# Multiplying spectra

Convolution is the process of multiplying the spectra of two sound files, creating a type of cross-synthesis in which common frequencies are reinforced.

Note: Convolution of two sounds that share few or no frequencies results in an empty file.

## Multiplying the spectra of two sound files

To multiply the spectra of two sound files, follow these steps:

1. Choose Convolution from the Hack menu.
2. In the dialog that appears, click Pick Impulse and select the impulse file.
3. Change the Length Used or Impulse Window if desired.
4. Click Process to convolve the current file with the impulse file.

#