Mitnick Michael > awful.drunkag.com

Coaxial musical instrument transducer
2010-03-11
AbstractA transducer for a stringed musical instrument utilizes a coaxial structure. An electromechanical film tape is disposed about an inner, electrically conductive core. An outer conductor is formed about the electromechanical film tape. The electromechanical film tape may be provided as a piezoelectric polymer film or an electret film having a permanent electric charge, and is formed about the inner core by wrapping or braiding. Prior to being disposed about the inner core, the film tape may be polarized through the application of a direct current through the film to substantially align the electrical domains in the film. The transducer is configured for placement underneath the saddle in a bridge of a stringed musical instrument.Claims

What is claimed is:

1. A musical instrument transducer comprising:

an inner conductor comprising electrically conductive material;

an electrically active transducer layer about the inner conductor, wherein the electrically active transducer layer is provided in the form of a film tape; and

an outer conductor, comprising electrically conductive material, disposed about the electrically active transducer layer.

2. The musical instrument transducer of claim 1, further comprising electrically conductive leads connected to the inner conductor and the outer conductor.

3. The musical instrument transducer of claim 1, wherein the thickness of the electrically active transducer layer is less than half the thickness of the inner conductor.

4. The musical instrument transducer of claim 1, wherein the inner conductor has a thickness of between 0.075 and 0.08 inches.

5. The musical instrument transducer of claim 1, wherein the electrically active transducer layer has a thickness of between 0.010 and 0.015 inches.

6. The musical instrument transducer of claim 1, wherein the electrically active transducer layer is formed by wrapping the film tape about the inner conductor.

7. The musical instrument transducer of claim 6, wherein the electrically active transducer layer is formed by helically wrapping the film tape about the inner conductor.

8. The musical instrument transducer of claim 1, wherein the electrically active transducer layer is formed by weaving the film tape about the inner conductor.

9. The musical instrument transducer of claim 1, wherein the inner conductor is a twisted bundle of wires.

10. The musical instrument transducer of claim 1, wherein the inner conductor is a solid, electrically conductive material.

11. The musical instrument transducer of claim 1, wherein the outer conductor is an electrically conductive ink formed on an outer surface of the electrically active transducer layer.

12. The musical instrument transducer of claim 1, wherein the outer conductor is an electrically conductive foil disposed on an outer surface of the electrically active transducer layer.

13. The musical instrument transducer of claim 1, wherein the outer conductor is an electrically conductive shrink tube disposed on an outer surface of the electrically active transducer layer.

14. The musical instrument transducer of claim 1, wherein the outer conductor is a braid of electrically conductive filaments disposed on an outer surface of the electrically active transducer layer.

15. The musical instrument transducer of claim 1, wherein the transducer has a substantially circular cross-section.

16. The musical instrument transducer of claim 1, wherein the transducer has a substantially rectangular cross-section.

17. The musical instrument transducer of claim 1, wherein the inner conductor further comprises a non-conductive filler material.

18. The musical instrument transducer of claim 1, further comprising a mechanically shielding layer disposed about the outer conductor.

19. The musical instrument transducer of claim 1, wherein the electrically active transducer film tape is polarized.

20. The musical instrument transducer of claim 1, wherein the electrically active transducer film tape is a piezoelectric polymer film tape selected from the group consisting of polyvinylidene fluoride copolymer film tape and polyvinylidene fluoride homopolymer film tape.

21. The musical instrument transducer of claim 1, wherein the electrically active transducer layer comprises a piezoelectric polymer layer.

22. A musical instrument transducer comprising:

an inner conductor comprising electrically conductive material;

an electret film layer about the inner conductor, wherein the electret film layer is provided in the form of an electret film tape having a permanent electric charge; and

an outer conductor, comprising electrically conductive material, disposed about the electret film layer.

23. The musical instrument transducer of claim 22, wherein the thickness of the electret film layer is less than half the thickness of the inner conductor.

24. The musical instrument transducer of claim 22, wherein the electret film layer is formed by wrapping or weaving the film tape about the inner conductor.

25. The musical instrument transducer of claim 22, wherein the outer conductor is selected from the group consisting of an electrically conductive ink, an electrically conductive foil, an electrically conductive shrink tube, and a braid of electrically conductive filaments.

26. The musical instrument transducer of claim 22, further comprising a mechanically shielding layer disposed about the outer conductor.

27. A method of fabricating a musical instrument transducer, comprising the steps of:

providing an electrically conductive central core;

providing an electrically active transducer layer in the form of a film tape about said electrically conductive central core;

forming an electrically conductive outer layer about said film tape to produce an assembly;

cutting said assembly to a desired length; and

disposing electrically conductive leads in communication with said electrically conductive central core and said electrically conductive outer layer.

28. The method of claim 27, wherein the step of providing an electrically conductive central core further comprises providing an electrically conductive central core comprising at least one electrically conductive fiber.

29. The method of claim 28, wherein the step of providing an electrically conductive central core further comprises providing an electrically conductive central core comprising said at least one electrically conductive fiber in conjunction with at least one non-conductive fiber.

30. The method of claim 27, wherein the step of providing an electrically active transducer layer in the form of a film tape further comprises wrapping the film tape about the electrically conductive central core.

31. The method of claim 27, wherein the step of providing an electrically active transducer layer in the form of a film tape further comprises helically wrapping the film tape about the electrically conductive central core.

32. The method of claim 27, wherein said step of providing an electrically active transducer layer in the form of a film tape further comprises weaving the film tape about the electrically conductive central core.

33. The method of claim 27, wherein the step of forming further comprises a step selected from the group of steps consisting of: braiding electrically conductive fibers about said film tape; applying an electrically conductive foil about the film tape; forming electrically conductive shrink tubing about the film tape; and applying an electrically conductive liquid on the film tape and allowing the applied electrically conductive liquid to dry.

34. The method of claim 17, further comprising the step of disposing a mechanically shielding layer about the electrically conductive outer layer.

35. The method of claim 27, wherein the steps of providing an electrically conductive central core, providing an electrically active transducer layer in the form of a film tape, and forming an electrically conductive outer layer collectively result in a musical instrument transducer having a substantially circular cross-section.

36. A method of fabricating a musical instrument transducer, comprising the steps of:

providing an electrically conductive central core;

providing an electret film tape having a permanent electric charge about said electrically conductive central core;

forming an electrically conductive outer layer about said electret film tape to produce an assembly;

cutting said assembly to a desired length; and

disposing electrically conductive leads in communication with said electrically conductive central core and said electrically conductive outer layer.

37. The method of claim 36, wherein the step of providing an electrically conductive central core further comprises providing an electrically conductive central core comprising at least one electrically conductive fiber.

38. The method of claim 37, wherein the step of providing an electrically conductive central core further comprises providing an electrically conductive central core comprising said at least one electrically conductive fiber in conjunction with at least one non-conductive fiber.

39. The method of claim 36, wherein the step of providing a electret film tape further comprises wrapping or weaving the electret film tape...

Bridge for stringed musical instrument
2010-03-01
AbstractThis invention relates to an improved bridge for stringed musical instruments which bridge is shaped, for preferred embodiments, so as to provide maximum, and substantially uniform, mechanical compliance between the bridge and the soundboard of the instrument over the full frequency range of the instrument while still being wide enough at each point along its length to effectively couple the frequency of vibrations to be driven by the bridge at that point. For alternative embodiments, the shape of the bridge is altered at one or more selected points along its length, altering the mechanical compliance at these points in a predetermined manner. These variations cause the instruments to have a predetermined frequency response characteristic.ClaimsWhat is claimed is:

1. In a stringed musical instrument having lower frequency or bass strings and higher frequency or treble strings, vibrations of the strings being coupled through a bridge toa soundboard, the mechanical compliance between the bridge and the soundboard at each point along the bridge from the bass end thereof to the treble end thereof being dependent on the frequency being coupled by the bridge to the soundboard at that point,a bridge having:

a first predetermined width at the bass end thereof, said width being sufficient to effectively couple the lowest frequency vibrations to be coupled by said bridge;

a second predetermined width at the treble end thereof, said second width being less than said first width and being sufficient to effectively couple the highest frequency vibrations to be coupled by said bridge; and

a width at each point intermediate said bass and treble ends which is both sufficient to effectively couple the frequency coupled at that point and is selected such that the mechanical compliance between the bridge and the soundboard issubstantially the same at all points along the bridge. by said bridge; a second predetermined width at the treble end thereof, said second width being less than said first width and being sufficient to effectively couple the highest frequency vibrationto be coupled by said bridge; and a width at each point intermediate said bass and said treble ends which is sufficient to effectively couple the frequency coupled at that point and is empirically determined by taking measurements over the octave rangeof the instrument for equivalent mechanical driving of the instrument so as to provide a selected mechanical compliance at that point.

2. A bridge as claimed in claim 1 wherein the bridge is shaped so as to be asymmetric about its center axis.

3. A bridge as claimed in claim 1 wherein the bridge is shaped so as to be symmetric about its center axis.

4. A bridge as claimed in claim 1 wherein the width of said bridge at each point is selected such that the mechanical compliance at that point is as large as possible while still being of sufficient width to effectively couple the frequencycoupled at that point.

5. A bridge as claimed in claim 1 wherein said bridge is particularly adapted for use as the bridge of an acoustic guitar.

6. In a stringed musical instrument having lower frequency or bass strings and higher frequency or treble strings, vibrations of the strings being coupled through a bridge to a soundboard, the mechanical compliance between the bridge and thesoundboard at each point along the bridge from the bass end thereof to the treble end thereof being dependent on the frequency being coupled by the bridge to the soundboard at that point, a bridge the mechanical parameters of which are such, at eachpoint along the bridge from the bass end thereof to the treble end thereof, that the mechanical compliance between the bridge and the soundboard is substantially the same at all said points.

7. In a stringed musical instrument having lower frequency or bass strings and higher frequency or treble strings, vibrations of the strings being coupled through a bridge to a soundboard, the mechanical compliance between the bridge and thesoundboard at each point along the bridge from the bass end thereof to the treble end thereof being dependent on the frequency being coupled by the bridge to the soundboard at that point, a bridge which is adapted to be in intimate physical contact withthe soundboard over its entire length, the bridge having a first predetermined width at the bass end thereof, said width being sufficient to effectively couple the lowest frequency vibrations to be coupled by said bridge; a second predetermined width atthe treble end thereof, said second width being less than said first width and being sufficient to effectively couple the highest frequency vibration to be coupled by said bridge; and a width at each point intermediate said bass and said treble endswhich is sufficient to effectively couple the frequency coupled at that point and is empirically determined by taking measurements over the octave range of the instrument for equivalent mechanical driving of the instrument so as to provide a selectedmechanical compliance at that point.DescriptionBACKGROUND

1. Field of the Invention

This invention relates to stringed musical instruments, and more particularly to an improved bridge for use with such instruments.

2. The Prior Art

In stringed musical instruments such as guitars, violins, pianos, and the like, sound is produced by causing one or more tightly stretched strings to vibrate, the frequency at which the string vibrates, and thus the resultant sound output, beingdependent on a number of factors including the string length, tension, and string caliper (thickness.) Vibrations of the strings are coupled through a bridge to a soundboard, and through the soundboard to a sound cavity. The strength or intensity of thesound obtained from the instrument is dependent to a large extent on the amplitude of the soundboard vibration. The quality or harmonic spectrum of the sound obtained from the string instrument is dependent to a large extent on the efficiency of drivingof the normal modes of the soundboard at each characteristic frequency defined by the soundboard structure.

An important factor in determining the amplitude of soundboard vibration, and thus the response of the instrument at various frequencies, is the efficiency of the coupling between the bridge and soundboard of the instrument at these frequencies. The efficiency of this coupling is governed by mechanical impedance, mechanical im...

Harmonic formant filter for an electronic musical instrument
2009-10-20
AbstractA fixed formant filter for a digital electronic instrument of the type in which musical tones are generated from waveshape data calculated independently of frequency of the tone from constituent generalized Fourier components. The Fourier components are individually scaled by scale factors selected from a set of stored scale factors which define the transfer characteristic of the fixed formant filter. Each separately addressable stored scale factor corresponds to a different frequency value in the musical scale. A scale factor is selected for separately scaling each harmonic of the tone generated in response to the particular note of the musical scale keyed on the instrument. The selected scale factors may be modified by a frequency deviation signal to provide vibrato or other frequency modulation effects. The selected scale factors are also corrected for any frequency deviation between the actual frequency of the harmonic of the keyed note being scaled and the frequency value associated with the selected scale factor.ClaimsWhat is claimed is:

1. A tone generator having a fixed formant filter characteristic for generating a tone having a pitch selected by operating a key on a keyboard comprising a harmonic counterfor counting the harmonic components of the tone being generated, means initiating a plurality of harmonic component calculation cycles, said means advancing the harmonic counter at the start of each calculation cycle, means storing a plurality ofharmonic coefficient values, means reading out a different coefficient value from the storing means with each advance of the harmonic counter, means storing a plurality of sinusoid values, means reading out a sequence of sinusoid values with each settingof the harmonic counter, adder-accumulator means, means multiplying the coefficient value for each harmonic calculation cycle with a sequence of sinusoid values and adding the product values to the adder-accumulator, addressable means storing a pluralityof scale factors corresponding to the relative amplitude values of the fixed formant filter characteristic at predetermined frequencies corresponding to the musical notes of the keyboard, means for addressing the addressable storage means in response tothe selected key on the keyboard and the state of the harmonic counter, means multiplying each of said product values added to the adder-accumulator by the associated scale factor read out of the storage means, and means converting each of the valuesstored in the adder-accumulator at the completion of said calculation cycles to an analog voltage in sequence at a rate determined by the pitch of the tone being generated, whereby the set of values stored in the adder-accumulator is converted to anaudio voltage signal having a fundamental frequency corresponding to the desired pitch of tone being generated, means for modifying the scale factor read out of the addressable scale factor storing means including means for generating the incrementaldifference between successive scale factors read out of the scale factor storing means, means generating a frequency deviation value, means multiplying said incremental difference by said deviation value, and means adding the content of the multiplyingmeans to the scale factor from the scale factor storing means.

2. Apparatus of claim 1 wherein the means generating the frequency deviation value is varied as a function of time to produce a frequency modulation effect.

3. Apparatus of claim 1 wherein the means generating a deviation value is controlled in response to the state of the harmonic counter.

4. Apparatus of claim 1 wherein said means multiplying said incremental difference by said deviation value includes means providing a one bit right shift of said incremental difference, means providing a two bit right shift of said incrementaldifference, means providing the sum of the output from the one bit right shift means and the two bit right shift means, and means responsive to said deviation value for selecting any one or none of said outputs as input to said means adding the output ofthe multiplying means to the scale factor.

5. A polyphonic digital tone synthesizer, comprising: a keyboard having keys for initiating one or more musical notes, a main register for storing a set of coded values corresponding to the relative amplitudes of a set of points defining onecycle of a periodic musical waveform, a digital-to-analog converter, means responsive to operation of a selected key for transferring the coded values in sequence from the main register to the converter at a rate proportional to the pitch of the noteinitiated by the selected key, means for computing the set of coded values and storing them in the main register including means storing a set of harmonic coefficients, means storing a set of orthogonal function values, means multiplying each harmoniccoefficient in succession with a set of orthogonal values to produce a succession of computed sets of values defining respectively each harmonic of the desired waveform, and means for adding the successive sets of values and accumulating the sums in themain register, addressable storage means storing at least one set of scale factors defining the gain characteristic of the fixed formant filter over the audio frequency range, means generating addresses for addressing the addressable storage meansincluding means generating a unique address for each key on the keyboard and means adding a unique incremental value to said address for each harmonic being computed, and means applying the scale factor addressed in said addressable storage means to saidscaler means to apply a different scale factor for each computed set of values defining each harmonic of the desired waveform, said means applying the scale factor including means for adjusting the scale factor read out of the addressable storage means,said adjusting means including means for providing the incremental difference between the scale factor read out of the storage means and the scale factor at the next successive address of the storage means, means for multiplying said incrementaldifference by a frequency deviation signal, and means for adding the output of the multiplying means to the scale factor read out of the storage means.

6. Apparatus of claim 5 further including means for storing incremental adjustment factors corresponding to the difference between the scale factor stored in said addressable storage means and the actual scale factor for the correspondingfrequency point on the desired fixed filter characteristic curve, there being a separate adjustment factor for each harmonic, and means addressing the incremental adjustment factor storing means by the number of the harmonic component being generated,the output adjustment factor being added to the frequency deviation signal applied to the multiplying means.DescriptionFIELD OF THE INVENTION

This invention relates to a fixed formant filter for an electronic musical instrument, and more particularly, is concerned with a digital type filter.

BACKGROUND OF THE INVENTION

Digital tone generators for musical instruments are well known in which the waveshape of a tone is the same for each musical note. In other words, the harmonic contents of each musical note over the full range of the musical scale issubstantially the same. The harmonic content can be modified to provide different waveshapes, as by setting "Stops". Such tone generation is particularly suited to electronic musical instruments that are intended to imitate the tonal characteristics ofpipe organs. However, most other musical instruments have resonant characteristics which do not change with the pitch of the note being produced. Thus the tones for notes sounded up and down the scale do not exhibit constant harmonic structure. Ratherthe harmonic structure can be characterized by a signal whose spectral content is modified by passing the signal through a fixed filter. The use of fixed filters on the output signals of analog type tone generators is well known. The use of fixedfilters on the analog output signals of a digital tone generator, of course, can be used to produce the same audio effects. However, the design of conventional analog filters to emulate the transfer characteristics of various acoustical instrumentsresults in rather complex filter designs. Moreover, to make such filters variable so as to provide resonances at various frequencies becomes impractical for anything but the simplest transfer characteristics.

The use of digital techniques to provide fixed format filtering has heretofore been proposed for use in a computer organ. See, for example, U.S. Patent No. 3,956,960. In the computer organ described in this patent the amplitudes of a series ofpoints defining the waveshape of the tone being generated are computed in real time by summing, for each point in time, the amplitudes of each of the Fourier components of the desired waveshape. Filtering is accomplished by applying a scale factor tothe amplitude coefficient of each Fourier component, the scale factor being selected according to the frequency of the Fourier component. Selection of the scale factor for each Fourier component is derived from a frequency number R whose value isdetermined by the particular key operated on the keyboard of the instrument. Frequency information is essential in the computer organ during the computation of the amplitude values in real time. The same frequency information is therefore available toselect the appropriate scale factor as a function of frequency to scale the Fourier components in conformance with the transfer characteristics of the fixed formant filter.

The present invention is directed to a fixed formant filter particularly suited for use in a polyphonic digital tone synthesizer of the type described in U.S. Pat. No. 4,085,644. In the polyphonic tone synthesizer, waveshape information iscomputed by calculating its constituent generalized Fourier components and summing the Fourier components to form a master data set corresponding to the amplitudes of a series of points defining the waveshape of one cycle (or half cycle) of the tone tobe generated. The amplitude defining words of the mast...