1.1 This Recommendation deals with sets of octave band and one-third-octave-band filters (filter sets), i.e. devices capable of providing, or designed for operation with devices capable of providing, time-average levels of frequency-band-filtered spectral information for a wide variety of signals, for example, time-varying, intermittent, and steady; broadband and discrete frequency; and long and short durations. The Recommendation contains an appropriate test scheme for pattern evaluation and verification and a test report format for pattern evaluation. 1.2 Devices to which the requirements of this Recom mendation apply include bandpass filter sets that are integral components of a measurement system or specific instrument. The requirements apply to filter sets that operate in real time over the complete frequency range of the system or instrument, or over a portion of the frequency range.