut-off frequency selected from the range from 700 Hz to 1200 Hz.

14. The in-ear earphone device according to claim 1, wherein the noise microphone is arranged to record predominantly sound from the external acoustic environment.

15. The in-ear earphone device according to claim 1, wherein the noise microphone is arranged to record predominantly sound from the ear canal.

16. The in-ear earphone device according to claim 1, wherein the in-ear earphone device comprises an auxiliary microphone.

17. The in-ear earphone device according to claim 1, wherein the microphone arranged to record predominantly sound from the ear canal is coupled to the ear canal via a separate microphone tube.

18. The in-ear earphone device according to claim 15, wherein the microphone arranged to record predominantly sound from the ear canal is coupled to the ear canal via a separate microphone tube.

19. The in-ear earphone device according to claim 16, wherein the microphone arranged to record predominantly sound from the ear canal is coupled to the ear canal via a separate microphone tube.

20. The in-ear earphone device according to claim 1, wherein a microphone is acoustically coupled to the ear canal via the damping vent.

21. The in-ear earphone device of claim 1, wherein the signal processor is based on an estimated inward total transfer function H TI provides the active noise control signal.

22. The in-ear earphone device of claim 21, wherein the estimated inward total transfer function H TI is based on an estimate of the inward vent transfer function H VI .

23. The in-ear earphone device of claim 21, wherein the estimated total transfer function H TI based on differences in sound recordings of the external acoustic environment and the ear canal, respectively.

24. The in-ear earphone device of claim 21, wherein the estimated total transfer function inward H TI based on the estimated total transfer function outward H TO .

25. The in-ear earphone device of claim 24, wherein the estimated total transfer function outwards H TO based on a difference between sound reproduced by the loudspeaker and sound recorded by the noise microphone.

26. The in-ear earphone device of claim 1, wherein the signal processor is arranged with an active noise control algorithm to provide the active noise control signal, the active noise control algorithm characterized by Step size.

27. The in-ear earphone device according to claim 26, wherein the active noise control algorithm is of the LMS algorithm type.

28. The in-ear earphone device according to claim 1, wherein the in-ear earphone device is arranged with a cross-over frequency, a voice extraction function, or other separation means between sound which is desired to be subjected to active noise control and sound which is desired to be heard unaffected or even enhanced.

29. The in-ear earphone device according to claim 1, wherein the in-ear earphone device is arranged with options for switching on or off, adjusting the frequency range of, or the noise pattern controlled by, the active noise control signal.

30. The in-ear earphone device of claim 21, wherein the estimated total in-ear transfer function H TI includes a time-varying in-ear transfer function component H LI and a static in-ear transfer function component H VI .

31. The in-ear earphone device of claim 21, wherein the signal processor is arranged to update the estimated inward total transfer function H TI in representation, with an algorithm iteration rate in the range from 800 to 4000 times per second.

32. The in-ear earphone device of claim 21, wherein the signal processor is arranged to update the estimated inward total transfer function H TI in representation, with an algorithm iteration rate in the range from 1200 to 3000 times per second.

33. The in-ear earphone device of claim 32, wherein the signal processor is arranged to update the representation of the estimated inward overall transfer function H TI in algorithmic step sizes.

34. The in-ear earphone device according to claim 1, wherein the signal processor is arranged to provide an active occlusion control signal, and the loudspeaker is arranged to reproduce the active occlusion control signal in the ear canal.

35. The in-ear earphone device according to claim 34, wherein the active occlusion control signal is based on a signal recorded from a microphone arranged to record predominantly sound from the ear canal.

36. The in-ear earphone device according to claim 34, wherein the active occlusion control signal is based on a signal recorded from the noise microphone arranged to record predominantly sound from the ear canal.

37. The in-ear earphone device of claim 1, wherein the resonance magnitude is the inward vent transfer function H VI any magnitude in the range from 100 Hz to 2 kHz.

38. The in-ear earphone device of claim 1, wherein the resonance magnitude is the inward vent transfer function H VI at 800 Hz.

39. The in-ear earphone device according to claim 1, wherein the resonance amplitude is at maximum 2 dB greater than the reference amplitude.

40. The in-ear earphone device of claim 1, wherein the resonance magnitude is at most 1 dB greater than the reference magnitude.

41. The in-ear earphone device of claim 1, wherein the resonance magnitude is at most 0 dB greater than the reference magnitude.

42. The in-ear earphone device of claim 1, wherein the reference magnitude is based on the inward venting transfer function H VI average magnitude in the range from 20 Hz to 100 Hz.

43. The in-ear earphone device of claim 1, wherein the reference magnitude is based on the inward venting transfer function H VI average magnitude in the range from 20 Hz to 60 Hz.

44. The in-ear earphone device of claim 1, wherein the reference magnitude is based on the inward venting transfer function H VI an average magnitude in a range from 60 Hz to 100 Hz.

45. The in-ear earphone device of claim 1, wherein the dampening element is arranged to provide a nominal attenuation in the range from 2 dB to 10 dB in a frequency band from 50 Hz to 500 Hz.

46. The in-ear earphone device of claim 1, wherein the dampening element is arranged to provide a nominal attenuation in the range from 3 dB to 4 dB in a frequency band from 50 Hz to 500 Hz.

47. The in-ear earphone device of claim 1, wherein the dampening element is arranged to provide a nominal attenuation in the range from 2 dB to 6 dB in a frequency band from 50 Hz to 500 Hz.

48. The in-ear earphone device of claim 1, wherein the inward venting transfer function H VI has a characteristic of a low-pass, wherein the inward venting transfer function H VI is at least 3 dB lower in amplitude than the reference amplitude from a low-pass cutoff frequency to 10 kHz.

49. The in-ear earphone device of claim 48, wherein the low-pass cutoff frequency is in the range from 400 Hz to 2000 Hz.

50. The in-ear earphone device of claim 48, wherein the low-pass cutoff frequency is in the range from 500 Hz to 1600 Hz.

51. The in-ear earphone device of claim 48, wherein the low-pass cutoff frequency is in the range from 600 Hz to 1200 Hz.

52. The in-ear earphone device of claim 1, wherein the device further comprises an electro- acoustic path comprising a microphone that primarily records ambient sound, a variable gain, and the loudspeaker, wherein the electro-acoustic path is arranged to couple the external acoustic environment to the ear canal.

53. The in-ear earphone device of claim 1, wherein the device further comprises an electro- acoustic path comprising the noise microphone, a variable gain, and the loudspeaker, wherein the electro-acoustic path is arranged to couple the external acoustic environment to the ear canal.

54. The in-ear earphone device of claim 52, wherein the electro-acoustic path is characterized by an inward electrical transfer function H EI with a high-pass characteristic having a high-pass cutoff frequency in the range from 400 Hz to 2000 Hz.

55. The in-ear earphone device of claim 52, wherein the electro-acoustic path is characterized by an inward electrical transfer function H EI with a high-pass characteristic having a high-pass cutoff frequency in the range from 500 Hz to 1600 Hz.

56. The in-ear earphone device of claim 52, wherein the electro-acoustic path is characterized by an inward electrical transfer function H EI with a high-pass characteristic having a high-pass cutoff frequency in the range from 600 Hz to 1200 Hz.

57. The in-ear earphone device of any one of claims 54 to 56, wherein the electro- acoustic path is arranged to apply a high-pass gain in the range from -30 dB to 20 dB at 3 kHz for frequencies above the high-pass cutoff frequency.

58. The in-ear earphone device of any one of claims 54 to 56, wherein the electro- acoustic path is arranged to apply a high-pass gain in the range from -25 dB to 15 dB at 3 kHz for frequencies above the high-pass cutoff frequency.

59. The in-ear earphone device of any one of claims 54 to 56, wherein the electro- acoustic path is arranged to apply a high-pass gain in the range from -20 dB to 10 dB at 3 kHz for frequencies above the high-pass cutoff frequency.

60. The in-ear earphone device of claim 1, wherein the arrangement of dampening vents for dampening the acoustic resonance is obtained by the dampening element.

61. The in-ear earphone device of claim 1, wherein the one or more vent elements comprise one or more of the one or more dampening elements.

62. The in-ear earphone device of claim 1, wherein the one or more dampening elements comprise one or more selected from a list of dampening cloth, dampening mesh, dampening foam, and dampening slits.

63. The in-ear earphone device of claim 1, wherein the one or more dampening elements are characterized by an acoustic impedance, wherein the acoustic impedance is in the range from 20 acoustical ohms to 500 acoustical ohms.

64. The in-ear earphone device of claim 1, wherein the one or more dampening elements are characterized by an acoustic impedance, wherein the acoustic impedance is in the range from 50 acoustical ohms to 400 acoustical ohms.

65. The in-ear earphone device of claim 1, wherein the in-ear earphone device is battery powered.

66. The in-ear earphone device of claim 1, wherein the in-ear earphone device is powered by a rechargeable battery.

67. The in-ear earphone device of claim 1, wherein the in-ear earphone device is arranged to receive an external audio signal, wherein the speaker is arranged to reproduce the external audio signal.

68. The in-ear earphone device of claim 1, wherein the in-ear earphone device is arranged to receive an external audio signal through an audio signal interface, wherein the speaker is arranged to reproduce the external audio signal.

69. The in-ear earphone device of claim 1, wherein the in-ear earphone device is configured as a true wireless earphone.

70. The in-ear earphone device of claim 1, wherein the in-ear earphone device is arranged to transmit a signal recorded by a microphone.

71. The in-ear earphone device of claim 1, wherein the in-ear earphone device is arranged to transmit a signal recorded by the noise microphone.

72. The in-ear earphone device of claim 16, wherein the in-ear earphone device is arranged to transmit a signal recorded by the secondary microphone.

73. A set of in-ear earphone devices, comprising: a first in-ear earphone device and a second in-ear earphone device; wherein the first in-ear earphone device is arranged to fit into a first concha of a user; and wherein the second in-ear earphone device is arranged to fit into a second concha of the user; wherein the first in-ear earphone device and the second in-ear earphone device each comprise: a noise microphone, a speaker, and a signal processor arranged to provide an active noise control signal based on a recorded audio signal from the noise microphone, wherein the speaker is arranged to reproduce the active noise control signal in an ear canal; and a damped vent comprising one or more vent elements and one or more dampening elements, the damped vent arranged to couple the ear canal to an external acoustic environment; 74. The set of in-ear earphone devices of claim 73, wherein the first in-ear earphone device and the second in-ear earphone device are identical.

75. The set of in-ear earphone devices of claim 73, wherein the first in-ear earphone device and the second in-ear earphone device are different. wherein said damping vent is characterized by an inward vent transfer function H from said external acoustic environment to said ear canal VI ; and wherein the damping vent is arranged to dampen acoustic resonance of the one or more venting elements, such that the inward vent transfer function H VI a resonance amplitude ratio in a resonance frequency range from 100 Hz to 2 kHz of the inward vent transfer function H VI a reference amplitude ratio in a reference frequency range from 20 Hz to 100 Hz of at most 3 dB.

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