looking for audio noise source - Page 1
Forum section: electronics / projects

author: qno
author_rank: Frequent Contributor
timestamp: June 27, 2013, 08:35:14 pm
content: Hi all,I am looking for an audio noise source.I now have a standard NPN transistor with emmiter base in reverse as zener.Problem is the Ueb is around 9 volts.Does anyone know a transistor with a lower breakdown voltage preferably around 5 V or another noisy PN junction device?I know you can use a PIC or Atmel with a random generator but the board is now analog only so I prefer an analog solution.

author: josko
author_rank: Newbie
timestamp: June 27, 2013, 11:07:10 pm
content: I would just use some longer wire/pcb track and high input impedance device like jfet/mosfet and it would pick up ambient/thermal noise.

author: edavid
author_rank: Super Contributor
timestamp: June 27, 2013, 11:40:09 pm
content: Low voltage zener...

author: SeanB
author_rank: Super Contributor
timestamp: June 28, 2013, 06:09:54 pm
content: Rf transistor is pretty noisy and normally has a lower breakdown voltage because of the thinner junctions.

author: Paul Price
author_rank: Super Contributor
timestamp: June 29, 2013, 12:36:16 pm
content: Build a pseudo-random sequence n-stage shift-register (n=8 or higher, the higher the better) anything in the high KHz for a clock, with xor feedback to the input. Lotsa random noise with a r-c filter for integration to restrict the spectrum in the black noise or gray noise range audio range. Must have anti-lockup detect if S-R has somehow figured out that generating a serial stream at some point of all 0's or all 1's as the optimal noise to fill the universe.Can easily be implemented with a few lines of MCU code.

author: nctnico
author_rank: Super Contributor
timestamp: June 30, 2013, 12:18:47 pm
content: The problem with digital solutions is that you often end up with something which sounds like noise but has poor frequency distribution. I'd recommend the old style method of using a transistor. There must be tons of schematics on the internet (IOW: use Google).

author: fpliuzzi
author_rank: Regular Contributor
timestamp: July 01, 2013, 12:36:56 pm
content: Would this pink noise generator circuit be of use to you?http://sound.westhost.com/project11.htmRegards,FrankEDIT: Pink noise is useful if the application requires the particular characteristic that pink noise provides, where the noise power in one octave (for example) 40 to 80Hz needs to be the same as in the octave 10kHz to 20kHz.

author: qno
author_rank: Frequent Contributor
timestamp: July 01, 2013, 09:51:36 pm
content: Hi all,Thanks for the reply.I will give the HF transistora try.

author: kimbal
author_rank: Newbie
timestamp: July 02, 2013, 12:16:58 pm
content: Unless your after a particular audio bandwidth of noise - pink, white, grey; etc - try using and a transistor AM radio receiver ( with the antenna circuit shorted out to kill station reception ) as the source - with a simple RC filter wired on the output to clean it up.The unmodified signal bandwidth is quite wide - somewhat like white noise.

author: _Steven_
author_rank: Contributor
timestamp: July 02, 2013, 12:23:47 pm
content: Quote from: kimbal on July 02, 2013, 12:16:58 pmindeed