The worker hears a yelled warning over the noise of the jackhammer. The bouncer makes his way towards angry voices across a crowded nightclub floor. The infantryman listens for voices upstairs through the tumult of a helicopter attack outside.

Noise cancellation is nothing new. These devices generate matched frequencies to cancel those from the environment, thus rendering the near side of the headphone quieter. Noice cancelling microphones are also available - these devices get rid of noise not in the frequency of the voice, and allow the microphone to be more effectively used in loud environments.

The NCVA hybridizes these two with some stochastic resonance thrown in to boot. The NCVA device allows people to operate in loud environments with retained perception for human voices. Sound with wavelengths outside the voice are cancelled, but voice wavelengths are allowed through.

One would not want these voice wavelengths amplified, for fear of deafening the user by amplifiying noise components (eg: cymbals) which happened to be in that wavelength as well. The NCVA improves the signal of voice sounds by adding a low background of white noise at these same voice frequencies. This will not make voices louder, but will make them sharper.

I imagine the NCVA as like night vision for noise: hear the important things and not the rest.
-- bungston, Mar 12 2007

These use a similar type concept based on volume http://www.elvex.com/Com-550.htm
[jhomrighaus, Mar 12 2007]

a number of other similar items http://www.westerns...or/peltorpage3.html
[jhomrighaus, Mar 12 2007]

Stochastic resonance http://en.wikipedia...tochastic_resonance
It is all about signal to noise ratio [bungston, Mar 13 2007]

Noise cancelling microphone http://www.adaptive...com/nc_mic.php?mm=4
and how it works. [bungston, Mar 13 2007]

I don't think I understand. Is this a noise-canceller that cancels only the noise outside of the human voice range?

Also, a query: what is the spectral width of the human voice (think of the range between a vowel like "ohh" and the hiss of a "th"), and to what extent would it be helpful to cancel out only the noise which was outside of this range?

Finally, I'm not clear about the white- noise benefit. Stochastic resonance helps (sometimes) when the signal is just very very weak, but I'm not sure it helps when the signal is strong but is swamped with noise.

But maybe I'm missing the point.
-- MaxwellBuchanan, Mar 13 2007


/a noise-canceller that cancels only the noise outside of the human voice range?/ Yes. Like a noise-cancelling microphone.

/Stochastic resonance helps (sometimes) when the signal is just very very weak/

Yes. After cancellation you will have the remaining frequencies in which there might be a voice. I am not sure if the added noise has to be similar in frequency to the desired signal, but I bet it does. This is a way to improve the perception of voices without simply making them louder. It is really the only new invention in this idea. I lashed it to the noise canceller because only in a situation that was already very noisy would you want to avoid simply amplifying ambient sounds to hear voices better.
-- bungston, Mar 13 2007


OK, but it still doesn't convince me that it'll work. (I have no idea, but it sounds dodgy). What evidence do you have to show:

(a) that cancelling only the noise outside of the voice range will really help, given that the voice range is probably quite wide, and given that the most "interfering" noise is likely to be the noise *within* the vocal range? and

(b) that white noise superimposed on top of "voice plus vocal-range-noise" is going to help in any way? Stochastic resonance is mean to help by pushing near-threshold signals over the edge into above-threshold; I don't think it helps with signal-to-noise problems.
-- MaxwellBuchanan, Mar 13 2007



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