Author Topic: Frequency Response Measurement?  (Read 6765 times)

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papalapapp

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Frequency Response Measurement?
« on: February 14, 2008, 07:41:22 AM »
Hi there,
I'm evaluating SignalScope. But I can't find out how to make a simple Frequency Response Measurement via sweep or noise. Just a simple task like SignalScope gives out a noise signal and makes a graph from the Microphone-imput. I have my Powermac G5, a normal Mic and my Speakers. Do I need some special additional hardware or software?

FaberAST

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Re: Frequency Response Measurement?
« Reply #1 on: February 14, 2008, 11:38:45 AM »
There are a few different options for making frequency response measurements, and which is right for you will depend on your specific needs.

If you are working with SignalScope, then you will need some additional software to produce a signal with a flat spectrum (white noise, special pseudorandom noise, linear frequency sweep, etc). You could then configure SignalScope's FFT Analyzer to measure a frequency response amplitude based on the assumption that your excitation signal is truly white. (The best approach is to have a white excitation signal that is periodic in the window of your FFT.) You could use SignalSuite for this.

An alternative would be to use SignalScope Pro, which includes a signal generator. In that case, I would recommend using the pseudorandom noise signal with a length equal to your FFT length. There's a tutorial that illustrates how to do this in SignalScope Pro's built-in Help.

If you need greater precision, or phase, coherence, group delay, etc, you should use a tool like the Dual FFT Analyzer in Electroacoustics Toolbox. That tool is extremely powerful, and will allow you to measure transfer functions and impulse responses with internal or external reference (excitation) signals (the SignalScope/Pro approach uses an internal reference).

If you need greater precision, I would also recommend using a lab-grade measurement microphone. If you need something like that, feel free to contact Faber Acoustical. We sell various Type 1 and Type 2 microphones, and less expensive phantom-powered microphones that use Type 1 and Type 2 microphone capsules.

I hope that helps!

Ben