Audio DSP

That looks nice, here is somethng that could possibly be useful

I havent used it

martin

For the headphones, you need a pure analog solution. May be a digitally adaptive, but the analog filter core.

Any DSP will introduce the processing delay at the order of 1ms or so, and this makes it inefficient for the headphone noise reduction applications.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

I don't understand. These headphones mute the speaker when the sound i too loud, why would a 1ms delay matter?

Can't one easily reach >40ksps processing rates with a DSP, and have no more than 1/40k, ie.

Ok well that makes sense but in my application its not necessary to cance noise. Bad example with the PRO EARS. I'm looking for the headphones t amplify low volume sound, suppress high volume sound and just act a simple cover-your-ears hearing protection at very high volume say ove

93db.

I see no reason why an MCU can't do this.

We have only one AAA battery and we don't have too much of $$$.

Certainly.

The headphones that I know use a fairly simple analog circuit.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

Natsemi have this recent announcement

[To listen to a demonstration of National?s LMV1088 far-field noise suppression microphone amplifier, visit

-jg

+1 for Vladimir.

A millisecond delayed signal mixed together with the non delayed signal will end up in a static comb filter. That is not a problem if the comb notches don't move around (e.g. delay remains constant), you hear a natural sound with lots of frequencies and you hear the mix of delay + non-delay from a a meter or two away from the sound-source, including all the reflections from the room ect.

However, if you hear it over headphones (e.g. isolated) some nasty things will happen to some of us.

The ear/brain is trained to extract a lot of informations from the delay between the left and right ear (e.g. in audio-frequency range that is phase-difference). Things like 3D positions, distance ect. are percieved through this.

If you mess this up my applying static comb filters it will feel funny at first. So far no problem.

However, you can divide mankind into two categories: The first half will adapt to such a hearing-situation easily, the other one will get nauseous in a sea-sick kind of way.

I belong to the second kind. And I can't stand phase-mud for no longer than 10 minutes. Afterwards the headache starts to kicks in.

This is like having one of the speakers of a home-stereo out of phase, just worse (I know - lots of ppl. don't even notice it for years).

Hearing is a delicate thing and the brain does not like to be fooled.

Nils

I don't think you need any DSP. Just a pure analog function....Attenuate High Volume Signals Amplfy Low volume signals.

george

On Mar 10, 12:04=A0pm, Brendan Gillatt

I'm pretty sure you've never fired a hot round ejected close to your head without hearing protection - the pressure wave you get is substantial and you would NOT want to strap on a speaker system capable of delivering the inverse of that same wave.

These hearing protectors are purely passive (at least, every single one I've seen); they provide as close as possible to an airtight seal around the ear. The mic/amp/speaker combination provides a SPL-limited audio input path so that you can hear range officer commands, robbery victims screaming "Don't shoot", gutshot enemies groaning in pain, etc.

On Mar 10, 12:47=A0pm, Vladimir Vassilevsky

Hearing protection as required on a firing range is not the same thing as noise cancellation, in exactly the same way that safety goggles used for observing nuclear tests are not the same thing as dollar store sunglasses.

The Russian army tank helmets have the active suppression of the muzzle blast in the addition to the passive shielding. This technology have been in use since T-54.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant