On Mon, Dec 31, 2012 at 5:44 PM, Tim E. Real <termtech@xxxxxxxxxx> wrote:
Just an offside comment and question:
I've repaired a lot of subwoofers.
After repair we had to let them run by themselves with audio.
I noticed a very strange phenomenon with all of them.
When you listen to a subwoofer all by itself, the music which
comes out of it seems to be noticeably off-key, until you
turn up the rest of the audio system.
The way our ears work, what frequency we actually hear shifts
slightly with intensity. There is a great book on acoustics by F. Alton
Everest that goes into this a bit in one of the earlier chapters. I am
still reading through all of it, but it is an interesting phenomenon.
Pitch is in actuality a subjective form of Frequency, not objective, and
this is reflected in this phenomenon.
> The level
of sound affects the perception of pitch. For low frequencies, the pitch
goes down as the level of sound is increased. At high frequencies, the
reverse takes place—the pitch increases with sound level.
> Everest, F. Alton (2000-09-22). Master Handbook of Acoustics (Kindle Locations 1553-1555). McGraw-Hill. Kindle Edition.
> Everest, F. Alton (2000-09-22). Master Handbook of Acoustics (Kindle Locations 1553-1555). McGraw-Hill. Kindle Edition.
There
is a nice experiment involving two oscillators they use to demonstrate
this. The book is well worth the money if you can get it and read
English natively(Not sure what translations exist or how good they
are). I am still working my way through it but it will likely take me
two or three times through before I fully understand most of it.
Seablade
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