Increasing frequency of sound input

[Ed1001]

A bit of background first.  I am currently trying to build an electronic stethoscope for someone with deafness using Labview 2011 with a myDAQ board

Currently I have managed to input the sound into labview using a microphone and the board, filter the sounds to remove background noise and then listen to the sounds through audio output.  The frequency of the sounds come in at around 200HZ (having used a FFT vi to get this value) and these can by heard fine by me as I have a full adult hearing range.

What I would like to do, is to somehow alter the frequency of this sound so it will become available in an increased frequency range, so that someone with deafness could hear the sound.  I experimented by simply altering the time values on the data acquisition from the myDAQ board, but by doing this it makes the heart beat sounds appear faster than they should which wouldn't be suitable clinically.  

If possible, is there a way to alter these sound waveforms so that they will have a higher frequency so that they will be within the users audible range without losing time or distorting the data?

Please let me know if you would like me to provide more information, it is my first time posting on these boards so I'm unfamiliar with what information I may need to provide.  Thanks in advance for any advice 🙂

[camerond]

Take the derivative of the signal and add it to the original. That will double the sound frequency of the transitions (but it will add some noise, don't know how quiet your signal is between beats).

Cameron

[mtedaldi]

So if I understand you correctly: What you want to do is pitch shifting.

Maybe this informations will help you get started: http://zone.ni.com/devzone/cda/epd/p/id/6219

Best regards

Marco

[Ed1001]

Thanks for your help!  Both options look like they could potentially do what's needed.  Will try both within the next few days and I will see how I get on! 🙂