Hi
The first problem is that the original sound was sped up by 16 while
the sample rate remained the same.
At normal speed, the reconstructable frequency spectrum is 22050 Hz at 44.1 kHz.
After that it goes rapidly down:
2x = 11025
...
16x = 1378.125
The second problem is that aliasing will occur if the resampling
wasn't performed with a low pass filter.
This holds true for both, up and down sampling.
The effect is that the higher frequencies are mirrored and mixed into
the lower ones.
A perfect harmony mess between 0 and 1300 Hz.
If it were sped up by three, I could imagine that Zynaptic's unchirp
could make some improvement to the top end but for 16x... no way
If you have normal speed in front or behind the fast-forward version,
you could try
- noise reduction, profile normal sound
- noise reduction -> residue on the fast section
Robert
On 26/09/2019, Tyler Zahnke <programmer651@xxxxxxxxx> wrote:
Hello! We have a collection of all kinds of sounds, and some of the
sounds are the little chattering sounds made by a tape machine
fast-forwarding or rewinding. Well, we realized that if we slowed down
the files enough (usually four applications of "change speed" at speed
multiplier 0.5, so slowed down to a sixteenth of its original speed),
we could get a vague hint of what that tape may have sounded like; of
course, if it's a rewinding chatter, we would have to reverse it too.
However, when you slow down a sound that much, you get major, and I
mean major, distortion. So now it sounds like a speaker playing behind
a closed door like that late 70s film Abigail's Party! So, is there
any way to slow down a sound (both pitch and tempo) but with less
distortion? Yeah, I can clearly hear the chattering of the sound
playing really quickly, and when we slow it down, we can hear what
clearly sounds like pop music and we can even pick out a few lyrics
through the audio fog, but is there any way I can slow down this tape
chatter sound and get something at least a little clearer, or is it
not possible because we're slowing it down an unbelievable amount
(like I said, 1/16 of the file speed)?
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