Binaural beats 1

Binaural beatsFor other uses, see Binaural (disambiguation).

Binaural beats

Binaural beats, or binaural tones, are auditory processing artifacts, orapparent sounds, caused by specific physical stimuli. This effect wasdiscovered in 1839 by Heinrich Wilhelm Dove and earned greaterpublic awareness in the late 20th century based on claims coming fromthe alternative medicine community that binaural beats could helpinduce relaxation, meditation, creativity and other desirable mentalstates. The effect on the brainwaves depends on the difference in frequencies of each tone: for example, if 300 Hzwas played in one ear and 310 in the other, then the binaural beat would have a frequency of 10 Hz.

The brain produces a phenomenon resulting in low-frequency pulsations in the amplitude and sound localization of aperceived sound when two tones at slightly different frequencies are presented separately, one to each of a subject'sears, using stereo headphones. A beating tone will be perceived, as if the two tones mixed naturally, out of the brain.The frequencies of the tones must be below 1,000 hertz for the beating to be noticeable. The difference between thetwo frequencies must be small (less than or equal to 30 Hz) for the effect to occur; otherwise, the two tones will beheard separately, and no beat will be perceived.Binaural beats are of interest to neurophysiologists investigating the sense of hearing.Binaural beats reportedly influence the brain in more subtle ways through the entrainment of brainwaves and provideother health benefits such as control over pain.[1]

Acoustical background

Interaural time differences (ITD) of binauralbeats

For sound localization, the human auditory system analyses interauraltime differences between both ears inside small frequency ranges,called critical bands. For frequencies below 1000 to 1500 Hz interauraltime differences are evaluated from interaural phase differencesbetween both ear signals.[2] The perceived sound is also evaluated fromthe analysis of both ear signals.

If different pure tones (sinusoidal signals with different frequencies)are presented to each ear, there will be time-dependent phase and timedifferences between both ears (see figure). The perceived sounddepends on the frequency difference between both ear signals:

• If the frequency difference between the ear signals is lower than a few hertz, the auditory system can follow thechanges in the interaural time differences. As a result, an auditory event is perceived, which is moving throughthe head. The perceived direction corresponds to the instantaneous interaural time difference.

•• For slightly bigger frequency differences between the ear signals (more than 10 Hz), the auditory system can nolonger follow the changes in the interaural parameters. A diffuse auditory event appears. The sound correspondsto an overlay of both ear signals, which means amplitude and loudness are changing rapidly (see figure in thechapter above).

• For frequency differences between the ear signals of above 30 Hz, the cocktail party effect begins to work, andthe auditory system is able to analyze the presented ear signals in terms of two different sound sources at twodifferent locations, and two distinct signals are perceived.

Binaural beats can also be experienced without headphones; they appear when playing two different pure tones through loudspeakers. The sound perceived is quite similar: with auditory events that move through the room, at

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low-frequency differences, and diffuse sound at slightly bigger frequency differences. At bigger frequencydifferences, apparent localized sound sources appear.[3] However, it is more effective to use headphones thanloudspeakers.

HistoryHeinrich Wilhelm Dove discovered binaural beats in 1839 and published his findings in the scientific journalRepertorium der Physik.[4] While research about them continued after that, the subject remained something of ascientific curiosity until 134 years later, with the publishing of Gerald Oster's article "Auditory Beats in the Brain"(Scientific American, 1973). Oster's article identified and assembled the scattered islands of relevant research sinceDove, offering fresh insight (and new laboratory findings) to research on binaural beats.In particular, Oster saw binaural beats as a powerful tool for cognitive and neurological research, addressingquestions such as how animals locate sounds in their three-dimensional environment, and also the remarkable abilityof animals to pick out and focus on specific sounds in a sea of noise (which is known as the cocktail party effect).Oster also considered binaural beats to be a potentially useful medical diagnostic tool, not merely for finding andassessing auditory impairments, but also for more general neurological conditions. (Binaural beats involve differentneurological pathways than ordinary auditory processing.) For example, Oster found that a number of his subjectsthat could not perceive binaural beats suffered from Parkinson's disease. In one particular case, Oster was able tofollow the subject through a week-long treatment of Parkinson's disease; at the outset, the patient could not perceivebinaural beats, but by the end of the week of treatment, the patient was able to hear them.In corroborating an earlier study, Oster also reported gender differences in the perception of beats. Specifically,women seemed to experience two separate peaks in their ability to perceive binaural beats—peaks possiblycorrelating with specific points in the menstrual cycle, onset of menstruation and during the luteal phase. These dataled Oster to wonder if binaural beats could be used as a tool for measuring relative levels of estrogen.The effects of binaural beats on consciousness were first examined by physicist Thomas Warren Campbell andelectrical engineer Dennis Mennerich, who under the direction of Robert Monroe sought to reproduce a subjectiveimpression of 4 Hz oscillation that they associated with out-of-body experience.[5] On the strength of their findings,Monroe created the binaural-beat technology self-development industry by forming The Monroe Institute, now acharitable binaural research and education organization.

Unverified claimsThere have been a number of claims regarding binaural beats, among them that they may simulate the effect ofrecreational drugs, help people memorize and learn, stop smoking, help dieting, tackle erectile dysfunction andimprove athletic performance.An uncontrolled pilot study of eight individuals indicated that binaural beats may have a relaxing effect. In absenceof positive evidence for a specific effect, claimed effects may be attributed to the power of suggestion (the placeboeffect).In a blind study (eight participants) of binaural beats' effects on meditation, 7 Hz frequencies were found to enhancemeditative focus while 15 Hz frequencies harmed it.A further study conducted at Goldsmiths, University of London found that there was no main effect for the use ofbinaural beats in order to alleviate cold pain. Musicians, however, demonstrated themselves to be better at copingwith the pain, suggesting that it may be the sound itself which is a distracting factor as opposed to any brainwaveinfluence.

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PhysiologyThe sensation of binaural beats is believed to originate in the superior olivary nucleus, a part of the brain stem. Theyappear to be related to the brain's ability to locate the sources of sounds in three dimensions and to track movingsounds, which also involves inferior colliculus (IC) neurons. Regarding entrainment, the study of rhythmicityprovides insights into the understanding of temporal information processing in the human brain. Auditory rhythmsrapidly entrain motor responses into stable steady synchronization states below and above conscious perceptionthresholds. Activated regions include primary sensorimotor and cingulate areas, bilateral opercular premotor areas,bilateral SII, ventral prefrontal cortex, and, subcortically, anterior insula, putamen, and thalamus. Within thecerebellum, vermal regions and anterior hemispheres ipsilateral to the movement became significantly activated.Tracking temporal modulations additionally activated predominantly right prefrontal, anterior cingulate, andintraparietal regions as well as posterior cerebellar hemispheres. A study of aphasic subjects who had a severe strokeversus normal subjects showed that the aphasic subject could not hear the binaural beats, whereas the normalsubjects could.

Hypothetical effects on brain functionFor more details on this topic, see brainwave entrainment.

OverviewBinaural beats may influence functions of the brain in ways besides those related to hearing. This phenomenon iscalled "frequency following response". The concept is that if one receives a stimulus with a frequency in the range ofbrain waves, the predominant brainwave frequency is said to be likely to move towards the frequency of the stimulus(a process called entrainment). In addition, binaural beats have been credibly documented to relate to both spatialperception and stereo auditory recognition, and, according to the frequency following response, activation of varioussites in the brain.The stimulus does not have to be aural; it can also be visual or a combination of aural and visual (one such examplewould be Dreamachine).Perceived human hearing is limited to the range of frequencies from 20 Hz to 20,000 Hz, but the frequencies ofhuman brain waves are below about 40 Hz. To account for this lack of perception, binaural beat frequencies are used.Beat frequencies of 40 Hz have been produced in the brain with binaural sound and measured experimentally.When the perceived beat frequency corresponds to the delta, theta, alpha, beta, or gamma range of brainwavefrequencies, the brainwaves entrain to or move towards the beat frequency. For example, if a 315 Hz sine wave isplayed into the right ear and a 325 Hz one into the left ear, the brain is entrained towards the beat frequency 10 Hz,in the alpha range. Since alpha range is associated with relaxation, this has a relaxing effect, or if in the theta range,more alertness. An experiment with binaural sound stimulation using beat frequencies in the beta range on someparticipants and the delta/theta range on other participants found better vigilance performance and mood in those onthe awake alert state of beta-range stimulation.Binaural beat stimulation has been used fairly extensively in attempts to induce a variety of states of consciousness,and there has been some work done in regards to the effects of these stimuli on relaxation, focus, attention, and statesof consciousness. Studies have shown that with repeated training to distinguish close frequency sounds that a plasticreorganization of the brain occurs for the trained frequencies and is capable of asymmetric hemispheric balancing.

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Brain wavesMain article: Electroencephalography

Frequency range Name Usually associated with:

> 40 Hz Gamma waves Higher mental activity, including perception, problem solving, fear, and consciousness

13–39 Hz Beta waves Active, busy or anxious thinking and active concentration, arousal, cognition, and or paranoia

7–13 Hz Alpha waves Relaxation (while awake), pre-sleep and pre-wake drowsiness, REM sleep, Dreams

8–12 Hz Mu waves Mu rhythm, Sensorimotor rhythm

4–7 Hz Theta waves Deep meditation/relaxation, NREM sleep

< 4 Hz Delta waves Deep dreamless sleep, loss of body awareness

(The precise boundaries between ranges vary among definitions, and there is no universally accepted standard.)The dominant frequency determines one's current state. For example, if in someone's brain, alpha waves aredominating, they are in the alpha state (this happens when one is relaxed but awake). However, other frequencieswill also be present, albeit with smaller amplitudes.The brain entraining is more effective if the entraining frequency is close to the user's starting dominant frequencyWikipedia:Citation needed. Therefore, it is suggested to start with a frequency near to one's current dominantfrequency (likely to be about 20 Hz or less for a waking person) and then slowly decrease or increase it towards thedesired frequency.Some people find pure sine waves unpleasant, so a pink noise or another background (e.g., natural sounds such asriver noises) can also be mixed with them. In addition to that, as long as the beat is audible, increasing the volumeshould not necessarily improve the effectiveness; therefore, using a low volume is usually suggested. One theory isto reduce the volume so low that the beating should not even be clearly audible, but this does not seem to be the case(see the next paragraph).

Other usesIn addition to lowering the brain frequency to relax the listener, there are other controversial, alleged effects ofbinaural beats. For example, that by using specific frequencies, an individual can stimulate certain glands to producedesired hormones. Beta-endorphin has been modulated in studies using alpha-theta brain wave training, anddopamine with binaural beats. Some have attempted to use them to induce lucid dreaming, but the role ofalpha-wave activity in lucid dreaming is subject to ongoing research.Alpha-theta brainwave training has also been used successfully for the treatment of addictions.It has been used for the recovery of repressed memories, but as with other techniques, this can lead to falsememories.An uncontrolled pilot study of delta binaural beat technology over 60 days has shown positive effects onself-reported psychologic measures, especially anxiety. However only 15 people participated in this study, therefore,providing insignificant results. Of the few people that participated, there was reported a significant decrease in traitanxiety, an increase in quality of life, and a decrease in insulin-like growth factor-1 and dopamine, and it has beenshown to decrease mild anxiety. Further research is warranted to explore the effects on anxiety using a larger,randomized and controlled trial. A randomised, controlled study concluded that binaural beat audio could lessenhospital acute pre-operative anxiety.Another claimed effect for sound-induced brain synchronization is enhanced learning ability. It was proposed in the 1970s that induced alpha brain waves enabled students to assimilate more information with greater long-term retention. In more recent times has come more understanding of the role of theta brain waves in behavioural learning. The presence of theta patterns in the brain has been associated with increased receptivity for learning and

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decreased filtering by the left hemisphere. Based on the association between theta activity (4–7 Hz) and workingmemory performance, biofeedback training suggests that normal healthy individuals can learn to increase a specificcomponent of their EEG activity, and that such enhanced activity may facilitate a working memory task and to alesser extent focused attention.A small media controversy was spawned in 2010 by an Oklahoma Bureau of Narcotics official comparing binauralbeats to illegal narcotics and warning that interest in websites offering binaural beats could lead to drug use.However, the entire collection of auditory binaural beat nd EEG literature may need to be re-evaluated. In 1996,while a student under Karl Pribram at the Behavioral Research And Informational Neural Sciences (BRAINS)Center, Dennis McClain-Furmanski noticed that virtually all studies followed the same equipment protocol, whichincluded electrostatic headphones for stimulus presentation, placed on the head over the EEG electrodes. In mostother EEG research this would be considered a source of artifact as the electromaagnets in the headphones wouldinduce signal into the EEG. To test this, he replicated one of the initial studies done at the Monroe Center, using ahead-shaped styrofoam wig stand as "subject". He was able to replicated the EEG results as given. In 2002,McClain-Furmanski, now at the National Institute for Deafness and other Communication Disorders (NIH,Bethesda) consulted for a colleague, Dr. James Horton of the University of Virginia at Wise, advising him and oneof his undergraduate lab courses in developing a more rigorous test. Horton and his students developed a series ofcommonly used binaural beat stimuli and arranged to have these presented to subjects twice. One battery of thestimuli would be presented the traditional way, with headphone on top of the EEG electrode cap. The second battery,however, would be presented through air conduction ear phones. These auditory stimulus presentation device usesseveral feet of rubber tubing to conduct the sound to the ear, separating the EEG electrodes from the electromagnetictransducer so as not to produce artifactual signal. Using the traditional arrangement, all the expected EEG resultswere seen. However, with the air conduction device, the same subjects and the same stimuli, no changes in EEGfrom resting baseline were seen. The results were presented at the Society for Psychophysiological Research in 2002.As a result, one researcher with whom the students had been corresponding during the experiment, had a previouslypublished binaural beat EEG paper withdrawn.

References[1] Hemispheric-synchronisation during anaesthesia: a double-blind randomised trial using audiotapes for intra-operative nociception control

(http:/ / www. ncbi. nlm. nih. gov/ pubmed/ 10460529), Jan 2000, Kliempt, Ruta, Ogston, Landeck & Martay[2][2] Blauert, J.: Spatial hearing - the psychophysics of human sound localization; MIT Press; Cambridge, Massachusetts (1983), ch. 2.4[3] Slatky, Harald (1992): Algorithms for direction specific Processing of Sound Signals - the Realization of a binaural

Cocktail-Party-Processor-System (http:/ / www. cocktail-party-processor. de/ english/ algo/ index. html), Dissertation, Ruhr-UniversityBochum, ch. 3

[4] Heinrich Wilhelm Dove (1839) Repertorium der Physik Vol.III p.494[5][5] "My Big TOE" book 1, Thomas Campbell, p79 ISBN 978-0-9725094-0-4

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