pd15. Amplitude Modulation in Pure Data

Using the send and receive, we can clean the layout, from previous saving examples, so the saving portion is on one side (right side here).

Amplitude Modulation (AM) refers to multiplying the signal with a modulating frequency. Here the signal is a sinusoid of 440 Hz, and modulating frequency is 5 Hz.

AM results in signal frequencies +/- modulating frequency, thus the frequencies will be spread from 435 Hz to 445 Hz.

We also have used a dac object for real-time playing of audio.

The saved audio, opened in Audacity, shows the effect

The file is 88,200 Bytes long, as one second contains 44,100 samples and each sample is represented by 16-bits (2 Bytes). If the file was stereo, it would be twice this size.