From early on in mans history they have discovered that nature and the universe vibrates in a range of harmonious frequencies. These early civilisations knew instinctively about these frequencies long before science could prove their existence. Many Tibetan gongs, Native American and Gregorian chants are all based on replicating these frequencies, with an aim to heal the body and mind.
There are many universal tones and each affects a different aspect of our souls. By having different tones in either ear you can also combine them to achieve a pulsing affect. There are many products available on the internet that cater for this technique ranging from CD’s to smart phone apps. I have several myself on my iPhone/iPad. If you would like to experiment with this method of meditation/self healing then this site is well worth looking at. Each beat last an hour and they are all free.
NOTE – The mp3 downloads can fail, as the owner doesn’t have the bandwidth to support that amount of traffic, but he does have Youtube video links at the bottom of each page that do always work.