Anechoic Chamber

In an anechoic chamber (also called camera silenta or dead room) all surfaces are of sound absorbent material, thus avoiding any reflection of sound waves. Such chambers are mainly designed for technical measurement reasons, e.g. in order to measure the sound pressure level of loudspeakers in any given direction without signal interference. The anechoic chamber is also used for recordings which later are to be put into a virtual room (»ambience«), either by adding artificial reverberation or by convolving the original signal with the impulse response of an existing room. With these recordings, the best results are achieved when the original signal is free of any ambience reverberation. The acoustic opposite to the anechoic chamber is the   reverberation room.

The anechoic chamber at the »SIM« was designed as a measuring room for researchers and for music productions in the first place. For that reason, it was designed as a spring stored house-in-house construction to avoid the transmission of airborne and structure-borne sound and to keep the basic noise level as low as possible. The basic level of NH 10 rises to 20 NH when operating the air-conditioning system. All six surfaces of the room are covered with wedge-shaped absorbers, which are 770 mm long and made of a mineral fibrous material. Thus, the lower limiting frequency is 100 Hz and above that frequency the absorption coefficient is always 0,99 for all frequencies. The wedges are completely covered with acoustically transparent fabric. The floor consists of a walkable netting with meshes of 60 mm. In addition, underneath the netting there is another sound permeable netting spread out with meshes of 3 mm. For heavy loads, an additional grate can be adjusted to a frame. In the centre of the room and with a radius of 1,2 m around it, a suspended device for the installation of microphones, etc. is attached to the ceiling with four carriers. The usable interior room has a volume of around 50 cubic metres.