While the human ear can detect a range of audible wavelengths between roughly 20 and 20,000 Hz, there are several ways we can also perceive signals outside of this range, through means other than actual auditory sound. One of these techniques is the use of binaural beats, tones or audio artifacts which are perceived by the brain within the difference between two separate audible signals. For instance, if one ear hears a steady tone of 440 Hz, while the other ear hears a steady tone of 424 Hz, the brain can perceive the difference in vibration of 16 Hz, and will “hear” that tone, despite it being below the range of human hearing. Note that the key factor in this effect is the separation between the two signals being heard by the individual ears; the use of headphones is absolutely essential in the perception of binaural beats, since even in a stereo recording played back on speakers, both ears hear essentially all of both stereo signals. Find a pair of headphones of reasonable quality and listen to the following sound:

The right channel plays a steady tone of 220 Hz, while the left channel plays a steady tone of 212.17 Hz. The brain will also perceive the difference of 7.83 Hz. This frequency, incidentally, is the root note of what are known as the Schumann resonances, the frequency at which the Earth’s electromagnetic field vibrates. Obviously, it cannot be heard with the naked ear, but using binaural beat frequencies, it can be approximated and perceived.

Using binaural beat frequencies in this way is interesting, but has little value beyond its simple novelty. The phenomenon was discovered in 1839 by the Prussian physicist and meteorologist Heinrich Wilhelm Dove, but it was not until the work of Gerald Oster in the 1970s that binaural beats were revisited and their potential fully explored. Oster himself made several advances in the treatment of multiple neurological ailments, using binaural beats as both a therapeutic and diagnostic tool (for instance, an inability to perceive binaural beats can be indicative of Parkinson’s disease), and began applying his research to biological studies as well, including noting a correlation between an ability to perceive certain low frequencies and the menstrual cycle in women. In the last forty years, the study of binaural beats has been seized upon by the fringe and pseudo-sciences, to varying degrees of credibility. The basic theories involving the use of binaural beats to mentally and physically influence the listener, however, are scientifically sound and intriguing. The phenomenon called the ‘frequency following response’ causes the human brain to synchronize its brainwave activity (to varying degrees) with any other frequency close to its own. Human brainwaves travel on very low frequencies, ranging from the 40 Hz or slightly higher of the Gamma wave (the brain at its maximum functionality), to the 7 to 13 Hz of the Alpha wave (the usual range of the brain while awake and alert), to the below 4 Hz of Delta waves (the brain in the deepest, dreamless sleep). Since we are not generally aware of these frequencies, and cannot replicate them easily using traditional musical instruments and sound equipment, the frequency following response rarely becomes a factor in our daily lives. Using binaural beats, however, these frequencies can be easily attained, and using the frequency following response we can increase or decrease the activity of various frequencies within the brain of the listener, guiding the activity of the brain from one state to another.

I may later discuss the further possibilities of binaural beat frequencies, but for now you have a basic understanding of the science behind Obdormiscere (found here). Underlying the ambient elements is a tone containing binaural beats which, over the course of 30 minutes, decrease from 15 Hz (A normal, waking Beta state) to 3 Hz (The threshold between Theta and Delta waves, comparable to sleep or deep meditation). Obviously, many factors will influence the degree to which this may or may not cause a specific listener's brain to follow the same pattern, but give it a try if you have an extra half hour, and let me know how it goes.