For the purpose of illustrating potential relationships between various musical frequencies and frequencies that occur in natural processes, I’ve generated a series of plots. Each plots displays frequency ranges for things like human heart rate, musical tempo, brain wave patterns, and respiration. A number of potential relationships are considered.
A few notes are warranted:
- This post is intended raise consideration and questions, not to offer any kind of authoritative answers.
- I welcome your thoughts and knowledge – if you can answer a question posed herein, or offer a thoughtful response, I’d be grateful.
- The data used in plotting is by no means infallible. Data was pulled from several different websites without fact-checking. When possible, several websites were consulted to ensure there was some agreement in the data values used.
- All sources are listed at the end of the post.
- Generally, the numbers used in the plots are estimates and averages, rather than precise values.
- For frequency ranges plotted below, the cycle in question varies depending on the process being considered – for tempo, beats per second are plotted, for breathing, breaths per second, and for running/walking, steps per second.
- Despite the fact that they are all fundamentally different, frequencies of electromagnetic radiation, frequencies of mechanical oscillation, and frequencies of occurrence are all considered and plotted together.
- All plots were generated using the Wolfram language.
Relationship between Respiration, Heart Rate, and Gross Body Movement
We know that breath, respiration, and movement are correlated – the more we move the faster our heart beats and the faster we breathe. The causal relationship between these can go many ways: faster(slower) breathing can increase(decrease) the heart rate and vice versa. Also faster(slower) movements can increase(decrease) the breath/heart rate cycle. Although altering the breath/heart rate does not induce more gross movement in the body, it’s worth noting that it may affect muscle contractions in the body nonetheless.
Comparing breath, respiration, and steps, it appears that our breath is the slowest cycle, followed by heart rate, followed by steps. So if we were to design music to entrain the breath, it may be a slower tempo than music design to entrain the heart rate, and even faster tempos would be required for music designed to entrain the gross movement of the body (dance music).
Do Tempos Track Gross Movement or Heart Rate?
We can see that the range of tempos commonly employed in music coincide with the range of heart rate from resting to exercise. We also see that slower tempos coincide with the tempo of slow walking, medium tempos with moderate intensity walking, and fast tempos with jogging. However, running tempo is faster than any common musical tempo. This lends support to the idea that musical tempo entrains or tracks heart rate, rather than gross body movement.
Binaural Beat Frequencies
In the 2nd plot (Fig. 2), we see a higher range of frequencies. Note that gamma brain wave patterns are defined as any pattern above a certain frequency (27 Hz to 40 Hz, depending the source) but the chart displays an arbitrary cut off for gamma brain wave frequencies.
Because the difference between frequencies used to produce binaural beat frequencies (BBF) must be small (less than 30 Hz), using BBFs is ideal for entraining brain wave patterns delta, theta, alpha, and beta brain waves which are all under 30 Hz. Depending on the source, gamma brain waves range from 27 Hz and up. Some sources say that gamma brain wave patterns begin at 40 Hz, putting them out of the range for BBF entrainment. Perhaps not surprisingly, human voice falls in the range of gamma brain wave patterns as this is the brain wave pattern associated with perception, problem solving, and everyday conscious awareness.
Brain wave Entrainment?
Brain wave entrainment is defined as any practice that causes the brain’s dominant frequencies (measured with EEG) to follow a periodic stimulus. Stimuli attested to cause brain wave entrainment include binaural and monaural beats, isochronic tones (sharp regular pulses of sound), and visual stimuli. Since the brain is the central processor of all bodily stimulus, it seems plausible that any periodic stimulus to the body could affect brain wave patterns.
In the 3rd plot (Fig. 3), we compare the two lowest brain wave frequency ranges (delta and theta) with other body and musical frequencies. We note that the tempo range of music falls within the range of delta and theta brain wave frequencies. Does musical tempo entrain delta brain wave patterns? Or are the frequencies of the sounds themselves, rather than the tempo at which they are played, of more significance to the brain wave frequency patterns produced while listening to music? In case of BBF infused music, it would be argued that those BBFs are the dominant factor influencing the brain wave patterns produced by the listener.
Also, the steps/s associated with jogging and theta brain wave frequencies seem to start at nearly the same frequency. Could jogging entrain theta brain wave patterns?