SYSTEM AND METHOD FOR EVALUATING AN ACOUSTIC CHARACTERISTIC OF AN ELECTRONIC DEVICE

Abstract

The present disclosure provides a method for evaluating an electronic device. The method comprises determining, with an acoustic tube, a value of a first parameter, the value of the first parameter being indicative of the acoustic impedance of a reference termination. The method further comprises determining, with the acoustic tube, a value of a second parameter, the value of the second parameter being indicative of the acoustic impedance of the reference termination, when occluded by the electronic device. The method then comprises calculating a value of a third parameter, the value of the third parameter being indicative of the acoustic impedance of the electronic device, based on the value of the first parameter and the value of the second parameter.

Claims

1. A method for evaluating an electronic device, the method comprising: determining, with an acoustic tube, a value of a first parameter, wherein the value of the first parameter is indicative of an acoustic impedance of a reference termination; determining, with the acoustic tube, a value of a second parameter, wherein the value of the second parameter is indicative of an acoustic impedance of the reference termination occluded by the electronic device; and calculating a value of a third parameter, wherein the value of the third parameter is indicative of an acoustic impedance of the electronic device, based on the value of the first parameter and the value of the second parameter.

2. The method according to claim 1, wherein: the value of third parameter is calculated based on a ratio between the value of the first parameter and the value of the second parameter.

3. The method according to claim 1, the method further comprising: calculating a value of a fourth parameter based on the value of the third parameter, wherein the value of the fourth parameter is an Occlusion Index, OI, that represents a strength of the acoustic impedance of the electronic device with respect to an occlusion effect.

4. The method according to claim 1, wherein: the reference termination is: an open end of a tube; an artificial ear, or a dummy head.

5. The method according to claim 1, wherein: the electronic device comprises: an Active Noise Cancellation, ANC, headphone; or an Active Noise Reduction, ANR, headphone.

6. The method according to claim 3, the method further comprising: selecting, based on the value of the fourth parameter, a frequency dependent weighting factor, K1, for a feedback filter of the electronic device responsive to determining that the value of the fourth parameter is larger than a threshold value; applying the K1 to the feedback filter of the electronic device; and recalculating the value of the fourth parameter after applying the K1 to the feedback filter of the electronic device.

7. The method according to claim 6, wherein: selecting the K1, applying the K1, and recalculating the value of the fourth parameter is performed iteratively until the recalculated value of the fourth parameter is equal to or smaller than a threshold value.

8. The method according to claim 3, the method further comprising: measuring a first transfer function value between an external loudspeaker and an additional microphone, wherein the additional microphone is placed inside the reference termination; measuring a second transfer function value between the external loudspeaker and the additional microphone; and calculating a value of a fifth parameter, wherein the value of the fifth parameter is indicative of a damping of the electronic device, based on the first transfer function value and the second transfer function value.

9. The method according to claim 8, the method further comprising: selecting, responsive to determining that the value of the fourth parameter is larger than a threshold value, a frequency dependent weighting factor, K2, for a feedforward filter of the electronic device, based on the value of the fifth parameter; applying the K2 to the feedforward filter of the electronic device; and recalculating the value of the fourth parameter as OI and the value of the fifth parameter, after applying the K2 to the feedforward filter of the electronic device.

10. The method according to claim 9, wherein: selecting the K2, applying the K2, and recalculating the value of the fourth parameter and the value of the fifth parameter is performed iteratively until the recalculated value of the fourth parameter is equal to or smaller than the threshold value.

11. The method according to claim 8, wherein: the first transfer function value is measured by producing a signal using the external loud speaker and capturing the signal by the additional microphone.

12. The method according to claim 8, wherein: the second transfer function value is measured by reproducing the signal using the external loud speaker and capturing the reproduced signal by the additional microphone.

13. A system for evaluating an electronic device, the system comprising: an acoustic tube; and a processing unit configured to: determine a value of a first parameter, wherein the value of the first parameter is indicative of an acoustic impedance of an open end of the acoustic tube; and determine a value of a second parameter, wherein the value of the second parameter is indicative of an acoustic impedance of the open end of the acoustic tube as occluded by the electronic device; and calculate a value of a third parameter, wherein the value of the third parameter is indicative of an acoustic impedance of the electronic device, based on the value of the first parameter and the value of the second parameter.

14. The system according to claim 13, further comprising an electronic device that includes: at least one loudspeaker configured to generate a signal, at least one microphone configured to capture the generated signal from the loudspeaker, and an Active Noise Cancellation, ANC, circuit and/or an Active Noise Reduction, ANR, circuit configured to generate a noise cancelation signal.

15. The system according to claim 13, wherein: the acoustic tube has a full audio band frequency range.

16. The system according to claim 13, further comprising: an external loudspeaker configured to generate a signal; an additional microphone configured to capture the generated signal, wherein the additional microphone is placed inside the acoustic tube at a predefined distance from the open end of the acoustic tube; and a damping measurement circuit configured to measure at least one of the first transfer function value or the second transfer function value.

17. The system according to claim 16, wherein: the predefined distance between the additional microphone and the open end of the acoustic tube is smaller than 5 cm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The above described aspects and implementation forms of the present disclosure will be explained in the following description of specific embodiments in relation to the enclosed drawings, in which:

[0062] FIG. 1 schematically illustrates a system for evaluating an electronic device, according to various embodiments of the disclosure.

[0063] FIG. 2 schematically illustrates a system for evaluating a headphone, according to various embodiments of the disclosure.

[0064] FIG. 3 illustrates the determined headphone impedance for three different headphones without any ANR/ANC system, according to various embodiments of the disclosure.

[0065] FIG. 4 illustrates an exemplarily scheme of one side of the ANR/ANC headphone, according to various embodiments of the disclosure.

[0066] FIG. 5 schematically illustrates a flow chart of a procedure for evaluating the ANR/ANC headphone based on calculating the OI and applying K.sub.1 for the feedback filter, according to various embodiments of the disclosure.

[0067] FIG. 6 illustrates an exemplarily scheme of the system including the acoustic impedance tube and the headphone with ANR/ANC system, according to various embodiments of the disclosure.

[0068] FIG. 7 schematically illustrates an exemplarily acoustic impedance tube, according to various embodiments of the disclosure.

[0069] FIG. 8 illustrates an exemplarily scheme of the ANR/ANC headphone comprising a feedback microphone path and a feedforward microphone path, according to various embodiments of the disclosure.

[0070] FIG. 9 illustrates an exemplarily scheme of the system comprising an additional microphone and an external loudspeaker for evaluating the ANR/ANC headphone, according to various embodiments of the disclosure.

[0071] FIG. 10 schematically illustrates a flow chart of a procedure for evaluating the ANR/ANC headphone based on calculating the OI, applying K.sub.1 for the feedback filter and K.sub.2 for the feedforward filter, according to various embodiments of the disclosure.

[0072] FIG. 11 schematically illustrates a method for evaluating an electronic device, according to various embodiments of the disclosure.

[0073] FIG. 12 illustrates the occlusion effect by comparing two sound pressure level spectra measured inside the ear canal, according to prior art.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0074] FIG. 1 schematically illustrates a system 1 for evaluating an electronic device 110, according to various embodiments of the disclosure.

[0075] The system 1 comprises an acoustic tube 100 configured to determine a value of a first parameter Z.sub.OE the value of the first parameter Z.sub.OE being indicative of the acoustic impedance of a reference termination 101; and determine a value of a second parameter Z.sub.OE.sup.Hp, the value of the second parameter Z.sub.OE.sup.Hp being indicative of the acoustic impedance of the reference termination 101, when occluded by the electronic device 110.

[0076] The system 1 further comprises a processing unit 120 configured to calculate a value of a third parameter Z.sub.HP, the value of the third parameter Z.sub.HP being indicative of the acoustic impedance of the electronic device 110, based on the value of the first parameter Z.sub.OE and the value of the second parameter Z.sub.OE.sup.Hp.

[0077] For example, the electronic device 110 may be the ANR/ANC headphone 110. Moreover, the acoustic impedance of the ANR/ANC headphones 110 may be determined. Furthermore, in some embodiments, the feedback filter and/or the feedforward filter of the ANR/ANC headphone may be configured. Moreover, the ANR/ANC headphone 110 may be evaluated, calibrated, etc.

[0078] FIG. 2 schematically illustrates the system 1 for evaluating a headphone, according to various embodiments of the disclosure.

[0079] The acoustic impedance of the headphones may be measured with a customized acoustic impedance tube, which may be based on the ISO-10534-2. The measurement tube may be designed and built such that it fits the geometries of a human ear canal, e.g., the inner diameter of the tube may be approx. 8 mm, and a frequency range between at least 60 Hz and 2 kHz. The determination of the acoustic impedance of the headphone may be done with 2 measurements. First, the acoustic impedance of the reference termination Z.sub.OE (i.e., the value of the first parameter) has to be measured (e.g., the system 1 in measuring set-up 201). The reference termination may be the “open-ended” tube or an artificial ear of a dummy head. Moreover, if an artificial ear is used, in some embodiments, it may lead to a better results. Note that, care must be taken to ensure that the inner diameter of the measuring tube corresponds to the inner diameter of the artificial ear. Second, the acoustic impedance of the reference termination occluded with the headphone Z.sub.OE.sup.Hp (i.e., the value of the second parameter) has to be measured (e.g., the system 1 in measuring set-up 202). The headphone impedance Z.sub.HP (i.e., the value of the third parameter) may be defined as the normalization of Z.sub.OE.sup.Hp to Z.sub.OE, as follows:

[00001]$\begin{array}{cc}{Z}_{\mathrm{HP}}=\frac{.Math.{\underset{\_}{Z}}_{\mathrm{OE}}^{\mathrm{Hp}}.Math.}{.Math.{\underset{\_}{Z}}_{\mathrm{OE}}.Math.},& \left(1\right)\end{array}$

[0080] This headphone impedance shows the impact of the headphone as the deviation to the reference impedance. An ideal open headphone may have a Z.sub.HP equal to 0 dB in all frequency bins.

[0081] FIG. 3 illustrates the determined headphone impedance for three different headphones without any ANR/ANC system, according to various embodiments of the disclosure.

[0082] The headphone impedance are determined for a closed over-ear headphone 301, an open headphone 302, and a closed in-ear headphone 303, in the frequency range between 100 Hz and 10000 Hz.

[0083] In some embodiments, the Occlusion Index (OI) may be determined and it may further be used to represent the strength of the acoustic impedance regarding the occlusion effect with a single value. For example, the OI (i.e., the value of the fourth parameter) may be calculated as follows:

[00002]$\begin{array}{cc}\mathrm{OI}=20{\log }_{10}\left(\sqrt{\frac{\underset{i=f_1}{\overset{f_u}{.Math.}}{\left(Z_{\mathrm{HP}}\left(i\right)-1\right)}^2}{N}+1}\right)\mathrm{in}\mathrm{dB},& \left(2\right)\end{array}$

where N is the number of frequency bins between the lower frequency limit f.sub.l and the upper frequency limit f.sub.u. In some embodiments, f.sub.1 may be between 20 Hz and 100 Hz, f.sub.u may be between 800 Hz and 2000 Hz. N may depend on the frequency resolution (Δf), which may be calculated as (f.sub.u−f.sub.l)/Δf+1. For example, if f.sub.l is equal 60 Hz, f.sub.u is equal to 1000 Hz, and the Δf is 1 Hz, N is equal to (1000 Hz-60 Hz)/1 Hz+1=941. The frequency limits may be based on the lower frequency limit of the acoustic impedance tube and the upper frequency limit, which may be defined up to 2 kHz. Typically, the occlusion effect is most pronounced in the low frequencies and decreases as frequency increases, depending on the design of the headphone. For circumaural (over-ear) headphones (e.g., as it is shown in FIG. 12) the occlusion effect is dominant up to 400 Hz. Moreover, for an in-ear headphone the occlusion effect may be extended up to 2 kHz.

[0084] In some embodiments, the acoustic impedance tube may be used, and different parameters may be determined and/or calculated (e.g., Z.sub.HP, OI), in order to iteratively configure the ANR/ANC system of the headphone.

[0085] In some embodiments the repeatable measurement for determining and/or reducing the occlusion effect may performed, e.g., by using the acoustic impedance tube, and the ANR/ANC Headphone may be configured, evaluated, etc.

[0086] FIG. 4 illustrates an exemplarily scheme of one side of the ANR/ANC headphone 110, according to various embodiments of the disclosure.

[0087] An example of one side of a typical ANR/ANC headphone 110 is illustrated, which consists of a microphone 401, an ANR/ANC circuit 402 and a loudspeaker 403. The microphone 401 captures the generated sound from the user, the ANR/ANC circuit 402 contains the ANR/ANC controller K.sub.1 with a frequency-dependent weighting to generate the cancellation signal which is played back by the loudspeaker 403. K.sub.1 is a frequency dependent gain factor for the feedback filter 404.

In the design process of the ANR/ANC system 1 using the acoustic impedance tube 100, it may be possible to set this gain factor (e.g., very precisely to the correct value) which may lead to a better reduction of the occlusion effect and an optimal noise reduction properties. Moreover, in some embodiments, K.sub.1 may be configured (e.g., selected, adjusted, etc.) by an iterative process.

[0088] FIG. 5 schematically illustrates a flow chart of a procedure 500 for evaluating the ANR/ANC headphone 110 based on calculating the OI and applying K.sub.1 for the feedback filter, according to various embodiments of the disclosure.

[0089] Moreover, the following steps may be performed: [0090] Step 501: measure the Z.sub.OE on the acoustic impedance tube as the reference termination. [0091] Step 502: measure the Z.sub.OE.sup.Hp on the acoustic impedance tube with ANR/ANC system. It should be noted, at the beginning, the feedback loop gain (K.sub.1) are zero. [0092] Step 503: calculate the Z.sub.HP as the ratio between |Z.sub.OE.sup.Hp| and |Z.sub.OE|, and further calculate the OI based on the Z.sub.HP. OI is a criterion to evaluate the performance of the ANR/ANC system 1. If the OI is equal or close to zero, or blow a threshold defined by the manufacturer, the measurement is completed (e.g., the headphone is calibrated), there is no need to go to steps 504 and 505 anymore. [0093] Step 504: select frequency dependent weighting factor for the ANR/ANC controller K.sub.1. For example, if Z.sub.HP shows 10 dB boost at 100 Hz, want 10 dB of feedback loop desensitivity at that frequency. [0094] Step 505: apply K.sub.1 for the ANR/ANC circuit 402 and go back to step 502.

[0095] FIG. 6 illustrates an exemplarily scheme of the system 1 including the acoustic impedance tube 100 and the headphone 110 with ANR/ANC circuit 402, according to various embodiments of the disclosure. Moreover, FIG. 7 schematically illustrates an exemplarily acoustic impedance tube 100, according to various embodiments of the disclosure.

[0096] Moreover, the system 1 (e.g., the measurement setup) and/or the acoustic impedance tube 100 may have the following configurations: [0097] The acoustic impedance tube 100 may be based on the ISO-150534-2. [0098] The number of microphones and the distances between different microphones may be selected based on the desired frequency range. [0099] For example, two microphones with a distance of 28 cm may achieve the measurement range between 60 Hz-600 Hz. [0100] The distance between the end of the tube and the position of the first (nearest to the end of the tube) microphone should be no larger than 5 cm (e.g., for example, it may be less than 2 cm). [0101] To achieve a wider frequency range, more than 2 microphone positions may be needed (e.g., four microphone positions are shown in the FIG. 7).

[0102] In some embodiments, the feedback filter 404 and/or the feedforward (hear-through) filter 804 may be configured with the system 1 including the acoustic impedance tube 100 and/or the method discussed above. Moreover, an additional hear-through filter and an external loudspeaker 903 may be used.

[0103] In some embodiments, a feed forward path combined with a feedback path may be provided, for example, to ensure a natural hear-through feeling with optimized occlusion reduction. Natural hear-through means that the ambient noise and the user's own voice while speaking is perceived naturally (like without using headphones). Moreover, in order to ensure a natural perception, not only the occlusion effect has to be reduced/cancelled, the passive attenuation/damping of the headphone in the high frequencies has to be compensated.

[0104] FIG. 8 illustrates an exemplarily scheme of the ANR/ANC headphone 110 comprising a feedback microphone path and a feedforward microphone path, according to various embodiments of the disclosure.

[0105] FIG. 8 illustrates the headphone 110 with a feedback microphone 401 path and a feedforward microphone 801 path. Both microphone paths are connected to the ANR/ANC circuit 402 and have different frequency dependent weighting functions K.sub.1, K.sub.2, respectively. Moreover, it may be possible to adjust K.sub.2 (frequency dependent gain factor for the feedforward filter 804), and it may also be possible to adjust K.sub.1 and K.sub.2 together, for example, by updating their values iteratively in order to find the best balance of the ambient response and the occlusion effect. Therefore, the headphones may be placed on the acoustic impedance tube 100 and an additional loudspeaker (e.g., speaker2 903) is placed approx. 1 m away of the headphone (e.g., in FIG. 9).

[0106] FIG. 9 illustrates an exemplarily scheme of the system 1 comprising an additional microphone 901 and an external loudspeaker 903 for evaluating the ANR/ANC headphone 110, according to various embodiments of the disclosure.

[0107] Moreover, the additional microphone 901 (nearest to the end of the tube, mic 3) inside the acoustic impedance tube 100 may be used and the frequency depending damping of the headphone may be measured. Therefore, the external speaker 903 (speaker2) and the additional microphone 901 (mic 3) are connected to the box headphone damping measurement 904. To measure the headphone damping, a measurement signal is reproduced via the external speaker 903 (i.e., the speaker 2) that is picked up by the additional microphone 901 (mic 3), for the covered impedance tube with headphone and without headphone. Furthermore, the ratio between the signals (covered/uncovered) may be the frequency dependent damping factor of the headphone 110. In addition, it may be possible to compensate the damping of the headphone 110 in the high frequency part above 1-2 kHz. For example, the measurement may be performed in two operation modes: The first operation mode may measure the acoustic impedance of the headphone 110 as it is described above (e.g., under FIG. 5 and/or FIG. 6). The second operation mode may measure the headphone damping with the external loud speaker 903 (speaker2) and the additional microphone 901 (mic 3), as it is illustrated in FIG. 9.

[0108] Moreover, the feedback and feed-forward paths may be configured, for example, using the system in FIG. 9 and/or the procedure 1000 in FIG. 10.

[0109] FIG. 10 schematically illustrates a flow chart of a procedure 1000 for evaluating the ANR/ANC headphone 110 based on calculating the OI, applying K.sub.1 for the feedback filter, and applying K.sub.2 for the feedforward filter, according to various embodiments of the disclosure.

[0110] Moreover, the following steps may be performed: [0111] Step 1001: measure transfer function (H.sub.1) between speaker 2 (external loud speaker 903) and mic 3 (additional microphone 901) without headphone as a hear-through reference. [0112] Step 1002: measure Z.sub.OE using the acoustic impedance tube 100 as the reference termination. [0113] Step 1003: measure Z.sub.OE.sup.Hp using the acoustic impedance tube 100 with ANR/ANC system (the ANR/ANC headphone 110). It should be noted, at the beginning, the feedback and feed-forward loop gain (K.sub.1 and K.sub.2) are zero. [0114] Step 1004: calculate Z.sub.HP as the ratio between |Z.sub.OE.sup.Hp| and |Z.sub.OE|, and further calculate the OI based on the Z.sub.HP. OI is a criterion to evaluate the performance of the ANR/ANC system. If OI is equal or close to zero, or blow a threshold defined by the manufacturer, the measurement is completed, there is no need to go to steps 1005-1009 anymore. [0115] Step 1005: select frequency dependent weighting factor for the feedback filter K.sub.1 404. For example, if Z.sub.HP shows 10 dB boost at 100 Hz, want 10 dB of feedback loop desensitivity at that frequency. [0116] Step 1006: measure transfer function (H.sub.2) between speaker 2 (external loudspeaker 903) and mic 3 (additional microphone 901) with the headphone 110. [0117] Step 1007: calculate the damping of the headphone (isolation curve) H.sub.iso=|H.sub.2|/|H.sub.1|. [0118] Step 1008: Configure the feed-forward loop gain K.sub.2 to reduce headphone damping in the high frequencies and to ensure a natural own voice perception. For example, if H.sub.iso shows a 4 dB drop at 3 kHz, a first approximation will add 3 dB gain to the feed forward path. [0119] Step 1009: apply K.sub.1 and K.sub.2 for the ANR/ANC circuit and go back to step 1003.

[0120] FIG. 11 shows a method 1100 according to an embodiment of the disclosure for evaluating an electronic device 110. The method 1100 may be carried out by the system 1, as it described above.

[0121] The method 1100 comprises a step 1101 of determining, with an acoustic tube, a value of a first parameter Z.sub.OE, the value of the first parameter Z.sub.OE being indicative of the acoustic impedance of a reference termination 101.

[0122] The method 1100 further comprises a step 1102 of determining, with the acoustic tube, a value of a second parameter Z.sub.OE.sup.Hp, the value of the second parameter Z.sub.OE.sup.Hp being indicative of the acoustic impedance of the reference termination 101, when occluded by the electronic device 110.

[0123] The method 1100 further comprises a step 1103 calculating a value of a third parameter Z.sub.HP, the value of the third parameter Z.sub.HP being indicative of the acoustic impedance of the electronic device 110, based on the value of the first parameter Z.sub.OE and the value of the second parameter Z.sub.OE.sup.Hp.

[0124] The present disclosure has been described in conjunction with various embodiments as examples as well as implementations. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed disclosure, from the studies of the drawings, this disclosure and the independent claims. In the claims as well as in the description the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation.