Python Deep Learning - Second Edition

Preprocessing

The recording of the audio signal in the preceding diagram was recorded over 1.2 seconds. To digitize the audio, it is sampled 44,100 times per second (44.1 kHz). This means that roughly 50,000 amplitude samples were taken for this 1.2-second audio signal.

For only a small example, these are a lot of points over the time dimension. To reduce the size of the input data, these audio signals are typically preprocessed to reduce the number of time steps before feeding them into speech recognition algorithms. A typical transformation transforms a signal to a spectrogram, which is a representation of how the frequencies in the signal change over time.

This spectral transformation is done by dividing the time signal in overlapping ...