Help!I want to analyse a sound is good or bad by sound card in LabWINDOWS.

[Lab]

Through THD and SNR I want to analyse a sound signal is good or bad by sound card,I could get the real-time sound wave.But I don't know what Y-axis of waveform is,it is very large value(thousands upon thousands).And I want to read data from a wave file in LabWINDOWS,how can I do?SDK don't directly give such function of reading data from a .wav file.

[JuanCarlos]

Hi,

when you read data from the sound card you are getting raw unscaled data. meaning you are getting the reading from the ADC in 16 bit format. The range will go from -32768 to 32767, to map this to real voltage will be dificult, that full range should map to around 1Vrms, but it will depend on you sound card. It may be a good idea to normilize your measurements and map the full range that you read to a range from -1 to 1.

Another possible problem is that if you use a poor quelity sound car the THD introduced by the card wqill be quite high and could be comparable to the one that you are measuring. Make sure that you test your card's THD.

To read wav files you have top follow the RIFF format, you can find here and example on how to do this.

I hope this helps.

Juan Carlos
N.I.

[Lab]

thank you very much.I use CREATIVE BLASTER AUDIGY LS sound card.