Sample Sweeping Audio Frequency

[ngay528]

I am able to do the harmonic analyzer on a specific frequency but wanted to get input on two things:

Analyzing a sweeped signal (say an audio range of 20Hz to 20kHz) - Do most programs just sample every few periods  within the file and then analyze the next?

How do programs do "real-time" analysis.  I assume there is some sort of aperture time of sampling so sample every 1 second of data?  In addition, I have only devised a way to analyze a wav file (converted to an array).  Is it possible to do "real-time" sampling from the incoming audio?

[Hassan_Atassi]

Hi ngay528, 

Can you expand on what you mean by "Do most programs just sample every few periods  within the file and then analyze the next?"

[ngay528]

I was wondering if it was acceptable practice or the correct way to decode this sweeped signal's power would be to sample small sections of this sweeping frequency signal and report data based on that small section at that given average frequency.

Currently CVI I saw has the Harmonic Analyzer which gives THD and THDN on an entire input signal at a specific frequency (Which is my current situation I get from a .wav file) What I would want is to get the THDN or power parameters of a sweeping signal from a .wav file at say interval frequencies.

[Hassan_Atassi]

Hi ngay528,

Essentially, you can't do a THDN analysis on a signal with a continuously changing frequency, as by definition, THDN required one fundamental frequency to get any useful information on it.  In order to get proper data from a THDN the best option is to acquire your data in chunks at discrete, or stepped frequencies.  If you know where these frequency changes are occurred you can then perform a THDN on those individual chunks of data.