How sound is produced and transmitted is a very important consideration when we think about the therapeutic effects of music.
New Type of Sound Wave
Traditionally, we have been taught that sound is transmitted only through longitudinal waves. However, Dr. Yoshiyasu Takefuji at Keio University discovered the possibility that sound may also be transmitted by what he describes as a "transverse wave," similar to an electromagnetic wave, through his many experiments. When a bent plastic sheet is attached to a music box, for example, it sounds much louder and richer, and the signal can travel a greater distance. Dr. Takefuji measured this signal 100 meters away from the source with a very low frequency antenna (which captures very high frequencies as sound waves, but very low frequencies as electromagnetic waves), and observed a measurable electromagnetic signal.
By applying these principles, Hibino Sound Therapy Lab has created a revolutionary transverse wave speaker system and has tested high frequency transmission into the air. A high-resolution microphone was used to measure frequency response one meter away from the speaker system with the spec of up to 100k. The results show that traditional longitudinal wave speakers alone experience a huge drop off in the high end (-50db at 16k) while the combination with our transverse wave speaker system resulted in a much less dramatic drop off (-20db at 16k).
Similar to X-rays and electromagnetic waves, these transverse waves are believed to penetrate the skin and resonate in deep tissues and cells. Using a basic principle of physics, the higher the frequency of a wave, the higher the amount of energy it contains and therefore delivers in this example. If this is applied to sound waves, although the human ear cannot perceive these high-frequency waves as sound, as long as these are delivered via our transverse wave speaker system, there may be a direct effect on human body at a cellular level.
This leads to our hypothesis below:
High frequency waves delivered in music may be transmitted through transverse waves and received by humans at a cellular level, affecting the human body directly without involvement of the brain since these frequencies are not recognized as sound.
Generation of Transverse Waves
Consider the vibrations created during an earthquake. When a solid mass like the Earth's surface receives pressure that is not strong enough to change its shape permanently, elastic waves are produced that consist of a primary wave (longitudinal) and secondary wave (transverse) as a result of the transition of intermolecular forces.
However, if the pressure is strong enough to change the shape of the mass permanently (like folding a paper in half with a crease rather than bending it in the previous example), the intermolecular forces are detached and the elastic wave cannot be delivered.
This idea can be applied to a bent plastic sheet where the shape is changed but in a reversible manner. This is seen commonly in music with guitars, pianos, violins and all kinds of acoustic instruments.
This is true not only because the shape of the instrument, but also how we perform. If the string on a guitar is plucked very hard, for example, it sounds bright and fun, but the vibration may exceed the pressure limit which produces elastic waves, resulting in fewer transverse waves being generated and less hypothesized effectiveness in sound therapy. Alternately, if the string is plucked softly, it moves gently and creates transverse waves which we believe will reach the human cell.
When we create music, we consider this in composition and arrangement so that each note achieves a good and natural vibration. As for which instruments are best at producing transverse waves, from our experience, we've seen the best therapeutic result using plucked string and wind instruments.
We're still investigating the effectiveness of note phrasing on therapeutic outcomes, but so far we've seen better results when the melody is in an ascending line as opposed to a descending line.