Robotic sound localization

Benjami Schmidt

Abstract


The purpose of this project was to build a system capable of estimating the direction of a sound source using a static array of sensors without measuring time delays. Such a system would aid in tracking a robotic vehicle over a short range and is a prototype for a radio-based tracking system. The project consisted of several parts, the first of which was the construction of an adjustable sound source, providing a constant amplitude and variable voltage. After testing many designs, a crystal earphone and a square wave tone source were used as the sound source. Next, a sound sensor consisting of a microphone and a housing to make the microphone response directional were constructed. Circuitry to convert the amplitude of the sound into a DC voltage, to be able to read by a microcontroller, was built. Several designs for directional sound sensors were tested. By rotating the sensor and sampling at different angles, the data that would be generated by a group of sensors pointing in different directions, was simulated. A static array based on the simulations, consisting of seven sensors arranged radially at 35° intervals, were used for the final design. A second-order polynomial regression was used as the basis of an algorithm to estimate the angle to the sound source. Experiments to determine the effect of the signal frequency, sampling protocols and microphone housing design on the accuracy of the angle estimates, were conducted. The best results were obtained for a frequency of 2.15 kHz. At distances of 50cm-100cm, the final array design was able to locate the direction of the sound source with an accuracy of about ±3°.

Keywords


Arrays; Delay circuits; Earphones; Microcontrollers; Microphones; Project management; Robotics; Sensors; Circuitry; Polynomial regression; Static arrays; Tracking systems

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