The forks give the notes cⁱⁱⁱ, c^iv, d^iv, e^iv, f^iv, the 11th harmonic of c¹, the 13th harmonic of c1, aiv, the 14th harmonic of c¹, b^v, and c^v (cⁱⁱⁱ and c^v have vibration frequencies of 1024 and 4096 respectively).

These forks are constructed to prove the following law:

The beats m and n –– m of the intervals n: hn + m, if they are sufficiently numerous and intense, become sounds. These sounds produced by the primary beats, if they are sufficiently near unison, or a harmonic interval, give rise to secondary beats, which in turn, if sufficiently rapid and intense, give rise to the sounds of secondary beats.

Experiments with this and similar apparatus led Dr. Koenig to doubt the existence of the differential and summational tones postulated by Helmholtz.

See Koenig, R. Quelques expériences d’acoustique (Paris, 1882), 102 and 123.

N.B. The above notes, found in the Museum’s technical file T/1890-20, probably date from the time of the Museum’s acquisition of the tuning forks in 1890.

© image: Dr. Aleksander Kolkowski