From: sfp@mars.ornl.gov (Phil Spelt)
Subject: Re: What is the resolution of human hearing?
Date: Fri, 19 Jul 91 13:24:08 GMT
Organization: Oak Ridge National Lab




Article 1832 of sci.virtual-worlds:
Date: 18 Jul 91 18:30:26 GMT

In article 1832, David asks:

|>What is the resolution of human hearing?

|>For vision I think it is 24 frames/sec.  What is it for sound?

|>Thanks in advance!

|>                -- David
|>                   dnettles@libserv1.ic.sunysb.edu

I think this is am ambiguous question:  "resolution" in vision usually
refers to the number of lines/dots per unit measure which can be discriminated
as separate stimuli at a known distance.  This is also known as visual
acuity.  For vision, there are 3 acuity measures:  recognition (as in the
eye chart at the optometrist's office), detection acuity (how close does one
have to be to detect the prtesence of a line of a known size & contrast), and
resolution acuity (what I was talking about in the first sentence, and what
David seems to be asking about).  The 24 frames per second is the typical
rate at which the human eye merges still photos into integraded and smooth
_perceived_ motion.  Of course, this is only a point in a range, which goes
from slow motion perception to speeded-up perceived motion.  There is good
evidence that this integration is a retinal phenomenon, as opposed to a central brain one.


|>[MODERATOR'S NOTE:  I think that the human ear is sensitive to frequencies
|>from about 60 Hz to 17KHz; the phone tops out at around 8 KHz.  The first
|>figure could be wrong, however; and of course, the body is sensitive to
|>vibrations way down into the single figures.  Other dimensions:  volume,
|>direction, separation, etc.  More input, please! -- Bob Jacobson]

What is the comparable measure for hearing?  Hearing is a different kind of
sensory process:  The eye (actually, I mean "vision") integrates information
spatially (over space) the ear (hearing) does so temporally (over time).  How
fast information can be presented to the ear for comprehension depends on
a number for factors:  how familiar the listener is with the material ( more
familiarity --> faster perception, as with vision);  what type of information
is being presented (music?, highly redundant spoken information?, complex
scientific material?), and porbably several others I'm not remembering at the
moment.  

In terms of acuity (detection) the sensitivity of hearing depends on the
pitch of the information.  The human ear is most sensitive (hears the softest
sounds) in the range of the human voice, most specifically the _FEMALE_
human voice.  Ain't evolution WONDERFUL????  Hence, one reason for the use
of female voices in cockpit and automobile warning systems.

There are, of course, a number of other considerations concerning hearing and
vision.  One (of many) good reference is the book: _Human Factors: Under-
standing People-System Relationships_, by Kantowitz & Sorkin, published by
Wiley.

IMHO, we MUST understand the fundamentals of human perception in order to
be best equiped to create "good" VR and conserve CPU power to move all these
polygons around the "world".  I'm sorry this is so long, but I hope it helps
clear up some thinking about vision and hearing.  They are NOT simply
analogous senses.

==============================================================================
MIND.  A mysterious form of matter secreted by the brain.  Its chief activity
consists in the edeavor to ascertain its own nature, the futility of the
attempt being due to the fact that it has nothing but itself to know itself
with.
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Phil Spelt, Cognitive Systems & Human Factors Group  sfp@epm.ornl.gov
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Any opinions expressed or implied are my own, IF I choose to own up to them.
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