**
Unit Encoding**

Units are encoded for presentation to the rest of the system. Current
representation is based on spectrograms. Unit is place in a 50000
point wide window, padded with zeroes on either side. A short-time
Fourier transform (spectrogram) function is applied. Everything above
4 KHz is thrown away. The matrix is compressed along the frequency
axis into 50 linearly spaced frequency bins. Previous work used 16
logarithmically spaced frequency bins covering 8000KHz.