Application of wave-number approach for room behaviour analysis and absorption coefficient measurement

With advances in signal processing technology and processing power of personal computers, new methods have been developed in the area of room acoustics. Using a robotic arm to hold a microphone during measurements, a virtual automated microphone array can be formed, as an alternative to rigid arrays. This type of system can be used for measuring impulse responses related to each microphone position, which in turn can be used as input data to calculate the wave-number spectrum of the sound field. An analysis was performed using the virtual automated microphone array in a laboratory room at UTFPR Curitiba Campus, prepared with a 10.8 m2 glass wool overlay. Using the wave-number approach, the reconstruction of the room transfer functions was calculated for a set of 30 validation points, and the average error in the reconstruction processing was calculated and averaged in third-of-octave bands. The error is limited under 10%. The absorption coefficient calculated shows the expected behaviour for the type of material, albeit lightly underestimated. The underestimated values are most likely due to the array characteristics in the frequency range analysed.