The 3561A set of measurement functions lets you approach problems from several different angles. Spectra can be displayed in a variety of formats and units, including a three-dimensional spectral map. This map displays up to 60 successive spectra and is extremely useful for analyzing transients and monitoring dynamic signals in other electronic and mechanical systems.
In addition to spectrum measurements, the 3561A displays time waveforms, and you can observe a signal in both the time and frequency domains simultaneously. A 40 ksample time buffer captures transients for later measurements and analysis. And this instrument is an excellent choice for acoustics measurements, with its 1/3 and 1/1 octave measurements, together with the built-in analog A-weighted filter.