What setting should a technologist use to control the frequency band of waveforms on a recording?

The correct answer pertains to the use of a low filter setting to control the frequency band of waveforms in polysomnography recordings. A low filter setting is designed to eliminate or reduce the higher frequency components of a signal, allowing lower frequency waveforms, such as delta and theta waves, to be recorded more clearly. This is particularly important in sleep studies, as many critical physiological signals, like slow-wave activity, occur at these lower frequencies.

In sleep study context, using a low filter helps enhance the clarity of the desired low-frequency signals while minimizing the interference from high-frequency noise that could obscure the analysis of the data. This is essential for accurate interpretation and diagnosis based on sleep stage analysis.

Other options such as a high filter are used primarily to remove low-frequency noise, which serves a different purpose than what's needed to adequately capture lower frequency waveforms. Similarly, a medium filter and band-pass filter have specific uses for particular frequency ranges but do not specifically allow control over low frequencies in the way that a low filter does. The emphasis in polysomnographic settings on accurately capturing low-frequency data justifies the selection of a low filter for that purpose.