I sent this message earlier this morning, but apparently it never left
Bluffton. I'm trying again. This speaks to John Denker's question about
how the tests are done that show people have a preference for stretched
octaves.
* * * * *
Philips has a compact disc called "Auditory Demonstrations." It is
designed/recorded by the "Institute for Perception Research" at Eindhoven,
Netherlands. This is an interesting CD. It is available from several
sources including Pasco scientific.
One of the trials on the CD involves the octave matching I described. The
listener is presented with a 500-Hz PURE TONE followed by a PURE TONE near
1000 Hz. The alternation of 500 followed by near-1000 is repeated as the
near-1000-Hz tone increases in frequency from 985 to 1035 in steps of 10.
The listener is supposed to indicate which of the near 1000-Hz tones is
exactly one octave above the first tone.
Here is what the manual for the CD says.
" Experiments in octave matching usually indicate a preference for ratios
that are greater than 2.0. This preference for stretched octaves is not
well understood. It is only partly related to our experience with hearing
stretch-tuned pianos."
The manual goes on to say that most listeners will pick a frequency of 1010
Hz as an octave above a 500-Hz tone. Indeed, this is quite a bit more
stretched than a piano, so the stretched preference is for a rather large
stretch. But I agree with their results because I use this CD in my
classes. Some students have no clue what an octave is supposed to sound
like, so they're lost. But those who have had some music training (and
"know" what an octave sounds like) definitely pick 1010 most often, while
some pick 1005 and some pick 1015. Almost none picks 1000 or less.
There is another track on the CD in which a melody is played with an
accompaniment. The melody is played stretched, compressed, and exact
compared to the accompaniment. Stretched means the melody (high
frequencies) is sharp compared to the accompaniment (low frequencies).
About 40% of listeners prefer the stretched melody whereas almost no one
chooses compressed... but most choose exact. I suspect in this case they
blew the test by making the difference too extreme. They made the melody so
sharp that a reasonably astute person would recognize that.
Some of the demos on the CD are ho-hum, others are quite useful, and a few
are astounding. I invested in a $150 CD player, $150 amplifier, and $100
bookshelf speakers. The system is on a roll-around cart I can push into the
classroom. The speakers have mounting brackets that allow them to be hung
from the "push-pin track" that runs along the top of the marker board. I
roll the cart in, hang the speakers on the board, plug it in, and the fun
begins.
Michael D. Edmiston, Ph.D. Phone/voice-mail: 419-358-3270
Professor of Chemistry & Physics FAX: 419-358-3323
Chairman, Science Department E-Mail edmiston@bluffton.edu
Bluffton College
280 West College Avenue
Bluffton, OH 45817