Acoustic insulation measurement apparatus

Abstract

Device enabling the direct measurement of the overall insulation level of an acoustic insulation medium with respect to a reference excitation noise signal when said medium is subject to an actual excitation noise signal deviating from the reference excitation noise signal. The device comprises two microphones receiving a first and a second alternating signal respectively representing the noise signal actually transmitted through the medium and the actual excitation noise signal and a read only memory storing spectral components of the reference excitation noise signal in a plurality of given spectral bands. The first and the second alternating signals are decomposed into alternating spectral components in these spectral bands and the alternating spectral components of the second signal are rectified in order to obtain rectified spectral components. These rectified spectral components are added to the alternating spectral components of the first signal relating to the same spectral bands thereby obtaining composite signals each having a direct and an alternating component. These composite signals are selectively passed through attenuators thereby forming attenuated alternating spectral components and attenuated rectified spectral components which are separated from each other. The attenuated rectified spectral components are compared to the spectral components of the reference excitation noise signal relating to the same spectral bands and thereby error signals are obtained respectively corresponding to the spectral bands, and these error signals control the attenuators.