Änderung der Nachhallzeit einer Platte durch Annähern eines Luftschallabsorbers

If a thin plate is excited to bending vibrations the far field of the bending wave will produce in the surrounding medium a space-wave above the cut-off frequency and a surface-wave below the cut-off frequency.

It is shown that the reverberation time of the plate can be continuously lessened by approaching an airborne-sound-absorber in the near field of the surface-wave. When a resonator is approached a selective sip in the frequency-characteristics of the reverberation time is achieved. The absorber resistance for the lowest reverberation time is specified. The calculations are compared with measurements.