Although we all do have predispositions towards vibrating at certain frequencies, a strong external vibration can still alter any of our internal rhythms through the phenomenon known as entrainment, which is the tendency of two oscillating bodies to fall into synchrony (identical oscillation). This was made famous by Dutch scientist Christian Huygens in 1665 when he found that two clocks left ticking next to each other always ended up perfectly synchronised, despite the fact there was no physical connection between them. There are many examples of synchrony in nature, from millions of fireflies flashing in unison on the banks of rivers in South East Asia to flocks of thousands of starlings swooping and swirling like a single living organism, all changing direction at the same instant, never colliding.
If one body's oscillation is much more powerful than the other, the synchronous frequency arrived at will be very close to the original frequency of the strong oscillator. This is similar to the way we experience gravity: we and the Earth are exerting pulls on each other but the Earth is so much more massive than we are that our gravitational influence on the planet is not detectable, while its influence on us holds us on its surface, counteracting the centrifugal force that would otherwise throw us off into space. In the same way, if I drop you in a nightclub where there is fast dance music playing at high volume, the measurable effect will be all one way: your heart rate will increase.
The combined physical effects of resonance and entrainment can be very powerful, as in the famous example of the Tacoma Narrows Bridge, where increasing oscillations caused the bridge to collapse. Because the frequency of marching feet on a bridge could match the structure's resonant frequency, creating a feedback loop to make the bridge oscillate more and more wildly until it collapses, soldiers always break step when crossing bridges.
Entrainment is a powerful force in our everyday lives, operating for example whenever music is deployed in public places: it can cause people to eat more or less quickly, alter their speed of shopping, and make them spend more or less money in a shop.
There is a great deal of work going on in the medical arena, both mainstream and ‘alternative', to explore the ways in which our bodies respond to external vibration, usually in the form of tones or music. Some of the results coming from the investigations even by the traditional healthcare sector are spectacular: sound has been shown to displace anaesthetic in operating theatres, to ameliorate the symptoms of various nervous and mental disorders, and to reduce recovery times from a variety of conditions including sports injuries.
It's likely that unconscious entrainment has a great deal to do with the establishment of rapport, which of course is an essential skill in most business conversations and particularly in sales. Most commentators and experts agree that the majority of face-to-face communication is in fact nonverbal (I have seen estimates up to 75 per cent); these days most serious communication trainers go well beyond optimising what is said and work on both delivery and conscious body language, such as matching pace of speech and tone of voice and posture mirroring; some go one level further and include more subtle rhythms such as intentional synchronising of breathing. It's still likely that much of this communication synchrony is beyond our active control, since it involves matching heart rates, blinking patterns, pheromone secretions and tiny, unconscious gestures. With the possible exception of advanced yogis, human beings are simply not able take conscious charge of these.
Also beyond our control for most of us are our brainwaves, yet researchers have shown that these, too, become synchronised during positive communication. Effective public speakers cause the brainwaves of their audiences to become synchronised with their own - in fact, the degree of synchronisation seems to be the major factor in determining whether most people rate a talk as good or not.
Entrainment should be considered in every soundscape we create in our homes, our offices and our commercial spaces - but it rarely is, which is why we encounter so many instances where sound is doing the opposite of what would benefit customer and vendor alike.
Author of the book "Sound Business"; Chairman of The Sound Agency; BrandSoundTM strategist;