The tuning fork was invented by John Shore in 1711 and helped improve the accuracy of tuning musical instruments. It later had a significant impact on the establishment of the standard frequency (440 Hz) and the study of acoustics.
A tuning fork is made by bending a square metal bar of uniform thickness into a U-shape and welding a metal rod firmly to the bottom. This device produces a sound of a certain frequency when struck with a small hammer. In general, the smaller the tuning fork, the higher the pitch. These tuning forks are widely used not only in music, but also in scientific experiments, and have become an important tool for studying the physical properties of sound.
The tuning fork was originally developed in 1711 by the British trumpeter John Shore as a tool for producing a reference tone when tuning an instrument. At the time, instrument tuning was largely dependent on the player’s ears, which inevitably led to inaccuracies. The invention of the tuning fork greatly improved the accuracy of tuning musical instruments, but in the early days, tuning forks were only known to produce certain notes on keyboard instruments, not how many times per second they vibrated. Instruments tuned with such tuning forks had slightly different reference tones depending on the region and the player. This was due to the lack of accurate measuring devices at the time.
It was a very difficult problem to determine the frequency of a tuning fork. This problem was solved by the German acoustician Johann Christian Haeffner in 1834. Haeffner used a method of counting the frequency of the beat produced by two tuning forks producing different tones. Macnolli refers to the phenomenon in which two sounds of slightly different frequencies interfere with each other, causing the sound to periodically become stronger and weaker. The frequency of the macnolli that occurs when two tones of different frequencies sound together is equal to the difference in the frequencies of the two tones. The macnolli frequency is suitable for hearing and measuring when it is about four times per second, or 4 Hz.
The phenomenon of beat generation is one of the phenomena of sound interference and plays an important role in music and physics. For example, beat generation occurs when two tones have nearly the same frequency, causing the sound to repeat in cycles of increasing and decreasing volume. This phenomenon occurs because the frequencies of the two tones are almost the same, and it is one of the most important concepts in acoustics.
Schaeffer’s experiment required several tuning forks. He tuned tuning fork #1 to produce the same note as the A note of a keyboard instrument, and tuned tuning fork #2 slightly higher than #1 so that the frequency of the beat between the two tuning forks was 4 Hz. This means that the natural frequency of the No. 1 tuning fork is 4 Hz higher than that of the No. 2 tuning fork. Next, Schaeffer made a larger No. 3 tuning fork so that when it was struck together with the No. 2 tuning fork, it would also produce four beats per second. In this way, the #3 tuning fork has a frequency that is 8 Hz lower than the #1 tuning fork. Schaeffer repeated this process to create a new tuning fork that produced a note exactly one octave lower than the first. In the end, tuning fork number 56 produced a note exactly one octave lower than tuning fork number 1. Schaible was able to calculate that the 56th tuning fork produced a sound 4 Hz × 55, or 220 Hz, lower than the 1st tuning fork.
Since it was already known that the frequency of the higher of the two tones differing by one octave is twice that of the lower tone, Schaeffer could easily calculate the natural frequency of the tuning forks. The natural frequency of the No. 1 tuning fork is twice that of the No. 56 tuning fork, and the difference is 220 Hz, so the natural frequency of the No. 1 tuning fork is 440 Hz and the natural frequency of the No. 56 tuning fork is 220 Hz.
Based on these findings, Schaeffer proposed that the A note of keyboard instruments be set at 440 Hz at a meeting of scientists in Stuttgart, Germany, in 1834. The resulting “Stuttgart Pitch” was later widely used as a reference tone for tuning in various European countries. This standardized the tuning of musical instruments throughout Europe, which contributed greatly to the consistency of musical performance and education. In modern times, 440 Hz is still used as the standard tuning, which shows how important Schaeffer’s achievement was.
