Does sound decelerate after bouncing off of something?

[jens]

No I'm not... Ivory Tickler said "IF it did". And I agree, IF it did (and it doesn't) it would change pitch (and it doesn't, so therefore it doesn't change speed)

oh well - you could need a lesson in logic or two:

here's what IvoryTiickler wrote:

If it did then an echo would change pitch!

you can deduct from this the thesis, that the pitch of a sound determines the speed with which it travels.

I said this thesis is wrong.

You said I am wrong.

Therefor you said this thesis is right.

Therefor you said:

'the pitch of a sound determines the speed with which it travels'


you also said:

it's not the sound that determines it's speed.. it's the medium

[progfusion74]

The speed of sound is indeed dependent on the medium (I have not read the entire thread). The speed of sound is independent of the frequency, i.e. the pitch in non-dispersive mediums (like air), i.e. for most practical purposes. Now, if you want to record underwater that's another matter . Most importantly, it is inversely proportional to the density of the medium.

After reflection, many things happen, but deceleration is not one of them. Whether you hear an echo or not also depends on how fast the reflection hits your ears. Has to be > 0.1 seconds (in air), otherwise its not perceived as an echo.

[IvoryTickler]

If it did then an echo would change pitch!

no

let's say it slowed to half speed - it would drop an octave. Yes?

[IvoryTickler]

It is indeed true that

It is important to note that the sound speed in air is determined by the air itself. It is not dependent upon the sound amplitude, frequency or wavelength.

However that is not the issue here. The pitch that your brain registers is directly related not to the "speed" of arrival of air compression waves on your eardrum, but to the rate at which they strike your eardrum.

Hence IF!!! the sound slowed down, the waves would strike your eardrum at a lower frequency!!! and the pitch perceived would be lower in direct proportion to the speed (every halving of the speed would drop the sound by 1 octave).

Humph!

[seldom]

If it did then an echo would change pitch!

no

let's say it slowed to half speed - it would drop an octave. Yes?

no.

[james0tucson]

If it did then an echo would change pitch!

no

let's say it slowed to half speed - it would drop an octave. Yes?

No, the frequency is relative to the reference frame in which the air moves.

[IvoryTickler]

If it did then an echo would change pitch!

no

let's say it slowed to half speed - it would drop an octave. Yes?

no.

A bit too monosyllabic, seldom! "Frequency" (pitch) is the rate of arrival of sound waves. Slow them down and they will arrive less "frequently" hence the "frequency" would drop. (All too hypothetical to get het up about though).

I'll save you the bother of replying by putting it in here ....

no.

[seldom]

A bit too monosyllabic, seldom! "Frequency" (pitch) is the rate of arrival of sound waves. Slow them down and they will arrive less "frequently" hence the "frequency" would drop. (All too hypothetical to get het up about though).

I'll save you the bother of replying by putting it in here ....

no. :?

you asked "Yes?" so i replied, no.

here's why if you're interested. if sound bounces off something and slows down, the event of bouncing off cannot affect the rate at which the waves reach the reflecting surface. so, in this hypothetical situation where the sound slows down after bouncing off a surface, the velocity of each wavefront would be altered but not the rate at which they then propagate off the surface. so, the waves would all be closer together - and the frequency would of course be the same. see?

[HanafiH]

Mr Cubase says: what a load of fookin wank arse.

[IvoryTickler]

A bit too monosyllabic, seldom! "Frequency" (pitch) is the rate of arrival of sound waves. Slow them down and they will arrive less "frequently" hence the "frequency" would drop. (All too hypothetical to get het up about though).

I'll save you the bother of replying by putting it in here ....

no.

you asked "Yes?" so i replied, no.

here's why if you're interested. if sound bounces off something and slows down, the event of bouncing off cannot affect the rate at which the waves reach the reflecting surface. so, in this hypothetical situation where the sound slows down after bouncing off a surface, the velocity of each wavefront would be altered but not the rate at which they then propagate off the surface. so, the waves would all be closer together - and the frequency would of course be the same. see?

OK. Thanks. And yes Mr Cubase sir, you sum things up so appropriately! Movin' on ...

[AdmiralQuality]

Yes, WE know it depends on the frame of reference, but the guy asking the question didn't. And if he was confused before... heheh.

But my understanding from the way it was worded (and I could be wrong, wasn't my question) was that he was thinking some property of the sound itself determined it's speed through any given medium, and that you could race sounds...with... i dunno, loud ones being faster? Like sounds were bullets or something. So who knows how these imaginary, magical, speed-changing-in-the-same-medium, bullet-sounds work? It just doesn't work like that AT ALL. Yes, if you had your head embedded IN the wall, the speed would change (in the wall), but not the pitch. But that's not what he asked, he asked about an echo, which by definiton has got to be travelling back into the same medium it came from (presumably air, in a nice warn comfy room). And therefore, the same speed (discouting any change of temperature, barometric pressure, or humidity during those milliseconds ).

Anyway, another heated agreement I think, we just have too many nested if statements. Mr. Cubase is right.