Ravi Narasimhan
Univ. of California at Berkeley, Berkeley, CA 94720
This event-driven system determines sound source location using CMOS-EPROM technology and a microprocessor interface. The time delay between a pair of microphones is measured. This time delay gives one direction. Another pair of microphones yields a necessary second direction. The source location is determined precisely by considering hyperbolic equations and the linear approximation. The microphone outputs are ~200 mV. These signals, amplified to logic high level, are inputs to the Altera EPM5032 erasable programmable logic device (EPLD). The EPLD is programmed using MAX+PLUS software and a hardware programmer. A circuit designed to determine which microphone belonging to a pair received the sound first together with a 2-MHz crystal oscillator and a 12-bit binary counter used to measure the time delay. The counts are fetched by an assembly code in the NSC888 microprocessor board and sent to a program in the Macintosh, to calculate the sound location, through the RS232 modem port. The program calculates and immediately displays the sound location. The test results of this system illustrate its reliability and accuracy.