How to band limit the excitation signal?

If you are using a sine sweep for your measurements, the signal is band limited by setting the sweep range. If you have selected a noise signal (such as MLS), the emphasis setting can be used to do the band limiting.

The reasons for band limiting the output signal are twofold:

•      You can get greater signal level out from the loudspeaker.

•      The bandwidth limited signal would eliminate very low and very high frequencies which could overload the loudspeaker or amplifier. E.g., Norsonic has this as a feature on one of their pink noise generators. The signal selection can be (1) bandwidth limited 89 to 5623 Hz (suitable for 125 to 4000 Hz octave frequency bands) and (2) full bandwidth (no bandwidth limiting). We have not investigated how much an improvement this will give in signal-to-noise ratio.

How? The band-limiting can be done by using the pre-filtering option and by using a proper filter. An example of generating a filter that bandlimits low frequencies to 80 Hz is given in the next section.

Emphasis is set in Measurement->Settings... as shown in the bottom of the figure below.