Nearfield spherical microphone arrays for speech enhancement and dereverberation
Download
1 / 25

Nearfield Spherical Microphone Arrays for speech enhancement and dereverberation - PowerPoint PPT Presentation


  • 226 Views
  • Uploaded on

Nearfield Spherical Microphone Arrays for speech enhancement and dereverberation. Etan Fisher Supervisor: Dr. Boaz Rafaely. Microphone Arrays. Spatial sound acquisition Sound enhancement Applications: reverberation parameter estimation dereverberation video conferencing. Spheres.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Nearfield Spherical Microphone Arrays for speech enhancement and dereverberation' - delila


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Nearfield spherical microphone arrays for speech enhancement and dereverberation l.jpg

Nearfield Spherical Microphone Arraysfor speech enhancement and dereverberation

Etan Fisher

Supervisor:

Dr. Boaz Rafaely


Microphone arrays l.jpg
Microphone Arrays

  • Spatial sound acquisition

  • Sound enhancement

  • Applications:

    • reverberation parameter estimation

    • dereverberation

    • video conferencing


Spheres l.jpg
Spheres

  • The sphere as a symmetrical, natural entity.

  • Spherical symmetry

  • Facilitates direct sound field analysis:

    • Spherical Fourier transform

    • Spherical harmonics

Photo by Aaron Logan


Nearfield spherical microphone array l.jpg
Nearfield Spherical Microphone Array

  • Generally, the farfield, plane wave assumption is made (Rafaely, Meyer & Elko).

  • In the nearfield, the spherical wave-front must be accounted for.

  • Examples:

    • Close-talk microphone

    • Nearfield music recording

    • Multiple speaker / video conferencing


Sound pressure spherical wave l.jpg
Sound Pressure - Spherical Wave

  • Sound pressure on sphere r due to point source rp (spherical wave):

  • Spherical harmonics:

From the solution to the wave equation (spherical coordinates):


Sound pressure spherical wave6 l.jpg
Sound Pressure - Spherical Wave

  • Sound pressure on sphere r due to point source rp :

  • Spherical harmonics:

    • The spherical harmonicsare orthogonal and complete.

From the solution to the wave equation (spherical coordinates):


Sound pressure spherical wave7 l.jpg
Sound Pressure - Spherical Wave

  • Sound pressure on sphere r due to point source rp:

  • is the spherical Hankel function.

  • is the modal frequency function (Bessel):




Point source decomposition l.jpg
Point Source Decomposition

  • Sound pressure on sphere r due to point source rp:

  • Spherical Fourier transform:

  • Spatial filter – cancel spherical wave-front, yielding unit amplitude at rp=r0.


Point source decomposition11 l.jpg
Point Source Decomposition

  • Amplitude density:

  • Using the identity:

    where Θ is the angle between Ω and Ωp,


Nearfield criteria l.jpg
Nearfield Criteria

N Order of array

k Wave number

rA

Array

radius

rs

Source

distance


Radial attenuation l.jpg
Radial Attenuation

N = 4; rA (array) = 0.1m; k = kmax

kmax = N/rA = 40

kmax = 2πfmax /343

fmax = 2184 Hz

r0 – Desired source location

rp – Interference location


Radial attenuation14 l.jpg
Radial Attenuation

N = 4; rA (array) = 0.1m; k = kmax/4

kmax = N/rA = 40

kmax = 2πfmax /343

fmax = 2184 Hz

r0 – Desired source location

rp – Interference location


Radial attenuation15 l.jpg
Radial Attenuation

N = 4; rA (array) = 0.1m; k = kmax/10

kmax = N/rA = 40

kmax = 2πfmax /343

fmax = 2184 Hz

r0 – Desired source location

rp – Interference location


Radial attenuation close talk l.jpg
Radial Attenuation –“Close Talk”

N = 2; rA (array) = 0.05 m; k = kmax

kmax = N/rA = 40

kmax = 2πfmax /343

fmax = 2184 Hz

r0 – Desired source location

rp – Interference location


Radial attenuation close talk17 l.jpg
Radial Attenuation –“Close Talk”

N = 2; rA (array) = 0.05 m; k = kmax /4

kmax = N/rA = 40

kmax = 2πfmax /343

fmax = 2184 Hz

r0 – Desired source location

rp – Interference location


Radial attenuation large array l.jpg
Radial Attenuation – Large Array

N = 12; rA (array) = 0.3 m; k = kmax /4

kmax = N/rA = 40

kmax = 2πfmax /343

fmax = 2184 Hz

r0 – Desired source location

rp – Interference location


Normalized beampattern l.jpg
Normalized Beampattern

N = 4; rA (array) = 0.1m; k = kmax

kmax = N/rA = 40

kmax = 2πfmax /343

fmax = 2184 Hz

The natural radial attenuation has been cancelled by multiplying the array output by the distance.


Normalized beampattern20 l.jpg
Normalized Beampattern

N = 4; rA (array) = 0.1m; k = kmax /4

kmax = N/rA = 40

kmax = 2πfmax /343

fmax = 2184 Hz

The natural radial attenuation has been cancelled by multiplying the array output by the distance.


Normalized beampattern21 l.jpg
Normalized Beampattern

N = 4; rA (array) = 0.1m; k = kmax /10

kmax = N/rA = 40

kmax = 2πfmax /343

fmax = 2184 Hz

The natural radial attenuation has been cancelled by multiplying the array output by the distance.


Directional impulse response l.jpg
Directional Impulse Response

  • Amplitude density:

  • Impulse response at direction Ω0:where is the ordinary inverse Fourier transform.


Speech dereverberation l.jpg
Speech Dereverberation

Room IR Directional IR

{4 X 3 X 2}

N = 4

r = 0.1 m

r0= 0.2 m

“Dry”

“Rev.”

“Derev.”


Music dereverberation l.jpg
Music Dereverberation

Room IR Directional IR

{ 8 X 6 X 3 }

N = 4

r = 0.1 m

r0= 1.9 m “Dry”

“Rev.”

“Derev.”


Conclusions l.jpg
Conclusions

  • Sphericalwave pressure on asphericalmicrophone array insphericalcoordinates.

  • Point source decomposition achieves radial attenuation as well as angular attenuation.

  • Directional impulse response (IR) vs. room IR.

  • Speech and music dereverberation.

  • Further work:

    • Develop optimal beamformer

    • Experimental study of array


ad