Sound waves(The behavior of soundboards)

[John Delacour]

At 5:53 PM -0500 1/14/02, JIMRPT@AOL.COM wrote:
>In a message dated 14/01/02 4:50:14 PM, JD@Pianomaker.co.uk writes:
>
><<"OF COURSE a body can experience a change in velocity without moving
>bodily.  If this did not happen, there would be no such thing as
>vibration.">>
>
>Uhh JD...the definition of "vibration as relates to physics is:
>
>vibration (n)
>...........
>"2. Physics. a. A rapid linear motion of a particle or of an elastic solid
>about an equilibrium position. b. A periodic process.
>3. A single complete vibrating motion; a quiver." AHD

Webster gives: "a periodic motion of the particles of an elastic body 
or medium in alternately opposite directions from the position of 
equilibrium when that equilibrium has been disturbed..."

When a shock or sound wave travels from one end of a rod to the 
other, the rod does not move and the particles of the rod will move 
at different times in different directions within a very limited 
range.

>
>and for "velocity it is:
>velocity (n)
>..........
>2. Abbr. V. Physics: A vector quantity whose magnitude is a body's speed and
>whose direction is the body's direction of motion. AHD

That is a very partial definition.  Even Webster does better:

2a time rate of linear motion in a given direction : a vector 
quantity equal to speed in a particular direction and relative to a 
_stated_frame_of_reference.

Note that the word "body" is not specified.  A particle within a body 
may have velocity and in fact always does except at absolute zero.

What AHD is, I don't know, but it strikes me that Webster, just an 
ordinary dictionary, has taken a lot more trouble to define the words.

A fuller definition of "vibration" would need to distinguish between 
'free vibration', 'damped vibration' and 'forced vibration', and then 
some quite complicated mathematics would need to be adduced to 
describe and quantify these phenomena.

I really see no point in these trite little points.  If you and 
others want to reduce the problem to the batting about of half-baked 
"definitions" and presume that it's all simple obvious stuff, then 
you may satisfy yourselves that you know all there is to know, but 
you won't add anything to our knowledge of the subject.

Frankly I'm sick and tired of the petty ignorant level this 
discussion is constantly reduced to by people who really seem to 
think they have nothing to learn.  I have a lot to learn and there 
are others who also wish to further their knowledge of this extremely 
complicated question, and I don't appreciate having to waste my time 
in some damn stupid fencing match with people who are only interested 
in scoring points because they're too lazy or ignorant to lay aside 
their preconceptions and do some proper thinking.

JD