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3D sound reproduction with “OPSODIS” and its commercial applications. Takashi Takeuchi, PhD Chief Technical Officer OPSODIS Limited Institute of Sound and Vibration Research, University of Southampton Kajima Technical Research Institute. History. MSc. PhD. (Invention). (OPSODIS). OPSODIS.

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3d sound reproduction with opsodis and its commercial applications

3D sound reproduction with “OPSODIS”andits commercial applications

Takashi Takeuchi, PhD

Chief Technical OfficerOPSODIS Limited

Institute of Sound and Vibration Research, University of SouthamptonKajima Technical Research Institute

history

History

MSc

PhD

(Invention)

(OPSODIS)

OPSODIS

Auralisation

Joint R&D

Joint R&D

Stereo Dipole

OPSODIS (UK Ltd.)

what is opsodis
What is OPSODIS™?

Optimal Source Distribution

  • Principle

- 3D sound reproduction

- Binaural

- Loudspeaker reproduction

- 2 channel system (3ch option)

- Stereo & Surround

- reproduction compatible

  • What is special?

- Lossless crosstalk cancellation!

- Signal processing by loudspeaker

- Good & natural sound quality

- Robust control

- Elevation (height) reproduction

- Multiple listeners

spatial hearing and binaural signal
Spatial hearing and binaural signal

Sound source signal

s

  • Physics

source signalpropagationtwo different signal at ears

  • Perception

Separates signal and spatial informationbinaural signals

Characteristics of space (physics)

(relative position,response of space)

Spatial hearing (human)

(source position,movement,room size,reverberation)

stereo

surround

A2

binaural

A1

d

Binaural signals

any number of sources …

inverse filtering crosstalk cancellation
Inverse filtering (crosstalk cancellation)
  • Loudspeaker reproduction interweaves loudspeaker position
  • In order to reproduce spatial information arbitrarily, independent transmission to each ear is necessary.
  • Minimum of two independent (real) sound source necessary

C22

Inverse filteringH

C12

binaural

Signals

d

Synthesised

binaural signals

C21

w

C11

conventional cross talk cancellation
Conventional cross-talk cancellation

Cancelling each other

Independent control at both ears

Right ear

t

t

Left ear

Loudspeaker output

t

t

R

Right ear

L

t

t

Left ear

conventional cross talk cancellation1
Conventional cross-talk cancellation

Independent control at both ears

Right ear

t

t

Left ear

Loudspeaker output

t

t

R

Right ear

L

t

t

Left ear

conventional cross talk cancellation2
Conventional cross-talk cancellation

Independent control at both ears

Massive destructive

interference

Right ear

t

t

Left ear

Loudspeaker output

t

t

R

Right ear

L

t

t

Repetitive delay = Large output

(Frequency dependent)

Left ear

crosstalk cancellation frequency
Crosstalk cancellation (frequency)

phase

amplitude

Destructive interference at both ears.

Inefficient, quality loss, sensitive to errors.

frequency dependency
Frequency dependency

Conventional

  • from Left SP
  • from Right SP
  • reproduced

frequency

frequency

Left ear

Right ear

why have 3d systems not performed well so far
Why have 3D systems not performed well so far?

Frequency response to listener

6dB

(two point sources)

(_____)

0dB

In-phase

signal

level

(_ _ _)

Out-of-phase

signal

-40dB

Frequency (linear)

20kHz

20Hz

Sound emitted by loudspeakers do not reach listener’s ears at certain frequencies.

Large output required to compensate it.

loss of performance through cross talk cancellation process
Loss of performance through cross-talk cancellation process
  • Typical frequency response of the inverse filters

for 3D reproduction.

0dB

Out-of-phase

signal

level

In-phase

signal

-40dB

20Hz

Frequency

20kHz

loss of performance through cross talk cancellation process1
Loss of performance through cross-talk cancellation process

0dB

Original

Performance

Dynamic range loss = Low Quality

≈ 5 bit

Synthesized sound

-30dB

Distortion

Noise

Exact matching

level

Frequency

20kHz

20Hz

Cross-talk cancellation degrades performance severely.

analogy to picture quality
Analogy to picture quality

Reduce;

Constant resolution

Magnify;

Pixel size

Quality Loss

loudspeaker span
Loudspeaker span

10°

180°

(Stereo Dipole)

Original Performance

0 dB

≈ - 3 bit

≈ - 7 bit

-16dB

Smaller loss

More complexity

Less complexity

-43dB

Larger loss

Synthesized sound

20Hz

20kHz

20Hz

20kHz

frequency (log)

frequency

optimal source distribution
Optimal Source Distribution

Conventional

OPSODIS

OPSODIS

Conventional

Stereo Dipole

frequency

high

low

low

Transducer position vs Performance

(excess amplification)

poor

20kHz

2kHz

frequency

200Hz

20Hz

good

180°

60°

120°

transducer position

slide17

Conventional

The worst conditioned frequency

dictates performance

for all frequencies!!

(Stereo Dipole)

OPSODIS

opsodis loudspeaker
OPSODIS loudspeaker
  • Frequency response to listener with OPSODIS.

No frequency dependency on

amplitude response and

phase response

OPSODIS

0dB

level

-40dB

frequency

opsodis principle
OPSODIS principle
  • Frequency response of the OPSODIS inverse filters.

No frequency dependency on

amplitude response and

phase response

0dB

robust

  • Simple process
  • No loss resulting from signal manipulations
  • High quality 3D reproduction
  • Natural & pure sound quality
  • Elevation reproduction

level

-40dB

frequency

slide20

Crosstalk cancellation of OPSODIS

Addition

Cancellation

Independent control at both ears

Right ear

amplitude

phase

Left ear

R

Right ear

½ amplitude, -90º phase

½ amplitude

Left ear

L

Loudspeaker output

slide21

Crosstalk cancellation of OPSODIS

Independent control at both ears

Right ear

amplitude

phase

Left ear

R

Right ear

½ amplitude, -90º phase

½ amplitude

Left ear

L

Loudspeaker output

slide22

Crosstalk cancellation of OPSODIS

Independent control at both ears

Right ear

amplitude

phase

Left ear

Destructive interference

R

Right ear

½ amplitude, -90º phase

Constructive interference

½ amplitude

Left ear

L

Loudspeaker output

Efficient, Lossless, Robust to errors.

reproduction quality
Reproduction quality

Example: 16bit hardware

Stereo Dipole

frequency

frequency

≈17 bit

Reproduced

dynamic range

≈ +3 dB

Reproduced

dynamic range

≈ -43 dB

16 bit

16 bit

OPSODIS

16 bit

16 bit

≈9 bit

  • L channel
  • R channel
  • reproduced
electro acoustic transducer for opsodis
Electro-acoustic transducer for OPSODIS
  • Flat panel loudspeakers

plate

high frequency low

shaker

driving plate

narrow width wide

  • Acoustic waveguide

large stiffness small

slot

driver

high frequency low

narrow slot wide

high frequency low

Variation in excited frequency and radiation impedance

discrete system
Discrete system

frequency(Hz)

transducer span

  • Width of n enables discretisation
  • 2 channel, multi-way system
    • Use of conventional transducers
    • Wide frequency range
  • U-shaped valley
  • Small performance loss
effects of room reflection sound radiation
Effects of room reflection (sound radiation)

Small radiation

by OPSODIS

Not affected by reflection

- dB

0 dB

- dB

0 dB

0 dB

Reference to radiation

by mono loudspeaker

  • Very large sound radiation other than receiver directions
  • Needs anechoic room

conventional

OPSODIS

radiation pattern of conventional
Radiation pattern of Conventional
  • Radiation pattern is different depending on the frequency.
  • Single listener.
  • Very small sweet area.

0dB

-∞dB

radiation pattern of opsodis
Radiation pattern of OPSODIS
  • Radiation pattern is constant regardless the frequency; Large sweet area
  • No spectral change; elevation works everywhere.
  • Multiple listener listening with a little performance loss.
  • The interval of L-R cross-talk cancellation is about 0.3m; Alternative seating positions.

A

B

B

A

A

0.6m

0.6m

A: 1 or 3 listener(s)

B: 2 listeners

reproduced sound level lateral position
Reproduced sound level (lateral position)
  • 3 seater or 2 seater

Left ear signal

Right ear signal

Lateral position (m)

aspects of the opsodis
Aspects of the “OPSODIS”
  • No dynamic range loss
    • Quality (Lossless)
    • Good S/N
    • No distortion
  • Robust to errors in plants and filters
    • Robust to individual difference in HRTFs
    • Generic inverse filters
  • Flat amplitude response of inverse filters
    • Elevation (height etc) works at any location
    • No colouration at any location
  • Small sound radiation other than receiver directions
    • Robust to room reflections
  • Consistent radiation over frequency
    • Multiple listener listening
inverse filter 2 channel osd
Inverse filter ~ 2 channel OSD

frequency

high

low

low

0dB

Out-of-phase

component

level

In-phase

component

2ch OSD

-40dB

Frequency/azimuth

inverse filter 3 channel osd
Inverse filter ~ 3 channel OSD

frequency

high

low

low

high

low

low

0dB

Out-of-phase

component

level

In-phase

component

3ch OSD

-40dB

Frequency/azimuth

extension to 3 channel
Extension to 3 channel

Out-of-phase

component

2ch OSD

3ch OSD

2ch

2ch OSD

In-phase

component

3ch

3ch OSD

Singular values of the inverse filter matrix H

3 channel osd
3 channel OSD

peak (in phase)

= valley (out of phase)

3ch OSD

3ch OSD

peak (out of phase)

= valley (in phase)

2ch OSD

excess amplification

peak

20kHz

2kHz

frequency

2ch OSD

200Hz

20Hz

valley

180°

60°

120°

transducer azimuth

slide36

Crosstalk cancellation of 3ch OPSODIS

Addition

Cancellation

Independent control at both ears

Right ear

amplitude

phase

Left ear

¼ amplitude, -90º phase

Right ear

R

C

½ amplitude

Left ear

L

¼ amplitude, +90º phase

Loudspeaker output

slide37

Crosstalk cancellation of 3ch OPSODIS

Independent control at both ears

Right ear

amplitude

phase

Left ear

¼ amplitude, -90º phase

Right ear

R

C

½ amplitude

Left ear

L

¼ amplitude, +90º phase

Loudspeaker output

slide38

Crosstalk cancellation of 3ch OPSODIS

Independent control at both ears

Right ear

amplitude

phase

Destructive interference

Left ear

¼ amplitude, -90º phase

Right ear

R

C

½ amplitude

Constructive interference

Left ear

L

¼ amplitude, +90º phase

Loudspeaker output

Efficient, Lossless, Quality, Robust to errors.

slide39

Crosstalk cancellation of 3ch OPSODIS

Independent control at both ears

Right ear

amplitude

phase

Destructive interference

Left ear

1/3 amplitude, -120º phase

Right ear

R

C

1/3 amplitude

Constructive interference

Left ear

L

1/3 amplitude, +120º phase

Loudspeaker output

Efficient, Lossless, Quality, Robust to errors.

summary
Summary

Combination of signal processing and the new type of loudspeaker based on a new principle

  • OPSODIS
    • Enabling high definition 3D sound reproduction with 2 channel (or 3ch) loudspeakers
    • Natural sound quality without distortion
    • Natural sound at any location
    • Effective in any room
    • Compatible with surround reproduction

enables ideal 3D sound

delivered to ears.