This week I worked on getting the circular beamforming code working and on collecting data to test it. For the initial approach, I’m coding our beamforming algorithm using the delay-and-sum method. From my reading, I’ve found several other beamforming methods that are more complicated to implement but that will likely work better than the delay-and-sum method. I’m using delay-and-sum for now because it’s the simplest method to implement. I decided to calculate the delay-and-sum coefficients in the frequency domain, rather than in the time domain, after learning from several papers that calculating coefficients in the time domain can lead to quantization errors in the coefficients. Right now, the code is able to take in 7 channels of audio recording (recorded using our mic array) and we are able to input the angle of the speaker we want to beamform towards. While the code runs, it currently doesn’t seem to do much to the audio from input to output. The output audios that I’ve listened to have all sounded just like their respective inputs, but with some of the highest-frequency noise removed, which may be a result of how the numbers are stored in MATLAB rather than anything my algorithm is doing.
In the coming week, my main goal will be to determine whether the lack of change from input to output audio comes from a bug in my code or from our hardware being inadequate to do any noticeable beamforming. I suspect there is at least one bug in the code since the output should not sound exactly like the input. If our 7-mic array is insufficient to do good beamforming once I fix the delay-and-sum algorithm, I will try to implement some of the other beamforming algorithms I found. To test my code, I will first check for bugs by visual inspection, then I’ll try simulating my own input data by making 7 channels of a sine wave and time-delaying each of them to reflect a physical setup using Charlie’s code for calculating time delays.
This week I also met up with Charlie to collect some more audio data from our mic array, and I started brainstorming ways we could make our test setup more precise for later testing, since we’re currently judging speaker distance and angle from the mic array by eye.
I initially expected to have completed the beamforming algorithm earlier in the semester, but I am on schedule according to our current plan.