Method and measuring device for the determination of the attenuation properties of sound absorbing installations

摘要

The configuration of sound absorbing installations, especially for internal combustion engines, is a complex acoustic and fluidic problem. Carrying out measures to improve the attenuation properties is made more difficult in that, in the case of measurements being undertaken in real operation and carrying out the alterations on sound absorbing installations, a cooling and heating of the absorbing system occurs or must be waited for, respectively. The invention allows the determination of the attenuation properties of sound absorbing installations to be carried out at ambient temperature, in that a measure of the frequency shift in the frequency spectrum between the excitation of the sound absorbing installation at operating temperature and at the ambient temperature is determined and this measure of the frequency shift is taken into account in the case of acoustic excitation at ambient temperature. In this case the acoustic excitation may be converted to the operating temperature by means of the previously determined measure of the frequency shift or the measured values can be recalculated to operating temperature, taking into account the measure of the frequency shift.