Recent results on unison quality, or finding objective and quantitative criteria to decide that a piano is perfectly tuned

cote interne IRCAM: Causse99c; /; National audience; The difference in tuning (mistuning) between the three strings of a unison group is the parameter used by the tuner to adjust for each note the double ecay of the sound, characteristic of piano tones, generally from the notes F1 to C5. However, in the case of important irregularities in hammer stricking, increasing the mistuning to adjust the double decay (slope and relative level of each decay) is not sufficient and only the proper adjustment of the regularity of the action of the hammer would lead to a better temporal evolution of the sound (Causse and al., Proc.ISMA'98). To further explore what tuners call "unison quality", which means finding objective and qualitative criteria to decide that a piano is well tuned, the double-decay of the first partials of notes of a piano with different "unison qualities" and different hammer stricking irregularities was measured. In parallel, a simple simulation was refined of the vibration of a unison group of strings where excitation irregularities were simulated by varying the initial displacements and velocities of the strings. In this presentation, results of simple listening tests done with piano tuners will be presented.