Headset with ambient noise reduction system
View Patent ↗A headset adapted to transmitting an outgoing audio signal (Tx) and comprising a voice microphone and at least one ambient microphone. The headset comprises an ambient noise reduction block (ANR), which is adapted to reduce the level of ambient noise in the outgoing audio signal (Tx). The ambient noise reduction block (ANR) includes the measuring the levels of the voice microphone signal (X) and ambient microphone signal (Y) to estimate a characteristic constant level drop between the voice microphone signal (X) and the ambient microphone signal (Y), which is characteristic for the headset user talking. A time-varying filter passes the voice microphone signal (X), when the level difference is larger than characteristic constant level drop (CLD) and attenuates the voice microphone signal (X), if the level difference is below characteristic constant level drop.
1. A headset adapted to transmitting an outgoing audio signal, the headset comprises:
a) a voice microphone generating a voice microphone signal (X),
b) at least one ambient microphone generating an ambient microphone signal (Y), wherein, when the headset is worn by a user, the voice microphone is arranged at a first distance (D 1 ) from the users mouth, and the ambient microphone is arranged at a second distance (D 2 ) from the users mouth, wherein the first distance (D 1 ) is smaller than the second distance (D 2 ), a right ambient microphone generating a right ambient microphone signal (YR) and a left ambient microphone generating a left ambient microphone signal (YL),
c) an ambient noise reduction block (ANR), which is adapted to reduce the level of ambient noise in the outgoing audio signal (Tx), wherein the ambient noise reduction block (ANR) includes the following steps:
I. detecting that a headset user is talking,
II. measuring the levels of the voice microphone signal (X) and ambient microphone signal (Y) to estimate a characteristic constant level drop between the voice microphone signal (X) and the ambient microphone signal (Y), which is characteristic for the headset user talking,
III. constructing a time-varying filter for removing noise,
IV. detecting a level difference between the voice microphone signal (X) and the ambient microphone signal (Y),
V. comparing the level difference between the voice microphone signal (X) and ambient microphone signal (Y) with the characteristic constant level drop,
VI. the time-varying filter passes the voice microphone signal (X), when the level difference is larger than characteristic constant level drop (CLD),
VII. the time-varying filter attenuates the voice microphone signal (X), if the level difference is below the characteristic constant level drop,
VIII. wherein, when the headset is worn by a user, the right ambient microphone and the left ambient microphone both are arranged at the second distance (D 2 ) from the users mouth, wherein the ambient microphone signal (Y) received by the ambient noise reduction block (ANR) is the difference between one of the first and second ambient microphone signals (YR) and an attenuated version (YL′) of the other of the first and second ambient microphone signals (YR, YL).
2. A headset according to claim 1 , wherein the steps 1.-VII. are taking place continuously.
3. A headset according to claim 2 , wherein the steps 1.-VII. are taking place multiple times per second.
4. A headset according to claim 3 , wherein the steps 1.-VII. are taking place more than 100 times per second.
5. A headset according to claim 1 , wherein the voice microphone signal (X) and the ambient microphone signal (Y) are separated into a number of frequency bands.
6. A headset according to claim 5 , wherein a fast Fourier transform algorithm transforms the voice microphone signal (X) and the ambient microphone signal (Y) into the frequency domain before reaching the ambient noise reduction block (ANR) and where an inverse Fourier transform algorithm transforms the Tx signal into the time domain.
7. A headset according to claim 6 , wherein the attenuated version (YL′) of the first or the second ambient microphone signal is attenuated between 3dB and 9dB, preferably approximately 6dB.
8. A headset according to claim 7 , wherein the right ambient microphone and the left ambient microphone are symmetrically arranged on each side of the sagittal plane when the headset is worn.
9. A headset according to claim 6 , wherein the headset comprises a first earphone and a second earphone wherein the right ambient microphone is located at the first earphone and the left ambient microphone is arranged at the second earphone.
10. A headset according to claim 1 wherein the at least one ambient microphone is an active noise cancellation microphone.
11. A headset according to claim 1 , wherein the headset comprises a microphone arm, wherein the voice microphone is located at the free end of the microphone arm.
12. A headset adapted to transmitting an outgoing audio signal, the headset comprises:
a) a voice microphone generating a voice microphone signal (X),
b) at least one ambient microphone generating an ambient microphone signal (Y), wherein, when the headset is worn by a user, the voice microphone is arranged at a first distance (D 1 ) from the users mouth, and the ambient microphone is arranged at a second distance (D 2 ) from the users mouth, wherein the first distance (D 1 ) is smaller than the second distance (D 2 ), a first ambient microphone generating a right ambient microphone signal (YR) and a second ambient microphone generating a left ambient microphone signal (YL),
c) an ambient noise reduction block (ANR), which is adapted to reduce the level of ambient noise in the outgoing audio signal (Tx), wherein the ambient noise reduction block (ANR) includes the following steps:
I. detecting that a headset user is talking,
II. measuring the levels of the voice microphone signal (X) and ambient microphone signal (Y) to estimate a characteristic constant level drop between the voice microphone signal (X) and the ambient microphone signal (Y), which is characteristic for the headset user talking,
III. constructing a time-varying filter for removing noise,
IV. detecting a level difference between the voice microphone signal (X) and the ambient microphone signal (Y),
V. comparing the level difference between the voice microphone signal (X) and ambient microphone signal (Y) with the characteristic constant level drop,
VI. the time-varying filter passes the voice microphone signal (X), when the level difference is larger than characteristic constant level drop (CLD),
VII. the time-varying filter attenuates the voice microphone signal (X), if the level difference is below the characteristic constant level drop,
VIII. wherein, when the headset is worn by a user, the first ambient microphone and the second ambient microphone both are arranged at the second distance (D 2 ) from the user's mouth, wherein the ambient microphone signal (Y) received by the ambient noise reduction block (ANR) is the difference between one of the first and second ambient microphone signals (YR) and an attenuated version (YL′) of the other of the first and second ambient microphone signals (YR, YL).