Relative Audio Measurement

I need a circuit that takes an audio signal, averages the signal over the course of say a second, repeats continuously every few seconds, and then outputs a DC signal that I can read on my voltmeter.

Has someone already designed such a beast?

Reply to
NuttyBee
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Tim has offered a very good review of this subject. Using his info as a guide, I would suggest you search for a peak follower circuit.. or ask and I'll send you a schematic.. it uses a simple op amp, diode, capacitor and resistor(s). A simple diode bridge like the AC rectifier configuration might work reasonably well for an approximate reading, with a capacitor in parallel with a resistor in parallel with the meter, and is cheap to make, requires no power.

Geoff

Reply to
grunt

Tim's post is good. But, can you tell us more about what you're trying to do? Reason being that audio measurements can be done a number of ways; without knowing the application there's no way to know whether it would be best to measure peak voltage, rms voltage, average voltage, or any of a slew of other possibilities.

Plus, if this is part of a bigger puzzle, there may be a solution you'd not thought of.

Reply to
Walter Harley

A rectifier and average-DC filter would work pretty reasonably... which coincidentially is what your voltmeter does on the AC setting, though maybe not as slowly as you want. The output is roughly the time-integral of the input minus a time constant, so it continuously "resamples" as time flows on.

If you *do* want an average-for-this-period-of-seconds result, you could chop it up with a sample-and-hold with a couple-second clock. Each discrete output level is the integral of the rough time period covered by the RC circuit.

To get even more particular, you could set up an ADC and sum samples in a register, then divide by the number of samples collected over the averaging period. To get a continuous result, you'd collect samples in a chain of RAM, incrementing (and looping) the address for each sample, again taking the average of the samples, this time at a rate of every clock cycle so as to get a continuously updated output. Since it's all digital, you could even store individual samples, entire durations, or samples or ranges of the output in seperate locations, or connect it to a computer and do even more... but I'm guessing this got over your head a while ago.

Tim

-- Deep Fryer: a very philosophical monk. Website:

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Reply to
Tim Williams

If you average an audio signal over a period of a few seconds the result will be close to zero.

Ian

Reply to
Ian Bell

What you feel is a new flame war coming on.

--
 Thanks,
    - Win
Reply to
Winfield Hill

"Ian Bell":

** Pedant.

.......... Phil

Reply to
Phil Allison

I feel a new law coming on... Something about if you average the usefulness of Usenet replies over a period of a few days the result will be close to zero.

Reply to
Derek Potter

"Derek Potter"

** That is being far too optimistic.

I'm certain the long term average has a massive negative offset.

......... Phil

Reply to
Phil Allison

Only when you're around.

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
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Reply to
Michael A. Terrell

"Michael A. Terrell"

** The negative offset is due entirely to thousands of know nothing pukes like you - Terrell.

You just added another bit of disinformation to the offset.

Kindly go drop dead.

......... Phil

Reply to
Phil Allison

What??? In a sci-dot newsgroup??? NEVER!!!

Reply to
Derek Potter

Children!

Reply to
Derek Potter

One needs to be like Maxwell's demon, sifting the randomness while not reacting to it :)

Reply to
Derek Potter

Yawn. I give it a -21.

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
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Reply to
Michael A. Terrell

"Michael A. Terrell"

** The negative offset on usenet is due entirely to thousands of know nothing pukes like you - Terrell.

You just add more and more disinformation to the offset.

Go drop dead.

......... Phil

Reply to
Phil Allison

I see that your sex change operation didn't work out for you. No matter how har d they treid, they still couldn't make a man out of you.

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
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Reply to
Michael A. Terrell

"Michael A. Terrell"

** The negative offset on usenet is due entirely to thousands of know nothing pukes like you - Terrell.

You just add more and more disinformation to the offset.

Go drop dead.

......... Phil

Reply to
Phil Allison

Can't you come up with any new material, or are you spending your meager income on cat food? You're quite boring, you know. You stopped being funny or entertaining years ago, and since then you have become the saddest joke on any of the electronics newsgroups. Its too bad, becasue you used to come up with something worth reading from time to time.

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
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Reply to
Michael A. Terrell

"Michael A. Terrell"

** Shame you cannot answer any of the "old material".

....... Phil

Reply to
Phil Allison

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