This tutorial shows you how to recreate the sound of the ocean by modulating filters applied to a white noise source. As in the previous tutorial, we’ll use a low-frequency oscillator, or LFO, as the modulating signal. We’ll begin by setting up a basic subtractive synthesis chain: [noise~] as the sound source, [lores~] as the filter, [gain~] as the volume control, and [dac~] for output. (We call this type of synthesis “subtractive” because we begin with a rich sound source, noise, and subtract energy from it with the use of a filter.)
Instead of using constant values for the filter parameters of cutoff frequency and resonance, we will use constantly changing values to more accurately capture the unpredictable movement of the sea. As in the previous tutorial, we will use [cycle~], a sine wave oscillator, to generate our modulating signal. We then use the [scale~] object to match the range of the output of the oscillator, -1 to 1, to our desired range of frequencies, which in the video is set from 300 to 800 Hz. We can do the same for the resonance value, shifting the output range to 0.3 to 0.9, and even add changes in volume by inserting a [*~] object.
The values chosen for many of these objects are subjective, and can be varied for different sonic and musical results. The frequency of the LFOs—set in the video to 0.11, 0.09, and 0.08 Hz, respectively—can certainly be changed for different results. Increasing these values a little will make the “ocean” sound more intense; increasing these values a lot will result in a completely different sound. One important principle to bear in mind in setting these values is choosing frequencies which are incommensurable—that is to say, frequencies which are not multiples or factors of one another. This principle, exploited by Brian Eno in his ambient music, ensures that the alignment of the different parameters will continually vary in unpredictable ways. This unpredictability is part of what makes the sound of the ocean more lifelike.
The final step in this tutorial is adding depth to the sound by adding a second channel. We can simply copy everything we’ve created so far and paste it to the right. We can leave the ranges within the [scale~] object the same; we just want to make sure the LFO frequencies are different so that the parametric changes don’t line up between the left and right channels. Finally, we will assign the patch on the left to the left channel and the patch on the right to the right channel by connecting each to the respective inlet of [dac~]. We can control the overall volume by linking the two [gain~] objects, from the right outlet of the left [gain~] object to the inlet of the right [gain~] object. This way, when we slide the left [gain~] object, it controls the right [gain~] object as well, like a pair of stereo faders.