From: malcolm@interval.com (Malcolm Slaney)
Date: Mon, 23 Jan 1995 09:39:06 -0800
Subject: Visualizing HRTFs
Message-Id: <v02110102ab4996ceb7b1@[192.203.7.70]>

Just what are these HRTFs?  Is there any rhyme or reason to them?

Here is the abstract I promised you for this Thursday's Hearing Seminar.

        Who:    William Martens (Spatial Media)
        What:   Stereoscopic explorations of HRTFs
        When:   Thursday January 26, 1995 at 11AM
        Where:  CCRMA Library (Top Floor of the Knoll at Stanford)

Depending on the AV setup, we might move the seminar downstairs.  Look for
us either in the library or on the main floor in the ballroom.

See you at CCRMA.

-- Malcolm
P.S.  It's interesting to note the results of a bit of playing we did with
Kemar and a live binaural listening experiment.  At last week's seminar we
had Kemar set up in a room and let everybody listen through Kemar's ears.
Everybody was wearing headphones and only one person reported hearing
sounds come from in front of Kemar.  Everybody else heard all the sounds,
both front and back, as coming from behind.




     A Stereographic Exploration of the Head-Related Transfer Function
                           William Martens

In the last twenty years of spatial hearing research Head-Related Transfer
Functions (HRTFs) have been measured and plotted for many human subjects
and dummy heads, but the overall spatial variation of this complex response
is not well characterized, and even harder to visualize as a whole.  In an
effort to become more familiar with patterns of directionally-dependent
modulation of the HRTF, a stereographic exploration of 614 KEMAR measurements
was undertaken.  This HRTF dataset, covering the sphere of incidence angles
with 10 degree resolution in both azimuth and elevation, was first used to
construct various 2D (surface) and 3D (volumetric) visualizations highlighting
interesting spatial features.  The data were then submitted to several
multivariate analyses (cluster & PCA) in order to summarize patterns of
variation in forms more readily grasped  by the viewer.

On Thursday, Jan.26, William Martens will present a stereo slide show that
will cover the high points of ten years of life with KEMAR.  The first 15
guests will be offered plastic-frame 3D glasses.  Everyone else will be
invited to don cardboard glasses just like those used for 1950s horror films.

Bio:

Dr. Martens was Research Coordinator of Northwestern University's computer
music studio (NCM) from 1983 to 1991.  With his partner Gary Kendall, he
co-authored several patents on spatial sound processing technology, and
co-founded Auris Corporation (1987-1991, RIP).  Since then he has consulted
in 3D media for such diverse enterprises as UCLA's department of physiological
science, Ono-Sendai Corporation (VR start-up), Magic Box Productions
(Computer Graphics Animation House), and the Joint E-mu/Creative Technology
Center.  He is now Chief Scientist for Spatial Media, Inc., (yet another
high-tech start-up).