Klarinet Archive - Posting 000483.txt from 2000/08

From: Tony@-----.uk (Tony Pay)
Subj: Re: [kl] inharmonic (anharmonic) vs. decay vs periodic vs recipe
Date: Thu, 17 Aug 2000 16:33:19 -0400

On Thu, 17 Aug 2000 12:56:52 -0700 (PDT), Bilwright@-----.net said:

> > > Thus sine waves are periodic, but not all periodic waves are
> > > harmonic.
>
> > Yes, all periodic waves are harmonic.
>
> ....harmonic refers to a special sort of oscillatory motion where the
> "elastic restoring force" [acting on the body in motion] is not
> constant but instead "varies during the motion" such that "the
> acceleration is directly proportional to the object's displacement
> [from the position where no force is active on the body]."
>
> The result of all this is our friend, the sinusoidal wave.
>
> ....before I go any further with this, I'll stop talking and give you
> an opprtunity to respond to this most basic assertion, if you disagree
> with it.

OK, I see where the difficulty is.

The terminology 'harmonic' in what I wrote is being used to characterise
a sound that *isn't* anharmonic. In other words, it is periodic, and
can be decomposed into a Fourier series.

In this terminology, an 'anharmonic' sound is one that isn't periodic,
and that *can't* therefore be decomposed into a Fourier series (although
it can be subjected to a Fourier transform, which we don't want to go
into here).

The other use of the word 'harmonic', that you're quoting from your
textbook, is to do with a vibration that is called 'simple harmonic
motion', and the vibration associated with SHM, as it's often
abbreviated, is indeed a simple sine wave.

So when I say, clarinets give a harmonic sound, bells an anharmonic
sound, that's what I meant. And I explained what I meant, too.

Indeed, I explained it all from quite a number of different viewpoints.
I would have expected to be criticised for repeating myself rather than
for being obscure. It's the ideas that are important.

It's true that there are terms 'harmonicity' and 'inharmonicity', used
by Benade, and perhaps that's what was confusing. But the adjective
derived from 'harmonicity' is surely 'harmonic'.

Tony
--
_________ Tony Pay
|ony:-) 79 Southmoor Rd Tony@-----.uk
| |ay Oxford OX2 6RE GMN family artist: www.gmn.com
tel/fax 01865 553339

... Biography: One of the terrors of death.

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