Tom, you are correct, in a way.
Try picturing this: two ball-bearings, same size, weight, and dropped from
the same height, therefore will has the same velocity(in this case
Frequency), into a still pool of water. The "ripples" are effectively sound
waves and you notice peaks and dips(constructive and de-constructive waves).
Where the "ripples" cross this is calles the "nodal" point, and is where the
peak of one sound wave will de-construct the dip of another. This is how the
sound cancels out. However if two of the same wave come together, they
obviously double.
After thought
Picture this also. We know sound travels in waves (circular) and light
travels in a straight line (if its not reflected, refracted, etc.), however
if sound were to made to travel in a straight line, effectively you could
create sound in thin air( ie no speaker). Picture the ball-bearings again
being the sound source. Say after dropping them, the outside ripple of one
source will cross the outside ripple of the other. If the ripples are not a
complete circle but a straight line, this would mean you could select a
given point along that line where you want the sound to be either amplified
or cancelled. If you want to move the sound further away or closer, just
change the frequency.
I have not heard of this actually being built, designed or tested, however
the mathematical theory behind it works out.
Steve
froggy 200B
----- Original Message -----
From: Tom Richardson <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Thursday, February 22, 2001 5:29 PM
Subject: Re: exhaust noises
> Damn wheres an acoustical engineer when you need one :)
>
> It's got to do with standing waves and the cancellation effect achieveable
> by exploiting them. IE with two sound waves of the same frequency but
> different phase, the peaks of one wave cancel the dips of the other
>
> Or something :)
>
> - Tom
>
> ----- Original Message -----
> From: "Lincoln Yeo" <[EMAIL PROTECTED]>
> To: <[EMAIL PROTECTED]>
> Sent: Friday, February 23, 2001 11:43 AM
> Subject: Re: exhaust noises
>
>
> > yeah, ive heard of a similar principle (i saw it on beyond 2000)
> > - basically it works by um... ok imagine the noise a helicopter
> > makes - sort of whup whup whup etc - well basically i think it
> > works by adding a whup inbetween the other whups, and it turns
> > out u cant hear a constant whup because it is actually a pulse -
> > so u end up with little sound...
> >
> > Linc
> >
> > __________________________________________________
> > Do You Yahoo!?
> > Yahoo! Auctions - Buy the things you want at great prices!
> http://auctions.yahoo.com/
> >
>
>
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