Earlier Transition to Slower Steady Modes of Oscillation.
The initial onset oscillation of the Stuart piano sound was found to transfer earlier to the after-sound oscillation than Steinway, especially when the Stuart fundamental frequency was of a larger amplitude. As a result of this transient characteristic, a heightened level of sustain was audibly and graphically presented in the Stuart sound.
The extended period of the vertical onset vibration of the Stuart piano string, tested in the chapter two of this research, enables a quicker release of the non- resonant frequencies, for a shorter period than Steinway, and is usually accompanied by a faster rapid decay. A smoother, quicker transition into the after-sound oscillation phase occurs, which establishes a heightened level of sustain in the sound. The Stuart piano design minimizes the production of non- resonant frequencies in its sound, with the implementation of Paulello wire materials, the reduced damping of the bridge agraffe coupling, the thinner more actively resonant soundboard, more detailed grading of hammer shanks thickness, and rare earth magnets in the keyboard action.
A piano string oscillates in the vertical plane at the onset, as a consequence of the vertical hammer strike. As the vertical oscillation is of a large amplitude, it has a more transferrable impedance to the narrow wooden bridge and the energy of the onset sound is transferred from the string to the soundboard at a faster rate, which causes the sound to decay at faster rate, the onset rate of decay. The onset vibrations contain non- resonant frequencies, which are expended quickly. As energy is reflected off the large plane of the soundboard of higher impedance, waves are returned to the oscillating string, and because certain amounts of resonant and non-resonant energy has been released, the string vibration transfers to a more settled, elliptical oscillation, with slower rates of decay, the after-sound (a-s) decay. The string vibrations test by Peter Phillips in chapter 2 found that the string coupling mechanism, the Stuart bridge agraffe, extended the time period of the vertical onset string oscillation. The extended period of the vertical vibration enables the faster transition to the after-sound oscillation.
The following pages will discuss four Stuart piano sounds, which illustrate the earlier transition to the after-sound oscillation:
