A Crazy Idea?



Perhaps, but now?… maybe not so crazy… What about stacking two Crescendos in the output chain? For conditions of serious hearing impairment, where using only one instance of Crescendo can lead to scintillating background sounds, would using two of them alleviate that situation?

The first one could use a lesser correction level to boost things up to a range that is easier to handle by the second one, which is tuned to your hearing?

Ten years ago that would have been a truly crazy idea because Crescendo was already prohibitively expensive. It took an outboard dedicated DSP audio computer just to run it. It would have bogged down a user’s PC mercilessly.

But today, Crescendo is a high performance VST/AU plugin that consumes 5-7% of typical CPU capacity. And since it is a plugin, it is easy to instantiate as many running copies as we need.

So let’s try that out… hmm… interesting… I don’t hear any trace of the scintillation in background sounds. So now, let’s pull out the trusty math and look at what happens in this situation.

This graph shows our uncorrected hearing as the bold red recruitment curve, for a typical case of 60 dB threshold elevation. The green diagonal line is ideal hearing.

The thick orange curve shows the sound field after being treated by a first Crescendo tuned to vTuning = 50 dB, at 10 dB below our actual threshold elevation.

The faint red curve shows the effective recruitment as a result of this pre-treatment.

And, of course, the second Crescendo, tuned to our actual threshold elevation with vTuning = 60 dB does an absolutely stellar job of making our perception match that thick orange curve.

So yes! It works, and it does even better than with pre-CLAS treatment, I should say… This goes all the way down to the room floor at 30 dB, whereas the CLAS pre-treatment only allowed us to reach down to about 40 dB.

Amazing! And not crazy after all!

  • DM

[ Yes… it doesn’t match ideal hearing, you say? You are correct, it doesn’t. Instead, it matches an enhancement at the lowest sound levels. And, as far as I’m concerned, that’s just fine with me. Those low levels are very faint. It is a huge improvement, getting rid of the background scintillation. ]


Author: dbmcclain

Astrophysicist, spook, musician, Lisp aficionado, deaf guy

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