Sound fields in small rooms are generally characterized by impulse responses and transfer functions, as are other linear and time invariant systems. Modern digital equipment makes measurements possible with very good reliability and background noise immunity. Broadband frequency curves or impulse responses are usually filtered to enable parameter evaluation in octave or one-third octave bands. Impulse responses in small rooms with very low reverberation times can be distorted by the application of band filters. However, the objective characterization of the subjective listening effect of single number quantities in frequency bands is quite different from the well-known criteria in room acoustics: reverberation time, clarity, center time, lateral energy fraction, and so forth. In small rooms, other criteria are relevant, particularly the temporal structure of the early reflections, the cut-off frequency of the room, the distribution of room resonances, and the corresponding effect of sound coloration.
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