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MUS_TECH 348
3-D Sound and Spatial Audio
Stereo Loudspeaker
Reproduction
Intensity Stereo
Side Image
Intensity Stereo
Center Image
Typical Pop/Rock and Classical Spatial Distribution
Off-Center Listening
“Precedence Effect”
Mono Compatibility
Why can’t we just reproduce binaural
recordings over loudspeakers?
Binaural Recording with
Loudspeaker Reproduction
Stereo Loudspeaker Reproduction
Creates Notch at 2kHz
How to Eliminate Crosstalk?
1) Use a baffle
2) Use out-of-phase signals
180° Out of Phase Signals
180° Out of Phase Loudspeakers
Alternatively
How to make Loudspeaker
Reproduction Transparent?
3) Crosstalk Cancellation from
Manfred Schroeder (late 1950s)
• Exact Solution
• Make loudspeaker listening
more like headphones
• All sounds externalized
Schroeder’s
Cross-talk
Cancellation
System
Schroeder’s
Cross-talk
Cancellation
System
One Step at a Time:
Equalization of Loudspeaker Response
EQ Filter
Result
But…
Introduce cross-talk cancellation signal:
But…
There is crosstalk
for the crosstalk
cancellation
signal!
Full Cross-talk Cancellation Solution:
“Sweet Spot”
The Problems?
1. Off-center positions. Only one sweet spot.
2. Individual Differences. Listener’s HRTFs,
including H30 and H330, don’t match.
3. High frequency cancellation. Wave lengths
are so short that very slight shifts in position
throw everything off.
4. 1/H30. Inverting the notches creates big peaks
that probably don’t match the listener.
5. Room Acoustics. Indirection sound reaches
the listener.
Off-Center Seating in Larger Spaces
Good
Each seating
position has
unique time of
arrival delay
and level
differences.
Only the center
seats can
provide spatial
imagery.
Off-Center Seating in Larger Spaces
The separation
of the stereo
loudspeakers
creates
different ranges
of differences
for time of
arrival delay.
Off-Center Seating in Larger Spaces
Delayed signal from
loudspeaker can
create a wide range
of subjective
impressions!
Off-Center Seating in Larger Spaces
The range of time
of arrival delays for
typical loudspeaker
separatations puts
the delay in the
range of these
different subjective
impressions
Loudspeaker Reproduction in Natural
Environments
Loudspeakers themselves create
indirect sound.
Frequency and Time Response of
Loudspeaker in an Empty Room
Impulse response and
amplitude response from
the loudspeaker to the
listener in an empty test
room.
Figure 2 shows change
with a few absorption
panels in place.
More,
Figure 6 finally
shows a rooms with
only slight indirect
sound between the
loudspeaker and
the listener.
Figure 6 impulse
response and
amplitude response.