During the year 2005 it has proceeded to the design and construction of a new anechoic chamber at Laboratorio de Sonido of the Universidad Politécnica de Madrid. This new chamber has a free volume of 70 cubic meters and is built with rock wool wedges covered with a porous cotton cloth. The chamber cutoff frequency is 150 Hz. The chamber has been qualified according to that established in the ISO 3745 standard for the determination of the maximum distance between the sound source and the measurement position where the inverse square law is observeded, within some tolerance. For the qualification, different types of excitation signals have been used as pure tones, broadband noise, narrow band noise and pseudorandom sequences MLS.
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