Many people who live close to the ocean have the benefit of being lulled to sleep by the sound of the surf. This circuit may provide a similar benefit to all those poor unfortunates who don’t live near the seaside but who do have the small consolation that they don’t have to worry about rust and corrosion in a salty atmosphere. The circuit consists of four unsynchronised oscillators which are mixed together to modulate a white noise source to simulate the more or less random nature of surf sounds. You won’t hear the waves crashing but the ebb and flow of the white noise will help mask other noises which would otherwise disturb your sleep. The four oscillators are based on four op amps in a TL074 or TL084 quad op amp package (IC1). IC1a, IC1b, IC1c & IC1d are configured as Schmitt trigger oscillators with their operating frequencies defined by the resistor connected between their outputs (pins 1, 7, 8 & 14) and the respective inverting inputs (pins 2, 6, 9 & 13), as well as ...