From: malcolm@interval.com (Malcolm Slaney)
Date: Mon, 13 Nov 1995 14:05:53 -0800
Subject: Attention and Auditory Filters at CCRMA
Message-Id: <v02120d03accd6e127909@[199.170.108.19]>

I'm please to announce that Erv Hafter, psychoacoustician extraordinaire,
will be leading this week's CCRMA Hearing Seminar.  Erv has been studing
the role of attention in auditory filters.  Normally these filters are
considered to be fixed by the physiology, but he has evidence that their
characteristics change with the task.

Good stuff.

        Who:    Erv Hafter (UC Berkeley)
        What:   Attention and Auditory Filters
        When:   Thursday, November 16 at 11AM
        Where:  CCRMA Library, Top floor of the Knoll at Stanford

Coming next week, Diane Schiano will be talking about the phenomena we all
know so well as the cocktail party.

-- Malcolm


Attending to and detecting signals at various levels
of processing," Ervin Hafter, U. C. Berkeley

The so-called "critical bands" or cochlear filters can be
thought of as the receptive fields for hearing. The
general consensus is that their widths are determined
by neuro-mechanical operations of the cochlea and so
immutable to the effects of such things as response
strategies.

However, in a study of the effects of
motivation on detection, Kaplan and I found evidence
for a changes in bandwidth in response to a combination
of high levels of attention and stimulus uncertainty.
Schlauch and I then measured bandwidths under
conditions of frequency uncertainty using a variant of
the "probe-signal" method. There, the subject in a
detection task is trained to expect a specific signal
(presented in noise) and, it is presumed, to attend to
the filter centered on the expected frequency. On
occasional probe-trials, the signal's frequency is
different from expectation and reduced performance is
attributed to attenuation by the skirts of the attended
filter.

In our study, pre-trial cues informed the
subject of the frequenc(ies) to be expected and the
degree of uncertainty was determined by the number of
simultaneously presented tones in the cue. Results showed
that increasing the uncertainty from 1 to 4 increased
the widths of the "listening bands" by about 15% (3/4
dB). While significant, this effect is relatively
small, indicating a form of analytic listening whereby
listeners in the four-frequency uncertainty condition
were able to hear out tnd respond to the four
filters with excellent, albeit imperfect, accuracy.

Follow-up experiments with Tang and Plamondon showed
that many different kinds of cues including musically related
tones, higher harmonics of the signal and even visual
cues for subjects with perfect pitch could focus
attention on the appropriate cochlear filter. However,
when the signal was a group of higher harmonics, cuing
with the missing fundamental (same pitch) as that group
had no effect. A hypothesis to explain this
argues that detection can take place at a level
of processing higher than the cochlear filters, a level
at which multiple frequencies have been combined to
produce a derived percept that is not present in any
frequency alone. Saberi and I tested this notion
by asking subjects were to detect multi-tonal signals
given attentional instructions designed to point
attention either at the ensemble of appropriate
cochlear filters or at the level of derived information
(in this case the level of musical pitch). As expected
from the title, this worked.

From: "Theodore C. Tanner, Jr." <ted@galaxy.nsc.com>
Date: Mon, 13 Nov 1995 12:38:09 -0800
Subject: DSP Position
Message-Id: <9511131238.AA09941@grunger.nsc.com>

		DSP ENGINEER FOR MUSIC SYNTHESIS -- BOULDER, CO
  
EuPhonics is seeking a DSP engineer for music synthesis programming.
EuPhonics is a leading software development firm specializing in
digital audio and digitally synthesized music for
multimedia. Euphonics is a technology intensive company which licenses
software and expertise to leading computer, semiconductor, and
peripheral manufacturers. Our technology is integrated into ICs, sound
cards, set-top games, and computer motherboards.

The ideal candidate has direct experience applying DSP theory to solve
real-world problems. DSP assembler language and C coding experience is
essential. Experience and enthusiasm for digital audio and music
synthesis is desirable. A knowledge of psychoacoustics and related
issues is a plus.

Some familiarity with Windows, Mac and OS/2, C++, Windows driver's,
hardware design, and GUI design is also desirable.

Candidates should have the equivalent of a Bachelor's degree or
greater in electrical engineering/computer science.

Euphonics is an equal opportunity employer.
 
Please send resume in confidence to:
  
John Strawn
S Systems Inc.
15 Willow Avenue
Larkspur California 94939
tel. 415 927 8856
fax. 415 927 2935
email ssys@netcom.com
 
[Normally S Systems Inc. is a DSP consulting firm. In this case we are
helping with the job search for Euphonics].