Background Information

Using an array of microphones, the position of an acoustic source can be calculated if the positions of the microphones and the sampling frequency are known. The system parameters consist of the distance between each microphone pair, d, and the distance between the midpoints of each pair, D. By placing the array on a xy-axis, the position equations for the source can be derived. This is shown in the figure below.

An important aspect when estimating a source’s position is whether the microphone array is in near field or far field. The type of field depends on how far the array is away from the source. If the array is in far field, the sound wave can be imagined as a flat plane approaching the microphones. This situation is undesirable because if the wave, as seen by the microphones, is flat an estimated position cannot be attained. Looking at the estimation equation above, we must have two different angles for each microphone pair, so when the plane is observed as flat in the far field, an estimation of the source is impossible. Therefore, we need to keep the microphone array out of the far field.

Previous research performed by Josh York contains further detail into the background and motivation behind this research project (link).

Robotic Microphone Sensing: Optimizing Source Estimation and Algorithms for Adaptive Control

Washington University in St. Louis

Department of Electrical and Systems Engineering

Chase LaFont - Undergraduate Research Summer/Fall ‘09