staplep wrote:> Thank you for all your responses. In fact, the situation is that my > supervisor is the head of my department, and has no time to meet me, and as > such, I am lost! Your responses have allowed me to revise my original post, > and I have realised that the problem wasn't that clear. I have only two > microphones, and yes, I am in control of the sound. What I am trying to > implement is a sound intensity probe. > > Since my original post, I have made some advances. I have done some > recordings in a field, so no errors occur. The microphones are held in a > constant position whilst recording. In each recording, the angle of arrival > of the sound is different (i.e. I have moved the sound source to a > different location on a circle of the same radius.) When I analyse the > data, I've plotted a graph of the phase versus the frequency. The resulting > graph is somewhat of a cut-saw image, such as: > > /|/|/| > > Excuse the crudeness of this diagram, it was the best I could do from the > characters on the keyboard! The slope of this graph should give me some > information about the sound location, and I should be able to > experimentally determine the angle of arrival, and the distance from the > two mics. > > I have used the fuction tfestimate in MATLAB, and the angle of the Tf for > the phase. I am somewhat confused as to how to work out the distance and > angle, could someone please clear it up!The phase illustration is typical of wraparound, the calculated phase being confines to "principal value", while the real phase can accumulate forever. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������