A saw wave is fed into a filter which then goes into an amplifier. The saw wave is the pitch of the sound, the filter the timbre of the sound, and the amplifier the volume of the sound.
Both the timbre and volume are being controlled by Maths. Ch. 1 of maths when looping is making the filter open and close giving us the feeling that the sound is "going underwater" or "getting muffled."
Ch. 2 of maths when looping is making the volume of the sound open and close giving us the feeling that the sound is "fading in and out" or "pinging" based on the rise and fall settings.
Treat maths like two LFOs in this patch.
Subtractive synthesis explained: