Binaural beats

Binaural beats are an acoustic illusion which is perceived when both ears each sound is supplied with a slightly different frequency. Unlike beats Binaural beats not arise by superposition of sound waves in the ear but in the brain. It is believed that this sound is generated in the brain stem, in the superior olivary nucleus, where the center for spatial hearing lies. In order to perceive a beat, the carrier frequencies it must be below 1500 Hz. The difference between the frequencies for the left and right ear must not be greater than 30 Hz, otherwise two different sounds are heard.

Example: If you listen to the left ear has a frequency of 440 Hz and the right ear has a frequency of 430 Hz, in the brain, a sound with a frequency of 435 Hz is generated. A beat similar to a pulsed tone is sensed. The frequency of the pulse ( that is, the binaural beats ) so 10 is the difference between the two frequencies, Hz

The interest in binaural beats can be divided into two categories. On the one hand, they serve to neurophysiology to explore the sense of hearing. Secondly, in neurophysiology, their influence on the processes in the brain is explored. They are also used by certain methods with the aim to stimulate brain waves to promote relaxation, sleep, meditation or concentration.

History

As the discoverer of binaural beats in 1839 applies Heinrich Wilhelm Dove. He found out that apparently beats are heard when the left and right ear separately, but simultaneously, two slightly different tones are fed. Dove won the finding that the perceived shocks must occur exclusively in the auditory system, since no acoustic mixing was present. He suspected that the shock arise in the part of the brain that is responsible for the binaural ( stereophonic ) hearing.

In the following years the subject of binaural beats was taken up sporadically, but kept it a long time the status of a physical oddity. Only G. Oster, a biophysicist at the Mount Sinai School of Medicine in New York, recognized the potential and possibilities that binaural beats. Easter 1973 published an article in Scientific American, where he was compiling the various research results of the last 134 years, ordered and, based on their own research results presented. So he found out for example that for the perception of binaural beats have the carrier frequencies below 1500 Hz. The difference between the carrier frequencies for the left and right ear must not be greater than 30 Hz, otherwise two different tones are perceived.

Easter saw the fields of application of binaural beats in both research as well as in the medical field. For the research, they were an important tool to analyze the neural processes of hearing, to examine spatial hearing and, for example, find out how a single tone from a mixture of many sounds one can hear ( cocktail party effect ).

For the medical field Easter held her for a suitable diagnostic tool for investigating the sense of hearing impairments, but he also found out that it could be used for diseases that have nothing to do with the hearing itself. He noted that shortly before the start of Parkinson's disease, significantly decreased the ability to hear binaural beats. In a particular case, he was able to accompany a Parkinson's patient for many weeks and document that under the medication 's ability to hear binaural beats, increased again. He also observed gender differences in the perception of binaural beats. In women, showed two peaks in the sensation of binaural beats, depending on their menstrual cycle, at the beginning and after 15 days. This data led Oster to the question of whether binaural beats could be used as a measurement tool for the estrogen levels.

An important point in Oster's research was the realization that a binaural beat is perceived when a carrier frequency below the human perception threshold is, or even if both carrier frequencies are so low that the human ear, they apparently no longer perceives them. These findings led Oster to believe that the binaural beats on a different path might form the sounds that we hear otherwise. The effect of the binaural beats only occurs beidohrigem and listening occurs in the brain as a result of the interaction of perceptions.

Physiology

The origin of the binaural beats the researchers suggest in the superior olivary nucleus, a part of the brainstem. The superior olivary nucleus is part of the auditory pathway and its neurons are involved in the localization of sound sources by evaluating run-time and level differences between the two ears ( binaural)

Possible effects ( on the brain )

Binaural beats can affect the brain waves and also the parts of the brain stimulate that are not associated with the hearing.

Information is passed in the brain by means of electrical voltage. The electrical currents active nerve cells can be visualized for example by electroencephalography (EEG). Starting from the externally measured electric pulses can calculate the frequencies on which the pulses based.

Already in 1924, with the development of the EEG by Hans Berger at the University of Jena, the phenomenon of alpha block was discovered. This is a significant change in the EEG when a healthy subject opens his eyes or is stopped to increased mental activity. According to studies, even calming neurotransmitters ( endorphins ) are released in the alpha range, which may be absent with increased stress emergence as humans.

With the possibility of recording the researchers discovered that the different states of consciousness different frequency bands can be assigned. Thus, the brainwaves of a sleeping person are completely different than that of a watch and mentally active people. They also realized that visual and acoustic stimuli can change our state of consciousness.

Our brain produces almost at any time all types of brain wave frequencies. But the frequencies are not equally weighted or distributed, but it always exists a dominant frequency, which indicates our present state of consciousness.

The human ear can detect acoustic events only within a certain frequency and volume range, wherein the frequency band from 20 Hz to 20,000 Hz range and the volume level from 0-130 dB ( threshold of pain ).

Most frequencies that produce the electrical impulses in our brain, below the threshold of perception of our sense of hearing. With the help of binaural beats these frequencies can be generated directly targeted in the brain but now, not for beat frequency is crucial, but the frequency with which these pulses oscillated. In this case, the brain a certain frequency is offered, whichever state of consciousness to be achieved.

The perceived frequency corresponds to one of five neurologically relevant frequency ranges (delta, theta, alpha, beta, gamma ) and causes the brain due to the resonance principle ( also frequency-following principle), to approach this frequency as EEG measurements have shown. This process of bringing the prevailing brain wave frequency to the frequency supplied from the outside is referred to as entrainment. Entrainment is a principle of physics, it is defined as the synchronization of two or more rhythm cycles.

The frequency-following principle is more effective when the perceived frequency of the binaural beats near the predominant brain frequency is (daytime around 20 Hz) and then, for example, for a relaxed state is lowered slowly.

Many people find the sound of pure sine waves unpleasant, so the binaural beats are usually embedded in carrier sounds like nature sounds or harmonious compositions.

Binaural beats are used for deep relaxation at the Hemi - Sync method and Mind Machines.

For a scientific study, 12 subjects were 7 minutes long binaural beats ( and as a control experiment, other sounds ) exposed. In this case, no change in blood pressure or heart rate was observed. The authors themselves admit shortcomings of the study (insufficient number of subjects, too little investigated frequencies, duration, age of the subjects).

Another study with only 9 subjects was different influences on the brain