Subwoofer or headphones are required to hear this well.

Here is another very simple and pure sound. This ambient noise was made from pure stereo pink noise which has been equalized way down so that only the very deep noisy rumble pushes through. Sounds to me very much like a spaceship noise from any number of tv shows and movies. Should be great for setting a relaxing mood to focus at work, for getting to sleep, or just pretending that you are in a spaceship.

" Pink noise or 1⁄f noise (sometimes also called flicker noise) is a signal or process with a frequency spectrum such that the power spectral density (energy or power per Hz) is inversely proportional to the frequency of the signal. In pink noise, each octave (halving/doubling in frequency) carries an equal amount of noise power. The name arises from the pink appearance of visible light with this power spectrum. " - https://en.wikipedia.org/wiki/Pink_noise