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.

Abstract: Prefabricated element arranged on a single wall of a room for forming a double sound insulating and sound absorbing wall. The prefabricated element provides efficient sound insulation of the room and a total sound absorption of sound waves whose frequency is centered at one of the natural frequencies of the room. The element comprises a frame supporting a flexible panel by means of elastic sealing means, the flexible panel being maintained at a predetermined distance from the single wall due to the thickness of said frame whereby the resonant frequency of the double wall becomes equal to a natural resonant frequency of the room corresponding to sound waves propagating perpendicularly to the single wall. In addition, the prefabricated element may also comprise an additional element placed in the middle of the panel which permits equalization of the natural resonant frequency of the assembly comprising the flexible panel and the additional element to the low natural frequency of the room.