earphone

Abstract

The present invention discloses an earphone, which includes an earphone assembly and a first electroacoustic transducer and a second electroacoustic transducer. The earphone assembly includes an earphone body, which has an inner surface, an acoustic opening, and a cavity defined by the inner surface and the acoustic opening inside the body. The earphone body also includes an acoustic impedance branch, such as a waveguide, which reduces the amplitude of the resonance of the occluded ear canal defined by the cavity of the earphone assembly and the ear canal of the user at a first resonant frequency when the earphone is at least partially inserted into the ear canal of the user. The first electroacoustic transducer is arranged at the inner surface of the earphone body and is configured to generate a first acoustic signal. The second electroacoustic transducer is arranged along the length of the acoustic impedance branch and is configured to generate a second acoustic signal.

Description

Background Art

[0001] The present disclosure relates to an in-ear audio device having one or more acoustic impedance branches that suppress the resonance of an occluded ear canal formed between a cavity of the earphone and an ear canal of a user. More specifically, the audio device may be an earphone and include one or more electroacoustic transducers coupled to one or more of the acoustic impedance branches that may be provided as acoustic waveguides. Summary of the invention

[0002] In one aspect, an earphone includes an earphone assembly, a first electroacoustic transducer, and a second electroacoustic transducer. The earphone assembly has an earphone body having an inner surface, an acoustic opening, and a cavity defined by the inner surface and the acoustic opening. The earphone assembly also includes a first acoustic impedance branch extending from an open end at the inner surface to a closed end inside the earphone body. The first acoustic impedance branch includes a branch volume that reduces the amplitude of resonance of an occluded ear canal defined by the cavity and the ear canal of the earphone assembly at a first resonant frequency when the earphone is at least partially inserted into the ear canal of a user. The first electroacoustic transducer is disposed inside the earphone assembly and is configured to generate a first acoustic signal in response to a first electrical signal. The second electroacoustic transducer is disposed inside the earphone body along the length of the first acoustic impedance branch and is configured to generate a second acoustic signal in response to a second electrical signal.

[0003] Various examples may include one or more of the following features:

[0004] The first acoustic impedance branch may include an acoustic waveguide. The length of the waveguide may be equal to one quarter of the acoustic wavelength of the first resonant frequency.

[0005] The first electroacoustic transducer may be disposed at an inner surface of the earphone body. The second electroacoustic transducer may be disposed at a closed end of the first acoustic impedance branch. The sizes of the first electroacoustic transducer and the second electroacoustic transducer may be different.

[0006] The earphone assembly may further include a second acoustic impedance branch extending from the inner surface into the earphone body. The first electroacoustic transducer may be disposed inside the earphone body along the length of the second acoustic impedance branch. The first electroacoustic transducer may be disposed at a closed end of the second acoustic impedance branch.

[0007] The first electro-acoustic transducer and the second electro-acoustic transducer may generate acoustic signals having different frequency contents.

[0008] According to another aspect, an acoustic noise reduction headset includes an earphone assembly, a first electroacoustic transducer, a second electroacoustic transducer, at least one of a feedforward microphone and a feedback microphone, and a circuit. The earphone assembly has an earphone body having an inner surface and an outer surface, an acoustic opening, and a cavity defined by the inner surface and the acoustic opening. The earphone assembly also includes a first acoustic impedance branch extending from an open end at the inner surface to a closed end inside the earphone body. The first acoustic impedance branch includes a branch volume, and when the earphone is at least partially inserted into the ear canal of the user, the branch volume reduces the amplitude of the resonance of the occluded ear canal defined by the cavity and the ear canal of the earphone assembly at a first resonant frequency. The first electroacoustic transducer is disposed inside the earphone assembly and is configured to generate a first acoustic signal in response to a first electrical signal, and the second electroacoustic transducer is disposed inside the earphone body along the length of the acoustic impedance branch and is configured to generate a second acoustic signal in response to a second electrical signal. The feedforward microphone is disposed on the outer surface of the earphone body and is configured to generate a feedforward electrical signal in response to an external acoustic signal. The feedback microphone is disposed in the cavity and is configured to generate a feedback electrical signal in response to a cavity acoustic signal (i.e., an acoustic signal propagating in the cavity). The circuit is electrically connected to the first electroacoustic transducer and the second electroacoustic transducer and is electrically connected to at least one of the feedforward microphone and the feedback microphone. The circuit generates a first electrical signal and a second electrical signal respectively received by the first electroacoustic transducer and the second electroacoustic transducer in response to at least one of the feedback electrical signal and the feedforward electrical signal.

[0009] Various examples may include one or more of the following features:

[0010] The first acoustic impedance branch may include an acoustic waveguide. The length of the waveguide may be equal to one quarter of the acoustic wavelength of the first resonant frequency.

[0011] The first electro-acoustic transducer and the second electro-acoustic transducer may generate acoustic signals having different frequency contents.

[0012] According to another aspect, an earphone includes an earphone assembly, a first electroacoustic transducer, and a second electroacoustic transducer. The earphone assembly has an earphone body having an inner surface, an acoustic opening, and a cavity defined by the inner surface and the acoustic opening. The earphone assembly also includes a waveguide extending from an open end at the inner surface to a closed end inside the earphone body. When the earphone is at least partially inserted into the ear canal, the waveguide reduces the amplitude of the resonance of the occluded ear canal defined by the cavity of the earphone assembly and the ear canal of the user at a first resonant frequency. The first electroacoustic transducer is disposed in the earphone assembly and is configured to generate a first acoustic signal in response to a first electrical signal. The second electroacoustic transducer is disposed in the earphone body along the length of the waveguide and is configured to generate a second acoustic signal in response to a second electrical signal.

[0013] Various examples may include one or more of the following features:

[0014] The length of the waveguide may be equal to one quarter of the acoustic wavelength of the first resonant frequency.

[0015] The first electroacoustic transducer may be disposed at an inner surface of the earphone body. The second electroacoustic transducer may be disposed at a closed end of the waveguide. The first electroacoustic transducer and the second electroacoustic transducer may generate acoustic signals having different frequency contents. The sizes of the first electroacoustic transducer and the second electroacoustic transducer may be different. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other advantages of the examples of the present inventive concept may be better understood by referring to the following description in conjunction with the accompanying drawings, wherein like numerals in the various drawings designate like structural elements and features. The drawings are not necessarily drawn to scale, emphasis instead being placed on illustrating the features and principles of specific implementations.

[0017] Figure 1 is an illustration of a typical in-ear audio device that is inserted into the ear canal to create an occluded ear canal.

[0018] Figure 2 is a graphical representation of an example of passive attenuation and total attenuation of acoustic noise cancelling headphones as a function of audio frequency.

[0019] Figure 3 is a diagram of an example of a headphone having an acoustic circuit including an acoustic impedance branch.

[0020] Figure 4 is a diagram of another example of a headphone having an acoustic circuit including an acoustic impedance branch.

[0021] Figure 5 is an illustration of an example of an earphone having a foam diverter acoustically coupled to a front chamber of the earphone.

[0022] Figure 6 is a graphical representation of an example of the acoustic power received at the eardrum as a function of audio frequency for an open ear canal and an ear canal occluded by an earphone providing only passive attenuation.

[0023] Figure 7 For open ears, ear canals blocked by headphones with only passive attenuation, and Figure 3 Graphical representation of an example of normalized acoustic power at the eardrum versus acoustic frequency for an ear canal occluded by an earphone for four different branching volumes constructed.

[0024] Figure 8 It is for open ears, ear canals occluded by nominal passive attenuating headphones, and ear canals blocked by nominal passive attenuating headphones. Figure 3 , Figure 4 and Figure 5One of the structures has a 0.05 cm 3 Graphical representation of an example of normalized acoustic power at the eardrum varying with audio frequency for an earphone occluded ear canal of a branch volume.

[0025] Fig. 9 is a graphical representation of the normalized electroacoustic transducer response to a feedback microphone, showing how the response improves as the branch volume of the acoustic impedance branch is increased.

[0026] Fig.10 is a cross-sectional side view of an earphone assembly having two electroacoustic transducers and two acoustic waveguides.

[0027] Fig.11 yes Fig.10 A cross-sectional view of an earphone assembly is shown, and illustrating the position of two waveguides relative to one of the electro-acoustic transducers.

[0028] Fig.12 is a graphical representation of the amplitude of the acoustic signal from an electro-acoustic transducer as a function of the acoustic frequency for different positions of the electro-acoustic transducer along the length of the acoustic waveguide. DETAILED DESCRIPTION

[0029] like Figure 1As shown, a typical in-ear audio device such as earphone 10 includes an electroacoustic transducer 12 (e.g., a speaker) in an earphone assembly. The earphone assembly includes a body, which includes a rigid body 14A and a compliant earphone end (eartip) 14B attached to the tube mouth portion of the rigid body 14A. As used herein, the tube mouth portion means the end portion of the rigid body 14A that is inserted farthest into the ear canal 20. The rigid body 14A can be formed as a hard plastic material. For example, the material can be a thermoplastic polymer, such as acrylonitrile butadiene styrene ("ABS"). The earphone assembly has an inner surface and an acoustic opening 17. The inner surface includes an inner surface 15A of the rigid body 14A and an inner surface 15B of the earphone end 14B, and the acoustic opening 17 is at the open end of the earphone end 14B. The earphone end 14B is formed by a material such as silicone that is comfortably conformable to the entrance of the user's ear canal 20. The earphone end 14B can be constructed to be removed from the rigid body 14A and reattached to the rigid body 14A. The electroacoustic transducer 12 is arranged inside the rigid body 14A so that the acoustic front cavity 16 is defined on the front side of the electroacoustic transducer 12, and the acoustic rear cavity 18 is defined on the rear side of the electroacoustic transducer 12. As shown, the acoustic rear cavity 18 can be sealed, or it can be shunted (i.e., "tapped") by one or more acoustic impedance paths leading to the external acoustic environment, to the front cavity 16, or to both the external acoustic environment and the front cavity 16. Although not shown, the earphone 10 may include one or more microphones located in the front cavity 16 and / or one or more microphones arranged on the outer surface of the rigid body 14A. In some specific implementations, the microphone may be a feedback microphone and / or a feedforward microphone. In other specific implementations, one or more microphones inside the earphone 10 can be used to enhance the voice picked up from the user, and one or more external microphones can be used for hearing aid or environment pass-through. As a non-limiting example, the earphone 10 can be used for different types of devices, such as devices that provide music playback, communication, hearing aid and / or augmented reality.

[0030] As shown, the electro-acoustic transducer 12 is provided at an acute angle relative to the length of the front cavity 16 extending from the area adjacent to the electro-acoustic transducer 12 to the acoustic opening. In other examples, the electro-acoustic transducer 12 is located at the end of the rigid body 14A so that the acoustic energy from the electro-acoustic transducer is directed substantially along the length of the front cavity 16.

[0031] The front cavity 16 is an open cavity while the earphone 10 is not worn; however, when the earphone 10 is inserted into the entrance of the ear canal 20, the front cavity 16 and the ear canal 20 are coupled together to form a sound cavity called an occluded ear canal. The occluded ear canal behaves essentially like an acoustic waveguide. The eardrum 22 is located at one end of the occluded ear canal, and the electroacoustic transducer 12 and the front cavity 16 are located at the other end of the occluded ear canal. This figure omits most of the length of the ear canal to accommodate the scale and clarity of the features shown. By way of example, the length of a user's ear canal is typically in the range of about 2 cm to about 3 cm.

[0032] It is known that a rigidly terminated acoustic waveguide has a first resonance at a certain frequency, where the length of the waveguide is equal to half the wavelength of the propagating sound wave. This first resonant frequency depends on several factors, including but not limited to the length of the ear canal, the earphone insertion depth, and the volume of the front cavity 16. For a typical earphone, the first resonant frequency is within a frequency range extending from about 4 kHz to about 8 kHz.

[0033] The first resonance of the occluded ear canal causes undesirable effects for a number of reasons. First, for both passive noise isolating earphones and active noise reducing (ANR) earphones, the resonance amplifies the transmission of external noise into the ear canal and, therefore, reduces the amount of passive noise attenuation around the first resonant frequency. The reduced attenuation is particularly evident in ANR earphones because the active components of the noise reduction typically include feedback systems and feedforward systems, both of which contribute to noise reduction primarily at frequencies below the first resonant frequency. Thus, the overall noise reduction is greatest at frequencies below the first resonant frequency, small near the resonant frequency, and modest at frequencies greater than the resonant frequency. It should be recognized that there are higher-order resonances defined by the occluded ear canal; however, these resonances occur at higher frequencies to which hearing is less sensitive, and these resonances interact with other dynamic features so that their effects are not as consistently prominent as the first resonance.

[0034] Figure 2 An example of noise attenuation achieved by an ANR headset that varies with audio frequency is shown. A typical ANR headset system includes one or more feed-forward microphones disposed on the outer surface of the headset, one or more feedback microphones disposed in the front chamber of the headset, and a circuit electrically connected to the microphone. The circuit generates an electrical signal based on, for example, an audio playback signal to drive an electroacoustic transducer. The electrical signal is also responsive to the feedback electrical signal and the feed-forward electrical signal generated by the microphone for noise reduction.

[0035] The graph shows attenuation as a function of audio frequency. The total attenuation 38 represents the sum of active (ie, feedback and / or feedforward) attenuation and passive attenuation 36. The negative effect of ear canal resonance on the passive attenuation 36, and therefore on the total attenuation 38, is manifested as a "notch" 40 at approximately 7 kHz.

[0036] It should be noted that a second undesirable effect of occluding ear canal resonance is the amplification of the electroacoustic transducer response at or around the resonant frequency, which is often problematic for audio playback.

[0037] The example of the earphone described below includes an impedance branch in acoustic communication with the front cavity of the earphone to effectively modify the boundary conditions of the waveguide defined by the occluded ear canal. The acoustic impedance branch reduces the undesirable effects from the first resonant frequency. As a result, the quality factor (Q) of the occluded ear canal is reduced and a substantially flatter spectral audio response is achieved.

[0038] Figure 3 An example of an earphone 50 is shown, in which an acoustic circuit defined in part by an acoustic impedance branch functions in a manner similar to an electronic series resistor and capacitor (RC) circuit. Specifically, the acoustic impedance branch includes an acoustic impedance element 52. The acoustic impedance branch also includes a "branch volume" cavity 54 that acts as a capacitor or compliance in the acoustic circuit. Examples of the acoustic impedance element 52 include soundproofing screens, screens, acoustic fabrics, and other substantially planar acoustic impedance elements. In one example, the acoustic impedance element 52 is a Saati Acoustex woven mesh available from Saati Americas Corporation of Fountain Inn, SC, in Fountain, South Carolina. In an alternative example, the acoustic mesh is available from Sefar AG, Heiden, Switzerland. The acoustic impedance element 52 is located at the impedance hole, where the front cavity 16 is connected to the branch volume 54.

[0039] The acoustic RC circuit has a corner frequency f c , at this corner frequency, the impedance of the acoustic resistance and acoustic capacitance are equal. c When set to approximately equal the first resonant frequency of the occluded ear canal, the acoustic resistance and acoustic capacitance are in balance to allow acoustic energy to enter the acoustic impedance branch and dissipate the acoustic energy. c is set to be approximately equal to (i.e., substantially equal to) the first resonant frequency, but the acoustic RC circuit may be detuned by a small frequency offset so that the two frequencies are not exactly equal. For example, the corner frequency f c is tuned to a value within 20% of the first resonant frequency (ie, at a frequency between 1.8 and 2.2 times the first resonant frequency). c Detuned to be slightly less than the first resonant frequency, the effective first resonance of the occluded ear canal can be shifted to a frequency closer to the second resonance of the open ear. It will be appreciated in conjunction with the alternative examples described below that similar detuning about the first resonance produces similar beneficial effects.

[0040] Due to the acoustic RC circuit, the Q of the first resonance is reduced. The size of the branch volume 54 relative to the volume of the occluded ear canal essentially determines how much the Q is reduced. By way of example, the branch volume 54 may be less than 0.02 cm 3 Up to 0.2cm 3 The volume of the occluded ear canal depends on the volume of the "open" ear canal (usually between about 1.0 cm 3 and 1.4cm 3 ), the insertion depth of the earphone and the volume of the front cavity.

[0041] In one non-limiting numerical example, the branch volume 54 is 0.05 cm 3 , the impedance hole has a radius of 1.2 mm, and the acoustic resistance element 52 is a sound insulation screen with an acoustic resistance of 260 Rayls.

[0042] Figure 4 An example of an earphone 60 is shown in which the acoustic circuit defined by the acoustic impedance branch functions in a manner similar to a resistor, inductor, and capacitor (RLC) circuit. The acoustic impedance branch includes a branch volume 62, an acoustic channel 64 (e.g., a thin tube) extending from the branch volume 62 to the front cavity 16, and an acoustic resistance element 66. The acoustic channel 64 acts as an inductor or mass, and the branch volume 62 acts as a capacitor or compliance. This type of circuit is often referred to as a Helmholtz resonator and has a resonant frequency f hr .

[0043] The acoustic resistance element 66 may be located at an impedance hole defined at a boundary between the front cavity 16 and the acoustic port, as shown, or may be located at a boundary between the acoustic passage 64 and the branch volume 62. Alternatively or in addition, the acoustic resistance element may be a volume acoustic resistance element disposed in at least a portion of the acoustic passage 64. For example, an acoustic resistance foam may be provided that partially or completely occupies the acoustic passage 64. By way of specific example, the acoustic resistance foam may be melamine foam.

[0044] When the acoustic Helmholtz resonator frequency f is appropriately tuned relative to the first resonance frequency of the occluded ear canal hr When the first resonance frequency is within 20% of the first resonant frequency, a significant reduction in the first resonance occurs. Similar systems are commonly used to manage mechanical vibrations and are referred to as tuned mass dampers or damped absorbers, where such systems are tuned to damp vibrations, as is known in the mechanical arts. It should be recognized that the structure of the ear canal may vary for different users. Therefore, an earphone assembly that may be optimally configured for one user may be detuned for another user, such that the first resonance is less damped.

[0045] In one non-limiting numerical example, the branch volume 62 is 0.052 cm 3, the impedance hole has a radius of 1.0 mm, the acoustic channel 64 has a length of 2.5 mm, and the acoustic resistance element 66 is a sound insulation screen with an acoustic resistance of 140 Rayls.

[0046] In an alternative example of a Helmholtz resonator configuration, a waveguide may be used instead of the acoustic channel and branch volume. For example, the waveguide may be formed as a channel in the rigid body 14A of the earphone assembly. The waveguide may have a constant cross-sectional area. Alternatively, the waveguide may have a cross-sectional area that varies along its length, such as a tapered or exponential waveguide. In order to reduce the first resonance of the occluded ear canal, the length of the waveguide may be tuned to have a first resonant frequency approximately equal to the first resonant frequency of the occluded ear canal. For example, the length of the constant area waveguide may be approximately one-quarter of the wavelength of the expected first resonant frequency.

[0047] Figure 5 An example of an earphone 70 is shown in which a foam diverter 72 is acoustically coupled to the front cavity 16 at an impedance hole 74, while the remainder of the foam diverter 72 is surrounded by the rigid body 14A. The foam diverter 72 acts as a fluid with a sound density and a sound velocity that are typically complex valued parameters, with an imaginary component associated with the acoustic impedance. A suitable foam has an acoustic impedance sufficient to allow acoustic energy to couple into the acoustic impedance branch and dissipate the coupled acoustic energy. Melamine foam is an example of a foam that can be used to form the foam diverter 72.

[0048] In a variation of the illustrated example, the foam diverter 72 may have a geometric form such that the foam diverter 72 acts as a waveguide having a first resonance that is tuned to be approximately equal to the first resonance frequency of the occluded ear canal. The waveguide may have a constant or varying cross-sectional area along its length. In this configuration, the foam diverter 72 acts as a tuned mass damper that significantly reduces the Q of the first resonance.

[0049] The headphone example above shows how the Q of the first resonance can be reduced. Thus, the undesirable effect of the first resonance of the occluded ear canal on the passive noise attenuation can be reduced. Figure 6 An example of passive attenuation as a function of acoustic frequency is shown in FIG. 1 , where one response 80 corresponds to the acoustic power received at the eardrum as a function of acoustic frequency for an open ear canal, and the other response 82 corresponds to the acoustic power received at the eardrum as a function of acoustic frequency when a nominal earphone providing only passive attenuation is inserted into the entrance of the ear canal. The amount of passive attenuation is defined as the difference between the two responses 80 and 82. The passive attenuation corresponds to a diffuse noise field, and the responses are normalized to the acoustic power received at the eardrum for an open ear canal at zero frequency. The first resonant frequency is evident in the inserted earphone response 82 at a frequency of approximately 7 kHz.

[0050] Figure 7 The above diagram shows the Figure 6Normalized acoustic power at the eardrum as a function of audio frequency for the open ear and nominal passive attenuating earphones (responses 80 and 82, respectively). Figure 7 Also shown are the variations of the acoustic power at the eardrum with the audio frequency for four different earphones, wherein each earphone is constructed with an acoustic impedance branch having the acoustic impedance branch described above for Figure 3 The four earphones have a 0.025cm 3 、0.05cm 3 、0.10cm 3 and 0.20cm 3 It can be seen that as the value of the branch volume increases, the first resonance decreases monotonically in both amplitude and frequency, with response 84 corresponding to 0.20 cm 3 The upper limit of the branching volume is usually attributed to the available space within the headphone body.

[0051] Figure 8 The above diagram shows the Figure 6 Normalized acoustic power at the eardrum as a function of audio frequency for the open ear and nominal passive attenuating earphones (responses 80 and 82, respectively). Figure 8 It also shows the Figure 3 The soundproofing screen and branch volume configuration, Figure 4 The Helmholtz resonator configuration and Figure 5 The acoustic power at the eardrum varies with frequency for earphones constructed with foam resonator configurations (responses 86, 88, and 90, respectively). All branch volumes are 0.05 cm 3 .

[0052] One significant advantage of the various examples of headphones described above relates to the ability to control the amplification of the electroacoustic transducer response in the feedback system, and in particular, to flatten it. More specifically, the feedback controller can include a frequency response characteristic that eliminates the amplification effect of ear canal resonance on the electroacoustic transducer to feedback microphone response. Reducing the amplitude of the resonance with the acoustic impedance branch allows a more robust feedback system to accommodate the effects of occluding ear canal resonance.

[0053] Fig. 9 is an example of how the response of an electroacoustic transducer to a feedback microphone improves as the branch volume increases. Response 92 corresponds to a nominal passive-only attenuation headphone, and responses 94, 96, 98, and 100 correspond to 0.025 cm, respectively. 3 、0.05cm 3 、0.10cm 3 and 0.20cm 3 The branch volume.

[0054] As mentioned above, in some headphones, the acoustic back cavity 18 (see Figure 3 ) can be shunted (transported) through the impedance path leading to the acoustic front cavity 16. In addition, the front cavity 16 can be shunted to the external acoustic environment. Such ports can be used for low-frequency pressure equalization and are referred to as PEQ ports. For example, the PEQ port can be implemented as a narrow tube. Alternatively, one or more PEQ ports can be shunted between the acoustic impedance branch and the back cavity 18 and / or between the acoustic impedance branch and the external acoustic environment. These alternative configurations are possible because the acoustic impedance branch is acoustically connected to the front cavity 16 and can be configured to effectively lead to the front cavity 16 at frequencies below several kHz. Therefore, the low-frequency sound energy from the PEQ port reaches the front cavity 16 through the acoustic impedance branch, and vice versa. In addition, the PEQ port can be configured to be effectively closed at frequencies higher than several hundred Hz. Therefore, the PEQ port has no substantial effect on the effect of the acoustic impedance branch on the first resonance of the occluded ear canal.

[0055] Although the various examples described above include acoustic impedance branches located within the rigid body of the earphone assembly, in alternative examples, the acoustic impedance branches are partially or completely located in the earphone end. For example, a portion of the branch cavity or the entire branch cavity can be formed in the earphone end.

[0056] In the various examples described above, a single electroacoustic transducer 12 for providing an acoustic signal is disposed within the earphone assembly. In the following examples, one or more additional electroacoustic transducers may be included in the earphone assembly. In these examples, the additional electroacoustic transducers are disposed in an acoustic impedance branch in the form of a waveguide. For example, Fig.10 An earphone is shown, which includes a first electroacoustic transducer (speaker) 112 and a second electroacoustic transducer 114 within a rigid body 116A, which is attached to a compliant earphone end 116B. The first electroacoustic transducer 112 separates a rear cavity 115 and a front cavity 116, and is configured to generate a first acoustic signal in response to a first electrical signal. Although shown as a long and thin cavity extending away from the nozzle end of the earphone, the rear cavity 115 can have a significantly different shape due to the shape and size constraints of the rigid body 116A. The second electroacoustic transducer 114 is configured to generate a second acoustic signal in response to the second electrical signal. The first acoustic signal and the second acoustic signal can be different, so that the first electroacoustic transducer 112 and the second electroacoustic transducer 114 generate acoustic signals with different amplitudes and frequency contents. The earphone has an acoustic opening 117 at the open end of the earphone end 116B, which, in combination with the inner surfaces 118A and 118B of the rigid body 116A and the earphone end 116B, respectively defines a front cavity 116 of the earphone. Optionally, the earphone may include one or more internal and / or external microphones, such as a feedback microphone and / or a feedforward microphone. When the earphone is at least partially inserted into the entrance of the ear canal 20, the acoustic cavity is defined by the obstruction of the ear canal. The acoustic cavity includes the earphone front cavity 116 and the portion of the ear canal not occupied by the earphone.

[0057] Two acoustic impedance branches in the form of acoustic waveguides 120A and 120B are formed in the rigid body 116A. Each waveguide has a substantially constant cross-sectional area and a length of about one quarter of the wavelength of the expected first resonant frequency. In some implementations, the length of the waveguide is in the range of about 10 mm to about 15 mm, and the total cross-sectional area of ​​each waveguide is about 2.0 mm. 2 To about 5.0mm 2 116A. Each waveguide extends from an aperture at inner surface 118A to a closed end within rigid body 116A. As shown, one of waveguides 120A is shunted to the external environment via port 122. Optionally, another waveguide 120B may alternatively shunted to the external environment, or both waveguides 120A and 120B may shunted.

[0058] The first electroacoustic transducer 112 is close to or arranged at the nozzle end of the rigid body 116A near the acoustic opening 117, so that the acoustic energy generated by the first electroacoustic transducer 112 is directly coupled into the ear and propagates downward substantially along the length of the ear canal 20. The second electroacoustic transducer 114 is arranged inside the rigid body 116A along the length of another waveguide 120B, and includes an acoustic hole, through which the acoustic energy generated by the second electroacoustic transducer 114 is introduced into the waveguide 120B, which is coupled to the acoustic cavity of the occluded ear canal at one end. As shown in the figure, the acoustic hole is located at about one quarter of the length of the waveguide away from the closed end of the waveguide 120B. In other examples, the second electroacoustic transducer 114 and the acoustic hole are located at different positions along the length of the waveguide 120B.

[0059] Fig.11 Observed from the end of the pipe Fig.10 1 and 12 are cross-sectional views of an earphone of the type shown in FIG. 1 , and two waveguides relative to the first electroacoustic transducer 112 are shown. The cross-sectional shape of each waveguide is a crescent shape, i.e., an area formed by the intersection of two non-concentric arcs. The crescent shape effectively resolves the space constraint at the nozzle end of the rigid body 116A where the first electroacoustic transducer 112 also exists. Other cross-sectional shapes with similar or different areas may be used within the available space of the rigid body 116A.

[0060] Preferably, each electro-acoustic transducer 112 and 114 provides an acoustic signal with a different frequency content. For example, the first electro-acoustic transducer 112 may provide basic bass coverage, and the second electro-acoustic transducer 114 may provide higher frequency content. The electro-acoustic transducers 112 and 114 may have different sizes. As a non-limiting numerical example, one or both of the electro-acoustic transducers 112 and 114 may be a balanced armature electro-acoustic transducer, and the size may range from less than 5mm×2.7mm×1mm device to more than 9.5mm×7mm×4mm device. Alternatively, one or both of the electro-acoustic transducers 112 and 114 may be a dynamic (moving coil) electro-acoustic transducer, and the size may range from less than 4mm diameter and 4mm length device to a substantially cylindrical device greater than 9mm diameter and 5mm length device. In yet another example, one or both of the electro-acoustic transducers 112 and 114 may be a piezoelectric transducer.

[0061] In other examples, the waveguide may have a different shape, such as a circular or rectangular cross-section. In addition, the number of waveguides may be different. For example, a single waveguide may be used (e.g., waveguide 120A may not be present). Alternatively, three or more waveguides may be included in the earphone.

[0062] The number of electroacoustic transducers can vary. Fig.10 In contrast, each waveguide may have an electro-acoustic transducer disposed along its length. More specifically, a third electro-acoustic transducer may be coupled to waveguide 120A, or the first electro-acoustic transducer may be relocated to a position along the length of waveguide 120A. In other examples, the number of waveguides may be different, and the number of electro-acoustic transducers coupled to the waveguides may be different.

[0063] The performance of an electroacoustic transducer coupled into a waveguide depends on the location of the electroacoustic transducer along the length of the waveguide. Fig.12 The diagram shows the electroacoustic transducer hole along the length of 12 mm and about 1.25 mm. 2 The amplitude of the response of the electroacoustic transducer of the balanced armature transducer to the feedback microphone varies with the sound frequency for different positions of the length of the waveguide with a constant cross-sectional area of ​​a circular cross-sectional area. The position of the electroacoustic transducer associated with each graph corresponds to the acoustic hole (e.g., Fig.10 The distance from the acoustic hole in the waveguide to the closed end.

[0064] Response 130 corresponds to an electroacoustic transducer located at the closed end of the waveguide, responses 132, 134, and 136 correspond to electroacoustic transducers located at 3 mm, 6 mm, and 9 mm from the closed end, respectively, and response 138 corresponds to an electroacoustic transducer located at the open end of the waveguide (similar to Fig.10 The position of the first electroacoustic transducer 112 in FIG.

[0065] For acoustic frequencies less than about 3kHz, the response amplitude is nearly identical. At higher frequencies, the peaks and notches in the amplitude response vary depending on the location of the electroacoustic transducer along the waveguide.

[0066] The available space for electro-acoustic transducers within an earbud or other type of earphone is often limited, particularly in the area closest to the earphone nozzle. As described above, if the earphone includes one or more acoustic impedance branches to modify the ear canal first resonant frequency, the electro-acoustic transducer can be coupled to the acoustic impedance branch at a location away from the nozzle where more space is available. The additional space allows for the use of larger sized electro-acoustic transducers and, in some implementations, allows for an increased number of electro-acoustic transducers. Thus, a waveguide or other form of acoustic impedance branching used to achieve the desired modification of the resonance of an occluded ear canal can also have the added independent advantage of being used to couple acoustic signals from one or more additional electro-acoustic transducers to the ear canal.

[0067] A number of specific implementations have been described. However, it should be understood that the above description is intended to illustrate, rather than limit, the scope of the inventive concept, which is defined by the scope of the claims. Other examples are within the scope of the following claims.

Claims

1. A headset, characterized in that: The earphone comprises: an earphone assembly having an earphone body having an inner surface, an acoustic opening, and a cavity defined by the inner surface and the acoustic opening, the earphone assembly further comprising a first acoustic impedance branch extending from an open end at the inner surface to a closed end inside the earphone body, wherein the first acoustic impedance branch comprises a branch volume that reduces the amplitude of resonance of an occluded ear canal defined by the cavity and the ear canal of the earphone assembly at a first resonant frequency when the earphone is at least partially inserted into an ear canal of a user; a first electro-acoustic transducer disposed inside the earphone assembly and configured to generate a first acoustic signal in response to a first electrical signal; and a second electroacoustic transducer disposed inside the earphone body along a length of the first acoustic impedance branch and configured to generate a second acoustic signal in response to a second electrical signal; The first acoustic impedance branch comprises an acoustic waveguide having a length equal to one quarter of the acoustic wavelength of the first resonant frequency.

2. The earphone according to claim 1, characterized in that The first electroacoustic transducer is disposed at the inner surface of the earphone body.

3. The earphone according to claim 1, characterized in that The second electroacoustic transducer is disposed at the closed end of the first acoustic impedance branch.

4. The earphone according to claim 1, characterized in that The earphone assembly also includes a second acoustic impedance branch extending from the inner surface into the earphone body.

5. The earphone according to claim 4, characterized in that: The first electroacoustic transducer is disposed inside the earphone body along the length of the second acoustic impedance branch.

6. The earphone according to claim 5, characterized in that The first electroacoustic transducer is disposed at the closed end of the second acoustic impedance branch.

7. The earphone according to claim 1, characterized in that The first electro-acoustic transducer and the second electro-acoustic transducer generate acoustic signals having different frequency contents.

8. The earphone according to claim 1, characterized in that The first electro-acoustic transducer and the second electro-acoustic transducer have different sizes.

9. An acoustic noise reduction headset, characterized in that: The acoustic noise reduction headset comprises: an earphone assembly having an earphone body having an inner surface and an outer surface, an acoustic opening, and a cavity defined by the inner surface and the acoustic opening, the earphone assembly further comprising a first acoustic impedance branch extending from an open end at the inner surface to a closed end inside the earphone body, wherein the first acoustic impedance branch includes a branch volume that reduces the amplitude of a resonance of an occluded ear canal defined by the cavity and the ear canal of the earphone assembly at a first resonant frequency when the earphone is at least partially inserted into an ear canal of a user; a first electroacoustic transducer disposed within the earphone assembly and configured to generate a first acoustic signal in response to a first electrical signal; a second electroacoustic transducer disposed inside the earphone body along a length of the acoustic impedance branch and configured to generate a second acoustic signal in response to a second electrical signal; at least one of a feedforward microphone disposed on the outer surface of the earphone body and configured to generate a feedforward electrical signal in response to an external acoustic signal and a feedback microphone disposed in the cavity and configured to generate a feedback electrical signal in response to a cavity acoustic signal; and a circuit electrically communicating with the first and second electroacoustic transducers and the at least one of the feedforward and feedback microphones, the circuit generating the first and second electrical signals respectively received by the first and second electroacoustic transducers in response to the at least one of the feedback and feedforward electrical signals; The first acoustic impedance branch comprises an acoustic waveguide having a length equal to one quarter of the acoustic wavelength of the first resonant frequency.

10. The earphone according to claim 9, characterized in that The first electro-acoustic transducer and the second electro-acoustic transducer generate acoustic signals having different frequency contents.

11. A headset, characterized in that: The earphone comprises: an earphone assembly having an earphone body having an inner surface, an acoustic opening, and a cavity defined by the inner surface and the acoustic opening, the earphone assembly further comprising a waveguide extending from an open end at the inner surface to a closed end inside the earphone body, wherein when the earphone is at least partially inserted into an ear canal of a user, the waveguide reduces the amplitude of a resonance of an occluded ear canal defined by the cavity and the ear canal of the earphone assembly at a first resonant frequency; a first electro-acoustic transducer disposed in the earphone assembly and configured to generate a first acoustic signal in response to a first electrical signal; and a second electro-acoustic transducer disposed in the earphone body along a length of the waveguide and configured to generate a second acoustic signal in response to a second electrical signal; wherein the waveguide has a length equal to one quarter of the acoustic wavelength of the first resonant frequency.

12. The earphone according to claim 11, characterized in that The first electroacoustic transducer is disposed at the inner surface of the earphone body.

13. The earphone according to claim 11, characterized in that The second electroacoustic transducer is disposed at the closed end of the waveguide.

14. The earphone according to claim 11, characterized in that The first electro-acoustic transducer and the second electro-acoustic transducer generate acoustic signals having different frequency contents.

15. The earphone according to claim 11, characterized in that The first electro-acoustic transducer and the second electro-acoustic transducer have different sizes.

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