Frequency Dependence of Reverb Time.

• Reverb time is not uniform over audible frequencies:
  • in a well designed concert hall, the low frequencies are the last to fade.
  • absorptive materials tend to reflect better at low frequencies
  • hard, nonporous reflectors (such as marble) reflect sounds of all frequencies with nearly equal efficiency.

• With small solid objects, the efficiency and the direction of reflections are both dependent of frequency (wavelength):
  • this causes frequency-dependent dispersion and an alteration of the waveform of a sound.