Hi, I wasn't really sure whether to put this post under Physics or Engineering. I was just wondering whether someone can gimme some help or info or guidance... I am currently working on a project in which I am using the FFT (Fast Fourier transform) algorithm. In a nutshell, I am trying to use two microphones (which are plugged into each of the two channels on the line-in of a soundcard) in order to track the motion of an object sliding over a surface (such as a finger or pencil sliding over a table-top). So basically I am trying to create a wireless mouse device that uses microphones to determine position. The microphones are placed on the table-top in a particular configuration. Then, as the object slides over the surface, the microphones receive the signals and analyse them to determine (for now) the position of the object. Here's some specifics: - I define a rectangular surface with a set height and width which could be, as I've said, a section of a table-top. - I have two microphones placed on the top-left and bottom-left corners of the rectangular surface. - As the object slides over the surface, I collect the samples (at a particular sampling rate) and put them into the FFT algorithm. (Ideally:) - I then use FFT information of the waves that the object generates in the solid to determine the position of the object from each microphone. (given I will have calibrated the system against background noise) - Lastly, I use the two distances ( from each microphone) to triangulate the position of the object. BIG PROBLEM: How do I analyse and use the FFT information to be able to determine a reproducible and correct distance from the microphone? Will audio fingerprinting be of any use here? If so, how? Then again, should I be using the FFT algorithm at all? Is there a better way? Basically, how do I do this thing?? I'll appreciate any comments, directions and thoughts greatly. Thanks again for your time and help. Jack.