DIY noise generator? Pink or white noise

[therecordingart]

My wife wants me to build a noise generator for bed time. We've tried dialing in to radio static, but sometimes you get a blast of an actual broadcast in there which can be startling at the volume we set the radio. I don't want to run my iPhone, and I don't have a CD player that I can loop.

Any ideas?

I have a bunch of little battery powered amplifiers and little speakers...just need the noise now.

[Ry]

There is a circuit in one of Thomas Henry's books, I think it's the electronic drums book, that has a noise circuit in it.  Now that I look at the site that has the book for sale, I see that there is a noise generator book that I hadn't seen as well:

http://www.magsmoke.com/thomas_henry_books.asp

Ry

[ashcat_lt]

Run DC voltage through a resistor or a diode.  AC couple it to the input of the amplifier circuit of your choice with plenty of gain.  It'll be pretty close to white noise.  Filter as necessary to generate pink, brown, whatever.  You'll want to shield it to avoid picking up radio stations and CBs and stuff.

[R.G.]

Read Geofex.

There is a semiconductor junction noise generator in the Lo-Fi filter.

You break over a semiconductor junction and keep the current through it low. The charge carriers falling across the depletion region cause little ticks, which add to a hissy noise.

It's not exactly white noise, or pink, or 1/F either, although it looks like 1/F if you low pass filter it.

Most noise generators produce white noise, or rather an approximation to it. That's often too trebly, but can be controlled somewhat by a treble cut filter.

In actuality, pink noise is noise which has a power which falls at -3db/octave. But a simple R-C filter always produces power which falls at -6db/octave, so one RC rolloff is too much. The trick to getting pink noise is a "pinking filter" where you use multiple R-C filters which get in each other's way and prevent the classical -6db.

Semiconductor junctions vary in the quality of the noise. If you can program microcontrollers, you can get higher quality noise by making a very long feedback shift register inside the uC. This ia high quality white noise, which can then be "pinked".

[electrosonic]

The Elliott Sound Web Page a pink noise filter project here....
http://sound.westhost.com/project11.htm

Andrew.

[ashcat_lt]

Of course, for this application it doesn't have to be "real" pink noise.

My wife and I use a box fan set on high.  Not quite as energy efficient, but readily available.

[jimbanzini]

http://www.musicfromouterspace.com/analogsynth/rayspinknoise.html

i built one of those a couple of years ago for the same purpose.  tacked it onto a lm386 power amp into a cheapo 8" i had laying around.  added a switch to choose between white and pink.  12v zener works great in that circuit.

[derevaun]

I found that disconnecting the radio's antenna got rid of the random signals. I haven't reconnected it yet, in fact, though I vastly prefer the forced-air noise machine we eventually bought.

Some folks with major headphone GAS buy a cheap 2g mp3 player (at drugstores, Big Lots, etc) and play a white noise mp3 on repeat, to burn in the drivers in their new cans.