[Ty Ford]

On Mon, 20 Apr 2009 15:37:40 -0400, wrote
(in article
):

On Apr 20, 3:06*pm, "Keith W. Blackwell"
wrote:
Scott Dorsey wrote:
Most commercial recordings don't look like that, because they have
been compressed and phase-rotated to make them louder.

Scott, this is the first time I've ever heard of
the concept of phase-rotating to increase loudness.
It seems to me that if you use a filter that merely
performs frequency-dependent phase-shifting but
without changing amplitude, you may make the
waveform have greater (or lesser) maxima, but the
actual volume should stay the same.

Can you elaborate?

Thanks,
--
Keith W. Blackwell
(my employer has nothing to do with this posting)

Keith,

I think the concept as applied to radio station processing is that the
phase manipulation reduces the peak value relative to the average,
which allows you to turn up the gain which does increase the volume
without exceeding the allowed peak.

Not a peak to RMS thing.

It's to even out commonplace asymetrical modulation of the waveform. With
positive and negative peaks closer to the same value, you can raise the
modulation more without having the previously higher peak (positive or
negative) clip or be illegal as per the FCC.

Regards,

Ty Ford


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