Six preamplifier circuits for our microphones. The change was made to using an National Instruments LM386, after noise issues around the SSM2019.
Bottom view of the preamplifier circuits.
Preamplifier circuits with the microphones connected. The grey wiring is shielded cable to help reduce noise.
Testing the output of the circuits by whistling at them.
Output of preamplifier circuits when whistling at them from the position above. Notice the phase lag and magnitude difference as a result of the
delayed arrival of sound to the second microphone and loss of amplitude between them.
Fixture for calibration of the microphones. We will attempt to minimize the differences in the preamplifiers and microphones by adjusting their
gain and phase with a filter so that their frequency responses match.
Two micriphones being calibrated. Playing sound from the speaker towards the microphone array. Data acquisition was done using Matlab to sample from our DAQ.
Another view of the calibration setup for the microphones.
Matlab simulation of a 1000 Hz sound wave generated by a point source.
We have our data acquisition cable now. Putting it to good use by testing the microphone array with the Time Delay of Arrival Algorithm.
