Hi Pdubber

thanks for your post.

When time stretching you generally will notice an increase in volume - the reason for this is that when the audio data is changed new samples have to be created, some of which will be louder than the original sample (this is due to the mathematical calculation known as polynomial interpolation).

Here is some horrid math:

en.wikipedia.org

You may need to use a compressor on the altered audio to decrease the parts which have become louder.

We should also mention that when you pitch shift you will find that this phenomena is due to a direct result of the overall frequency spectrum shifting (either up or down) and the resultant shift in acoustic energy, particularly with the fundamental frequencies. Any EQ boosts etc will also be shifted, as we know lower freqs carry more acoustic energy then higher freqs. You may also find that by pitching up subsonic freqs shift also shift up and will start to effect the level of the mix. Conversley pitching down will also result in a shift in the level of acoustic energy due to the shift in frequency centre.

We (and I suspect others) do model the frequency response in PnT on the behavior of the human hearing tract. Without getting into the technical malaise its all to do with Fletcher Munson equal loudness contours:

en.wikipedia.org

You could try processing the files with a lower gain from within PnT, knock it back to -6dB, process and then boost it back up to your required levels. Or start with a lower level to start with and then add your compression/ limiting.

Hope this helps explain it a little.

Cheers

S

Sean -

Thanks very much for your informative reply.

As far as the time stretching goes, I had suspected it had to do with the calculations inherently involved, since every different plug-in I had tried was affecting the levels. Thanks for confirming my suspicions. It's nice to know it wasn't "operator error". I think I won't bother reading the detailed description of polynomial interpolation.

As for the pitch shifting, I'm familiar with the Fletcher Munson curves and now that you mention them, your explanation makes perfect sense.

In the end, I went back and applied my compression/limiting after the time squeezing rather than before.

Thanks again.

Yes thanks for the answer Sean :)

I'll close this thread for now as this issue is resolved :)