Aleksander Wittlin wrote:

> Hi all,
> 
> I am looking for a simple and cheap  design of a sound delay box for
> science fair exhibit. It should simply delay  microphone signal
> within the range (regulated) from  0.1 to 5 seconds.
> Sound quality does not really matter.
> I considered a PC with sound card (bulky) or professional
> audio console (expensive). Perhaps a simple DSP  board
> with codec and some memory plus a small preamplifier would
> be sufficient.  Any suggestions?
> 
>                                             Aleksander 

Aleksander,

Decent speech quality needs at least 8000 samples per second, so a 5
second delay needs 40,000 samples at that rate. Even using two bytes to
store each sample, this is a reasonable amount of memory for a program
on a laptop or desktop PC. Your program can implement a circular buffer
with one pointer. Read from the pointed-to location and send the sample
there to the audio output. Get the new sample from the microphone, and
write it to the same location, then  Check to see if the end of the
buffer has been reached. If so, reset the pointer. If not, advance it.
Then wait for the new sample and begin again. The size of the buffer
determines the delay.

Depending on the hardware and the signals it sends, you might need to
modify the procedure a bit. If you have trouble getting it to work, let
us know what it is and we'll try to help.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������

So you need two microphones and two speaker outputs?  Most standard soundcards
or laptop audio I/O only have one microphone input, so that probably means you
need a external 2-channel microphone pre-amp.  But then you could use the line
level inputs of either a laptop or a DSP or micro-controller demo board.  For
this simple application, most any commercially available boards will probably
work as long as you have enough memory.  Reducing the sample rate could save
memory, as could more processing-intensive solutions such as lossy compression
(MP3 or similar).

For robustness (child-proof) and ease of programming, I would suggest the
laptop, as everything is in a sealed package.  You may even be able to disable
the keyboard and mouse, or at least move it to where it is not easily
accessible.

"Aleksander Wittlin" <a.wittlin@aster.pl> wrote in message
news:cocoub$2t2m$1@mamut1.aster.pl...
>
> U&#4294967295;ytkownik "Mike Yarwood" <mpyarwood@btopenworld.com> napisa&#4294967295; w wiadomo&#4294967295;ci
> news:cocbj2$5j8$1@titan.btinternet.com...
> >
> > "Aleksander Wittlin" <wittlin@aster.pl> wrote in message
> > news:coav49$1ofm$1@mamut1.aster.pl...
> >> Hi all,
> >>
> >> I am looking for a simple and cheap  design of a sound delay box for
> >> science fair exhibit. It should simply delay  microphone signal
> >> within the range (regulated) from  0.1 to 5 seconds.
> >> Sound quality does not really matter.
> >> I considered a PC with sound card (bulky) or professional
> >> audio console (expensive). Perhaps a simple DSP  board
> >> with codec and some memory plus a small preamplifier would
> >> be sufficient.  Any suggestions?
> >>
> >>                                             Aleksander
> >>
> >>
> > Hi Aleksander , if  quality isn't a problem I would start thinking of two
> > cheap scrap cassette recorders screwed to a length of wood. If  you put a
> > few idle wheels here and there you should be able to arrange for the delay
> > between record from one player and play from the second to roughly fit
> > your
> > interval ( 0.1 second could be difficult though - maybe this technique not
> > possible?)
> >
> > Best of Luck - Mike
> >
> Nice idea, thanks. However, it would be rather fragile, due to the tape. It
> should be
> children/teenagers/visitors proof. Moreover, I would either run out of tape
> after a while,
> or have to deal with a tape loop. Also I didn not mention that it should be
> duplex
> system (both participants talk and listen). Then I would need four recorders
> and two tapes. It may be too cumbersome to operate at the fair.
>
>
regards,
>
Aleksander
> >
>
>

"Aleksander Wittlin" <wittlin@aster.pl> wrote in message
news:coav49$1ofm$1@mamut1.aster.pl...
> Hi all,
>
> I am looking for a simple and cheap  design of a sound delay box for
> science fair exhibit. It should simply delay  microphone signal
> within the range (regulated) from  0.1 to 5 seconds.
> Sound quality does not really matter.
> I considered a PC with sound card (bulky) or professional
> audio console (expensive). Perhaps a simple DSP  board
> with codec and some memory plus a small preamplifier would
> be sufficient.  Any suggestions?

Cheap microcontroller like Atmel AVR ATmega32 and external 128 Kb RAM will
do the job, even a duplex communication with delay.
Micro has built-in ADC (8-channels), DAC may be built by R-2R net and
op-amp, or some cheap serial DAC chip, or by using micro's PWMs (the best
choice). Counter like CMOS 4040 may be needed (in the case of R-2R net).
Of course, you need a MIC pre-amps (micro has two ADC inputs with 200x gain,
that may helps to reduce component number, but ADC resolution is then only 7
bits) and some audio driver for speakers.
Computer speakers may be modified for that surpose.
Complete device with all cables, housing etc. may be built and programmed
for under 50 euro in one afternoon (experienced programmer).

Best regards,
Tomislav Canic

"Mike Yarwood" <mpyarwood@btopenworld.com> wrote 

> Hi Aleksander , if  quality isn't a problem I would start thinking of two
> cheap scrap cassette recorders screwed to a length of wood. If  you put a
> few idle wheels here and there you should be able to arrange for the delay
> between record from one player and play from the second to roughly fit your
> interval ( 0.1 second could be difficult though - maybe this technique not
> possible?)

Isn't that the way they used to do video delay loops?  Except with
wire instead of tape? :-)

Ciao,

Peter K.

U&#4294967295;ytkownik "Mike Yarwood" <mpyarwood@btopenworld.com> napisa&#4294967295; w wiadomo&#4294967295;ci 
news:cocbj2$5j8$1@titan.btinternet.com...
>
> "Aleksander Wittlin" <wittlin@aster.pl> wrote in message
> news:coav49$1ofm$1@mamut1.aster.pl...
>> Hi all,
>>
>> I am looking for a simple and cheap  design of a sound delay box for
>> science fair exhibit. It should simply delay  microphone signal
>> within the range (regulated) from  0.1 to 5 seconds.
>> Sound quality does not really matter.
>> I considered a PC with sound card (bulky) or professional
>> audio console (expensive). Perhaps a simple DSP  board
>> with codec and some memory plus a small preamplifier would
>> be sufficient.  Any suggestions?
>>
>>                                             Aleksander
>>
>>
> Hi Aleksander , if  quality isn't a problem I would start thinking of two
> cheap scrap cassette recorders screwed to a length of wood. If  you put a
> few idle wheels here and there you should be able to arrange for the delay
> between record from one player and play from the second to roughly fit 
> your
> interval ( 0.1 second could be difficult though - maybe this technique not
> possible?)
>
> Best of Luck - Mike
>
Nice idea, thanks. However, it would be rather fragile, due to the tape. It 
should be
children/teenagers/visitors proof. Moreover, I would either run out of tape 
after a while,
or have to deal with a tape loop. Also I didn not mention that it should be 
duplex
system (both participants talk and listen). Then I would need four recorders
and two tapes. It may be too cumbersome to operate at the fair.

                                                                       regards,
                                                                       Aleksander
> 

"Aleksander Wittlin" <wittlin@aster.pl> wrote in message
news:coav49$1ofm$1@mamut1.aster.pl...
> Hi all,
>
> I am looking for a simple and cheap  design of a sound delay box for
> science fair exhibit. It should simply delay  microphone signal
> within the range (regulated) from  0.1 to 5 seconds.
> Sound quality does not really matter.
> I considered a PC with sound card (bulky) or professional
> audio console (expensive). Perhaps a simple DSP  board
> with codec and some memory plus a small preamplifier would
> be sufficient.  Any suggestions?
>
>                                             Aleksander
>
>
Hi Aleksander , if  quality isn't a problem I would start thinking of two
cheap scrap cassette recorders screwed to a length of wood. If  you put a
few idle wheels here and there you should be able to arrange for the delay
between record from one player and play from the second to roughly fit your
interval ( 0.1 second could be difficult though - maybe this technique not
possible?)

Best of Luck - Mike

"Aleksander Wittlin" <wittlin@aster.pl> wrote

> I am looking for a simple and cheap  design of a sound delay box for
> science fair exhibit. It should simply delay  microphone signal
> within the range (regulated) from  0.1 to 5 seconds.
> Sound quality does not really matter.
> I considered a PC with sound card (bulky) or professional
> audio console (expensive). Perhaps a simple DSP  board
> with codec and some memory plus a small preamplifier would
> be sufficient.  Any suggestions?

A recent laptop with DirectX ?  Heck, even my clunky second-oldest
laptop (c. 1999) has sound in, sound out and can run DirectX.

The laptop won't be bulky, and the DirectX SDK is downloadable from
Microsoft and has many excellent pieces of example code.  One should
be able to be easily tweaked to do what you want.

Sound quality should be as good as source.

Ciao,

Peter K.

Hi all,

I am looking for a simple and cheap  design of a sound delay box for
science fair exhibit. It should simply delay  microphone signal
within the range (regulated) from  0.1 to 5 seconds.
Sound quality does not really matter.
I considered a PC with sound card (bulky) or professional
audio console (expensive). Perhaps a simple DSP  board
with codec and some memory plus a small preamplifier would
be sufficient.  Any suggestions?

                                            Aleksander