INTRODUCTION TO SOUND THERAPY WITH TUNING FORKS
A tuning fork is an acoustic resonator in the form of a two-pronged fork with the prongs (tines) formed from a U-shaped bar of elastic metal, usually aluminium or steel (though in some case quartz crystal).
It resonates at a specific constant pitch when set vibrating by striking it against a surface or with an object, and emits a pure musical tone after waiting a moment to allow some high overtones to die out.
The pitch that a particular tuning fork generates depends on the length of the two prongs.
Tuning forks are mostly used to produce a standard of pitch to tune other musical instruments, though they are also used to calibrate radar guns (e.g. for measuring the speed of vehicles); in gyroscopes and in clocks and watches.
Tuning forks are also used by medical practitioners a variety of ways:
- Tuning forks, usually C512 Hz, are used to assess a patient’s hearing
- Lower-pitched ones (usually C128 Hz) are also used to check vibration sense as part of the examination of the peripheral nervous system.
They are also commonly used alongside healing modalities such as polarity, massage, shiatsu and crystal therapies.
Like many of the instruments that are employed in sound therapy, tuning forks can be used therapeutically either as a stand-alone instrument or they can be combined with other sound tools as part of a harmonic sound therapy session.
The U shape of the tuning fork produces a very pure tone, which means that they have a unique sonic precision, unlike most instruments.
There are 2 aspects to this:
1. Few overtones
Most of the vibrational energy is created at a fundamental frequency with little audible overtones or harmonics. The reason for this is the frequency of the first overtone is about 2.5 octaves above the fundamental. With most other instruments, the first overtone is 1 octave above the fundamental. So when a single fork is struck little of the energy goes into the overtone modes.
2. Short sustain of overtones
Also, the overtone frequencies in a struck fork die out relatively quickly, leaving only the fundamental note as a pure tone.
The pure tones of tuning forks, combined with their compact, light-weight form, make them an ideal instrument for sound therapy. They can be moved very easily around the aura of clients, held near their ears and placed on their bodies.
Another reason for using the fork shape is that, when it vibrates in its principal mode, the handle vibrates up and down as the prongs move apart and together. The handle motion is small, allowing the fork to be held by the handle without damping the vibration, but it allows the handle to transmit the vibration to a resonator (sounding board) which amplifies the sound of the fork. Without a resonator (which may be as simple as a table top to which the handle is pressed), the sound is very faint.
The reason for this is that the sound waves produced by each fork prong are 180° out of phase with the other, so at a distance from the fork they interfere and largely cancel each other out. If a sound absorbing sheet is slid in between the prongs of a vibrating fork, reducing the waves reaching the ear from one prong, the volume heard will actually increase, due to a reduction of this cancellation.
All parts of the body can act a resonator for tuning forks, though certain bones such as the sacrum, sternum and cranium are especially good for this.
All this means that tuning forks can be used effectively both on and off the bodies of clients to balance the nervous system and etheric fields, induce relaxation, reduce stress and enhance energy levels.
They are however not typically used in group work such a sound baths, as their audible sounds are quiet unless struck together to amplify the sound harmonics.
As you will see throughout these articles, there are many references to the frequencies or pitch of tuning forks measured in Hertz (Hz). This is because tuning forks are deigned to create a specific pitch when struck, and so knowledge of their frequencies is fundamental.