Monaural beats are derived from the convergence of two frequencies within a single speaker to create a perceivable pulse or beat. As such they are a purely physical phenomenon; see beats for a more complete discussion of the acoustics. For example, if a 400 Hz tone and a 410 Hz tone are played through a speaker, one would hear a 10 Hz beat amidst the original tones. Monaural beats are similar to binaural beats in that two frequencies are combined to create a perceivable beat. However, they vary in two distinct ways. First, binaural beats are created by introducing two different tones, 400 Hz and 410 Hz, via separate speakers (e.g., headphones). Second, binaural beats seem to be “created” or perceived by cortical areas combining the two different frequencies, whereas monaural beats are due to direct stimulation of the basilar membrane.
The most frequently commercialized use of monaural and binaural beats are in software or apps aimed at achieving brainwave entrainment. Brainwave entrainment is the use of masked monaural or binaural beats to induce a specific brainwave state. It is hypothesized that listening to these beats of certain frequencies one can induce a desired state of consciousness that corresponds with specific neural activity. It is widely accepted that patterns of neural firing, measured in Hz, correspond with states of alertness such as focused attention, deep sleep, etc.
- Beta: A brainwave state associated with high levels of focus and concentration. This is when the brain is actively working and alert. The brainwave patterns that corresponds to this state of consciousness is 12 Hz and above.
- Alpha: While this state of neural firing is slower than Beta at around 8 Hz – 12 Hz this is a state often targeted by brainwave entrainment software. The alpha brainwave state is associated with a relaxed, reflective frame of mind and is also used for problem solving and increased creativity.
- Theta: Theta waves are much slower than beta wave and correspond with states of mind that include meditation, release of stress, and lucid dreaming. At a frequency of 4 Hz – 8 Hz this is the most sought after brain state for mindfulness meditation.
- Delta: This is a brain state that is associated with deep dreamless sleep. The slowest of the brainwave states at 1 Hz – 4 Hz this state is possible to achieve while still awake by some experienced meditators.
- Gamma: Is a brainwave state not given much attention but it is thought to correspond with a moment of insight or eureka moment. 40 Hz and above.
While these brain states are what brainwave entrainment is hoping to achieve the effectiveness of monaural and binaural beats are up for debate. There are many companies that produce software for purchase that stand behind their product saying that “research shows” binaural / monaural beats are effective for inducing a desired brainwave state. However, no published scientific studies have found statistically significant data that indicate monaural / binaural beats induce a specific brainwave state in human participants. No significant change in human EEG readings were found when using binaural beats to induce a theta brain state. Many applications and software continue to be sold. No evidence supporting their claims has yet been found.
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