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Guesstimate of Size/Practicality

 
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victorf



Joined: 01 Jan 2006
Posts: 342
Location: Schenectady, New York
Posted: 17 January 2008, 2:29 AM    Post subject: Guesstimate of Size/Practicality Reply with quote
I would like to get your guesstimate of smallest size audio recording/playback device that could be built using today's technology. The device should be able to record at least one to two minutes of speech and play it back (on demand) with reasonable fidelity. It should be practical to build.

Any enlightenment will be appreciated.

Vic
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mikep



Joined: 24 Sep 2005
Posts: 771
Location: Austin, TX
Posted: 17 January 2008, 3:20 AM    Post subject: Reply with quote
Your requirement is so fuzzy there are too many possible answers.

Which technology? Thru-hole? SMD? VHDL? uC? DAC?

Practical to build by who? You? Chinese manufacturing company? Me?

I suggest you read ZBasic application note AN-06 and try it out. Then you would have a better idea of "reasonable" quality" and what is achievable with ZBasic technology.
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spamiam



Joined: 13 Nov 2005
Posts: 689
Posted: 17 January 2008, 3:28 AM    Post subject: Re: Guesstimate of Size/Practicality Reply with quote
victorf wrote:
I would like to get your guesstimate of smallest size audio recording/playback device that could be built using today's technology. The device should be able to record at least one to two minutes of speech and play it back (on demand) with reasonable fidelity. It should be practical to build.

Any enlightenment will be appreciated.

Vic


Well, that is a good question. Part of the answer of this would be the amount of data you need to process. This will tell you how big and fast the chips need to be. To answer that, you need to be able to say what frequency range you need to have it understandable. I would imagine that 4000Hz would do it, and likely less! 2000Hz?

Replication of a 4000 Hz waveform, requires 8000Hz sampling. Then you need to be able to say how many amplitude levels are needed. 256 is a nice round number, and I would bet that 64 would be adequate. Unfortunately, I doubt that only 16 levels (4 bits) would be all that good, but it might be understandable, so the next "reasonable" size would be 8 bits. However, depending on your encoding you COULD use any number of bits to code the amplitude. Compression algorithms could shrink the resulting encoded data stream

So, I think that 8000 bytes per second (uncompressed) would sound OK. I think that 2000 bytes per second would not sound too good, but might be understandable.

A simple, fast, compression algorithm might shrink those sizes by a factor of 2 to 4.

These are just my thoughts off the top of my head.....

BTW, I think that there are TINY record and playback devices (like in kids toys) that are single chip devices with little batteries, and little piezo speakers.

-Tony
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dkinzer
Site Admin


Joined: 03 Sep 2005
Posts: 2593
Location: Portland, OR
Posted: 17 January 2008, 4:18 AM    Post subject: Re: Guesstimate of Size/Practicality Reply with quote
spamiam wrote:
I would imagine that 4000Hz would do it [...]

If you have an audio editor (like the freely downloadable GoldWave, for example) you can experiment with different sampling rates to determine what is suitable for your needs.
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stevech



Joined: 23 Feb 2006
Posts: 688
Posted: 17 January 2008, 5:15 AM    Post subject: Reply with quote
smallest possible - requires very specialized implementation/mechanical acumen.

My brother-in-law's new hearing aids are impressive: they work like noise-canceling headsets, use DSP for an equalizer. Room for a battery. Certainly room for a few MB of sampled sound.
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dlh



Joined: 15 Dec 2006
Posts: 287
Location: ~Cincinnati
Posted: 17 January 2008, 11:34 AM    Post subject: Reply with quote
There are chips available that let you store/playback wave files. The cost is proportional to the length of the recording. Here's an example - there are many others.

http://www.eletech.com/Products/QuikVoice_Chips/quikvoice_chips.htm

There are other techniques which might be adaptable to the ZX chips but you will likely run into EEPROM size limits.

http://www.romanblack.com/picsound.htm
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victorf



Joined: 01 Jan 2006
Posts: 342
Location: Schenectady, New York
Posted: 19 January 2008, 10:25 AM    Post subject: Reply with quote
Thanks for the replies.

It has been pointed out to me elsewhere that devices to digitally record a couple of minutes of voice already exist and that I would be better served looking into them. There are even kids toys that fit the bill and these are sometimes given away at McDonald's so they must be cheap. Of course, so is the sound quality.

I guess I do not need to re-invent the wheel. Confused My next move is a trip Best Buy or Sharper Image. Smile

Thanks again

Vic
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