Binaural beats to entrain the brain? A systematic review of the effects of binaural beat stimulation on brain oscillatory activity, and the implications for psychological research and intervention

Summary & key facts

Binaural beats happen when two slightly different tones are played to each ear and you hear a third, pulsing tone at the difference between them. This review looked at 14 studies that measured brain activity after binaural-beat sounds. The results were mixed: some studies found brain activity that matched the beat frequency, but more studies did not. The studies used many different methods and measurements, so it is hard to draw firm conclusions. The authors say we need clearer, more standardized studies before we can know whether binaural beats reliably change brain oscillations.

Key facts:

• Binaural beats are heard when two tones of different frequencies are presented separately to each ear and produce a perceived beat at the difference frequency, typically in the 1–30 Hz range.
• The systematic review included 14 published studies that measured brain activity after binaural-beat stimulation.
• Out of the 14 studies, 5 reported results consistent with the brainwave entrainment hypothesis, 8 reported results that contradicted it, and 1 reported mixed results.
• The reviewed studies were very heterogeneous in how binaural beats were made, the experimental designs used, and the EEG measures and analyses, which limits how comparable the results are.
• Some earlier studies showed that binaural-beat stimulation can elicit measurable neural responses such as auditory steady-state responses (ASSRs) and frequency-following responses (FFRs) in EEG or MEG recordings.
• Perception limits reported in the literature include: carrier tones must be ≤1000 Hz to produce binaural beats; binaural beats are often best perceived with carrier tones around 400 Hz; and the two tones’ frequency difference is usually eff
• Perceptual qualities change with beat rate: differences up to ~20 Hz are described as a loudness fluctuation, differences above ~20 Hz sound rough, and differences below ~3 Hz can be perceived as a rotating tone; these thresholds are approx
• The authors conclude that standardization of methods is needed in future research to allow reliable conclusions about whether binaural beats entrain brain oscillations.

Abstract

Binaural beats are an auditory phenomenon that occurs when two tones of different frequencies, which are presented separately to each ear, elicit the sensation of a third tone oscillating at the difference frequency of the two tones. Binaural beats can be perceived in the frequency range of about 1-30 Hz, a range that coincides with the main human EEG frequency bands. The brainwave entrainment hypothesis, which assumes that external stimulation at a certain frequency leads to the brain's electrocortical activity oscillating at the same frequency, provides the basis for research on the effects of binaural beat stimulation on cognitive and affective states. Studies, particularly in more applied fields, usually refer to neuroscientific research demonstrating that binaural beats elicit systematic changes in EEG parameters. At first glance, however, the available literature on brainwave entrainment effects due to binaural beat stimulation appears to be inconclusive at best. The aim of the present systematic review is, thus, to synthesize existing empirical research. A sample of fourteen published studies met our criteria for inclusion. The results corroborate the impression of an overall inconsistency of empirical outcomes, with five studies reporting results in line with the brainwave entrainment hypothesis, eight studies reporting contradictory, and one mixed results. What is to be noticed is that the fourteen studies included in this review were very heterogeneous regarding the implementation of the binaural beats, the experimental designs, and the EEG parameters and analyses. The methodological heterogeneity in this field of study ultimately limits the comparability of research outcomes. The results of the present systematic review emphasize the need for standardization in study approaches so as to allow for reliable insight into brainwave entrainment effects in the future.

Topics

Music Therapy and Health Neuroscience and Music Perception Phonocardiography and Auscultation Techniques

Categories

Cognitive Neuroscience Life Sciences Neuroscience

Tags

Acoustics Audiology Beat (acoustics) Binaural recording Brain activity and meditation Brain stimulation Cognitive psychology Electroencephalography Entrainment (biomusicology) Medicine Neuroscience Physics Psychology Rhythm Stimulation