Best place for an active filter?

[bountyhunter]

Generally that's a VERY bad idea - far better to have a manual gain control, so YOU are in charge of what's going on.

But I suspect you won't be able to turn the volume down fast enough when you have your parabolic mic aimed at something and somebody six feet away coughs or sneezes. I know that it's not that hard to do because many of the low cost electronic ear muffs have 85 dBA limiting circuitry for the internal audio amp/speaker so that spoken conversation is very audible but gunshots get limited almost instantly.

 

[bountyhunter]

DSP seems to be the "real" way to deal with this.

Probably so. These days, digital is the best way to process most everything.

 

[Nigel Goodwin]

I know that the electronic ear muffs for shooting have some limiting circuits that work pretty well.

A limiter is a very different thing from AGC

 

[atferrari]

Yeah, it would save my ears too when there's an expected loud noise.

This is how I dealt with it. Limitation works somehow.

By the time I completed the building of the circuit, I realized that my right ear hearing is seriously impaired so I couldn't test in detail with the associated directional horn.

My left ear you ask? In few hours, about 35 years ago, an infection at sea, took away my hearing and I just perceive noise. Pain is not strange to that if loud. It was then when I started to learn digital techniques. True.

 

[AnalogKid]

DSP seems to be the "real" way to deal with this.

Naw, just the latest way. If you break down the processing algorithms, they are translations of the analog building blocks. With DSP you get memory, and that can be used to fine tune the response actions. And (if you spend the money on extended code development) you can apply different correction curves to different frequency bands, but high end volume processors for radio stations were doing that in the 60's. It still cannot do the context analysis necessary for human-grade reactions. The overall system for a DSP AGC is pretty much the same, just smaller and cheaper than all of those analog components.

ak

 

[audioguru]

Isn't a spy mic used to hear distant people talking? Then high fidelity is not needed to hear a loud motorcycle driving past, clip the noise with diodes.

 

[AnalogKid]

I agree, a soft clip and a manual volume control probably are a better fit than a feedback control method. I did the Popular Electronics shotgun mic as a science fair project lllllong ago, and even though at the time I didn't understand how the diodes made things better, they did.

ak

 

[crutschow]

You can control the degree of "softness" of the clipping by adding a resistor in series with the diodes.

 

[AnalogKid]

Yeah, I know that *now*.

 

[StellarRat]

So....how does one clip with diodes?

 

[crutschow]

So....how does one clip with diodes?

One way is to put them in parallel, back-to-back, in the feedback loop of an inverting op amp amplifier circuit.
A resistor in series with the diodes affects the sharpness of the clipping which affects the harshness of the sound when clipping.
That will clip the signal starting at about .6V peak or 1.2Vpp.