Music – Instruments – Electrical musical tone generation
Reexamination Certificate
2000-05-03
2001-06-19
Witkowski, Stanley J. (Department: 2837)
Music
Instruments
Electrical musical tone generation
C084SDIG002, C310S334000, C310S370000, C029S025350
Reexamination Certificate
active
06248947
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to transducers or pickups for musical instruments and, more particularly, to an improved transducer that is flexible, shielded, light weight, accurate, and repositionable, and that may conveniently be used with a variety of stringed and percussive instruments.
Existing products for recording and amplifying sounds produced by musical instruments generally fall into the categories of microphones, magnetic pickups, contact pickups, and in-the-saddle pickups.
Microphones are generally expensive and have inherent frequency response limitations due to the size, shape, and mass of the diaphragm element that produces the electrical signal. Microphones require air pressure to actuate a diaphragm, which in turn produces an electrical signal. Thus, the electrical signal is not produced instantaneously, but is instead slightly delayed due to the compressive nature of air. Furthermore, microphones have a resonant frequency in the range of 8 kHz-14 kHz, which colors the sound produced with an un-natural boost in output in that frequency range.
Magnetic pickups require the use of ferrous metal strings on the instrument to which they are attached and are placed in positions along the length of those strings in order to produce electrical images of the strings at those harmonic points. The total harmonic content of the signal is limited to the position of the pickup. Magnetic pickups exert a very strong magnetic force on the instrument strings, thereby altering their natural movements and reducing sustain, harmonic balance, and string energy considerably. Magnetic pickups are not practical for use with instruments having more than twelve strings, such as pianos, since the length of the coil windings and the weight of the magnets would substantially reduce the performance of those types of instruments.
Contact pickups are usually rigid ceramic/crystalline piezo materials that are typically deposited onto rigid metal substrates. Most of these pickups are further limited by being encapsulated into plastic cases using epoxy resins. The resulting rigidity and mass diminishes the accurate performance of the pickup. The mass creates audible resonant frequencies, and also alters the natural sound of the instrument. Ceramic piezo materials have a mass that creates a non-musical self resonance between
6
and
16
kHz, and they exhibit a very non-linear frequency response that resembles white noise.
In-the-saddle pickups place a compressible material precisely at the point where the string energy enters the body of the instrument through the bridge, thus noticeably altering the natural tone, sustain, and dynamic response. Saddle pickups respond primarily to the strings of the instrument, rather than to the instrument itself. String balance is difficult to achieve with saddle pickups, resulting in one or more of the strings being too loud or too quiet, relative to the others.
Exemplary of prior art transducers or pickups are those described in U.S. Pat. No. 4,727,634 to Fishman, U.S. Pat. No. 5,123,325 to Turner, U.S. Pat. No. 5,204,487 to Turner, U.S. Pat. No. 5,319,153 to Fishman, U.S. Pat. No. 5,670,733 to Fishman, U.S. Pat. No. 5,817,966 to Fishman, U.S. Pat. No. 5,866,835 to Baggs, U.S. Pat. No. 5,900,572 to Aaroe, and U.S. Pat. No. 6,023,019 to Baggs.
SUMMARY OF THE INVENTION
The present invention is directed to a transducer for musical instruments, the transducer being a sandwich structure that utilizes a length of polarized fluoropolymer polyvinylidene fluoride (PVDF) film folded over itself to form a U-shape over a center conductor of a length of shielded coaxial cable. Conductive silver epoxy is used to attach the center conductor to the inner surface electrode of the PVDF film. A length of double-sided tape is sandwiched between the two legs of the folded U-shape PVDF film. The free end of the coaxial cable is bent over a side edge of the folded U-shaped PVDF film such that an outer shield of the coaxial cable is exposed to the outside of the PVDF film. A U-shaped brass channel, whose inner surface has been coated with conductive epoxy, is then crimped over both the outer shield of the coaxial cable and the closed end of the laminated U-shape PVDF film to form a transducer assembly, which is then laminated to a length of double-sided tape having an outer removable backing layer. The free end of the coaxial cable may be terminated in any desired type of audio connector. In use, the backing layer of the double-sided tape is removed to permit adhesive mounting of the transducer assembly to a desired acoustic surface to be monitored.
REFERENCES:
patent: 4727634 (1988-03-01), Fishman
patent: 5123325 (1992-06-01), Turner
patent: 5204487 (1993-04-01), Turner
patent: 5319153 (1994-06-01), Fishman
patent: 5670733 (1997-09-01), Fishman
patent: 5817966 (1998-10-01), Fishman
patent: 5866835 (1999-02-01), Baggs
patent: 5900572 (1999-05-01), Aaroe
patent: 6023019 (2000-02-01), Baggs
Hein William E.
Pick-up the World, Inc.
Witkowski Stanley J.
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