APPLIED ACOUSTICS SYSTEMS STRINGSTUDIO Manuel d'utilisateur télécharger pdf (Page 25)

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string and connected to a plate with the help of a spring. The purpose of the plectrum is to impose

an initial displacement to the string before it is set into free vibration. As can be understood from

ﬁgure 9, a vertical motion of the plate (which could be a hand holding the plectrum) will lift the

string with the plectrum but will also result in a compression of the spring and an horizontal motion

of the plectrum. The string will move with the plectrum until the protrusion (Prot) of the plectrum

is equal to the compression of the spring and the string is released. The motion and behavior of

the plectrum is controlled by adjusting the different geometrical and mechanical properties of the

system.

The Prot knob is used to determine the protrusion of the plectrum with respect to the string

while the stiffness and damping of the spring is controlled with the help of the Stiff and Damp

knobs. The vertical velocity of the plectrum is adjusted with the Velocity knob. Note that the Prot,

Stiff, and Velocity controls can be modulated with the pitch of the note played or the velocity signal

from the keyboard.

String

Plectrum

Damping

Stiffness

Velocity

Prot

Figure 9: Functioning of the Plectrum

Hammer

The Hammer is used to play instruments such as the piano or other percus-

sive instruments. With this exciter, the string is set into free vibration following

a force impact with the hammer. The hammer can be used in two modes, Ham-

mer 1 and Hammer 2, as illustrated in Figure 10. In the Hammer 1 mode, the

hammer is located below the string and can only interact once with the string

because of the action of gravity which brings it down after it has been raised to

hit the string. In the Hammer 2 mode, the hammer is located above the string

and can bounce on the string after the initial impact.

The illustration in Figure 10 shows that the action of the hammer can be

modeled by the motion of a head connected to a mass. The mass of the hammer

is adjusted with the Mass knob while the stiffness of the head is controlled with

the Stiff knob. The velocity of the hammer when it hits the string is set with the velocity knob. The

motion of the hammer can further be characterized by a damping coefﬁcient, adjusted with the

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APPLIED ACOUSTICS SYSTEMS STRINGSTUDIO Manuel d'utilisateur Page 25