Using a 555 timer as an analog frequency divider?

[crono1009]

Hey guys,

I'm trying to build a circuit where I can put in an analog signal (my voice) and have it output the same signal with a much lower pitch (speech synthesizer). Is there any way I could do this with primarily a 555 timer?

I'm able to pulse width modulate the analog signal, but I don't really know where I can go from there. I was thinking about bringing in the analog signal via ADCs and then changing the frequency of all of the bits via a few 555 timers and finally DACing the signal into a speaker, but all I get is junk (sampling frequency issue?).

Any ideas?

 

[vk6kro]

Your voice doesn't just have one frequency. It has a lot of frequencies and harmonics of those frequencies.

So, it won't sound like you unless you can reproduce those frequencies or at least the relationship between them.

One way might be to use an A to D converter to record your voice into a memory chip and then play it back with a different clock rate and feed this output to a D to A converter.

This might give you something like the effect you are after, but it is complex and difficult to do.

 

[crono1009]

Your voice doesn't just have one frequency. It has a lot of frequencies and harmonics of those frequencies.

So, it won't sound like you unless you can reproduce those frequencies or at least the relationship between them.

One way might be to use an A to D converter to record your voice into a memory chip and then play it back with a different clock rate and feed this output to a D to A converter.

This might give you something like the effect you are after, but it is complex and difficult to do.

Yeah, I figured as much. I've been simulating with only one input frequency, I could see how this would be cumbersome. Thanks for the tip!

 

[dlgoff]

I guess you are trying to do it as close as possible to "real time"? That would be a analog nightmare so a uP, which is what vk6kro I believe is suggesting, is the way to go.

Edit: When my daughter was a kid, she had a program that would modify (maybe 4 built-in styles) and the ability to play it backwards. Actually she got good at speaking backwards then playing it back backwards and it sound perfect. lol Anyway I just did a search and you can get software for voice modification. e.g. http://www.screamingbee.com/product/download.aspx"