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Author Topic: Cockroach /Insect noise generator.  (Read 2218 times)
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A friend of mine needs a simple device for making pseudo Cockroach/ insect noises to go with a fancy dress outfit  thats to be worn to an open air event.  

Here's what I've come up with so far:



Uses a 6 bit r2r ladder as a D/A convertor and a 1W single chip amp.  No filtering is done after the converter, this needs high and dirty harmonics IMHO.

Andy
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Now that's what I'm talking about!

As many times as I've held a cockroach up to my ear, I've never once been able to coax it to emit a single peep. I've had equally bad luck trying a twisted pair.

I think you have recreated the essence of cockroach speech quite nicely. My only suggestion would be to crank it up another octave to get that really spooky ultrasonic sizzle.

(Shouldn't this be in Bugs and Suggestions?)
« Last Edit: July 11, 2009, 02:38:09 pm by EmilyJane » Logged

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Someone needs to put that poor cockroach out of its misery!

@EmilyJane, best reply I've read today. I can logout happy now.
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Thanks! I couldn't help myself. ;D
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If you are looking for something like cricket sounds, since you are using an Arduino, check out this thing:

http://www.hvwtech.com/products_view.asp?ProductID=1002

Throw a cricket recording onto on SD card, and have it play whenever button is pressed.
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@brutus,    thats an interesting card.  However I had a look around on line and couldn't find a suitable noise.   This program uses a FM (LFO) modulated sinewave and AM modulated by a much higher frequency squarewave.    I'll try and post the code a bit later.

Andy
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I'd like to know a little more about your circuit. For instance, are you using the "reference" input to the R2R network to do the modulation or are you doing everything in software? Or what?
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@Emily,

The software is of course on my work machine and remote from me at the moment.  I'll try and post it tomorrow.

However all the sound generation is in software.  The sin wave just uses a sin function. It's Fm modulated by simply adding a slow sin to the angle sin(theta + modtheta).

The final value is simple out=sinvalue*squarevalue*ADSRvalue

I use digital outputs 7->2 as the value output.  That goes into the D/A converter (Based on this http://www.allaboutcircuits.com/vol_4/chpt_13/3.html but with no op amp following it).  This goes into a TDA7052 amp using the simple circuit from the datasheet. It's dirty, but for this app thats fine.  I might need to add a volume control as I *think* I'm overloading the amp at the moment !

Andy
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Oh, okay. Very clever. I've used multiplying DACs for similar, but not nearly as much fun, things before. You can amplitude modulate anything coming in on the reference to the R2R network by varying the digital fraction on the switch side or vice versa.

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Quote
As many times as I've held a cockroach up to my ear

As reluctant as I am to admit in a public forum the depths of morbidity to which my curiosity can sink,  I find myself compelled to speak on behalf of all the other readers who are also wondering just how many times that would be.    smiley

In addition to the standard "Ewwww" factor,  a group like this one is also faced with all the images from science fiction of insect(oid)s being inserted in people's ears to subjugate them to the will of the new alien overlords (Assuming I could actually hear anything over the cocking of the pistol being held to my other ear,  I would half expect the bug to make a noise that sounded like "rich Corinthian Leather"...),  so the very existence of your experimentation seems all the more remarkable.

Inquiring minds want to know.  Sorta...

Ran
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@EmilyJane  full source code is here:

http://hackday.computing.dundee.ac.uk:8080/roachnoiseproto/roachnoise.zip

Andy
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