Measurements of anechoic room characteristics

A simple measurement system with a computer as the main unit is developed for the measurements of the characteristics of an anechoic room, such as measurements of the sound-pressure decay in space, the sound-pressure decay in time, and the sound insulation. The measurements are performed in two steps. The room response signals are first recorded and stored in the PC memory. Then, these signals are processed by designed software depending on the type of measurement. The departure of sound-pressure decay in space from the ideal characteristic is observed. The sound-pressure decay in time is obtained by the integrated-impulse method using the maximum-length sequence technique. The sound insulation is measured only for a specially designed door between the anechoic and the control room because of its insulation, which is rather low in regard to the other parts of an anechoic room. The measurements performed in the anechoic room of the Faculty of Electronic Engineering in Nis have shown that the departure of sound-pressure decay in space from the ideal characteristic is rather below the limit of 1 dB in frequency range from 50 Hz upward. The door sound insulation is above 55 dB.