Direction of arrival estimation and sound source enhancement in the presence of a reflective surface apparatuses, methods, and systems

1. A processor-implemented method for sound-source enhancement in the presence of a reflective surface, the method comprising:

capturing a signal from a sound source using a sensor array having a plurality of sensors, the sensor array being positioned between the sound source and the reflective surface;

calculating a half-space propagation model by determining a modified steering vector associated with a plane sound wave produced by the sound source as a function of signal direction and a reflectivity value;

calculating a half-space spatial coherence model by dividing a sphere with its center on the reflective surface into two mirror symmetric parts intersected by a plane to create two half spheres and accounting for a finite number of uniformly distributed plane wave sources originating from a surface of a half sphere of the two half spheres which includes the sensor array by considering a uniform distribution of plane wave sources on the half sphere and letting a signature of each plane wave be expressed by the half-space propagation model;

creating a half-space signal-enhancement module using the half-space propagation model and the half-space spatial coherence model; and

applying the half-space signal-enhancement module to the signal to enhance the signal.

2. The method of claim 1 , wherein the signal is a plurality of signals, and wherein the method further comprises applying a filter to the plurality of signals to increase separation of the signals.

3. The method of claim 1 , wherein the signal-enhancement module is a beamformer.

4. The method of claim 1 , wherein the reflectivity value is assumed to be constant with frequency.

5. The method of claim 1 , further comprising calculating the reflectivity value by:

treating the sound source as a single source at a known direction with respect to an acoustic center for the sound source;

defining a model of auto-spectra and inter-channel cross-spectra terms for the single source as a function of a frequency of the sound source; and

estimating g mirror source relative gain at a plurality of time-frequency points based on the model.

6. The method of claim 5 , further comprising using an auxiliary function and forming a histogram from time-frequency estimates of reflectivity values to estimate a final reflectivity value.

7. The method of claim 1 , wherein the signal direction is received at the signal enhancement module from an external direction-of-arrival (DOA) module.

8. The method of claim 1 , further comprising deriving the signal direction by:

estimating a direction of arrival (DOA) of the sound source by using a predefined grid search to find a plurality of DOAs by finding the most energetic DOA at each time-frequency point;

processing the plurality of DOAs across time to form a histogram; and

localizing the most prominent peaks in the histogram.

9. A system for sound-source enhancement in the presence of a reflective surface, the system comprising:

a sensor array having a plurality of sensors, the sensor array being positioned between a sound source and the reflective surface;

a half-space signal enhancer configured to:

calculate a half-space propagation model by determining a modified steering vector associated with a plane sound wave produced by the sound source as a function of signal direction and a reflectivity value;

calculate half-space spatial coherence model by dividing a sphere with its center on the reflective surface into two mirror symmetric parts intersected by a plane to create two half spheres and accounting for a finite number of uniformly distributed plane wave sources originating from a surface of a half sphere of the two half spheres which includes the sensor array by considering a uniform distribution of plane wave sources on the half sphere and letting a signature of each plane wave be expressed by the half-space propagation model;

enhance the signal based on the half-space propagation model and the half-space coherence model.

10. The system of claim 9 , wherein the signal is a plurality of signals, and wherein the system is further configured to apply a filter to the plurality of signals to increase separation of the signals.

11. The system of claim 9 , wherein the signal enhancer is a beamformer.

12. The system of claim 9 , wherein the reflectivity value is assumed to be constant with frequency.

13. The system of claim 9 , wherein the half-space signal enhancer is further configured to:

treat the sound source as a single source at a known direction with respect to an acoustic center for the sound source;

define a model of auto-spectra and inter-channel cross-spectra terms for the single source as a function of a frequency of the sound source; and

estimate a mirror source relative gain at a plurality of time-frequency points based on the model.

14. The system of claim 13 wherein the half-space signal enhancer is further configured to use an auxiliary function and form a histogram from time-frequency estimates of reflectivity values to estimate a final reflectivity value.

15. The system of claim 9 , wherein the signal direction is received at the signal enhancer from a direction-of-arrival module external to the signal enhancer.

16. The system of claim 9 , wherein the signal enhancer is configured to derive the signal direction by:

estimating a direction of arrival (DOA) of the sound source by using a predefined grid search to find a plurality of DOAs by finding the most energetic DOA at each time-frequency point;

processing the plurality of DOAs across time to form a histogram; and

localizing the most prominent peaks in the histogram.

17. A processor-readable non-transitory tangible medium for sound-source enhancement in the presence of a reflective surface, the medium storing processor-issuable-and-generated instructions to:

capture a signal from a sound source using a sensor array having a plurality of sensors, the sensor array being positioned between the sound source and the reflective surface at a predetermined distance from the reflective surface;

calculate a half-space propagation model by determining a modified steering vector associated with a plane sound wave produced by the sound source as a function of signal direction and a reflectivity value;

calculate a half-space spatial coherence model by dividing a sphere with its center on the reflective surface into two mirror symmetric parts intersected by a plane to create two half spheres and accounting for a finite number of uniformly distributed plane wave sources originating from a surface of a half sphere of the two half spheres which includes the sensor array by considering a uniform distribution of plane wave sources on the half sphere and letting g signature of each plane wave be expressed by the half-space propagation model;

create a half-space signal-enhancement module using the half-space propagation model and the half-space coherence model; and

apply the half-space signal-enhancement module to the signal to enhance the signal.

18. The processor-readable tangible medium of claim 17 , wherein the medium includes processor-issuable-and-generated instructions to:

treat the sound source as a single source at a known direction with respect to an acoustic center for the sound source;

define a model of auto-spectra and inter-channel cross-spectra terms for the single source as a function of a frequency of the sound source; and

estimate 8 mirror source relative gain at a plurality of time-frequency points based on the model.

19. The processor-readable tangible medium of claim 17 , wherein the medium includes processor-issuable-and-generated instructions to:

estimate a direction of arrival (DOA) of the sound source by using a predefined grid search to find a plurality of DOAs by finding the most energetic DOA at each time-frequency point;

process the plurality of DOAs across time to form a histogram; and

localize the most prominent peaks in the histogram.

20. The processor-readable tangible medium of claim 17 , wherein the medium includes processor-issuable-and-generated instructions to apply a filter to a plurality of signals to increase separation of the signals.