Original Oster

Original Oster

Psychoacoustics: Binaural Beats

Psychoacoustic is the study of perception of sounds. It basically focuses on how we listen and the physiological effect of music and sound on the nervous system.

Human auditory perception

The typical human hearing range is between 20 Hz and 20,000 Hz.  Software and the psychoacoustic models are based on the ear’s limitation in perceiving sounds. They provide lossy compression, which determines which frequencies can be removed without significantly affecting the perceived sound quality.

Masking effects

One of the main elements of psychoacoustics is the masking of spectral sound elements in an audio signal like tones and noise. This is done by the use of special encoding programs that “mask” frequencies that is beyond or below the human hearing range. Masking is when a softer sound is covered by the presence of the louder sound. For example, in an audio signal a masking threshold is calculated. If a certain tone is below the masking threshold it will be masked by the louder tone.

Binaural beats

Binaural beats were discovered in 1839 by a German experimenter, Heinrich Wilhelm Dove. However it was Gerald Oster’s article “Auditory beats in the Brain” published in 1973 that brought new insight on the research of Binaural Beats.

Binaural beats or binaural tones are auditory responses, the perception of which arises in the superior olivary nucleus of the brainstem. They result from the interaction of two different frequencies, originating in opposite ears simultaneously using headphones. The frequencies must be below 1000 Hz in order to “hear” the beats. The two opposing frequencies must have a difference between 1 and 30 Hz in order for the effect to take place. For example, if a pure tone of 500 Hz is presented to the right ear and a pure tone of 510 Hz is presented simultaneously to the left ear, a “binaural beat” of 10 Hz, the difference between the two tones, is experienced. The brain’s ability to detect a waveform phase is what enables it to perceive binaural beats.

Effects of Listening to Binaural Beats

Binaural beats may influence functions of the brain. Since they are perceived as auditory beats, they can theoretically be used to entrain specific neural rhythms through frequency-following response (FFR). This is when brain waves tend to entrain to or resonate at the frequency of an external stimulus. Therefore, it is theoretically possible to utilize a specific binaural-beat frequency as a consciousness management technique to entrain a specific brainwave activity.

Binaural beats are usually used to induce various states of consciousness. Depending on the frequency of binaural beat stimulation, the effect on someone may be stimulating or relaxing. Binaural beats frequencies that range between 1 to 4 Hz (Delta) and 4 to 8 Hz (Theta) have been associated with relaxed, creative, sleepy and meditative states. Alpha frequencies (8 to 12 Hz) have increased brain wave activity, which could correspond to a relaxed while awake state. Beta frequencies (16 to 24 Hz) have been associated with active, busy, arousal, stress and alertness.

 

Research and interest on the neurological component of sound in the field of psychoacoustics have rapidly grown in the past few decades. Binaural Beating is being used in a variety of fields like music, therapy, neurosciences and education.

 

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