Vibroacoustic therapy is the use of low frequency vibrations to stimulate body cells into therapeutic states of relaxation and healing. Low frequencies of about 40hertz work best. This can be heard and felt like the open string of a bass guitar. You can buy some pricey tech to sleep on or just get a cat that purrs loudly. Note that white noise machines are not for this purpose.
Unfortunately, the "Sound Oasis Vibroacoustic Therapy System" is no longer available. Fortunately, cats are plentiful.
Tibetan singing bowls have been used for centuries to provide pleasing effects. You can simulate the affect using a wine glass. First, fill the glass and drink all but a few teaspoons. Dip a finger in the remains and run it gently around the rim of glass so that it starts to resonate. A large glass is better for low frequencies.