Method of harmonic tuning of at least one gong of a watch striking mechanism

A method of harmonic tuning of a gong (1) of a striking watch, the gong (1) being fastened to at least one gong holder (2) by at least one of a first end or a second end or by an intermediate portion located between the first end and the second end of the gong (1), and for which a ratio of vibration frequencies generated in a watch plane XY, and outside the watch plane along an axis Z following a strike of a hammer against the gong (1),

• the method comprising:
• placing the gong (1) by means of its gong holder (2) on an adapted support of a measuring instrument or placing a watch case comprising a striking mechanism with the gong (1) on an adapted support of the measuring instrument,
• striking the gong (1) in a direction defined by the hammer which is external or forming part of the striking mechanism of the watch,
• picking up a dynamic response of the gong activated and vibrated by the strike of the hammer, by the measuring instrument,
• processing a dynamic response signal of the gong by performing a fast Fourier transform in a processor unit or in a microcontroller of the measuring instrument,
• determining at least two frequency peaks which correspond, in a selected natural mode, to the vibration frequencies in the plane XY and along the axis Z of the vibrating gong in an audible frequency band from 20 Hz to 5 kHz,
• calculating at least one ratio r=|fip−fih|/fip≤0.006 or r′=|fih−fip|/fih≤0.006, where fip is the vibration frequency in the plane XY of a ith selected natural mode, and fih is the vibration frequency outside the plane Z of the ith natural mode, the calculation of the ratio r or r′ depending on the direction of striking of the hammer against the gong, and
• comparing the ratio r or r′ to a desired value equal to 0.006 in such a way that if r or r′ is equal to or less than the desired value of 0.006 the gong is considered tuned and if r or r′ is greater than the desired value, a gong adjustment operation is carried out before repeating the steps of the method from the striking of the gong by the hammer.