Noise Generator

One more thing, it has to be small, portable and inexpensive (should not cost more than $25 to build). So it can not be done using a computer or an off the shelf expensive device.

How many samples do you need per sound and how precise do you need it? E.g. number of bits per sample, oversampling for different frequencies, how many levels for the volume etc. Is it for precise measurement or for something like a toy device?

A simple solution for less than 10 dollars would be to use a cheap microcontroller with sufficient large flash for the samples and a R2R networkt, maybe 8 bit, with an OpAmp for amplifying the signal and a digital potentiometer for adjusting the volume. Could be powered by a single 1.5V battery with voltage regulators like the MAX1724 (I like this chip :-)

Search on pseudo-random-binary-sequence generators. Horowitz and (Winfield) Hill's "The Art of Electronics" ISBN 0-521-37095-7 has a useful section on the subject at chapter 9.32 and 9.33.

There are lots of ways of realising such a device. The smallest and probably the cheapest would be to program some kind of single-chip microprocessor - such as an Microchip Technology PIC or an Atmel AVR - though you could also build it all into a single relatively small programmable logic chip from someone like Lattice.

-- Bill Sloman, Nijmegen

What is it that you call "noise"? We use hifi recorded aircraft noise in some tests.. is it something like that? Or is it something like a sine wave test frequency? Or do you want "pink" noise or some other kind of standard type of noise?

Best regards, Spehro Pefhany

A laptop running cooledit can generate white, pink and brown noise out the line out....

Here's a wild idea.. Buy a one of those cheapo pocket am radios (dollar store?) and tune to dead air.

D from BC

"Frequency"???? NOISE has all frequencies.

Hell, i will send him one...

Maybe he means "noise" in the non-technical sense of "sound", like the sound of a bell or the sound of a piano, or maybe even "noise music" (

snipped-for-privacy@frank-buss.dehttp://www.frank-buss.de,http://www.it4-systems.de

Hi Frank:

Thanks for your reply. I do not know how precise it should be as yet. I do not think it needs to be precise.I would like to be able to download sounds through some sort of serial protocol. I would like to be able to store different kinds of sounds - birds, animals, vehicles etc.

Let me know your further thoughts.

Thanks

Hi Bill:

Thanks. Quick question, can I store sounds using this kind of approach?

Hi Spehro:

A great question. I would like to store sounds such as birds, animals, vehicles etc. and I would like an ability to modulate the frequency and volume of these sounds through a serial protocol. Any thoughts?

Thanks

Hi Bob:

Thanks. I do not think that would work for me.

Hi Robert:

I am looking to store sounds such as bird, animal or vehicle sounds. Thanks

snipped-for-privacy@frank-buss.dehttp://www.frank-buss.de,http://www.it4-systems.de

Hi Frank:

You are right on. I am looking to store bird, animal and vehicle sounds. Thanks

I described a random noise generator, so the answer is no.You can use a single chip microprocessor to read and write data into and out of memory. The chips themselves don't tend to have all that much built-in RAM, but you can use them to write data into a RAM chip - you can buy

On the other hand, every teen-ager on the block has some kind of digital sound storage gadget stuck in their ears belting out arbitrary lumps of noise they've downloaded from the web.

-- Bill Sloman, Nijmegen

If you want to build something, it is important to describe it more detailed, otherwise possible solutions ranges from $5 telephone quality with sound length less than a second and $50 devices with hifi quality and sound length of a hour. Recording birds and animals is not a technical description and we can't help you with good ideas how such a device could look like.

You wrote you want to record sounds through a serial protocol and change volume through a serial protocol, but then you wrote that it has to be mobile and should work without a computer, so where does the serial signal come from for changing the volume? A good idea would be to describe the use case, e.g.: I want to record 10 sounds, 2 seconds each, mono, 8 bit, 12kHz sampling frequency, with a RS232 connection from a PC with 115200 baud. Then I want to set a fixed volume and frequency with the RS232 connection. The volume should be adjustable in 5 steps: 1/4, 1/2, 1, 2, 4. After this I want to unplug the device from the PC and want to use a battery for supplying power for mobile usage. The device should have a button to select the sound and a button to play the sound. One 7-segment digit shows the selected sound. The sound should be played with an integrated piezo speaker.

Search Digikey for ISD4004. Note: They also have direct pushbutton devices, but I'm not that familiar with them, or how much audio storage they have. Duration is trade off with fidelity.

I'm thinking the ISD4004 (available in DIP), and a small inexpensive micro might get you close to budget. The R2R would get you there too, but might be more difficult to implement to code.?

-mpm