Engineering & Computer Sc ience - ANU College of ... · Engineering & Computer Sc ience ... 1.1...
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ANU College of Engineering & Computer Science Recording and Reproducing Large Sound Fields By Prasanga Samarasinghe * , ANU CECS ASP Group, [email protected]. Supervisors: Thushara Abhayapala † , Mark Poletti ‡ . 1 Introduction Recording and reproduction of spatial sound fields over a large area is an unresolved problem in acoustic signal processing. As the frequency increases and as the region of interest becomes large the number of microphones/loudspeakers needed in effective recording/reproduction increases beyond practicality. Our intention is to minimise these numbers with the use of distributed arrays of higher order microphone/loudspeaker units. 2 Practical Applications 1.1 Cancelling the noise pollution in mining towns 1.2 Creating virtual realities (Ex. Experience a real sporting encounter in your living room) 3 Theory A 2D or 3D sound field in space may be described with respect to a defined origin based on several representations and the commonly used ones are, Several approaches to the problem of accurately recording/reproducing spatial sound fields are, Wave Field Synthesis approach based on the Kirchhoff-Helmholtz integral Inverse method Ambisonics approach Spherical arrays of omnidirectional microphones/loudspeakers All of the above approaches fail when applied in large sound fields due to the inherent restriction in recording/reproducing higher order harmonic components. Our approach …. It is based on effectively capturing/recreating the sound field coefficients in the harmonic representation with the use of realizable higher order microphone/loudspeaker units. 4 Solution 4.1 Work done so far A successful 2D recording system has been theoretically formulated using higher order microphones. The system is capable of accurately recording interior sound fields It’s ability of successfully recording exterior sound fields beyond source locations has also been demonstrated. A similar design for the reproduction of large 2D sound fields with the use of higher order loudspeaker units has been carried out by Mark Poletti and Thushara Abhayapala. 4.2 Future work Extend current findings in to the three dimensional space in order to facilitate any natural field. Work on more realizable approaches to design higher order microphone and loudspeaker units. 6 References [1] Poletti, Mark and Abhayapala, Thushara D, ‟Spatial sound reproduction systems using higher order loudspeakers”, in IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2011, pp. 57 – 60. [2] Samarasinghe, Prasanga N, Abhayapala, Thushara D and Poletti, Mark, (forthcoming 2011) ‟Spatial sound field recording over a large area using distributed higher order microphones” in IEEE Workshop on Applications of Signal Processing to Audio and Acoustics (WASPAA) [3] Poletti, Mark, ‟Three-dimensional surround sound systems based on spherical harmonics”, J. Audio Engin. Soc., 53(11), pp 1004-1025, November 2005 n in n n e kR J k k x p ) ( ) ( ) , ( * Advanced Signal Processing Group, College of Engineering & Computer Science, Australian National University † Research School of Engineering, College of Engineering & Computer Science, Australian National University ‡ Industrial Research Limited, PO Box 31-310, Lower Hutt, New Zealand Can we ever get rid of the mass noise pollution happening in mining communities? Yes The existing sound field over the entire mine can be recorded and a new inverting sound field can be produced in order to cancel it out. Do you hear the true sounds from conventional stereo systems or even the surround sound systems ? No you are made to believe the sound is generated at the speaker positions and recordings are static We are trying to recreate that original sound exactly as it is, enabling you to listen to anywhere in the field you wish to, even a conversation between two umpires in a cricket match. Figure 2: A Cricket field Figure 1: A Mining Neighbourhood The Kirchhoff-Helmholtz integral A Taylor series expansion Cylindrical and Spherical harmonics representation, Ex. The pressure at a 2D interior sound field can be represented as Unknown Known Figure 3: Sound field representation Figure 6: Exterior field : Recorded sound field for M=1 and the existing sound field of f=575Hz Figure 4: Interior field : Recorded sound field for M=1 and the existing sound field of f=140Hz Figure 5: Interior field : Recorded sound field for M=3 and the existing sound field of f=340Hz Figure 7: Exterior field : Recorded sound field for M=3 and the existing sound field of f=1.37kHz A higher order microphone of order ‘M’ A higher order loudspeaker of order ‘M’ Extracts sound field coefficients up to order ‘M’ Reproduces sound field coefficients up to order ‘M’
Transcript of Engineering & Computer Sc ience - ANU College of ... · Engineering & Computer Sc ience ... 1.1...
ANU College of
Engineering & Computer Science
Recording and Reproducing Large Sound FieldsBy Prasanga Samarasinghe*, ANU CECS ASP Group, [email protected]. Supervisors: Thushara Abhayapala†, Mark Poletti‡.
1 Introduction
Recording and reproduction of spatial sound fields over a large area is an
unresolved problem in acoustic signal processing.
As the frequency increases and as the region of interest becomes large the
number of microphones/loudspeakers needed in effective
recording/reproduction increases beyond practicality.
Our intention is to minimise these numbers with the use of distributed
arrays of higher order microphone/loudspeaker units.
2 Practical Applications
1.1 Cancelling the noise pollution in mining towns
1.2 Creating virtual realities (Ex. Experience a real sporting encounter
in your living room)
3 Theory
A 2D or 3D sound field in space may be described with respect to a defined
origin based on several representations and the commonly used ones are,
Several approaches to the problem of accurately
recording/reproducing spatial sound fields are,
Wave Field Synthesis approach based on the Kirchhoff-Helmholtz integral
Inverse method
Ambisonics approach
Spherical arrays of omnidirectional microphones/loudspeakers
All of the above approaches fail when applied in large sound fields due to
the inherent restriction in recording/reproducing higher order harmonic
components.
Our approach ….
It is based on effectively capturing/recreating the sound field coefficients in
the harmonic representation with the use of realizable higher order
microphone/loudspeaker units.
4 Solution
4.1 Work done so far
A successful 2D recording system has been theoretically formulated using
higher order microphones.
The system is capable of accurately recording interior sound fields
It’s ability of successfully recording exterior sound fields beyond source
locations has also been demonstrated.
A similar design for the reproduction of large 2D sound fields with the
use of higher order loudspeaker units has been carried out by Mark
Poletti and Thushara Abhayapala.
4.2 Future work
Extend current findings in to the three dimensional space in order to
facilitate any natural field.
Work on more realizable approaches to design higher order microphone
and loudspeaker units.
6 References[1] Poletti, Mark and Abhayapala, Thushara D, ‟Spatial sound reproduction systems using higher
order loudspeakers”, in IEEE International Conference on Acoustics, Speech and Signal
Processing (ICASSP), 2011, pp. 57 – 60.
[2] Samarasinghe, Prasanga N, Abhayapala, Thushara D and Poletti, Mark, (forthcoming 2011)
‟Spatial sound field recording over a large area using distributed higher order microphones” in
IEEE Workshop on Applications of Signal Processing to Audio and Acoustics (WASPAA)
[3] Poletti, Mark, ‟Three-dimensional surround sound systems based on spherical harmonics”, J.
Audio Engin. Soc., 53(11), pp 1004-1025, November 2005
n
in
nn ekRJkkxp )()(),(
* Advanced Signal Processing Group, College of Engineering & Computer Science, Australian National University
† Research School of Engineering, College of Engineering & Computer Science, Australian National University
‡ Industrial Research Limited, PO Box 31-310, Lower Hutt, New Zealand
Can we ever get rid of the
mass noise pollution
happening in mining
communities? Yes
The existing sound field
over the entire mine can be
recorded and a new
inverting sound field can be
produced in order to cancel
it out.
Do you hear the true sounds
from conventional stereo
systems or even the
surround sound systems ?No you are made to believe the
sound is generated at the speaker
positions and recordings are static
We are trying to recreate
that original sound exactly
as it is, enabling you to
listen to anywhere in the
field you wish to, even a
conversation between two
umpires in a cricket match.Figure 2: A Cricket field
Figure 1: A Mining Neighbourhood
The Kirchhoff-Helmholtz integral
A Taylor series expansion
Cylindrical and Spherical
harmonics representation,
Ex. The pressure at a 2D interior sound
field can be represented as
Unknown Known
Figure 3: Sound field representation
Figure 6: Exterior field : Recorded sound field for M=1 and the existing sound field of f=575Hz
Figure 4: Interior field : Recorded sound field for M=1 and the existing sound field of f=140Hz
Figure 5: Interior field : Recorded sound field for M=3 and the existing sound field of f=340Hz
Figure 7: Exterior field : Recorded sound field for M=3 and the existing sound field of f=1.37kHz
A higher order
microphone of order ‘M’
A higher order
loudspeaker of order ‘M’
Extracts sound field
coefficients up to order ‘M’
Reproduces sound field
coefficients up to order ‘M’
