Here is our new sound localizing robot called Nic_3. It is capable of fixing the azimuth of a sound source that is located in the horizontal plane. The localizing process is done using the stereo audio amplifier that we already used with Nic_1 and Nic_2. (For several reasons Nic_2 has not been published yet.) The amplifier is directly connected to the RCX inputs 2 and 3. (input 1 is used to power the sensor).
The RCX samples 2 x 1000 data-points on each ear at a frequency of 36kHz. Then it processes the time-lag between both signals within 100ms. This is impressively fast, because we apply a high speed phase detection.
The RCX repeats the sampling and detection process 10 times and takes the average of the measurements. Then the RCX computes the azimuth from the time-lag and sends the angle to the NXT through the HiTechnic IR-link.
The RCX program has been written in ULTIMATE ROBOLAB and H8-Assembler, while the NXT has been programmed using the LabVIEW NXT-toolkit.