Wearable electronic device with low frequency noise reduction

Abstract

A method at a wearable electronic device with: a first electro-acoustic input transducer and a second electro-acoustic input transducer arranged to pick up a first acoustic signal and convert the first acoustic signal to a first microphone signal and second microphone signal; and a third electro-acoustic input transducer arranged to pick up a second acoustic signal and convert the second acoustic signal to a third microphone signal; and a processor (140). The method comprises: generating a beamformed signal based on the first microphone signal (x1) and the second microphone signal; estimating a first frequency value representing a fundamental frequency in one or more of: the first microphone signal, the second microphone signal and the third microphone signal; configuring a first filter with one or more passbands at one or more integer multiples of the first frequency value and one or more stop bands adjacent the one or more stop bands; and filtering, using the first filter, one or more of: the first microphone signal, the second microphone signal and the beamformed signal.

Claims

1. A method comprising: at a wearable electronic device capable of detecting a voiced speech component, the device having: a first electro-acoustic input transducer and a second electro-acoustic input transducer arranged to pick up a first acoustic signal and convert the first acoustic signal to a first microphone signal and a second microphone signal; and a third electro-acoustic input transducer arranged to pick up a second acoustic signal and convert the second acoustic signal to a third microphone signal; and a processor: generating a beamformed signal based on the first microphone signal and the second microphone signal; estimating a first frequency value representing a fundamental frequency of a voiced speech component in one or more of: the first microphone signal, the second microphone signal and the third microphone signal; configuring a first filter with one or more first passbands, including an upper first passband, at one or more integer multiples of the first frequency value; and one or more first stop bands adjacent the one or more passbands; wherein the first filter has a second passband above the upper passband; filtering, using the first filter, one or more of: the first microphone signal, the second microphone signal and the beamformed signal.

2. A method according to claim 1, wherein the first electro-acoustic input transducer and the second electro-acoustic input transducer are arranged to pick up the first acoustic signal from an ambient space; and wherein the third electro-acoustic input transducer is arranged to pick up the second acoustic signal from an enclosed space different from the ambient space; and wherein the first frequency value is estimated based on the third microphone signal.

3. A method according to claim 1, comprising: detecting periods with presence of voiced speech and periods with absence of voiced speech in one or more of: the first microphone signal, the second microphone signal and the third microphone signal; in accordance with detecting presence of voiced speech, estimating the first frequency value based on a period with presence of voiced speech.

4. A method according to claim 1, comprising: detecting periods with presence of voiced speech and periods with absence of voiced speech in one or more of: the first microphone signal, the second microphone signal and the third microphone signal; in accordance with detecting absence of voiced speech, reconfiguring the first filter, including dispensing with at least one of the one or more first stop bands.

5. A method comprising: at a wearable electronic device with: a first electro-acoustic input transducer and a second electro-acoustic input transducer arranged to pick up a first acoustic signal and convert the first acoustic signal to a first microphone signal and a second microphone signal; and a third electro-acoustic input transducer arranged to pick up a second acoustic signal and convert the second acoustic signal to a third microphone signal; and a processor: generating a beamformed signal based on the first microphone signal and the second microphone signal; estimating a first frequency value representing a fundamental frequency in one or more of: the first microphone signal, the second microphone signal and the third microphone signal; configuring a first filter with one or more first passbands, including an upper first passband, at one or more integer multiples of the first frequency value; and one or more first stop bands adjacent the one or more passbands; wherein the first filter has a second passband above the upper passband; filtering, using the first filter, one or more of: the first microphone signal, the second microphone signal and the beamformed signal and wherein the second passband is implemented by a high-pass filter with a lower cut-off frequency; comprising: detecting periods with presence of voiced speech and periods with absence of voiced speech in one or more of: the first microphone signal, the second microphone signal and the third microphone signal; in accordance with determining absence of voiced speech, reconfiguring the first filter, including setting a lower cut-off frequency of the high-pass filter at a predetermined lower cut-off frequency value.

6. A method according to claim 1, comprising: performing frequency spectrum equalization, using a second filter, to compensate for a low-frequency roll-off, of the beamformer.

7. A method according to claim 1, wherein the first filter has respective gains at the one or more passbands at the one or more integer multiples of the first frequency value; wherein the respective gains compensate for a low frequency roll-off, of the beamformer.

8. A method according to claim 1, wherein the first filter comprises a comb filter.

9. A method according to claim 1, wherein the upper first passband is located at a first integer multiple of the first frequency value; and wherein the first integer multiple is determined based on one or both of: a predetermined integer value and a value based on one or more of: the first microphone signal, the second microphone signal and the third microphone signal.

10. A method according to claim 1, comprising: transmitting a signal which is based on the beamformed signal to a remote electronic device.

11. A method according to claim 1, wherein the wearable electronic device comprises a first electro-acoustic output transducer arranged to emit an acoustic signal at an enclosed space established by at least a portion of the wearable electronic device at a wearer's ear.

12. A method according to claim 1, comprising: performing active noise cancellation based on a feedback signal, which is based on the third microphone signal; wherein an active noise cancellation signal is emitted by the first electro-mechanical output transducer.

13. A method according to claim 1, comprising: performing short term Fourier transform of one or more of: the first microphone signal, the second microphone signal, the third microphone signal, the first microphone signal when filtered using the first filter, the second microphone signal when filtered using the first filter; and performing inverse short term Fourier transform of a signal based on the beamformed signal; wherein one or more of the first filtering, the second filtering, equalization and beamforming is performed in the frequency domain.

14. A wearable electronic device comprising: a first electro-acoustic input transducer and a second electro-acoustic input transducer arranged to pick up a first acoustic signal and convert the first acoustic signal to a first microphone signal and second microphone signal; a third electro-acoustic input transducer arranged to pick up a second acoustic signal and convert the second acoustic signal to a third microphone signal; and a processor configured to generate a beamformed signal based on the first microphone signal and the second microphone signal; estimate a first frequency value representing a fundamental frequency in one or more of: the first microphone signal, the second microphone signal and the third microphone signal; configure a first filter with one or more first passbands, including an upper first passband, at one or more integer multiples of the first frequency value; and one or more first stop bands adjacent the one or more passbands; wherein the first filter has a second passband above the upper passband; filter, using the first filter, one or more of: the first microphone signal, the second microphone signal and the beamformed signal and wherein the second passband is implemented by a high-pass filter with a lower cut-off frequency; and detecting periods with presence of voiced speech and periods with absence of voiced speech in one or more of: the first microphone signal, the second microphone signal and the third microphone signal; in accordance with determining absence of voiced speech, reconfiguring the first filter, including setting a lower cut-off frequency of the high-pass filter at a predetermined lower cut-off frequency value.

15. A signal processing module for a headphone, an earphone or a headset; wherein the signal processing module is configured to perform the method according to claim 14.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) A more detailed description follows below with reference to the drawing, in which:

(2) FIG. 1 shows a block diagram of a wearable electronic device with a processor in a first embodiment;

(3) FIG. 2 shows a block diagram of a wearable electronic device with a processor in a second embodiment;

(4) FIG. 3 shows a first example of an illustrative frequency gain characteristic;

(5) FIG. 4 shows a second example of an illustrative frequency gain characteristic;

(6) FIG. 5 shows a first embodiment of the first filter;

(7) FIG. 6 shows a second embodiment of the first filter;

(8) FIG. 7 shows a first embodiment including an equalizer;

(9) FIG. 8 shows a second embodiment including an equalizer;

(10) FIG. 9 shows a wearable electronic device embodied as a pair of headphones or as a pair of earphones; and

(11) FIG. 10 shows a wearable electronic device configured as a headset or a hearing instrument.

DETAILED DESCRIPTION

(12) FIG. 1 shows a block diagram of a wearable electronic device with a processor in a first embodiment. The block diagram shows a wearable electronic device 100 with a first electro-acoustic input transducer 121 in the form of a first microphone and a second electro-acoustic input transducer 122 in the form of a second microphone. The microphones are arranged to pick up a first acoustic signal and convert the first acoustic signal to a first microphone signal, x1, and a second microphone signal, x2. The wearable electronic device also comprises a third electro-acoustic input transducer 131 in the form of a third microphone arranged to pick up a second acoustic signal and convert the second acoustic signal to a third microphone signal x3; a first electro-acoustical output transducer 132 in the form of a loudspeaker and a processor 140. The processor 140 may be comprised by a processing module. The processor 140 may be in communication with a remote electronic device (not shown) via a bi-directional port transmitting or receiving a communication signal t1 including, in an outgoing direction, a representation of the first acoustic signal. In an ingoing direction, the communication signal t1 may include a representation of a signal for being reproduced as an acoustic signal e.g. by means of the electro-acoustic output transducer 132.

(13) The first electro-acoustic input transducer 121 and the second electro-acoustic input transducer 122 are commonly designated electro-acoustic transducer elements 120. The electro-acoustic transducer elements 120 may be arranged e.g. in a left side earpiece and a further electro-acoustic transducer element 120 may be arranged in a right side earpiece. The electro-acoustic transducer elements 120 may comprise one or more additional electro-acoustic input transducers e.g. arranged in an array.

(14) The electro-acoustic output transducer 132 and the third electro-acoustic input transducer 131 are commonly designated electro-acoustic transducer elements 130. The electro-acoustic transducer elements 130 may be arranged e.g. in a left side earpiece and a further electro-acoustic transducer elements 130 may be arranged in a right side earpiece.

(15) The processor 140 receives the first microphone signal x1 and the second microphone signal x2, which in some examples are digital microphone signals, and is configured to generate a beamformed signal b1 based on at least the first microphone signal x1 and the second microphone signal x2.

(16) The processor 140 estimates, by a frequency estimator F-EST, 141, a first frequency value, f1, representing a fundamental frequency in the third microphone signal x3. In some examples the frequency estimator 141 alternatively or additionally receives one or more of: the first microphone signal (x1) and the second microphone signal (x2).

(17) The first frequency value, f1, is received by a filter configurator F-config, 142 that configures a first filter 150 with: one or more first passbands including an upper first passband, at one or more integer multiples of the first frequency value, f1; and one or more first stop bands adjacent the one or more passbands.

(18) This enables suppression of noise at other frequencies than at least at the fundamental frequency and at zero, one or more higher order harmonic frequencies. The filter configurator F-config, 142 may output signals c1 or c1 and c2 with a representation, e.g. filter coefficients, of the first filter or at least a portion thereof.

(19) To also pass signals at higher frequencies, which may not relate to or be different from a particular harmonic frequencies, the first filter 150 also has a second passband above the upper first passband. Thus, above one, two, three or any number of harmonic frequencies, all frequencies can be passed. In some embodiments the number of first passbands is fixed and in other embodiments, the number of passbands is adjusted dynamically.

(20) The first filter 150 performs the filtering of the first microphone signal, x1, and the second microphone signal, x2. In this example, the first filter comprises a first filter section 151 and a second filter section 152 filtering the first microphone signal, x1, and the second microphone signal, x2, respectively. The first filter section and the second filter section may be identical or different.

(21) In some examples the first signal c1 is similar or identical to the second signal c2 or at least the first signal c1 and the second signal c2 represents the same set of filter coefficients. In some examples, as shown herein in connection with FIG. 2, the first filter may be arranged to filter the beamformed signal b1. The first filter may be implemented in many different ways, some of which are described herein. Some characteristics of the first filter are illustrated herein. A filtered first microphone signal, z1, and a filtered second microphone signal, z2, are output from the first filter 150 and input to beamformer 143, wherein beamforming based on the filtered microphone signals is performed.

(22) The filter configurator F-config, 142 may operate on a recurring basis to adapt the first filter, e.g. by reconfiguration of the first filter, to a currently estimated fundamental frequency. Reconfiguration of the first filter may include updating filter coefficients of the first filter.

(23) In some embodiments, the beamformed signal, b1, is transmitted to a remote electronic device via the transceiver 144. In some examples, the beamformed signal b1 or a signal based on the beamformed signal is sent to the electro-acoustic output transducer 132 e.g. to compensate for a hearing loss of the user of the wearable electronic device and/or to provide a so-called side-tone signal to the user of the wearable device as it is known in the art. In some examples, the beamformed signal, b1, or a signal based on the beamformed signal is mixed, by a first mixer 147, with a received signal, r1, from a remote electronic device via the transceiver 144. The mixer 147 may be an adder or a switch selecting either the beamformed signal or a signal based on the beamformed signal and the received signal, r1.

(24) In some embodiments, active noise cancellation is performed by unit ANC, 145, which receives the microphone signal x3 and outputs an active noise cancellation signal, a1, which is provided as a feedback signal to the electro-acoustic output transducer 132 via a second mixer 146. The second mixer 146 mixes the signal al with a signal from the first adder or with one or both of: a received signal, r1, and the beamformed signal b1 or a signal based thereon.

(25) FIG. 2 shows a block diagram of a wearable electronic device with a processor in a second embodiment. In this second embodiment the first filter is designated by reference numeral 250 and is arranged to filter the beamformed signal, b1, and to provide a filtered signal, z1. On the one hand, an advantage of the second embodiment, compared to the first embodiment, is that the first filter, here designated by reference numeral 250, can be simpler since it may be sufficient to filter one channel, rather than two channels or more. On the other hand, an advantage of the first embodiment is that first filter suppresses noise before beamforming is performed. Thereby, noise suppressed microphone signals, rather than the microphone signals, are input to the beamformer 143.

(26) It should be noted that the second embodiment may include one or more of the elements described in connection with the first configuration. For instance, the second embodiment may include elements related to one or more of: active noise cancellation, side-tone generation, and compensation for a hearing loss.

(27) FIG. 3 shows a first example of an illustrative frequency gain transfer function. The frequency gain transfer function is shown in a diagram with an abscissa (x-axis) designating frequencies, F, and an ordinate (y-axis) designating gain. The first filter 150; 250 described above has a characteristic with one or more first passbands 303; 304; 305 at one or more integer multiples of the first frequency value f1. The one or more first passbands includes an uppermost first passband 305, which is located at a higher frequency than the other first passbands 303; 304. These first passbands passes components of voiced speech having a fundamental frequency at a lowermost first passband 303. It is shown that the first filter has three first passbands, however the first filter may have one, two, four, five or a higher number of first passbands.

(28) The one or more first passbands 303; 304; 305 are each separated by a first stop band. Thus, one or more first stop bands 306;307; 308 are located adjacent the one or more first passbands.

(29) At least in some embodiments, but not necessarily in all embodiments, the first filter has a second passband 311 at or above the upper passband 305. The second passband 311 lets frequencies above at least one harmonic of the voiced speech signal pass through. The second passband may extend up to or beyond 5-20 Khz. The second passband may have a lower cut-off frequency at fn1 at least when the first filter includes the one or more first passbands. The lower cut-off frequency at fn1 may be located at or above the uppermost first passband 305; in some examples at one or more harmonic frequencies above the uppermost first passband.

(30) The uppermost first passband 305 may be located below 500 Hz or below a lower or higher frequency. As an illustrative example, the transfer function of the first filter, or at least a portion thereof, including the first passbands and the second passband is shown in FIG. 4 and is designated by reference numeral 402—and in another example designated by reference numeral 403.

(31) Also shown is an example of a transfer function 310 of a beamformer with a low frequency roll-off. The transfer function 310 may roll off at a corner frequency, fbf. Also shown is a transfer function 309 of an equalizer configured to compensate for the low frequency roll-off of the beamformer. The equalizer may have a transfer function that compensates for the low frequency roll-off of the beamformer.

(32) In some embodiments the first filter has respective gains G1; G2; G3 at the one or more first passbands 306; 307;308 at the one or more integer multiples of the first frequency value; wherein the respective gains compensate for the low frequency roll-off of the beamformer. This is illustrated in FIG. 4 by transfer function 403 (dashed curve). Thereby the first filter is enabled to perform at least some frequency spectrum equalization. In some examples, the respective gains are computed as a function of a respective integer multiple of the first frequency value and a transfer function of the beamformer.

(33) FIG. 4 shows a second example of an illustrative frequency gain transfer function. In this example it is further shown that the first filter may be (re-)configured with a second passband 401 that is different from the second passband 311 shown above. In particular it can be seen that the lower cut-off frequency of the second passband is changed from a frequency fn1 to another frequency fn2. Frequency fn2 may be at a lower or higher frequency than fn1.

(34) In some embodiments, in accordance with detecting absence of voiced speech, the first filter 150; 250 may be reconfigured, including dispensing with at least one of the one or more first stop bands. Then, the first filter may be further reconfigured including setting a lower cut-off frequency of the second passband at a predetermined lower cut-off frequency value, fn2. As shown the second passband 311; 401 may be a high-pass band.

(35) FIG. 5 shows a first embodiment of the first filter. In this embodiment, the first filter comprises parallel filter sections each dedicated to respective passbands. Inputs {b1;x1;x2} and outputs {b1;x1;x2} refer to the above reference numerals e.g. in FIGS. 1 and 2.

(36) The first filter section 502 may be a band-pass filter with a passband at the fundamental frequency f1. Correspondingly, the second filter section 503 and the third filter section 504 may be band-pass filters with a passband at two and three times the fundamental frequency f1, respectively, i.e. at 2×f1 and 3×f1.

(37) The first filter also comprises a fourth filter section, 505, dedicated to the second passband, which may be a high-pass band.

(38) In this embodiment the filter sections, e.g. related to the first passbands, may be followed by gain stages G1, G2 and G3, respectively. The gain stages may provide frequency equalization as described above. Signals from the parallel filter sections are added or otherwise mixed by mixer 506.

(39) FIG. 6 shows a second embodiment of the first filter. This embodiment of the first filter 601 may be used in connection with an implementation of the first filter using a comb filter 603. Here, in a first parallel filter section, the comb filter is band-limited by means of a low-pass filter 602. The low-pass filter 602 may thus determine an uppermost first passband of the first filter. In particular an upper cut-off frequency of the low-pass filter 602 may determine an uppermost first passband of the first filter since the output from the comb filter 603 is band limited. The order of the comb filter and the low-pass filter may be interchanged. In a second parallel filter section, a high-pass filter 604 passes at least some frequencies above the uppermost first passband. Signals from the parallel filter sections are added or otherwise mixed by mixer 605.

(40) FIG. 7 shows a first embodiment including an equalizer. In this embodiment an equalizer 701 follows the first filter 250. Output, z2, from the equalizer may be used as signal z1 in the embodiment shown in FIG. 2.

(41) FIG. 8 shows a second embodiment including an equalizer. In this embodiment the equalizer 701 follows the beamformer 143 e.g. in accordance with FIG. 1. Thus, the equalizer receives the beamformed signal b1. Output, z2, from the equalizer 701 may be used as signal b1 in the embodiment shown in FIG. 1.

(42) FIG. 9 shows a wearable electronic device embodied as a pair of headphones or as a pair of earphones. The pair of headphones 901 comprises a headband 904 carrying a left earpiece 902 and a right earpiece 903 which may also be designated earcups. The pair of earphones 910 comprises a left earpiece 911 and a right earpiece 912.

(43) The earpieces comprise at least one electro-mechanical output transducer, e.g. a loudspeaker, in each earpiece. The earpieces also comprise at least a first electro-mechanical input transducer and a second electro-mechanical input transducer, e.g. in the form of microphones. The earpieces may also comprise the third electro-mechanical input transducer e.g. in the form a microphone.

(44) For the headphones 901, the first electro-mechanical input transducer and the second electro-mechanical input transducer may be arranged pairwise e.g. at a rim 905 of one or both of the earpieces 902 and 903 e.g. as outside microphones to pick up a first acoustic signal predominantly from an ambient space surrounding the earpiece. The third electro-mechanical input transducer may be arranged to pick up a second acoustic signal predominantly from an enclosed space 906 established between the earpiece and the user.

(45) For the pair of earphones 910, the first electro-mechanical input transducer and the second electro-mechanical input transducer may be arranged pairwise e.g. at a protrusion 913 of one or both of the earpieces 911 and 912 e.g. as outside microphones to pick up a first acoustic signal predominantly from an ambient space surrounding of the earpiece. The third electro-mechanical input transducer may be arranged to pick up the second acoustic signal predominantly from an enclosed space 914 established between the earpiece and the user.

(46) The headphone or pair of earphones may include a processing module.

(47) FIG. 10 shows a wearable electronic device configured as a headset or a hearing instrument. There is shown a top-view of a person's head 151 in connection with a headset left device 152 and a headset right device 153. The headset left device 152 and the headset right device 153 may be in wired or wireless communication as it is known in the art.

(48) The headset left device 152 comprises first and second microphones 154, 155, a miniature loudspeaker 157 and a processor 156. Additionally, the headset left device 152 comprises a third microphone 162. Correspondingly, the headset right device 13 comprises microphones 157, 158, a miniature loudspeaker 160 and a processor 159. Additionally, the headset right device 153 comprises a third microphone 161.

(49) The microphones 154, 155 may be arranged in an array of microphones comprising further microphones e.g. one, two, or three further microphones. Correspondingly, microphones 157, 158 may be arranged in an array of microphones comprising further microphones e.g. one, two, or three further microphones. The further microphones may be input to beamforming.