🚀 go-pugleaf

In article <CK90ox.Gv@brunel.ac.uk>,
David Martland <David.Martland@brunel.ac.uk> wrote:
>
>I have a particular interest in coding waveforms, and I am interested in
>trying to find out what distortions are apparent in the waveforms.

I will have to reply to this again, after giving it some more thought,
but perhaps this note will inspire some discussion and jog my memory.

>1.  addition of noise (not signal related) doesn't distort the signal
>    much, but changes the subjective loudness (possibly considerably)

>3.  Signal related noise is easily detectable, even though it may be
>    at a very low level.

You might want to read some of S.S. Stevens' work, which is now several
decades old.  There is a book (Stevens & Davis, (1938) _Hearing: Its 
psychology and physiology_, Wiley), and I am sure there are at least
a few articles.  Much of Stevens' work concerned psychological scaling.
There must be more recent work, but I am embarrassed to say, I am not
acquainted with it.

>2.  There appears not to be an equivalent of persistence of vision.
>    The auditory system cannot detect small and infrequent changes to
>    the signal, but systematic changes, even if small, can have dramatic
>    effects. 

This is true.   In some sense, the visual and auditory systems are
performing different tasks.  Visual stimuli are generally "slow" and
of moderate duration--usually several score msec at a minimum, under
normal conditions.  Various paradigms have shown early visual integration 
times of ~100 msec.  Even with brief displays, the visual system is not 
really sensitive to rapid changes (say less than 50 msec?), but more to 
the total energy of the stimulus.  Audition requires more precise 
temporal accuracy.  Localization due to the delay in stimulation between
the two ears really necessitates a fast neural response.  There just
isn't a lot of time for the receptors to integrate energy.

>
>Besides this, I'm just interested ......!!
>

There's no better reason, really.  :)

-- 
Howard Crosby Warren				crosby@ren.psy.jhu.edu
Department of Psychology
The Johns Hopkins University