On Tue, 22 Jun 2004 18:53:32 +0100, Nick Gorham
wrote:

Dave Plowman (News) wrote:
In article ,
Andy Evans wrote:

How does the cochlea separate a complex sound into its different
frequency components?


It doesn't - it's part of a simple microphone. The brain does the clever
bits.


I woudn't argue that the brain does the clever bits, but the little I
have read about the subject shows that the operation of the cochlea is
nothing like any microphone I have seen, and is far from simple.

OK, it's a broad-band mechanical transducer connected to a series of
narrow-band electro-mechanical transducers. Still relatively simple.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

In article , Nick Gorham
wrote:
Dave Plowman (News) wrote:
In article , Andy Evans
wrote:

How does the cochlea separate a complex sound into its different
frequency components?


It doesn't - it's part of a simple microphone. The brain does the
clever bits.


I woudn't argue that the brain does the clever bits, but the little I
have read about the subject shows that the operation of the cochlea is
nothing like any microphone I have seen, and is far from simple.

It is. :-) I've been looking into this in recent years, and the current
physiological understanding of the cochlea is mind-bogglingly complex. One
model is to regard it as a non-linear dispersive set of linked transmission
lines (with characteristics that vary along their lengths) upon which the
sensors are a series of non-linear *active* resonant detectors whose
effective gain and bandwidth vary with the signal levels they experience.

(This only covers the physical/mechanical side. After that comes the
nerves.. and I've also ignored the biochemistry of what 'pumps' the active
parts of the system. ;- )

I've now written a few articles on this for mags like "Hi Fi News", and
some of the material is now at

http://www.st-and.demon.co.uk/AudioM...ing/index.html

if anyone is interested.

Bear in mind that what I've written is very much a *simplified* version of
what the physiologists now use as a model, but even so it has some
surprising implications for audio/hifi... :-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

"Dave Plowman (News)" wrote in message

In article ,
Andy Evans wrote:
How does the cochlea separate a complex sound into its different
frequency components?

It doesn't - it's part of a simple microphone. The brain does the
clever bits.

More than a microphone, the ear embodies a pretty interesting spectrum
analyzer as well.

Arny Krueger wrote:

More than a microphone, the ear embodies a pretty interesting spectrum
analyzer as well.

....and if you take enough drugs you get to see the graphical display that
goes with the analyser :-))



--
The presence of this sig indicates that I'm under the influence of
excess alcohol. Until I'm sober enough to remember to switch this sig
file off, please treat the above as merely drunken ranting and treat it
with the contempt it probably deserves.

I apologise in advance for any offence caused :-)

"Andy Evans" wrote in message

As they say, audio is engineering, music is art.

...you can see engineering, you can touch engineering and you can
measure engineering but you can't hear engineering.

I don't know about that "You can't hear engineering" stuff. You can
definately hear some examples of bad engineering.

Isn't hearing phenomena called psychoacoustics?

It's related.

"Psychoacoustics can be defined simply as the psychological study of
hearing."

You have obviously not read some of the best-known and classic works related
to psychoustics, Zwicker and Fastl for example.

The aim of psychoacoustic research is to find out how
hearing works.

That's more like it.

In other words, the aim is to discover how sounds
entering the ear are processed by the ear and the brain in order to
give the listener useful information about the world outside.

That goes well afield of "the psychological study of hearing". For example,
psychoacoustics included the physiological study of hearing.

Some of the hot areas of psychoacoustic research at the time of writing
a

How do we separate sounds occurring simultaneously (e.g. two speakers
speaking at once)?

A mixture of temporal and spectral separation of sounds and decoding.

How do we localize sounds in space?

A mixture of temporal and spectral analysis of sounds.

How do we determine the pitch of, say, a musical instrument?

That's spectral analysis.

How does the cochlea separate a complex sound into its different
frequency components?

Vibrating hairs acting on the basilar membrane activating nerves connected
to the brain.

Determining the abilities and limitations of human hearing is
invaluable in helping us to use sounds in our environment.

The biggest milestone in psychoacoustics to date is arguably perceptual
coding, an example of which is the well-known MP3 coding of music and
speech. It's an interesting process - the information content of sounds are
reduced by 90% or more with minimal perceptual loss.

Any device that produces sound for the purpose of human listening should
take
account of what the listener's ears are going to do with that sound."

Which is one reason why I don't take all those earnest reports of sonic
differences due to different choices among well-engineered capacitors, too
seriously.

On 22 Jun 2004 14:07:42 GMT, ohawker (Andy
Evans) wrote:

As they say, audio is engineering, music is art.

...you can see engineering, you can touch engineering and you can measure
engineering but you can't hear engineering. Isn't hearing phenomena called
psychoacoustics?
"Psychoacoustics can be defined simply as the psychological study of hearing.
The aim of psychoacoustic research is to find out how hearing works. In other
words, the aim is to discover how sounds entering the ear are processed by the
ear and the brain in order to give the listener useful information about the
world outside.Some of the hot areas of psychoacoustic research at the time of
writing a
How do we separate sounds occurring simultaneously (e.g. two speakers speaking
at once)?
How do we localise sounds in space?
How do we determine the pitch of, say, a musical instrument?
How does the cochlea separate a complex sound into its different frequency
components?
Determining the abilities and limitations of human hearing is invaluable in
helping us to use sounds in our environment. Any device that produces sound for
the purpose of human listening should take account of what the listener's ears
are going to do with that sound. "

The above are well-known to many branches of neurophysiology and
psychology.

And your point is?

--

Stewart Pinkerton | Music is Art - Audio is Engineering

In article , Andy Evans
wrote:
As they say, audio is engineering, music is art.

"Psychoacoustics can be defined simply as the psychological study of
hearing. The aim of psychoacoustic research is to find out how hearing
works.

I am not sure that it would be sufficient to call these things (and some of
the specific areas you mention below) Psycho-acoustics. I'd add in a fair
bit of physiology and other rather more 'physical' sciences.

To pick just one example from your list.

[snip]

How does the cochlea separate a complex sound into its different
frequency components?

There has in recent years been a lot of *measurements* on this process.
These seem to have established a number of the physical mechanisms involved
in the hair bundles, etc. Goes some way to explaining some of the more
remarkable features of human hearing in terms of sensitivity, pitch
discrimination, masking, etc.

[snip]

Any device that produces sound for the purpose of human listening should
take account of what the listener's ears are going to do with that
sound. "

Alas, the above is at present a council of perfection since we are a long
way from knowing about or understanding all the relevant details of what
our ears and brain do in this process. We can only take into account
factors when we are aware of them. :-)

Hence we may tend to have to fall back on a more pragmatic approach. So,
for example, we can aim to ensure that a sound reproduction system would
provide the ears with the same pressure-time patterns as they would have
been subjected to if listening to the original sounds that have been
recorded or broadcast. Provided we can get near enough to this, we can
relax how much we have to know about the physiology and psychology aspects.

In reality, of course, having some knowledge of the physiology, etc, makes
it easer for us to assess when we get "The closest approach to the original
sound..." (TM ;- )

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

"Andy Evans" wrote in message
...
Is this an audio group,


Yes, it says so on the tin......


a group for music lovers or an engineering group?


Ideally, elements of both to some degree, I would have thought, or what's
the point of subscribing here?


(Just testing to see if Pipex is still eating all my emails and/or
posts....)

"Keith G" wrote


(Just testing to see if Pipex is still eating all my emails and/or
posts....)



Great! That's my Debut turntable FS: posts gone west then!

On 22 Jun 2004 10:05:58 GMT, ohawker (Andy
Evans) wrote:

Is this an audio group, a group for music lovers or an engineering group?

It's an audio group, as you might hopefully have deduced from its
title..........

--

Stewart Pinkerton | Music is Art - Audio is Engineering