METHOD AND APPARATUS AND MEASURING LOSS FACTOR OF STRING

PURPOSE:To simply calculate the loss factor of a string from the damped vibration behavior of the string, by a method wherein the string is resonated to the sonic wave of an electrooptical converter and the max. displacement value of the string is measured at an abdominal position by a sensor and the max. value is held to a constant state before the sonic wave is stopped. CONSTITUTION:A string 1 is provided between Japanese harp (KOTO) posts 2, 3 under tension to be touched by a finger and the vibration displacement of the string is caught by a sensor (an Al foil is adhered at a measuring point in a non-conductive string) and the output of the sensor is amplified by an amplifier A1 and the frequency of the amplified output is analyzed by a frequency analyzer SA to be displayed on CRT to know resonance frequency. A sonic wave is emitted from an oscillator OS through an amplifier A2, a speaker 16 and a sonic wave radiation surface throttling apparatus 18 so as to start from a frequency level lower by about DELTAf and said frequency level is successively increased while a level recorder LR is observed to be made max. (resonance frequency f0). The max. value is held to a constant one CS and the recording paper of a recorder KL is fed at a constant speed and the emission of the sonic wave is stopped. A decay curve L contains a straight line l and the loss factor etaof the string can be calculated as decay quantity D/sec from a known formula. Further, the resonance frequency f0 is cleared by the counter of the oscillator OS.