Music – Instruments – Electrical musical tone generation
Reexamination Certificate
2002-11-14
2004-09-14
Donels, Jeffrey W (Department: 2837)
Music
Instruments
Electrical musical tone generation
Reexamination Certificate
active
06791023
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an electric musical instrument and, more particularly, to an electric bowed stringed musical instrument equipped with a plurality of mechanical vibration-to-electric signal converters.
DESCRIPTION OF THE RELATED ART
Electric bowed stringed musical instruments are new members of the violin family. Strings are stretched over bodies, and the players bow the strings as similar to the members of the violin family, i.e., violins, violas and cellos. The players give rise to vibrations of the strings through the bowing, and the vibrating strings generate tones. Although the acoustic members of the violin family have respective resonators for increasing the loudness of the tones, the electric bowed stringed musical instruments do not have the resonators, but are equipped with pickup units. The pickup units convert the vibrations of the strings to electric signals representative of the waveforms of the mechanical vibrations, and the electric signals are amplified before conversion to electric tones through speaker systems. Thus, the electric bowed stringed musical instruments electrically increase the tones, and the resonators are not required for the electric bowed stringed musical instruments.
There is a compromise between the acoustic bowed stringed musical instrument and the electric bowed stringed musical instrument. An acoustic bowed stringed musical instrument is equipped with a pickup unit, and the pickup unit converts the vibrations of strings to an electric signal. The compromise is hereinbelow referred to as “electric acoustic bowed stringed musical instrument”.
One of the attractive features of the electric bowed musical instrument is the silent mode. The resonators are indispensable for the acoustic bowed stringed musical instruments, and always increase the loudness through the resonation. It is not easy to deactivate the resonators. This means that players disturb the neighborhood. However, the resonators are eliminated from the electric bowed stringed musical instruments. The loudness is electrically increased. If the user connects a headphone to the amplifier, he or she can practice the bowing without disturbance of the neighborhood.
FIG. 1
shows a typical example of the electric violin. The electric violin
1
comprises a trunk
2
, a frame body
3
, a fingerboard
4
, a peg box
5
and a chin rest
6
. The frame body
3
has a contour like a half of the outline of the resonator, and sideward projects from the trunk
2
. The chin rest
6
sideward projects from the rear portion of the trunk
2
, and a player puts his or her chin on the chin rest
6
during the bowing. The fingerboard
4
projects from the front end of the trunk
2
, and the peg box
5
is fixed to the leading end of the fingerboard
4
.
The electric violin
1
further comprises four strings
7
, peg screws
8
, a tailpiece
9
, a bridge
10
and a pickup unit
11
. The peg screws
8
are turnably supported by the peg box
5
, and the tailpiece is fixed to the upper surface of the rear portion of the trunk
2
. The strings
7
are anchored to the tailpiece
9
, and are wound up at the other end portions around the peg screws
8
. The bridge
10
is provided on the upper surface of the trunk
2
, and exerts tension to the strings
7
. Although the component part
10
is not same as the bridge of the acoustic violin, the component part
10
is referred to as “bridge” in the description. The pickup unit
11
is provided between the upper surface of the trunk
2
and the lower surface of the bridge
10
, and converts the vibrations to an electric signal.
FIG. 2
illustrates the bridge
10
and pickup unit
11
on the trunk
2
. The bridge
10
is formed from a thin plate, and has a gently curved upper surface. Notches
10
a
are formed in the bridge
10
, and are open to the outside on the gently curved upper surface. The strings
7
are received in the notches
10
a
so that the bridge
10
keeps the strings
7
spaced at intervals. While a player is bowing the strings
7
, the strings
7
vibrate, and the vibrating strings
7
gives rise to vibrations of the bridge
10
.
The bridge
10
has leg portions
10
b
and
10
c
, and piezoelectric transducers
11
a
and
11
b
are sandwiched between the lower surfaces of the leg portions
10
b
/
10
c
and the upper surface of the trunk
2
. The piezoelectric transducers
11
a
/
11
b
convert the vibrations of the leg portions
10
b
/
10
c
to the electric signal.
The electric signal is amplified, and the amplified electric signal passes through a filter circuit for producing an analog tone signal. The analog tone signal is supplied to a speaker system. However, if the analog tone signal is directly supplied to the speaker system, the audience feels the tones flat. This is because of the fact that the prior art electric violin does not have any resonator. The vibrations of the leg portions
10
b
/
10
c
do not contain any reverb produced by the resonator. In order to impart the reverb to the tones, the amplified electric signal is supplied to a digital signal processor in another prior art system. The digital signal processor processes the electric signal for imparting the reverberation components to the electric signal, and, thereafter, the electric signal is supplied from the digital signal processor to the speaker system.
The first problem inherent in the prior art electric violin is poor promptitude in following up the bowing. In detail, the piezoelectric transducers
11
a
/
11
b
are liable to respond to the transverse vibrations indicated by arrow AR
1
. While the strings
7
are vibrating through the bowing, the transverse vibration components give rise to rocking motion of the bridge
10
as indicated by arrows AR
2
and AR
3
and vice versa. The piezoelectric transducers
11
a
/
11
b
are arranged in such a manner as to be oppositely polarized. In this situation, when the leg portions
10
b
/
10
c
are moved in the directions of arrows AR
2
/AR
3
, the piezoelectric transducers
11
a
/
11
b
are polarized as shown in
FIG. 3
, and a large amount of electric charges flow.
The arrangement of piezoelectric transducers
11
a
/
11
b
is less desirable for the vertical vibration components. If the strings
7
vertically vibrate as indicated by arrow AR
4
(see FIG.
4
), the leg portions
10
b
/
10
c
vibrate in the same direction as indicated by arrows AR
5
and vice versa, and the piezoelectric transducers
11
a
/
11
b
are oppositely polarized. Most of the electric charges in one piezoelectric transducer
11
a
/
11
b
are canceled with the electric charges in the other piezoelectric transducer
11
b
/
11
a
, and only a negligible amount current flows. Thus, the piezoelectric transducers
11
a
/
11
b
hardly convert the vertical vibration components to the electric signal.
However, the bowing is not always reflected on the transverse vibrations. Although the transverse vibration components are the major factor of certain sorts of bowing, other sorts of bowing is influential in the vertical vibration components. This means that the prior art electric violin can not promptly respond to the other sorts of bowing. This is the first problem inherent in the prior art electric violin.
The second problem is poor fidelity of the tones. The piezoelectric transducers
11
a
/
11
b
are corresponding to condensers in an equivalent circuit, and have strong influence on the output impedance of the pickup unit
11
. If the condensers, i.e., the piezoelectric transducers have large capacitance, the out-put impedance becomes small, and the cut-off frequency is low. On the other hand, when the capacitance is small, the output impedance is large, and the cut-off frequency is high. This means that the electric signal does not contain the low frequency components. In other words, the electric tones generated from the electric signal are different from the acoustic tones produced by a corresponding acoustic bowed stringed instrument. Another drawback due to the large output impedance is a large amount of noise. The thinner the piez
Donels Jeffrey W
Morrison & Foerster / LLP
Yamaha Corporation
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