linuxaudio.org

On Mon, Jun 20, 2011 at 04:41:46PM -0500, Charles Henry wrote:

quoted text
> On Fri, Jun 17, 2011 at 12:48 PM, Fons Adriaensen wrote:

>

> > For a real single sound source the direction of the

> > vector V(t) is that towards the source, and P(t) and

> > V(t) in any given point are closely related. They are

> > of course measured in different units (Pascal, and

> > meters/second resp.), one is a scalar and the other

> > a vector, but they are proportional.

>

>

> This doesn't matter to the rest of your analysis/description, but I'd offer

> a correction to this paragraph.

>

> V(x,t) is proportional to the spatial gradient of P(x,t).

>

> Note that this means pressure and velocity waves are 90 degrees out of sync

> with each other.

No, this is wrong. The gradient is 90 degrees out of

phase w.r.t. pressure, and rises by 6 dB/oct w.r.t.

pressure.
The velocity vector is the time integral of the

gradient, and consequently it is in phase with

pressure, and the P/V ratio is independent of

frequency (assuming far field).
Ciao,
--

FA
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