||Absorption in Loudspeaker Cabinets
||Olesen, Tobias Schmidt
||Jacobsen, Finn (Acoustic Technology, Department of Electrical Engineering, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
Agerkvist, Finn T. (Acoustic Technology, Department of Electrical Engineering, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
||Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark
||The effect of filling a loudspeaker enclosure with porous material is modeled as
a transition in the propagation of sound from an adiabatic process to an isothermal
process. The result is a lowering of the resonance frequency of the loudspeaker
system. This is due to a decrease in the sound velocity causing the acoustic volume
to increase and compliance to increase.
The frequency range in which isothermal conditions can be assumed is examined
and analytical expressions describing the effect of the porous materials on the loud-speaker system is derived. The theory is then compared to measurements of the
acoustic compliance of a loudspeaker enclosure filled with porous material and the
speed of sound through porous material.
Four different kinds of porous materials are used as ling at variating densities.
This gives different increases in the compliance due to
differences in the proper-
ties of the materials. This difference is discussed and the best filling material is
Creation date: 2009-03-26
Update date: 2009-08-07