The aim of the project is the development of an automated measuring system for the active spectral homogenization of enclosed spaces at low frequencies. The homogenization method is based on the control of the interference spatial pattern of a multi-source system using phase and pan techniques. The experimental setup requires a microphone, a set of amplified loudspeakers, an audio interface and a computer. To achieve the optimal spectral homogenization, the room response spectrum, as a function of phase difference and pan, is measured in various places inside the experimental room. Data is collected in a three dimensional tensor (space, frequency and phase-pan), the optimal phase and amplitude filter for each loudspeaker is found. The optimal filter response is then applied to the reference signal in order to obtain the minimum spatial deviation of measured spectra. The system characterization was carried out at the impact sound laboratory located at I.N.RI.M. in Turin. This method can reduce the sound intensity mean spatial deviation up to 30% using just two loudspeakers. The automated system was developed in MAX/MSP and the correction method can be applied to public address systems as well as to the acoustic metrology research.
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