Rumbler Is an Analog Red Noise Machine Built for Sound Sleep

If you don’t have trouble sleeping well every night, then you’re actually in the minority. Most people have some difficulty falling asleep or staying asleep. There are many explanations for that, from stressful jobs to blue light. Unless you live in an isolated rural area, sound is also likely a factor. Cars driving on nearby roads, your neighbor’s TV, and all of the other noise pollution in populated areas can make it difficult to sleep. You’ll want to drown those sounds out if you value your sleep, and that’s why Tim Alex Jacobs (AKA mitxela) built the Rumbler analog red noise machine.

Most people are familiar with the term “white noise,” and we often think of it as any kind of indistinct droning sound, such as TV static. In the audio engineering world, however, the term has a more specific definition. White noise has a flat frequency spectrum, meaning every frequency in the human range of hearing is represented equally. Other colors refer to different kinds of spectrum patterns. Red noise (also called Brownian or Brown noise, because of its relation to Brownian motion), has much more power density in the lower frequencies. That is ideal for this project, because it matches the frequencies that usually pass easily through walls and windows.

Instead of just using a smartphone app to play red noise, Jacobs used common analog components to build the Rumbler red noise machine. The circuit for this project is surprisingly simple, and is designed around a pair of op amps. Other than those, the circuit is made entirely from components almost every maker has on hand, like resistors, capacitors, and potentiometers. That circuit was placed on a small piece of perf board, and then crammed inside a small extruded aluminum enclosure. Power comes from a DC power supply, and sound is pushed out through a 3.5mm audio jack. I’d describe its sound as something like a large waterfall or maybe a strong wind on top of a mountain peak. It is quite pleasing to listen to, and would certainly lull me into a sound slumber.