Tuning fork

A tuning fork is an acoustic resonator in the form of a two-pronged fork. It is used to produce a fixed tone when struck against a surface or with an object. The tuning fork was invented in 1711 by John Shore, a British musician.

Design and Function

A tuning fork vibrating at 659 Hz

A tuning fork consists of a handle and two prongs, or tines, made of elastic metal, usually steel. When the tines are struck, they vibrate at a specific frequency, producing a pure musical tone. The frequency of the sound produced depends on the length and mass of the tines.

The tuning fork is designed to vibrate at a specific frequency, which is determined by the length and mass of its tines. The most common tuning fork frequency is 440 Hz, which is the standard pitch for A440, used as a tuning standard for musical instruments.

Physics of Vibration

Mode shape of a tuning fork at eigenfrequency 440.09 Hz

When a tuning fork is struck, the tines begin to vibrate in a complex pattern. The fundamental frequency is the primary tone heard, but the tines also vibrate at higher harmonics. The shape of the tines and the material of the fork influence the overtones produced.

The vibration of the tines causes the surrounding air to vibrate, creating sound waves. The handle of the fork remains relatively still, allowing the user to hold it without damping the vibrations.

Applications

Tuning forks are used in various applications, including:

Music

Tuning forks are commonly used by musicians to tune instruments. The fork is struck and held near the instrument, allowing the musician to adjust the instrument's pitch to match the fork's tone.

Medical

In medicine, tuning forks are used in audiometry to test hearing. They are also used in neurology to assess vibratory sensation and bone conduction.

Horology

A tuning fork watch mechanism

Tuning forks have been used in watches to maintain accurate time. The Bulova Accutron was the first watch to use a tuning fork as its timekeeping element, vibrating at 360 Hz.

Scientific Instruments

Tuning fork oscillator frequency standard

Tuning forks are used in scientific instruments as frequency standards. They provide a stable reference frequency for calibrating other devices.

Quartz Crystal Tuning Forks

Inside view of a quartz crystal tuning fork

Quartz crystal tuning forks are used in quartz clocks and quartz watches. These devices use the piezoelectric properties of quartz to maintain a precise frequency, which is used to keep accurate time.

Related Pages

• A440
• Frequency
• Sound
• Vibration
• Piezoelectricity