Musical Soundwaves

[Bill Ballard]

At 9:10 AM -0400 8/2/02, Farrell wrote:
>Why does a flute sound like a flute? Why does an obo sound like an 
>obo? Why does a guitar sound like a >guitar? And last, but certainly 
>not least, why does a piano sound like a piano?

Why does Terry's voice sound like his instead of his wife's? The 
answer doesn't lie in the proportions of the lower eight or sixteen 
partials but in the entire spectrum of acoustical energy delivered by 
the particular instrument, as the human being plays it.

>Does anyone have a simplistic explanation for what is the cause of 
>unique sounds/tones among various >instruments? If you play A4 at a 
>pitch of 440 Hz on any instument, you will hear the pitch of 400 
>Hz. >But they will all sound different.

(BTW, that's some wicked negative inharmonicity operating on that 
fundamental, and is that "obo" beginning with an "h" or ending with 
an "e", my Spelch-Ecker couldn't make up it mind. <g>) Your 
assumption that all these sounds are construction from the same 
materials, ie. periodic fluctuations (sine wave or other) in air 
pressure is a good one. In fact it's the basis behind the Fast 
Fourier Transform analysis which produces the 3D graphs of sound 
which we all swear by. (Fourier analysis assumes all vibrations are 
sine waves.)

But as you understand sound production in any of these instruments 
and the complexity of the local variables involved, you realize that 
while one skilled violinist might be able to imitate the sound of 
another violinist, that violinist's skill is completely useless at 
imitating a piccolo or a xylophone, even just concentrating on the 
same note on the scale. Local variables include, for all wind 
instruments, the internal cavities (chest and throat) of the 
individual players, say for flutes whether the tubes are palladium or 
nickel-plated "mystery metal", for single reed instruments 
(clarinets/saxes) whether the mouthpiece is bakalite or steel.....You 
get the picture. As an aside, a classical saxophonist once told me 
that in his student days he made a saxophone out of cardboard (no 
holes or keys, just the tube) and had to conclude that 90% of the 
identity of the resulting sound came from the saxophone mouthpiece up 
at the top.

>So I guess they all do something different to the soundwave that 
>reaches your ear. What is that >difference? How does a speaker 
>reproduce these differences of they only move in and out?

In/out happens to be the speakers mode of production, as opposed to 
the high speed stuttering of a violin bow. As long as the sound 
system driving the speaker cone has a good electrical analog of the 
sound of a violin, the speakers' in/out will produce a good facsimile 
of a violin. Or xylophone or piccolo.

Getting back to your voice compared to your wife's, Terry, part of 
the difference comes because you shave your face every day, where as 
she's shaving her legs. How that relates to timbre at a common pitch 
is unclear, but for the time being, I'd classify this observation as 
a local variable.

Next?

Bill Ballard RPT
NH Chapter, P.T.G.

"Never try to teach a pig to sing.
It wastes time and annoys the pig."
     ...........Sign on the wall of a college voice teacher's studio.
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