Electronics

Guest

Hi,
Why do not the oscilloscope used for noise measurement, where we can
use the FFT feature of the scope. Most of the time it is seen that
expensive spectrum analysers are used. Any comments on it and
discussion are most welcomed.

Robert Lacoste · Guest

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awright · Joined: 20 May 2005 Posts: 10 Location: Oakland, CA USA

I just stumbled across this forum, so I hope this late post is still of interest to you. I assume "noise" in the question refers to acoustic noise, not electrical noise.

While it is true that oscilloscopes with FFT options have a lot in common with spectrum analyzers, most of the software packages I've seen (and I haven't seen recent ones) would be awkward to use for acoustical noise analysis because they lack features that optimize some spectrum analyzers for acoustical measurements. These might include receptacles and power for some industry standard measurement microphone preamplifiers, commonly used weighting networks (always including "A" weighting, and sometimes "B" and "C" weighting), convenient gain switching in 10 dB steps (as opposed to 1,2,5 steps which would be a real pain to use for noise measurements), sometimes the built-in capability to print out spectra in ANSI standard format, certification to "Type 1" (precision) or "Type 2" (survey) ANSI standards for sound measurement devices, optimization for handheld use under difficult field conditions, ability to perform specialized procedures (reverberation time measurements, transmission loss measurements, statistical noise measurements, order analysis for machinery vibration), and the ability to produce 1/1 octave or 1/3 octave spectra that are much more convenient to use for many types of noise studies in which the detail in a typical FFT analysis would be excessive and confusing.

I've been measuring noise for about 40 years and I would hate to have to do field measurements with any of the oscilloscopes with FFT options that I am familiar with (much as I love them for other purposes). Of course, the basic electronic technology is the same for the two types of devices, but the implementation to create an acoustical spectrum analyzer makes the analyzer much more convenient to use for its intended application. The sophistication of the software packages is always evolving rapidly and there may be FFT options out there that provide many of these features on a standard DSO, but I haven't seen them.

Hope this answers your question (and that you are still interrested).

awright

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