Supervisor: Dr. Boaz Rafaely Student: Limor Eger Dept. of Electrical and Computer Engineering, Ben-Gurion University Goal Directional analysis of sound fields in rooms using a spherical measurement array. Conclusion The project includes operating a measurement system, performing signal processing and analyzing the results with regard to psychoacoustics. The system will be used to perform measurements in real auditoria. The processing of the measured data will allow spatial characterization of the sound field. Further research in the field of psychoacoustics will be conducted to achieve a better understanding of the relation between the physical measurements and the human perception of sound. Measurement System The system suggested in the project is a spherical measurement array which consists of a computer-controlled-rotating microphone. A typical measurement cycle starts with the generation of a sound signal by the computer and the transmission of the signal through the loudspeaker. The transmitted signal is received by the microphone and sampled with the sampling card. The second channel of the sampling card is used to sample the signal directly from the sound card. Later, the microphone is moved to a different point on the sphere and again sampling is performed. This procedure repeats itself for all desired points on the sphere. The position of the microphone is set by the computer electromechanically. Applications Assessment and improvement of acoustic performance in auditoria. Psychoacoustics Psychoacoustics is the study of subjective human perception of sounds, based on psychology and on the physiology of the hearing system. Psychoacoustics attempts to explain how the waves composing the sound field are perceived by the human brain. This could indicate, for example, which characteristics of the sound field in a concert hall make the music sound good. The results of plane-wave decomposition, w( ,  ),can be used to calculate psychoacoustic quantifiers, which give indication of the acoustic performance. In this way, speech intelligibility in lecture rooms and quality of music in auditoria can be assessed. An example of a psychoacoustic characteristic which can be estimated is the perception of envelopment, which is the feeling of sound coming from all directions. This characteristic is related to the lateral reflections, which can be extracted from the results of the plane- wave decomposition. Signal Processing The output signals of the measurement system are used to evaluate the sound pressure on the sphere. An algorithm of plane-wave decomposition is applied in order to find the waves composing the sound pressure. One way of analyzing the product of the process is by observing the graph of the directivity function at a specific frequency. The graph shows the amplitude and direction of the plane waves composing the sound field, in relation to the center of the sphere. The dark regions represent the direct wave from the sound source and waves reflected from the walls, floor and furniture. The bright regions indicate absence of reflections. 1.Simulated directivity function for a single incident plane-wave at a specific frequency. 2.Directivity function at a specific frequency derived from lab measurements. Two examples are given: The measurement microphone positioned in one of the sampling points: