Trying to build a white noise microphone blocker

I looked around to buy one but they cost may too much. I have some Arduinos and I read if you run digitalWrite(random(255)) in a tight loop will give you white noise. I thought about outputting this so a bunch of different speakers aiming in different directions to fully cover my room. Does anyone have any experience doing this or have any tips thanks.



Yes I wrote something like that in 6802 assembly language many years ago.

Here's an updated version:

    // get exclusive or feedback from tap 28 and 31, i.e. bit 27 and 30

    tempXor = (shiftRegister & ((unsigned long)1 << 30)) ^ ((shiftRegister << 3) & ((unsigned long)1 << 30));
    shiftRegister = shiftRegister << 1;
    if (tempXor != 0)
      shiftRegister |= 1;
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white noise circuit

Using a Arduino is a bit of $ overkill.


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This is for privacy so nobody can record you or listen to you? It would have to be annoyingly loud unless you build a room-within-a-room to reduce the noise you hear.

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You don't have to be paranoid to do this project, but it helps.

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Yes it is

Hey so what does this code do exactly

It does what you asked for, generates a pseudo random sequence.

I found this would this digital to analog circuit work for this white noise loop. Can I Hook up the output to a speaker. I found this. Would this work or does anyone known any better way to output the sound.

For the 6802 implementation, I didn't use a DAC. I just pumped the raw bits to an on board passive piezo transducer, attached to a digital I/O pin.

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Yes, you don't want to to DAC from the Arduino, just use the pseudorandom bit stream directly. One output pin with the random bit on it.

The sequence will repeat periodically, period depending on the length of your shift register and where you tap it.

I have a wave thing on a clock and it repeats every 12-15 seconds, no good!

A simple transistor circuit will give you real random noise that will not repeat. Besides costing a great deal less.


shows the circuit I had in mind - google

white noise circuit

and look at images, you will see several many two-transistor white noise generators, small variations in component values &c., but all exploiting the fact that transistors be noisy.

If the first transistor you try isn't (noisy) or you don't like the noise it makes try a few different ones for the noise generating transistor, the one w/ only the base and emitter connected.

I did a white noise blanket the room thing, well two sources, each had its own noise circuit, very much the one linked above +/-.

Sleep well. :expressionless:


The code I posted would repeat a pattern every 60 hours, at a 10k sampling rate. I don't think you would notice that. :slight_smile: As far as cost, I think something like a Pro Mini and piezo together might be competitive with a Zener/BJT source along with amplifier... even a proto board costs money.

Also, reading the original post again, why not simply try the suggestion you mentioned? Don't you think it would give you more concrete questions and experiences to post here?

Another thing you could do, is get some cheap FM radios and tune them between stations... :slight_smile:

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It all depends on what kind of fun you want to have.

I haven't heard your piezo transducer IRL, I wonder if it is nice like my 386 and old computer speaker set up.

I think cost is at best a secondary consideration, given the value of time, a perspective that will surely change as one ages.

We know the @aarg is 60++ (61? :wink: ) not being pessimistic when I say more years lived than remaining… I too am in such a place. A little further along, never mind precisely how much further.

Nevertheless long habits of finding the cheapest way to solve a problem no matter how long it takes to do tend to mask the real cost - I often refer to my $180 this or that what I might have just trashed and replaced instead of spending precious time fixing.


Argh @aarg a giant step backwards when we can't tune in between stations. Many the night in a bad hotel in a noisy city was made tolerable by "adjusting" the television for white noise.

A little trick I picked up from Hunter S. Thompson.


Truly, the cheapest way depends on what the OP has on hand to work with. The solid state generators do have some "cool" factor. I've even seen a circuit that implements "fractal chaos".

Here, the FM stations are jam packed from one end of the band to another, so it wouldn't work where I am, either...

[quote="johnboyman, post:10, topic:927973"]
Can I Hook up the output to a speaker. [/quote]
You can directly drive a piezo transducer but you probably won't get enough volume. Regular speakers require an amplifier, or powered computer speakers have a built-in amplifier.

Basically, each speaker needs its own amplifier, and of course a stereo amplifier can drive a pair of speakers. Depending on the amplifier & speakers you may be able to double-up on the speakers. i.e. Two 8-Ohm speakers in parallel is 4-Ohms, etc., and if the impedance is too low you'll burn-up the amplifier.

For "experimental purposes" you can generate a white-noise or pink-noise file with Audacity and then you can play it in a loop on your computer or phone. You can build a dedicated noise generator later.

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Hey so could I record a white noise audio file on my computer then plug it into the input of the amplifier and the output is where I Hook up the speakers. Do I need one amplifier per speaker?

Please go and research the topics that have been presented. Audacity can generate waveforms, you don't need to produce and record noise for that. Same thing with amplifiers, there is an abundance of online information about that. A thread can not be a semester long.

If you then have issues or questions about what you find, we'd be happy to answer those.