Off-axis audio suppression in an automobile cabin
View Patent ↗The suppression of off-axis audio in an audio environment is provided. Off-axis audio may be considered audio that does not originate from a region of interest. The off-axis audio is suppressed by comparing a phase difference between signals from two microphones to a target slope of the phase difference between signals originating from the region of interest. The target slope can be adapted to allow the region of interest to move with the location of a human speaker such as a driver.
1. A method of off-axis audio suppression in an audio environment comprising:
receiving first and second audio signals from first and second microphones positioned within the audio environment;
calculating a phase difference between the first and second audio signals;
calculating a direction error between the calculated phase difference and a target slope, the target slope defining a desired phase difference between signals from the first and second microphones corresponding to audio originating from a region of interest; and
processing the first and second audio signals based on the calculated direction error to determine if the first and second audio signals correspond to audio originating from the region of interest and to suppress off-axis audio relative to the positions of the first and second microphones and the region of interest and further comprising adjusting the target slope based on the calculated phase difference between the first and second audio signals to adapt the region of interest based on a location of a human speaker within the audio environment.
2. The method of claim 1 , wherein the first and second audio signals are frequency domain representations of a frame of audio received at the corresponding microphone over a time interval, and wherein the method is repeated for subsequent frames of audio.
3. The method of claim 2 , wherein processing the first and second audio signals comprises:
determining if the direction error is less than an on-axis threshold, indicating that the frame of audio represented by the first and second audio signals corresponds to voice audio originating from the region of interest; and
combining the first and second audio signals to enhance the frame of audio when the direction error is less than the on-axis threshold.
4. The method of claim 2 , wherein processing the first and second audio signals comprises:
determining if the direction error is greater than an off-axis threshold, indicating that the frame of audio represented by the first and second audio signals corresponds to noise audio or to voice audio originating from outside the region of interest; and
combining the first and second audio signals to suppress the frame of audio when the direction error is greater than the off-axis threshold.
5. The method of claim 2 , wherein processing the first and second audio signals comprises:
determining if the direction error is between an off-axis threshold and an on-axis threshold, indicating that the frame of audio represented by the first and second audio signals corresponds to a combination of voice audio originating from the region of interest and noise audio or to voice audio originating from outside the region of interest;
calculating a mixing mask as a function of frequency; and
combining the first and second audio signals using the mixing mask when the direction error is between than the off-axis threshold and the on-axis threshold.
6. An apparatus performing off-axis audio suppression in an audio environment comprising:
a processor and memory configuring the apparatus to provide:
a target slope stored in memory defining a desired phase difference between signals from first and second microphones corresponding to audio originating from a region of interest;
a target adaptation component adjusting the target slope based on a calculated phase difference between the first and second audio signals to adapt the region of interest based on a location of a human speaker within the audio environment
a source-locating component calculating a direction error between the target slope and a phase difference between first and second audio signals received from the first and second microphones; and
an audio mixer processing the first and second audio signals based on the calculated direction error to suppress off-axis audio relative to the positions of the first and second microphones and the region of interest.
7. The apparatus of claim 6 , further comprising a signal processing component to convert the first and second audio signals to frequency domain representations of a frame of audio received at the corresponding microphone over a time interval.
8. The apparatus of claim 7 , wherein the audio mixer determines if the direction error is less than an on-axis threshold, indicating that the frame of audio represented by the first and second audio signals corresponds to voice audio originating from the region of interest and combines the first and second audio signals to enhance the frame of audio when the direction error is less than the on-axis threshold.
9. The apparatus of claim 7 , wherein the audio mixer determines if the direction error is greater than an off-axis threshold, indicating that the frame of audio represented by the first and second audio signals corresponds to noise audio or to voice audio originating from outside the region of interest and combines the first and second audio signals to suppress the frame of audio when the direction error is greater than the off-axis threshold.
10. The apparatus of claim 7 , wherein the audio mixer determines if the direction error is between an off-axis threshold and an on-axis threshold, indicating that the frame of audio represented by the first and second audio signals corresponds to a combination of voice audio originating from the region of interest and noise audio or to voice audio originating from outside the region of interest and combines the first and second audio signals using a mixing mask calculated as a function of frequency when the direction error is between the off-axis threshold and the on-axis threshold.
11. A computer readable non-transitory memory containing instructions which when executed by a processor perform a method of off-axis audio suppression in an audio environment comprising:
receiving first and second audio signals from first and second microphones positioned within the audio environment;
calculating a phase difference between the first and second audio signals;
calculating a direction error between the calculated phase difference and a target slope, the target slope defining a desired phase difference between signals from the first and second microphones corresponding to audio originating from a region of interest; and
processing the first and second audio signals based on the calculated direction error to determine if the first and second audio signals correspond to audio originating from the region of interest and to suppress off-axis audio relative to the positions of the first and second microphones and the region of interest and further comprising adjusting the target slope based on the calculated phase difference between the first and second audio signals to adapt the region of interest based on a location of a human speaker within the audio environment.
12. The computer readable non-transitory memory of claim 11 , wherein the first and second audio signals are frequency domain representations of a frame of audio received at the corresponding microphone over a time interval, and wherein the method is repeated for subsequent frames of audio.
13. The computer readable non-transitory memory of claim 11 , wherein processing the first and second audio signals comprises:
determining if the direction error is less than an on-axis threshold, indicating that the frame of audio represented by the first and second audio signals corresponds to voice audio originating from the region of interest; and
combining the first and second audio signals to enhance the frame of audio when the direction error is less than the on-axis threshold.
14. The computer readable non-transitory memory of claim 11 , wherein processing the first and second audio signals comprises:
determining if the direction error is greater than an off-axis threshold, indicating that the frame of audio represented by the first and second audio signals corresponds to noise audio or to voice audio originating from outside the region of interest; and
combining the first and second audio signals to suppress the frame of audio when the direction error is greater than the off-axis threshold.
15. The computer readable non-transitory memory of claim 11 , wherein processing the first and second audio signals comprises:
determining if the direction error is between an off-axis threshold and an on-axis threshold, indicating that the frame of audio represented by the first and second audio signals corresponds to a combination of voice audio originating from the region of interest and noise audio or to voice audio originating from outside the region of interest;
calculating a mixing mask as a function of frequency; and
combining the first and second audio signals using the mixing mask when the direction error is between than the off-axis threshold and the on-axis threshold.