White noise, by definition, has equal average energy at all frequencies. Thus, if you measure its spectrum you might expect to see a perfectly flat line. And you will, in fact, but only after a long Spectrum Average to smooth out the moment-to-moment random variations.

White noise has a higher average energy than Impulse or Step signals, roughly 32 mV per spectral line (- 30 dB) for a +/-1 volt noise signal. The equivalent instantaneous waveform voltage is about 0.5 volts RMS. If you use this to obtain an absolute calibration, instead of just a response shape, then you can reduce the External Gain on the Input line by a factor of 32. If you are starting from a default of 1.00, just change it to 0.03125. Daqarta will compensate by reporting a 32x higher response.

White noise is sometimes used to avoid acoustic standing waves when measuring room responses, but Pink noise response is usually preferred. The reason is that sound systems are designed to handle higher amounts of power at low frequencies; since White noise puts out equal power at all frequencies, the overall power must be kept within the limits of the high-frequency drivers.

Note that you should never use a Window function to view a noise response; use them only for continuous waveforms.

See also Frequency Response Measurement

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