White Noise Source

"Chiron"

** I think you will find this microwave sauce recipe most satisfactory:

Not to mention tasty too.

And may I supply a word of advice -

leave the imaginary voices to the experts -

ie the genuine schizophrenics.

... Phil

Download my Daqarta software... it's free for signal generation use. Midway down the Generator dialog, click the left Waveform Controls button. Click Wave on the dialog that appears and select Noise: White. Toggle the Generator button on in the main toolbar. The first time the Generator goes on the volume control dialog will pop up, plus a cautionary message about loud levels. You'll need to cancel the message before the sound starts. (In WinXP you may also need to unMute, at the bottom of that dialog.) Later, you can open the volume dialog via the F9 key at any time.

Now I'm going to give away a secret: In the next version of Daqarta (v7.00, in a month or so) there will be a whole Help section on EVP-related stuff, and a demo on how to hear it for yourself. Well, not exactly what the woo-woo folks are talking about, but a phenomenon I call "Phantom Signals" that I think is at the root of the EVP nonsense... as well as "dental radio".

The trick for phantom signals is to use headphones and put the white noise in *one ear only*. The loudness should be about 30-40 dB above your detection threshold. (You'll need to be in a fairly quiet room, with no music, TV, or voices.)

I'll provide a simple way to set that level. Let me know if you want me to explain a manual approach here. It's not super-critical, but it needs to be loud enough to hear easily, but not too loud.

Listen for a few minutes, and you will start to hear a "radio station". You might hear music or voices, but you won't be able to tell exactly what the song is, or understand what they are talking about... nevertheless you'll be convinced there is a "signal" there. You might categorize the station as "Country", or "Talk Radio", or whatever, based on what you hear. You'll probably have an overpowering feeling that if only you could just improve the S/N a *teeny* bit you would understand everything. But you can't.

And if you switch the noise source to *both* ears, the phantom signal vanishes and you just hear noise. (Sometimes you can get the effect with both ears, but it may take a

*lot* of listening.)

I actually discovered this a long time ago, while designing a diode-based noise generator. Since that sort of circuit involves a lot of gain, when I heard the "radio station" I naturally assumed that's *exactly* what it was hearing. I tried all kinds of filtering before I finally got rid of it... coincidentally having switched from a single-ear lineman's test set to stereo phones. Problem solved!

Then I built a completely digital version, which doesn't involve gain and is not susceptible to AM pickup... or so I assumed. Yet it was back again, but only with the mono headset, not stereo or speakers. Took a lot of testing to convince myself that it wasn't a circuit problem... at least not in my hardware circuit, only the "wetware" between my ears!

Then when I showed the phantom signals effect to others they were absolutely convinced it was a real radio station, and that there was some defect in my hardware. Had to go through all the steps with them to prove it was only in their heads. The really convincing proof was that it vanished instantly when heard through both ears... hard to explain if it was AM pick-up!

For a long time I didn't want to announce this to the general public because I hoped to recruit subjects for an unbiased test. But that got put on the back burner for so long that I've given up on it.

So enjoy!

Best regards,

Bob Masta DAQARTA v6.02 Data AcQuisition And Real-Time Analysis

Scope, Spectrum, Spectrogram, Sound Level Meter Frequency Counter, FREE Signal Generator Pitch Track, Pitch-to-MIDI Science with your sound card!

Zeners do work. I had used a 6V zener feeding it through a 1 meg resistor from 15V. The spectrum was lacking in much of the audio range though. I had better success reverse biasing the base-emitter junction of any garden variety transistor. The NPNs that I tried break down in the range of 8 volts, so again, a 1 Meg feed from 15V is a good starting point.

the '15V' can be either from two 9V batteries or a boost converter.

OR you can look up "white noise schematic"

Pseudo Random Noise can be digitally generated with a recirculating shift register that has the feedback tapped at a few points and XORed as shown in this diagram

It shows 12V power but modern logic elements will work at lower voltages. I used a similar circuit for calibrating a sonar system (signal of interest burried in 90 db of noise).

Thanks, Oppie. I might try the idea with the transistor. Seems like it might be what I'm looking for...

--
Exercise caution in your daily affairs.

ipate

I really like 20V 1/2 watt zeners for this... bias from +/-15 volts through a 1 meg resistor. Lotsa noise and flat out to ~500kHz or so. The voltage is a bit asymmetric, but that can be fixed..... by adding two of opposite polarity.

George H.

Thanks, George. Is there anything special about the zener being 20V? In other words, would a 20V zener be better than using, say, a 5.1V?

--
Tart words make no friends; a spoonful of honey will catch more flies than
a gallon of vinegar.
		-- B. Franklin

Yes, the higher voltage zeners have a little negative resistance in part of their curve. That is why you can build an oscillator using just the diode a capacitor and resistor. Try it. Fun. Look closely at the curves on the higher voltage zeners.

=A0In

n

Yeah a big difference. In low voltage Zeners the current is from tunneling electrons (one at a time) and only have shot noise. (Which is pretty small). High voltage 'Zeners' do this avalanche break down...big random current pulses. Lot's more noise 'amplitude'. I looked at a bunch of different voltages. (Above somethiing like 6V is where you start to get some avalanching.) 10 and 12 Volt Zeners showed more than shot noise, but there was a lot of part to part variation in the amount of noise. For some reason* 20V zeners all give about the same signal levels... I posted a 'scope shot some time back. If you use glass encapsulated diodes then wrap some black electrical tape around them... else the room lights leak in and ruin everthing.

George H.

• So here's a WAG as to why 20V (or there abouts) has uniform noise piece to piece. At lower volatage the break down is at some channel in the diode. There's a lot of variation in the 'golden' channel for different diodes. So different sizes of current pulses... (different capacitances in each channel).

But at some voltage, (20V?) the whole diode breaks down and you get a current pulse that is the whole diode capacitance. Since this is pretty constant, you get about the same size of pulses piece to piece. (I'll mave to 'measure' the pulse size and see if that fits...)

.

=A0In

Interesting, can you post a schematic? It may not be negative resistance.... With a long enough time constant, you may be seeing the random 'firing' of the zeners discharging the RC, then waiting a few RC for the voltage to rise. Once above some 'thershold' you only have to wait about a micro second till the next random firing.

George H.

This is interesting. Who knew there was so much to something as (seemingly) simple as a zener diode? Not me, anyway.

Thanks for the info.

--
Afternoon, n.:
	That part of the day we spend worrying about how we wasted the 
morning.

is

big

is

ed

Grin... You caught me at golden moment, I'm waiting for a pcb with a Zener noise source on it to come back from the board house.

Diodes look simple, but there is lots of nice physics to be got out of them. Decent thermometers for instance.

George H.

d the

.9

Never even thought of that; I'll do it.

I think I recall something similar from Don Lancaster's CMOS Cookbook... but IIRC, the "noise" repeated. Not sure whether that would be a problem, though...

Anyway, thanks for the ideas.

--
Some of us are becoming the men we wanted to marry.
		-- Gloria Steinem

It depends on what you want, and how long the sequence is.

Sound generator ICs like the AY-5-8910 (I think I got that number right) or those from Texas Instruments used that scheme. If the sound generator in the Commodore 64 included a white noise source (I can't remember), then it used that scheme.

For a while in the seventies, National Semiconductor had an IC that generated noise using that scheme, it was sold as a "pink noise generator", where you'd add an external filter to make the noise "pink". Another company had a similar device.

Of course, PAIA just used a 2N2712 for the noie source in their projects. It was never clear if they found that device was better at it, or if they just found a cheap device.

Michael

IIRC, the C-64 did have some sort of noise function... we're going back a ways now. That was about the last time I played around with electronics, too. Things have changed a wee bit since then - what, 1988 or so?

I found a circuit that looks promising. I'll have to refer you to the Website, since I don't yet know how to draw schematics using ASCII:

This circuit uses 2 resistors, 2 capacitors, a diode and a 2N3904. I doubt I'm going to find anything simpler, unless it's an IC like you described.

I think my main problem was I didn't hit upon the right Google search words, so I was chasing down all kinds of stuff that had nothing to do with what I wanted.

Thanks, all, for your help.

--
The profession of book writing makes horse racing seem like a solid,
stable business.
		-- John Steinbeck
	[Horse racing *is* a stable business ...]

You give them a solution - and for free that they can use right now - and they continue to talk about using Zeners to make noise. I have a horse. I showed him where the water is and he drinks it. Not sure about these people though.

G=B2

How about, I ask for a cheeseburger; someone offers me a free glass of water; but I keep talking about the cheeseburger, because I'm hungry, not thirsty. Besides, your horse is drinking out of the glass, and that's just plain gross.

To be honest, I never saw the post you quoted. It didn't get past the killfile - too many lines. Unfortunately, one of the problems with a killfile is that you may wind up blocking perfectly legitimate posts, as you try to get rid of all the crap.

OK, I'll have a look on Google and see what he said...

--
You can always tell luck from ability by its duration.

A whole lot that I missed...

Bob, I apologize for not responding to your thoughtful post. I keep a fairly stringent killfile, and one of the things I filter on is the length of the post. Unfortunately, the filter doesn't distinguish between someone endlessly ranting, and someone who has troubled to write a lengthy response. I'll have to rework the filter somehow to make sure you don't get blocked again.

Your suggestion to use only a single ear is intriguing, and something I'd not heard about before. Had you not mentioned it, I'd have used both earphones; but now I will follow your idea and use only one.

To be honest, I am highly doubtful of this EVP. My guess is that people, when encountering auditory or visual "noise." tend to perceive patterns where none exist. Of course, then you get into the question of whether someone is hearing voices that don't exist, or whether someone is simply deaf to those voices. An interesting philosophical

You asked for an audio noise source and mentioned Zeners but you have to build something to actually use Zeners. You obviously have a computer which very likely has audio capabilities. You can build something in a few days or you can have your noise source in minutes. You were offered a noise source. What's your time worth?

G=B2

Yeah, well, as I was saying, it's an interesting question, but not one I feel up to answering.

I've listened to recorded samples where people thought they heard a voice, but I never got anything other than the noise. So I figured I'd just try it myself and see what happens. Since I am doubtful, I didn't want to invest a whole lot of effort building a circuit.

Thanks for your offer. I don't think I can use it, because I'm not using Windows. But I do appreciate the offer, and I again apologize for seeming to ignore you.

-B