Alarm MP3 & chips and hardware

Hi,

I'm working on a homebuilt circuit, that will provide an anti-theft
alarm for a bicycle.

I've been going down the routes of looking at various 555 timer
circuits, making various beep beep noises, but prefer the sounds of
some of the free mp3 sound files that are out on the net.

I've downloaded some of these files, and am wondering how I could put
them on a memory chip of some type, and then be able to 'output' them
at appropriate times, into a loud speaker..

Clearly, I'd need a chip to interpret the files held on the ROM chip
(?), before it's output to the speaker? What would that chip be? Are
there any off the shelf chips to do this sort of thing?

Sorry, I can't be more specific, as I don't know too much about
electronics.

Thanks
Jeremy Watts

 

Cheers

 

alarm for a bicycle.

OK, you want to "build" your own device.

If you really want to do that, you need to do more homework.

As a starting point:
1) learn what an MP3 file is.
2) learn about solid state storage devices
3) learn about how to program a device that will take advantage of the
devices in 1 & 2.

Let me help you out:

http://lmgtfy.com/?q=build+mp3+player

with About 73,600,000 results (0.14 seconds)

you should be able to see what needs to be done.

Your Welcome

PS: Second link will tell you every thing you need to know.

 

mp3 decoder.

But you need to know the trade-offs. MP3 is Discret Fourier Transform (DFT) of time domain samplings, so you need to reverse the transform before outputting to the speaker. Storing/outputting the real time audio samples might be easier, but it would take more than 10x memory storage.