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David Carlstrom David Carlstrom is offline
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Default Detroit Audio Club Meeting 1/20/07

SMWTMS is the Detroit Area's Audio Construction Society. Meetings occur on
the second or third Saturday of odd numbered months. There is a door charge
of $5. Meetings are announced in the club publication named, LC, The SMWTMS
Network.

For information on the club, visit the SMWTMS Web Site at:
http://provide.net/~djcarlst/smwtms.htm

For directions to this meeting send complete snail address with phone to



191 ST SMWTMS MEETING DETAILS

DATE: Saturday January 20, 2007

TIME: 2 PM Until ?

FORMAL MEETING: 4 PM

COHOST: John Greenstreet

HOST: Mark Ziemba

LECTU David Clark will speak on "Measuring Imaging Performance"

David's old company, DLC Design, has been working on "Imaging" for the PTF
system (Perceptual Transfer Function) for many years. David will present
progress on the fourth try in the past 10 years. He says it shows promise.

The new Spatial Module is based on a model of the human ear-brain system.
This is a complicated system, so effort was put into simplifying the
problem. The new software module assumes we are listening to music or
speech, not sine waves. It also assumes free head movement and a listener
willingness to allow "suspension of disbelief" for reproduced music. With
these and other assumptions, spatial reproduction comes down to localization
of intended images in angle and distance, plus sounds that create
envelopment of ambience.

Like other modules in PTF, a very known and specific test signal is
generated to test imaging. The test signal is a Gaussian windowed sine wave
pulse of the "wavelet" family. This results in approximately 1/3 octave
bandwidth of the pulse at all frequencies. The "boink" sound is received by
the binaural mikes of PTF and analyzed for interaural differences in
amplitude, phase and group delay. These interaural differences are all
plotted versus frequency and by psychoacoustic knowledge of the
time-intensity trade off, a plot of image location versus frequency is made.




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