Automatically calibrating an in-ear headphone

Abstract

A method for calibrating an in-ear earpiece to improve a frequency response heard by a user is provided. The method includes generating a sound signal and playing the sound signal at a driver while the in-ear earpiece is placed within an ear canal of a user, receiving a reflected sound signal at a first microphone, generating a frequency response based on the reflected sound signal, generating a user eardrum response based on the frequency response, generating a second sound signal, modifying the second sound signal based on the user eardrum response, and playing the modified second sound signal at the driver.

Description

Technical Field

[0001] This document generally covers automatic calibration methods and corresponding equipment for in-ear headphones. Calibration is used to improve the frequency response heard by the user. Background Technology

[0002] With increasing technological advancements in the audio industry, it has become possible to reproduce high-quality sound from smaller and more complex drivers within headphones. However, due to individual characteristics of users' ears—such as the specific size and shape of the ear canal and how much sound is absorbed within it—users will receive different frequency responses at their eardrums. To achieve optimized and similar frequency responses for all users, headphones should be calibrated (i.e., individually equalized). The headphone transfer function (HpTF) describes how sound is filtered by the ear along its path from the sound source to the eardrum. By using an appropriate individual HpTF, the HpTF can be used as a filter at the eardrum to equalize the headphones. Therefore, after HpTF filtering and playback through the headphones in question, the audio signal can be reproduced more accurately at the eardrum. Measuring HpTF with conventional headphones is very difficult, and the task requires expensive / expert-grade professional equipment.

[0003] Previous attempts to measure HpTF involved generating a sound scan in the user's ear using a transducer within a specially molded earpiece and recording ear properties using a microphone placed inside the earpiece. However, these attempts did not include accurate models to predict ear canal properties and the interaction between the individual user's ear and the molded earpiece. Furthermore, previous attempts to equalize headphones using filters only aimed to produce a flat frequency response (i.e., a flat spectrum) at the eardrum. However, this did not take into account the individual user's head-related transfer function (HrTF). Therefore, the user may still experience a frequency response different from the one generated by the headphones.

[0004] Furthermore, in-ear headphones are known to provide high-quality sound to users by creating a sealed environment between the eardrum and the outside world, thus blocking out most ambient or background noise. To provide further immersive sealing to the outside world, some in-ear headphones include active noise cancellation (ANC) control systems. However, blocking out ambient noise can be problematic when it is necessary for safety or other reasons (such as at a construction site or when a user is crossing a road). Users can pause the music and turn off the ANC control system, providing reduced noise cancellation. However, this still attenuates ambient noise due to the sealed environment of the in-ear headphones. Users will then have to remove the in-ear headphones to hear the ambient background noise.

[0005] While it's possible to use an ANC control system to record ambient noise and play it back to the user, previous attempts haven't taken into account the individual characteristics of the user's ears. Therefore, the user doesn't perceive ambient sounds as accurately as if they weren't wearing headphones.

[0006] Therefore, there is a need in the industry for an improved method to equalize headphones (e.g., noise-cancelling in-ear headphones) based on the individual characteristics of the user's ear (auricle and ear canal), so that the user hears the expected sound (frequency response) and integrates ambient listening patterns into the headphones so that the user can hear ambient background noise as if he / she were not wearing headphones without removing the headphones.

[0007] Therefore, the aim is to measure the anatomy of the user's ear and modify the sound generated at the headphones accordingly, so that the user experiences the expected sound reproduction. Furthermore, the aim is to provide a noise-canceling in-ear headphone that can reproduce and similarly modify ambient and background noise to the user at the headphones, so that the user experiences ambient and background noise as if he / she were not wearing headphones without removing the headphones. Summary of the Invention

[0008] To overcome the problems detailed above, the inventors have designed a novel and inventive automatic calibration device and technology.

[0009] More specifically, technical solution 1 provides a method for calibrating in-ear headphones according to one embodiment. When the in-ear headphones are placed in a user's ear canal, an integrated circuit within the in-ear headphones can generate an audio signal (e.g., logarithmic scan) and play the audio signal at a driver. The audio signal passes through the user's ear canal, reflects off the eardrum, and returns to the in-ear headphones, where the reflected audio signal is received and recorded by a first microphone of the in-ear headphones. The integrated circuit can generate a frequency response based on the reflected audio signal, and further generate a user's eardrum response based on the frequency response (e.g., by determining the length of the user's ear canal and estimating the attenuation coefficient of the user's ear canal using a secondary transmission line and an eardrum pressure transfer function). The integrated circuit of the in-ear headphones can further generate a second audio signal based on an audio input (e.g., a laptop computer, smartphone, or the like), and modify the second audio signal based on the user's eardrum response. Furthermore, the driver of the in-ear headphones can play back the modified second audio signal to the user. Advantageously, the modified sound (e.g., music or audio) can be generated by the in-ear headphones such that frequencies attenuated in the user's ear canal are compensated. Therefore, the user hears the expected sound (frequency response).

[0010] In one implementation, a third sound signal may be generated by a separate (e.g., external) driver, which may be received at the entrance to the user's ear canal (e.g., via a second microphone of the in-ear headphones and / or via a separate test microphone arrangement). An integrated circuit may generate a second frequency response based on the received third sound signal, which is equivalent to the user's objective function. Furthermore, the integrated circuit may further modify the second sound signal toward the user's objective function. Advantageously, the in-ear headphones may compensate for sound (frequency response) loss due to the outer ear (auricle) within the ear canal and at the entrance to the ear canal. Furthermore, the in-ear headphones may receive and modify ambient (e.g., environmental and background) sounds to produce improved active noise cancellation. Additionally, the in-ear headphones may modify recorded ambient sounds to reproduce those sounds to the user via the in-ear headphones, thereby providing transparent hearing to the user without requiring the removal of the in-ear headphones.

[0011] Technical claim 11 describes an in-ear headphone. The in-ear headphone includes a housing having a main body portion and a nozzle portion, wherein the nozzle portion includes an aperture. The housing also includes a driver, a first microphone, a second microphone opposite the first microphone, and an integrated circuit coupled to the first microphone, the second microphone, and the driver. When the in-ear headphone is placed in a user's ear canal, the integrated circuit is operable to generate a sound signal (e.g., logarithmic scan) and play the sound signal at the driver. The sound signal passes through the user's ear canal, reflects off the eardrum, and returns to the in-ear headphone, where the reflected sound signal is received and recorded by the first microphone of the in-ear headphone. The integrated circuit can generate a frequency response based on the reflected sound signal, and further generate a user eardrum response based on the frequency response (e.g., by determining the length of the user's ear canal and estimating the attenuation coefficient of the user's ear canal using a secondary transmission line and an eardrum pressure transfer function). The integrated circuit of the in-ear headphone can further generate a second sound signal based on an audio input (e.g., a laptop computer, smartphone, or the like), and modify the second sound signal based on the user eardrum response. Furthermore, the drivers of the in-ear headphones can reproduce a modified second sound signal to the user. Advantageously, the modified sound (e.g., music or audio) can be generated by the in-ear headphones so that frequencies attenuating in the user's ear canal are compensated. Therefore, the user hears the expected sound (frequency response).

[0012] Advantageously, this embodiment can automatically and accurately measure the user's eardrum response and the user's objective function. Therefore, the in-ear headphones can modify the sound signal so that the frequency response received at the user's eardrum is as close as possible to the objective function, thereby providing the user with the sound experience expected from the sound source. Furthermore, this embodiment allows the user to hear ambient noise transparently and binaurally without removing the in-ear headphones, while equally providing effective active noise cancellation, all within a small package. Attached Figure Description

[0013] Figure 1 This is a flowchart illustrating the process of calibrating in-ear headphones;

[0014] Figure 2 An exemplary frequency response of four people recorded at the first microphone of an in-ear headphone is shown;

[0015] Figure 3 The microphone equalizer function used to compensate for the connection pipe to the first microphone is shown;

[0016] Figure 4 The frequency response recorded by the first microphone of an in-ear headphone coupled to an acoustic coupler is shown.

[0017] Figure 5 The frequency response calculated and recorded using a secondary transmission line by a first microphone in an in-ear headphone coupled to an acoustic coupler is shown.

[0018] Figure 6 The frequency response of an in-ear headphone, measured at a simulated eardrum of an acoustic coupler, is shown.

[0019] Figures 7 to 9 Exemplary tympanic membrane responses of the ear canals of three individuals are shown with and without the use of secondary transmission line calculations and microphone equalizer functions;

[0020] Figure 10 The exemplary objective function (measurement of the open tympanic membrane response (frequency response) from an external sound source) of three test subjects is shown, recorded by a test microphone array placed at the entrances of the user's left and right ear canals.

[0021] Figure 11 An exemplary objective function (measurement of closed tympanic membrane response (frequency response)) of three test subjects is shown, recorded by the second microphone of an in-ear headphone placed at the entrance of the user's left and right ear canals;

[0022] Figure 12 It shows in Figure 10 and Figure 11 The difference in objective functions (frequency response) between them;

[0023] Figure 13 It shows the method for fine adjustment Figure 12 Multiple equalizer functions for the objective function;

[0024] Figures 14 to 15 It shows the basis Figure 12 The normalized objective function of the objective function;

[0025] Figures 16 to 18 It shows the basis from Figures 10 to 12 objective function minus Figures 7 to 9 Exemplary equalizer functions for three test subjects' tympanic membrane responses;

[0026] Figure 19 The tympanic membrane response is shown when calculated using a two-stage transmission line, where the attenuation coefficient varies between 0.1 and 1 in increments of one decimal place.

[0027] Figure 20 It shows the range between 1200 Hz and 1500 Hz. Figure 19 The observation intervals have been calculated using both soft and strong smoothing techniques.

[0028] Figure 21 This is a side view of an in-ear headphone, showing two microphones, a first connecting pipe and a second connecting pipe, and a driver;

[0029] Figure 22 This is an exemplary view of an integrated circuit for an in-ear headphone;

[0030] Figure 23 This is a side view of a test microphone, which is part of a test microphone arrangement that can be coupled to an in-ear headphone, and shows a spring wire support and multiple rods;

[0031] Figure 24 This is a perspective view of the test microphone. Detailed Implementation

[0032] Automatic calibration method

[0033] The method for implementing automatic calibration in in-ear headphones will now be described in detail.

[0034] Figure 1 A simplified flowchart of a method for automatically calibrating in-ear headphones is shown. The method can be performed by, for example... Figure 21 and Figure 22The in-ear headphones shown below perform this function, and the in-ear headphones include a driver, a first microphone, and an integrated circuit. Further details of the in-ear headphones are discussed below. At step 102, when the in-ear headphones are placed in the user's ear canal, the integrated circuit of the in-ear headphones generates an audio signal to play to the user. The audio signal may be a logarithmic scan generated by the integrated circuit of the in-ear headphones and may have a duration of one second. The audio signal may be played by the driver of the in-ear headphones, wherein the driver may be any well-known speaker capable of reproducing high-quality sound to the user. Alternatively, the driver may be a dynamic (moving coil) type driver and may have a diameter of 5mm to 8mm, a balanced armature (BA) driver, or a combination of both.

[0035] The sound signal played by the driver will be reflected from the user's eardrum, and at step 104, the first microphone of the in-ear headphones receives the reflected sound signal. The reflected sound signal is transmitted from the first microphone to an integrated circuit, which at step 106 generates a frequency response based on the reflected sound signal received at the first microphone using well-known signal processing methods. If the frequency response drops at low frequencies (indicating a poor seal at the ear canal entrance (i.e., between the headphones and the user's ear), the integrated circuit may generate an error message. Figure 2 An example of the frequency response generated based on a logarithmic scan used for four test subjects is shown. Figure 2 As shown, the exemplary frequency responses of the four test subjects are different, thus proving that in-ear headphones need to be individually calibrated.

[0036] At step 108, the integrated circuit can generate the user's eardrum response based on the measured frequency response. For example, the integrated circuit can use a simple two-stage acoustic transmission line to obtain the unknown length of the user's ear canal at the first recorded minimum frequency. In the acoustic transmission line (a conduit with a constant cross-section), the output variable p can be obtained by multiplying the output vector by the transfer matrix C. out and q out Calculate the input sound pressure p in and volume velocity q in ,as follows:

[0037] [Equation 1]

[0038] (l = catheter length, A = cross-sectional area, α = attenuation coefficient, and Z) T =Input impedance).

[0039] In the described embodiment, the channel from the headphone driver to the outlet hole of the in-ear headphone and the ear canal is considered as two separate transmission lines ('channel' is also referred to herein as 'nozzle' or 'connecting conduit'). The cascading of the two transmission lines... Where C1 represents the nozzle (i.e., the transmission line / channel / connection tube between the driver and the end of the in-ear headphone), and C2 represents the ear canal, which is longer and has a larger radius. Therefore, taking into account the abrupt transition from the small diameter of the in-ear headphone nozzle to the larger diameter of the ear canal results in a more accurate measurement of the frequency response at the user's ear canal. In one embodiment, the calculation approximates the inner wall of the tympanic membrane as a hard reflective surface; thus, the output velocity q can be... out Set to zero. Under this approximation, the tympanic membrane pressure transfer function H can be calculated as follows: D =p out / p in :

[0040]

[0041] [Equation 2]

[0042] The tympanic membrane pressure can be determined based on the measured response at the first microphone using unknown parameters l1, l2, A1, A2, α1, and α2. In one embodiment, fixed values, such as 0.02, can be used for the attenuation coefficients α1 and α2. However, the attenuation coefficients can be varied to achieve more accurate results, as will be described later. The nozzle length l1 is fixed (e.g., 6 mm).

[0043] The minimum value f can be recorded based on the first frequency response function measured at the nozzle. m Derive the remaining unknown length parameters of the ear canal l2, the minimum value f. m It can vary between 900Hz and 2100Hz, such as Figure 2 As shown in the figure. This minimum value is at frequency f. m The location corresponds to the pressure transfer function H. D The zero. To obtain a usable equation, one can consider the case of no decay (e.g., by setting the coefficients α1 and α2 to 0), and can replace the sinh / cosh terms with sin / cos terms, resulting in the following equation:

[0044]

[0045] (c = speed of sound) [Equation 3]

[0046] The unknown parameter α2 can then be calculated as follows:

[0047]

[0048] [Equation 4]

[0049] Therefore, l2 can be defined as l2 = (c / 2π)α2.

[0050] In one implementation, an in-ear headphone can be provided to a user with ear tips having several different outer diameters but the same size of the first acoustic transmission line (nozzle). Thus, the user can choose an ear tip that best fits their own ear, but the size of the first acoustic transmission line (nozzle) will remain the same. The outer diameter and inner diameter values ​​can be stored in an integrated circuit of the in-ear headphone. When the method is performed, the user can input which of the multiple ear tips they have selected (e.g., via a physical switch on the in-ear headphone, a user interface on the in-ear headphone, a wired or wireless connection from the in-ear headphone to a controller (such as a smartphone), or any combination thereof), allowing the in-ear headphone to calculate the ear canal to nozzle area ratio (A2 / A1).

[0051] Figure 3 The diagram illustrates a microphone equalizer function (e.g., using two dual second-order low-order filters) that can be applied to the first microphone of an in-ear headphone (i.e., the first microphone attached to the channel / nozzle / transmission line of the in-ear headphone) to compensate for the effect of the transmission line as... Figure 21 The microphone connection pipe shown compensates for the frequency response measured by the first microphone.

[0052] The microphone equalizer can be determined by comparing the frequency response recorded by the first microphone with the frequency response recorded by a microphone of the same type as the first microphone located outside the in-ear headphones (i.e., without a conduit attached to the in-ear headphones). This can be performed using a test setup where a sound source is coupled to one end of a simple acoustic coupler (e.g., a foam tube), and the in-ear headphones are coupled to the opposite end of the acoustic coupler. As discussed above, the sound source can play back a logarithmic scan, which can be recorded and stored by the in-ear headphones (see results). Figure 4 This demonstrates what a nozzle microphone records. Simple second-order acoustic transmission line calculations (as discussed above) can be applied to... Figure 4 The recorded results are shown, where C1 represents the nozzle (i.e., the transmission line between the first microphone and the end of the in-ear headphone), and C2 represents a longer, simpler acoustic coupler with a larger radius (i.e., a foam tube). A more accurate model of the frequency response received by the nozzle microphone is achieved by applying a second-order transmission line calculation. Figure 5 The results are shown in the figure.

[0053] The test setup can be repeated using a microphone of the same type as that used in in-ear headphones (i.e., the first microphone), but the microphone is directly coupled to the acoustic coupler (i.e., it does not have a channel / transmission line attached to the microphone), and the results are recorded and stored by the microphone (see results). Figure 6This demonstrates the frequency response recorded by the microphone without a microphone conduit. Test setups from microphones within in-ear headphones and microphone test setups (in...) are compared separately. Figure 5 and Figure 6 The results shown in the diagram demonstrate which frequencies are lost in the pipeline. As discussed above, Figure 3 The microphone equalizer can be applied to the first microphone of in-ear headphones to ensure that the frequency response measured by the in-ear headphones in the user's ear canal takes into account the loss of the connecting tube, resulting in a more accurate measurement of the user's eardrum response.

[0054] Figures 7 to 9 A comparison is shown between the following two, based on the steps described above: the frequency response measured at the first microphone of the in-ear headphones (i.e., before applying the second-level transmission line calculation and microphone equalizer); and the calculated frequency response of the user's eardrums of the three test subjects (i.e., after applying both the second-level transmission line calculation and microphone equalizer).

[0055] After determining the user's eardrum response, at step 110, the integrated circuit of the in-ear headphones can generate a second sound signal, which may be a signal received from a separate audio input (e.g., a laptop computer, smartphone, MP3 player, or the like).

[0056] At step 112, the integrated circuit of the in-ear headphones can modify the second audio signal based on the user's eardrum response by applying an equalizer function to the second audio signal, as discussed above. This takes into account the user's eardrum response. The equalizer function can be applied via an equalizer coupled to the integrated circuit.

[0057] At step 114, the modified second audio signal can be transmitted to the driver of the in-ear headphones and subsequently played by the driver, such that the modified second audio signal is individually customized according to the user's eardrum response as outlined above. Therefore, the frequency response at the user's eardrum can be varied across the entire frequency range, allowing the user to experience the desired sound generated by the driver.

[0058] In one implementation, the second audio signal can be further modified based on a user-specific objective function. This user-specific objective function can be measured by generating a frequency response at the entrance to the user's ear canal based on an external sound source (such as an external loudspeaker). In other words, the user-specific objective function identifies how the external sound wave input is filtered through diffraction and reflection by individual characteristics of the user's ear (such as the auricle and ear canal) and the user's corresponding tympanic membrane response to the external sound waves. Further modifications can alter the second audio signal toward the user-specific objective function, allowing the user to experience the desired sound generated by the driver.

[0059] To accurately measure a user-specific objective function, a test microphone setup can be used to measure the open tympanic membrane response from an external sound source. This test microphone setup includes microphones for the left and right ears, such as... Figure 23 and Figure 24 The two microphones shown are identical, along with the integrated circuit. The microphones can be placed 1mm to 5mm inside the user's ear canal entrance. The following section discusses... Figure 23 and Figure 24 Further details of the test microphone arrangement are discussed. A third sound signal (such as a logarithmic scan) can be generated by an external sound source (e.g., a loudspeaker), which can be positioned such that it is perpendicular (90°) to the user's face to the left and right, respectively. This ensures an accurate and direct sound signal. The microphones of the test microphone arrangement can record the third sound signal at the entrance of the user's ear canal and transmit the recorded third sound signal to an integrated circuit of the test microphone arrangement, where it can be stored. Alternatively, the recorded third sound signal can be transmitted directly to an integrated circuit of an in-ear headphone, wherein the test microphone arrangement can be coupled (wired or wirelessly) to the in-ear headphone.

[0060] The integrated circuit of the in-ear headphone or the integrated circuit of the test microphone arrangement can be based on the inverse transfer function H of the single-stage acoustic transmission line model of the third sound signal recorded at the user's left and right ears, respectively. EQ This generates the frequency responses for the user's left and right ears. As mentioned above, it has q... out Inverse transfer function H = 0 EQ Corresponding to:

[0061] [Equation 5]

[0062] It has an attenuation coefficient α and a first peak frequency f. c This function can be used to predict the tympanic membrane response from a microphone located at the entrance of the ear canal (or in other words, a user-specific objective function) and to identify which specific sound frequencies from external sources are more or less common to an individual. Figure 10 Exemplary frequency responses (i.e., objective functions) at the tympanic membranes in the left and right ear canals of three users are shown. Differences in the measured frequency responses (objective functions) indicate the need for individual modification (calibration) of the sound reproduced at the user's earpiece.

[0063] The integrated circuit of the in-ear headphone (e.g., an equalizer coupled to the integrated circuit) can further modify the aforementioned second sound signal toward the frequency curve of the generated user-specific objective function, thereby achieving a more desirable frequency response at the eardrum in the user's ear canal.

[0064] In the above measurements with a user-specific objective function, audible sound coloration can be introduced depending on the location of the third sound source (e.g., to the side or in front). To avoid such coloration, the average frequency response from sources distributed around the head can be recorded. Alternatively, tests can be performed in the diffuse sound field from a multi-channel home theater system or reverberation chamber to minimize sound coloration. However, these measurements are difficult to replicate with the same parameters and can still lead to inaccurate results depending on the test subject's ear canal shape, proper microphone placement, etc.

[0065] To address the issue of sound coloration, a user-specific objective function can be measured from the closed (as opposed to open) tympanic membrane response. This closed tympanic membrane response from an external sound source can be measured by a second microphone within the in-ear headphone (facing outwards and opposite to the first microphone). In-ear headphones, such as those related to... Figure 21 and Figure 22 The described in-ear headphones can be placed in a user's left and right ear canals, with the second microphone of each (left and right) in-ear headphone facing outwards from the ear canal, and the in-ear headphone positioned flush with the user's outer ear (auricle). Therefore, the second microphone of each in-ear headphone can record the same third sound signal at the entrance of the user's ear canal and transmit the recorded sound signal to the integrated circuit of each (left and right) in-ear headphone. The integrated circuit of each in-ear headphone can then generate a frequency response (i.e., a user-specific objective function at the left and right ears). Similarly, the second microphone and integrated circuit of each in-ear headphone can determine the head-related transfer function (HrTF) and / or headphone-related transfer function (HpTF) from the third sound source. Figure 11 Exemplary objective function (i.e., frequency response at the entrance to the ear canal) results are shown for three test subjects using in-ear headphones, each including a second microphone.

[0066] Figure 12 A user-specific objective function is shown, where measurements obtained from the test microphone arrangement (i.e., open tympanic membrane response) are normalized (i.e., subtracted) relative to measurements from the second microphone of the in-ear headphones (i.e., closed tympanic membrane response). This shows a more accurate user-specific objective function (frequency response) at the user's tympanic membrane from an external sound source with minimized sound coloration. Therefore, in one embodiment, the user-specific objective function can be further determined by the integrated circuit of the in-ear headphones based on the difference between the closed and open tympanic membrane responses. As mentioned above... Figure 12As described, the integrated circuit can therefore further modify (e.g., equalize) the second sound signal toward a user-specific objective function, thereby bringing the frequency response at the entrance of the user's ear canal to another more desirable level (e.g., making the frequency response at the user's eardrum substantially equalized toward the user's specific objective function, so that the user experiences the expected sound generated by the driver).

[0067] Alternatively, the integrated circuit of in-ear headphones can be oriented towards Figure 11 The user-specific objective function measured (i.e., measured by the in-ear headphones) modifies the second sound signal, and no initial measurement is required. Figure 10 The user-specific objective function (i.e., measured by a test microphone setup). Therefore, the in-ear headphones can generate the user-specific objective function and modify (e.g., equalize) the second sound signal toward said objective function, thereby achieving the desired sound generated by the driver at the user's eardrum without the need for a separate test microphone setup.

[0068] Using as described above Figure 23 and Figure 24 Test microphone setup, Figure 21 and Figure 22 After the second microphone of the in-ear headphones, or a combination of both, measures the user's left and right objective functions, such as... Figure 13 As shown, a simplified equalizer function can be applied to implement a user-specific objective function. The equalizer function may include a peak / notch filter (followed by a chevron filter), and the equalizer function is controlled by the corresponding gain of each filter. The equalizer allows the user to manually adjust the final objective function curve (i.e., the in-ear headphones will be oriented towards their modified (e.g., equalized) frequency response of a second sound source) to obtain optimal individual sound quality.

[0069] Figure 12 The objective functions measured for the user's right and left ears can be normalized by the integrated circuit of the in-ear headphone using an equalizer function. For example, the normalized, measured objective function for the right ear... Figure 14 And for the example of the left ear Figure 15 As shown in the image.

[0070] In one implementation, further modification of the second audio signal by the integrated circuit of the in-ear headphones can be based on, for example, Figures 10 to 12 (or Figures 14 to 15 The user-specific objective function shown in the figure is subtracted from the objective function shown in the figure. Figures 7 to 9 The user's tympanic membrane response is shown in the image. Figures 16 to 18The image shows the final modification of the second sound signal for three test subjects, which produces a frequency response at the user's eardrum that most closely resembles the user's specific objective function across the entire frequency range, allowing the user to experience the intended sound generated by the driver. A bandwidth cap can be introduced at 8kHz to avoid excessive enhancement at higher frequencies. Figures 16 to 18 As shown, there is a difference of about 10dB in the final headphone equalization filter, which proves that in-ear headphones need to be calibrated separately.

[0071] In one embodiment, the integrated circuit may include a digital signal processor (DSP) that can be used to process active noise cancellation (ANC), which includes a delay of less than 20 µs. Minimizing this delay results in a more stable sound delivery to the driver, and thus a smoother experience for the user. Therefore, normal binaural hearing can be improved while wearing in-ear headphones.

[0072] As discussed above, when generating the user's eardrum response from the driver of an in-ear headphone, an attenuation factor can optionally be estimated indirectly to achieve a more accurate frequency response. For example, the attenuation factor α can vary between 0.1 and 1 in increments of 0.1 (e.g., 0.1, 0.2, 0.3…1.0). Therefore, multiple frequency response results can be generated at the first microphone, such as… Figure 19 As shown in the diagram. The results can be observed in an observation interval (e.g., between 1200 Hz and 1500 Hz), and then smoothed in two levels (as shown in the diagram). Figure 20 (Showing soft and strong smoothing). Smoothing of curves within the observation interval can be performed according to the following equation:

[0073]

[0074] Where the block length N = 2048, and for a softly smooth curve, s = 1.1, and for a strongly smooth curve, s = 1.5. The curve with the minimum area between curves (e.g., Figure 20 The curve in 3) is the smoothest response and can be selected, thus resulting in sufficient compensation for the destructive interference caused by the echo in the ear canal.

[0075] In one implementation, the in-ear headphones can be placed in an "ambient listening mode," where the user hears / experiences ambient (i.e., background and environment) sounds as if he / she were not wearing headphones. In this ambient listening mode, the second microphone of the in-ear headphones records ambient sounds from the external world, which are temporarily stored in the integrated circuit of the in-ear headphones. The integrated circuit of the in-ear headphones can then modify the stored ambient sounds based on the user's eardrum response, the user's specific target function (for the left and right ears), or a combination of both, and transmit the modified ambient sounds to the driver of the in-ear headphones, which can then play back the modified ambient sounds to the user. Thus, the user experiences binaural hearing and feels as if he / she is listening naturally without timbre or positional variations, just as if not wearing headphones. This allows for the automatic calibration of sound to ensure the user hears the desired sound (e.g., the desired frequency response) in the small package of noise-cancelling and sound-isolating in-ear headphones. In addition, the ambient listening mode allows for increased safety in situations where noise-canceling in-ear headphones previously posed a danger to the user, such as on a construction site or when the user is crossing the road.

[0076] To further enhance the effect of hearing ambient noise as if one were not wearing headphones, the integrated circuit of the in-ear headphones may include a digital signal processor (DSP) as described above. The DSP may have a latency of less than 20µs. This ensures that ambient sounds recorded by a second microphone are relayed to the in-ear headphone driver, allowing the user to experience ambient noise instantly.

[0077] The second microphone and DSP described above can be used to perform active noise cancellation (ANC) using well-known methods. In-ear headphones can also use the second microphone and integrated circuits (e.g., DSP) to perform ANC in situations where an ambient listening mode is present or absent within the in-ear headphones.

[0078] The steps described above can be performed with two in-ear headphones, allowing the user to wear one in-ear headphone in each ear, thus creating a binaural hearing experience.

[0079] in-ear headphones

[0080] Figure 21An exemplary in-ear headphone 2100 is shown, which, as in the method described above, can be automatically calibrated to modify the sound received from an audio input such as a mobile phone, laptop computer, MP3 player, or any other suitable sound source. The in-ear headphone includes a housing 2102 that holds a first microphone 2108, a driver 2110, an integrated circuit (not shown), and may include a second microphone (2112). The first microphone 2108, the second microphone 2112, and the driver 2110 are each electrically coupled to the integrated circuit (not shown). The driver 2110 can be any well-known driver capable of reproducing high-quality sound to the user. The driver 2110 can be a dynamic (moving coil) type driver and may have a diameter of 5.8 mm. The first microphone 2108 and the second microphone 2112 can be a standard ECM (electro-mechanical capsule), analog MEMS, digital MEMS, or any other suitable microphone known in the industry.

[0081] The housing may include a wider "body portion" 2104 at one end and a narrower "nozzle portion" 2106 attached to the body portion 2104 at the opposite end. The body portion 2104 may include a first microphone 2108 and a driver 2110 pointing toward the nozzle portion 2106 (i.e., toward the user's ear canal). The body portion 2104 may also include a second microphone 2112 pointing in the opposite direction to the first microphone 2108 (i.e., away from the user's ear canal and outwards), such that the second microphone can record ambient (e.g., environmental and background) noise. The body portion 2104 of the in-ear headphone 2100 may also include an integrated circuit (not shown). The nozzle portion 2106 may be an elongated cannula shape that fits comfortably into the user's ear canal. The nozzle portion 2106 may have a maximum diameter of 3 mm. The nozzle portion 2106 may be attached to the body portion 2104 at one end, while the opposite end of the nozzle portion 2106 includes a lip suitable for placing well-known ear tips of different sizes (e.g., silicone or rubber ear tips from the hearing industry) onto an in-ear headphone 2100 as described above.

[0082] Nozzle portion 2106 may include a first channel / nozzle / channel 2114 that can directly couple driver 2110 to the outlet port of in-ear headphone 2100, thus providing a direct sound source from in-ear headphone 2100 to the user's ear canal. Furthermore, nozzle portion 2106 may include a second channel / nozzle / channel 2116 (equivalent to the nozzle and first transmission line discussed above regarding the method) that can couple first microphone 2108 to first channel / nozzle / channel 2114. Second channel / nozzle / channel 2116 may have a cross-sectional area substantially smaller than that of first channel / nozzle / channel 2114 (e.g., second channel / nozzle / channel 2116 may have a cross-sectional area of ​​0.28 mm). 2 The cross-sectional area, and the first channel / nozzle / pipe 2114 may have 2.29 mm. 2 (Cross-sectional area). The second channel / nozzle / pipe 2116 can be installed at a bent angle to the first channel / nozzle / pipe 2114, such as... Figure 21 As shown in the diagram. When the in-ear headphones are placed in the user's ear, this minimizes the complex acoustic interaction at the exit of the second channel / nozzle / duct 2116 with the reflected echo from the user's ear canal.

[0083] The in-ear headphone 2100 may include a transceiver (not shown) to allow the in-ear headphone to wirelessly communicate with an audio input sound source, such as a mobile phone, laptop computer, MP3 player, or any other suitable sound source. Alternatively or additionally, the in-ear headphone 2100 may include any standard connection to couple a wire between the in-ear headphone 2100 and the audio input sound source. Furthermore, the in-ear headphone 2100 may include additional wired and / or wireless connections to... Figure 23 and Figure 24 The test microphone is coupled to the in-ear headphone 2100, as described later.

[0084] Figure 22An exemplary block diagram of an in-ear headphone 2100 and an integrated circuit within the in-ear headphone is shown. For example, the integrated circuit may include a first core processor 2202 coupled to a second core processor 2204. The first processor 2202 may be an active noise cancellation (ANC) processor, and the second processor 2204 may be a multi-chip unit (MCU). The ANC processor may be a digital signal processor (DSP) or any other suitable processor with a latency (delay) of less than 20 µs, which ensures that the negative feedback ANC control loop is stable over a sufficient frequency bandwidth. The ANC may be coupled to a first microphone 2208, a second microphone 2210, and a driver 2206, wherein an analog-to-digital (A / D) or digital-to-analog (D / A) converter 2212 is positioned between the microphone / driver and the ANC. The ANC may also be coupled to an audio input sound source 2214. The ANC may include a first equalizer 2216 to perform standard noise cancellation functions by equalizing the acoustic paths of the second microphone 2210 and the audio input sound source 2214. The ANC may also include a second equalizer 2218 to perform sound modification (e.g., equalization) functions, as described in more detail in the Methods section.

[0085] When a user wears in-ear headphones 2100, MCU 2204 can generate sound signals to be played to the user, with the goal of generating the user's eardrum response and a user-specific objective function, as previously described. MCU 2204 can also be coupled (wirelessly or wired) to test microphone arrangements 2300, 2400, as described later, to measure portions of the user's specific objective function. MCU 2204 can also simultaneously record ambient (e.g., environmental or background) sound or logarithmic sound signals (as described above) from both ears via a second microphone 2210, which can later be played back from memory. Other applications that can run in MCU 2204 include rendering multi-channel stereo music via a binaural processor (3D audio) or enhanced audio / machine learning algorithms.

[0086] Test microphone setup

[0087] Figure 23 and Figure 24Test microphones 2300 and 2400, as described in more detail above, are shown for accurately measuring a user's specific objective function. Test microphones 2300 and 2400 may be part of a test microphone arrangement including two identical test microphones 2300 and 2400 coupled to in-ear headphones 2100 and 2200. The test microphone arrangement may also include an integrated circuit directly coupled to the two test microphones 2300 and 2400. A user can wear the test microphone arrangement to measure the acoustic sound pressure (frequency response) at the entrance of the user's ear canal from an external sound source (e.g., a loudspeaker as described above) to determine the user's specific objective function. Microphones 2302 and 2402 of the test microphones may each be mounted on a first side 2304 and 2404 of a spring wire bracket 2306 and 2406, with the second and opposite sides 2308 and 2408 coupled (directly or indirectly) to the in-ear headphones 2100 and 2200. The spring wire brackets 2306 and 2406 ensure that the microphones 2302 and 2402 do not record unwanted feedback from cables and / or receivers placed on the opposite sides 2308 and 2408 of the spring wire brackets 2306 and 2406. The microphones 2302 and 2402 can be mounted such that they are positioned 1 mm to 5 mm from the entrance of the user's ear canal.

[0088] Each spring wire bracket 2306, 2406 may also include a plurality of rods 2310, 2410 (e.g., three or more) mounted around the microphone 2302, 2402 to ensure that the microphone 2302, 2402 is guided into ear canals of all sizes, thereby creating a universal fit without producing an hermetically sealed area. The rods 2310, 2410 may be made of plastic, metal, rubber, or any combination thereof.

Claims

1. A method for calibrating in-ear headphones, the method comprising: When the in-ear headphones are placed in the user's ear canal, an integrated circuit generates a sound signal and plays the sound signal at the driver of the in-ear headphones; The in-ear headphones receive a reflected sound signal at a first microphone, wherein the reflected sound signal corresponds to a sound signal generated by reflection from the user's eardrum; The integrated circuit generates a frequency response based on the reflected sound signal; The integrated circuit generates a user tympanic membrane response based on the frequency response, wherein generating the user tympanic membrane response by the integrated circuit includes: determining the length of the user's ear canal based on a first minimum value of the measured frequency response, and estimating the attenuation coefficient of the user's ear canal; The integrated circuit generates a second sound signal; The integrated circuit modifies the second sound signal based on the user's tympanic membrane response; and The modified second sound signal is played at the driver.

2. The method of claim 1, wherein the sound signal generated by the integrated circuit is a logarithmic scan.

3. The method of claim 1, further comprising applying a microphone equalizer to the first microphone, wherein the first microphone is coupled to the nozzle, and the microphone equalizer is based on a comparison between: The frequency response received by the first microphone attached to the nozzle; and The test frequency response is performed using a test setup, wherein the test frequency response corresponds to the frequency response directly received by a first microphone that does not have the attached nozzle.

4. The method of claim 1, further comprising: A third sound signal is generated by a driver separate from the in-ear headphones; The third sound signal is received at the entrance of the user's ear canal and stored in the integrated circuit of the in-ear headphone; The integrated circuit generates a second frequency response based on the received third audio signal, the second frequency response corresponding to a user objective function; and The modification of the second sound signal by the integrated circuit based on the user's tympanic membrane response further includes: modifying the second sound signal by the integrated circuit toward the user's objective function.

5. The method of claim 4, wherein: The third sound signal is received at the second microphone of the in-ear headphones, wherein the second microphone is positioned opposite the first microphone and located on the outside of the in-ear headphones; or The third sound signal is received at a test microphone arrangement coupled to the in-ear headphones.

6. The method of claim 4, wherein: The third sound signal is received at the second microphone of the in-ear headphones, wherein the second microphone is placed opposite the first microphone and is located on the outside of the in-ear headphones; A fourth sound signal, identical to the third sound signal, is generated by the driver separate from the in-ear headphones; the fourth sound signal is received by a test microphone coupled to the in-ear headphones and positioned at the entrance of the user's ear; and a third frequency response is generated based on the received fourth sound signal; and The user objective function is further determined based on the difference between the third frequency response and the second frequency response.

7. The method of claim 6, further comprising: The in-ear headphones are placed in ambient listening mode, which includes: The second microphone receives ambient sound. The ambient sound is stored in the integrated circuit. The stored ambient sound is modified based on the user's tympanic membrane response, the user's objective function, or a combination of the user's tympanic membrane response and the user's objective function; and The modified ambient sound is played at the driver of the in-ear headphones.

8. The method of claim 6, further comprising: Active noise cancellation is performed by the integrated circuit connected to the second microphone.

9. The method of claim 1, further comprising: The attenuation coefficient of the tympanic membrane response is calculated by changing the integrated circuit between 0.1 and 1 in increments of one decimal place. The integrated circuit smooths the tympanic membrane response as a result; as well as The frequency response with the smoothest response is selected by the integrated circuit.

10. An in-ear headphone (2100, 2200), said in-ear headphone comprising: A housing (2102) comprising a main body portion (2104) and a nozzle portion (2106), wherein the nozzle portion includes an orifice therein; A driver (2110, 2206), the driver being located within the housing; The first microphone (2108, 2208) is located inside the housing; The second microphone (2112, 2210) is located inside the housing and is opposite to the first microphone (2108, 2208); and An integrated circuit coupled to the first microphone (2108, 2208), the second microphone (2112, 2210), and the driver (2110, 2206), the integrated circuit being operable to perform the method as described in any one of claims 1 to 9.

11. The in-ear headphone as claimed in claim 10, further comprising: A first connecting conduit (2114) is attached to the hole and the driver; and The second connecting conduit (2116) includes a first end attached to the first microphone and a second end bent and attached to the first connecting conduit.

12. The in-ear headphone of claim 11, wherein the cross-sectional area of ​​the second connecting channel is substantially smaller than the cross-sectional area of ​​the first connecting channel.

13. A system comprising: A test microphone arrangement of a third microphone (2302, 2402) and a fourth microphone (2302, 2402), the test microphone arrangement being operable to record the frequency response of an external sound source at the entrance of a user's ear canal; as well as The in-ear headphones as claimed in any one of claims 10 to 12, wherein the test microphone arrangement is coupled to the in-ear headphones (2100, 2200).

14. The system of claim 13, wherein: The third microphone (2302, 2402) and the fourth microphone (2302, 2402) are each attached to a first side (2304, 2404) of a separate spring wire bracket (2306, 2406), and the second and opposite sides (2308, 2408) of the spring wire bracket (2306, 2406) are coupled to the in-ear headphones (2100, 2200); and The first side (2304, 2404) of each spring wire bracket (2306, 2406) also includes a plurality of rods (2310, 2410) attached to the spring wire bracket (2306, 2406), the plurality of rods being adapted to hold the third microphone (2302, 2402) and the fourth microphone (2302, 2402) in the user's ear canal without creating an airtight seal.

Images