Abstract:
An acoustic pickup transducer device for converting sounds produced by a musical instrument into electrical signals proportional in amplitude and frequency to the instrument sounds includes a housing which has protruding therefrom a suction cup for removably attaching the device to an instrument, and a microphone interconnected through interface circuitry including a volume control potentiometer within the housing to an audio output signal jack. In a preferred embodiment, the microphone is fastened to the outer end of a flexible “gooseneck” stalk which extends from the housing at an angle adjustable by manually bending the stalk to a desired shape, which is retained by a bent wire within the stalk, thus enabling adjustment of the direction of peak sound responsivity or directivity over a wide range of angles. Preferably, the microphone is an electret type supplied with a D.C. bias voltage by a coin-cell battery within the housing.

Description:
This application claims priority of and to provisional application No. 61/879,974, filed Sep. 19, 2013. 
    
    
     BACKGROUND OF THE INVENTION 
     A. Field of the Invention 
     The present invention relates to accessories for musical instruments. More particularly, the invention relates to a versatile acoustic pickup for converting musical sounds to electronic signals, which is quickly attachable to and removable from a wide variety of musical instruments, and has a sound directivity that is easily adjustable over a wide range of orientations relative to an instrument to which it is attached. 
     B. Description of Background Art 
     There are a wide variety of musical instruments which may be optionally equipped with a transducer or “pickup” to convert musical sounds produced by the instrument to electrical signals. Typically, the electrical signals output from a pickup are input to an amplifier, and amplified to a level sufficient to drive a loudspeaker. The signals may also be input to an analog or digital recording device. 
     Musical instruments which may utilize sound pickups include drums and other percussion instruments, upright and double basses, autoharps, violins, cellos, acoustic guitars, 12-string guitars, dulcimers, tenor banjos, resonator guitars, gypsy jazz guitars, mandolins, accordions, and keyboards, as well as other instruments. 
     One type of musical instrument pickup which has been in extensive use for many years is a magnetic pickup used on guitars, which produces electrical signals in response to motions of a vibrating guitar string in the vicinity of a magnetic field produced by the pickup. Such pickups are used primarily with guitars and other stringed instruments, must be positioned precisely in close proximity to strings, and usually require permanent or semi-permanent attachment to a musical instrument. 
     Another type of pickup in common use with musical instruments includes a vibration-sensitive device such as a piezoelectric sensor which is fastened to the soundboard of a stringed instrument, or to the shell or other part of a percussion instrument such as a drum, and produces electrical output signals proportional to the amplitude and frequency of vibrations of the soundboard, drumhead, or drum body caused by sounds produced by the instrument. Vibration sensitive pickups of the type described above require careful positioning, and oftentimes permanent or semi-permanent attachment to a musical instrument. 
     A third type of pickup used with musical instruments, and which may be referred to generally as an acoustic pickup, consists essentially of a microphone which is attachable to various parts of a musical instrument such as a stringed instrument, drum, or other percussion instrument. 
     Acoustic pickups are in relatively widespread use, but there are problems with the present generation of such devices. The problems include large size, cumbersomeness, difficulty of mounting the pickup to a musical instrument, and undesirable feedback of vibrations of the instrument to the device, which by design preferably would respond primarily to acoustic signals transmitted through the air rather than vibrations transmitted through the body of an instrument. 
     Another problem with existing acoustic pickups for musical instruments is the difficulty with which the sound directivity of the pickup may be adjusted, and a requirement that typical current generation pickups must be permanently or semi-permanently attached to a musical instrument. The adjustable directivity pickup for musical instruments according to the present invention was developed by the present inventor to address problems of the type described above encountered with present generation pickups. 
     OBJECTS OF THE INVENTION 
     An object of the present invention is to provide an adjustable directivity acoustic pickup for musical instruments. 
     Another object of the present invention is to provide an adjustable directivity acoustic pickup for musical instruments which is quickly and easily attachable to a variety of musical instruments without requiring that holes be made in the instrument, or that the instrument be otherwise defaced. 
     Another object of the invention is to provide an adjustable directivity acoustic pickup for musical instruments which has a peak acoustic response direction angle that is quickly and easily adjustable without the use of tools, by removing the pickup from an instrument, re-orienting the pickup, and re-attaching the pickup to the instrument. 
     Another object of the invention is to provide an adjustable directivity acoustic pickup for musical instruments which has a sound response directivity that is adjustable over a first range of polar angles relative to a musical instrument by positioning the body of the pickup at a desired polar angle relative to an instrument, and adjustable over a second range of polar angles and a range of inclination angles by orienting a flexible microphone support member of the pickup at various polar and elevation angles. 
     Another object of the invention is to provide an adjustable directivity acoustic pickup for musical instruments which has a fastening member that facilitates quick and easy attachment, removal and re-positioning, and re-attachment to a musical instrument, and which also isolates the pickup from responding to vibration of the instrument. 
     Various other objects and advantages of the present invention, and its most novel features, will become apparent to those skilled in the art by perusing the accompanying specification, drawings and claims. 
     It is to be understood that although the invention disclosed herein is fully capable of achieving the objects and providing the advantages described, the characteristics of the invention described herein are merely illustrative of the preferred embodiments. Accordingly, I do not intend that the scope of my exclusive rights and privileges in the invention be limited to details of the embodiments described. I do intend that equivalents, adaptations and modifications of the invention reasonably inferable from the description contained herein be included within the scope of the invention as defined by the appended claims. 
     SUMMARY OF THE INVENTION 
     Briefly stated, the present invention comprehends an adjustable directivity acoustic transducer, or pickup device, for converting sounds produced by a musical instrument to electrical signals. The novel design and construction of the pickup device according to the present invention enables the device to be easily attachable to and removable from a wide variety of string and percussion instruments. Moreover, the novel design and construction of the pickup device according to the present invention enables the sound directivity of the device relative to sound-producing elements of a musical instrument to which it is attached to be quickly an easily adjusted over a wide range of direction angles, without requiring the use of tools, drilling holes in the instrument, or otherwise defacing the instrument. 
     A basic embodiment of an adjustable directivity acoustic pickup device for musical instruments according to the present invention has generally the form of a small, rectangularly shaped box or housing which has protruding from a flat lower base wall thereof a suction cup fastener that is removably attachable to a flat surface such as a soundboard of a musical instrument, by pressing the lower surface of the suction cup into hermetically sealing contact with the surface. 
     The pickup device according to the present invention includes a microphone, preferably an electret type microphone, which is powered by a small lithium-ion, button-cell type battery held in a battery holder located within the housing. The pickup device has an electrical output jack which is connected in series with the microphone and the wiper of a potentiometer that is connected to the microphone and receives electrical signals output from the microphone in response to sound waves received by the microphone. In a preferred embodiment, the output jack is a switch-type phono jack that has a normally open internal switch which is closed by inserting an input plug of an audio output signal cable into the jack. The switch terminals are connected in a series with the battery and microphone, thus applying D.C. power to the microphone only when an audio signal plug is inserted into the jack. 
     In a preferred embodiment of an acoustic pickup device according to the present invention, the electret microphone is fastened to the outer end of a flexible “gooseneck” stalk. The inner end of the stalk extends through a rear side wall into an interior space in the housing. A pair of flexible insulated wires which run through a passageway or lumen disposed through the length of the stalk interconnects terminals of the electret microphone with electrical circuitry located within the interior space of the housing. 
     The novel construction of the pickup device according to the present invention enables it to be quickly and easily attached to a flat surface such as the soundboard of a guitar or other musical instrument. Attachment is made by first orienting the housing of the pickup device so that the rear side wall and microphone stalk are positioned at a desired polar angle relative to the mounting surface of an instrument. 
     For example, if the pickup device is to be attached to the soundboard of a guitar, the pickup device may be positioned between an outer peripheral edge of the soundboard and the strings, with the back, microphone-side of the housing facing in the direction of the strings. The pickup device may then be grasped and pivoted about a normal vertical axis perpendicular to the upper side panel wall of the pickup housing, to thereby adjust the rear, microphone-side panel wall to a desired polar angle relative to the instrument strings. 
     After orienting the acoustic pickup device relative to a musical instrument as described above, the suction cup base of the device is placed in contact with the instrument surface and finger pressure applied downwards to the upper side of the device to thus deform and hermetically fasten the suction cup to the instrument surface. 
     From the foregoing description it may be understood that the rear panel wall and microphone may be oriented over a range of polar angles on the surface of a musical instrument. The housing may be rotated about a vertical axis through the suction cup to any polar angle, i.e. over a range of 360 degrees. As a practical matter, the audio signal output jack and signal output cable attached to the pickup device would generally be oriented to face an outer edge of the instrument so that the cable may be deployed away from the instrument and connected to an amplifier. Consequently, a practical adjustability range of polar angles would be limited to a value of, for example, about 90 degrees. This smaller range of polar angle adjustability would in any event be more than adequate for many applications. 
     In a preferred embodiment of the pickup device with a flexible stalk supporting the microphone, a perpendicular normal collinear with the longitudinal axis of the microphone, which determines the direction of peak sound responsivity, or directivity, may be flexibly adjustable over a second range of polar angles. This second range is in addition to the range provided by orienting the device housing to a particular polar angle relative to a musical instrument. The stalk may also be flexed to position and hold the microphone at various inclination angles relative to the surface of a musical instrument. 
     Also, the microphone stalk may be flexed in a vertical direction to adjustably position the microphone located at the outer end of the stalk at different distances from the device housing. This additional degree of vertical adjustability enables adjustment of the distance between the microphone relative to sound-producing elements such as vibrating strings. 
     A simplified embodiment of an adjustable directivity acoustic pickup for musical instruments according to the present invention eliminates the flexible microphone stalk. In this embodiment, an electret microphone is mounted in the rear panel wall of the device housing, preferably with the longitudinal axis of the microphone which coincides with its direction of peak sound responsivity perpendicular to the rear panel wall. As may be understood by referring to the description of the basic embodiment of the pickup device given above, the modified embodiment of the pickup device has a sound directivity which is adjustable over a range of polar angles at least as large as 90 degrees. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view on an enlarged scale of an Adjustable Directivity Pickup for Musical Instruments according to the present invention. 
         FIG. 2  is a front elevation view of the pickup device of  FIG. 1 . 
         FIG. 3  is a rear elevation view of the pickup device of  FIG. 1 . 
         FIG. 4  is a right side elevation view of the pickup device of  FIG. 1 . 
         FIG. 5  is a left side elevation view of the pickup device of  FIG. 1 . 
         FIG. 6  is an upper plan view of the pickup device of  FIG. 1 . 
         FIG. 7A  is a lower plan view of the pickup device of  FIG. 1 . 
         FIG. 7B  is a fragmentary view showing on an enlarged scale a microphone and bendable support stalk component of the device of  FIG. 1 . 
         FIG. 7C  is a longitudinal sectional view of the microphone and bendable support stalk component of  FIG. 7B . 
         FIG. 7D  is fragmentary view of the microphone and bendable support stalk component of  FIG. 7B , showing on an enlarged scale a microphone component thereof. 
         FIG. 8  is a perspective view on a reduced scale of the pickup device of  FIG. 1 , showing the device mounted to a self-resonator guitar in correct size relationship to the guitar. 
         FIG. 9  is a perspective view on a reduced scale of the pickup device of  FIG. 1 , showing the device mounted to a 12-string guitar in correct size relationship to the guitar. 
         FIG. 10  is a partially disassembled upper plan view of the pickup device of  FIG. 9  showing the mounting of the button cell battery and holder on the potentiometer housing. 
         FIG. 11  is a partially disassembled upper front perspective view of the pickup device of  FIG. 1 , showing lid-fastening screws of the device removed and the lid tilted backwards to reveal a button battery and holder of the device. 
         FIG. 12  is an electrical schematic diagram of the pickup device of  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1-7D  illustrate a basic embodiment of an adjustable directivity acoustic pickup device for musical instruments according to the present invention.  FIGS. 8 and 9  show the device of  FIGS. 1-7D  mounted to two different type stringed musical instruments.  FIGS. 10 and 11  illustrate details of the construction of the pickup device of  FIGS. 1-9 .  FIG. 12  is an electrical schematic diagram of the device of  FIGS. 1-11 . 
     As shown in  FIGS. 1-7D , a basic embodiment  20  of an acoustic pickup device according to the present invention includes a thin, rectangular box-shaped housing  21 . Housing  21  has a rectangular, flat upper panel wall  22 , and a lower panel wall  23  which is parallel to the upper panel wall and has the same size and shape. 
     As is also shown in  FIGS. 1-7D , housing  21  of pickup device  20  has a short, flat laterally elongated rectangular front panel wall  24  which is disposed perpendicularly between the front edge  25  of upper panel wall  22 , and the front edge  26  of lower panel wall  23 . As shown in  FIG. 2 , housing  21  of device  20  also has a rear panel wall  27  which is parallel to and has the same size and shape as front panel wall  24 . Rear panel wall  27  is disposed perpendicularly between the rear edge  28  of upper panel wall  22 , and the rear edge  29  of lower panel wall  23 . 
     Referring again to  FIG. 1 , it may be seen that housing  21  of device  20  has a short, laterally elongated, rectangularly shaped left side panel wall  30 . Left side panel wall  30  has the same height as front and rear panel walls  24  and  27 , and is disposed perpendicularly between the left edge  31  of upper panel wall  22 , and the left edge  32  of lower panel wall  23 . 
     As shown in  FIGS. 1 and 4 , housing  21  of pickup device  20  also has a short, laterally elongated right side panel wall  33 . Right side panel wall  33  is parallel to and has the same size and shape as left side panel wall  30 , and is disposed perpendicularly between the right edge  34  of upper panel wall  22 , and the right edge  35  of lower panel wall  23 . 
     As may be seen by referring to  FIGS. 1-5 and 7A , pickup device  20  includes a suction cup fastener  36  which protrudes downwards from lower panel wall  23 . Suction cup fastener  36  includes an upwardly concave lenticular-shaped base  37  which is made of an elastomeric material such as a natural or synthetic rubber. Base  37  has a flat lower outer annular ring-shaped peripheral sealing surface  38  which peripherally circumscribes a concave suction cavity  39  within the base. 
     As shown in  FIGS. 2-5 , suction cup fastener  36  also has a cylindrically-shaped neck  40  which extends coaxially upwards from upper convex wall  41  of base  37 . Neck  40  is attached coaxially to a stud  42 . As shown in  FIGS. 2 and 10 , stud  42  protrudes upwards through a hole  43  in lower panel wall  23 , and is secured to the lower panel wall by a hexagonal ring nut  44 . 
     Referring to  FIGS. 1-7D , pickup device  20  may be seen to include a microphone  45  which is fastened to the outer, distal end  46  of a flexible tubular stalk  47 . The inner, proximal end  48  of stalk  47  is disposed through a perforation  49  in rear panel wall  27  into a hollow interior space  50  of housing  21 . 
     As shown in  FIGS. 1-7D , microphone  45  includes a small cylindrically-shaped body  51  held within a tubular sheath  52  made of an electrically non-conductive material such as 2:1 heat-shrinkable insulated tubing. Body  51  of microphone  45  has at an outer end thereof a circular, transversely disposed, circular perforated screen  53 . Perforations  54  in screen  53  permit the transit therethrough of sound pressure waves which are effective in producing at microphone output terminals  55 ,  56  electrical output signals proportional in frequency and amplitude to sound waves received by the microphone. 
     As shown in  FIGS. 7B and 7C  microphone support stalk  47  has generally the shape of a circular cross-section, uniform diameter flexible tube made of an electrically non-conductive material such as 2:1 heat-shrinkable insulated tubing which has disposed through its length a bore or lumen  57 . Bore  57  has disposed through its length a bendable, shape-retaining wire  58  made of 0.032-inch diameter soft-tempered stainless-steel wire With this construction, stalk  47  may be manually bent into different serpentine shapes, which are retained by bent wire  58 . 
     As may be understood by referring to  FIGS. 6 and 10-12 , bore  57  through stalk  57  also contains therein a pair of flexible insulated electrical microphone wires  59  and  60  which are disposed through the length of the bore. Microphone wires  59 ,  60  are connected at outer ends thereof to microphone terminals  55 ,  56 , respectively. Inner ends of wires  59 ,  60  are electrically conductively connected to electrical circuitry  61  located within hollow interior space  50  of housing  21 . The structure and function of circuits  61  will be described below. 
     Referring to  FIGS. 1 and 10-12 , it may be seen that pickup device  20  includes an audio signal output connector  62 . Output connector  62  may be of any suitable type electrical connector which has at least two conductors. Preferably, output connector  62  is a standard type audio connector jack such as a ¼-inch, phono plug-in jack. In a most preferred embodiment, connector  62  consists of a ¼-inch phono jack which includes an internal normally open switch that closes a circuit in response to insertion of a plug into the jack. 
     As shown in  FIGS. 1 and 10-12 , phono jack connector  62  includes a rectangular block-shaped body  63  that has protruding forward from a front wall  64  thereof a hollow circular cross-section bushing  65 . Bushing  65  protrudes outwards through a mounting hole  66  through front panel  24  of housing  21 . 
     As shown in  FIGS. 10 and 11 , bushing  65  has an external helically-threaded surface  67 . Connector jack  62  is fastened to front panel  29  of housing  21  by threadingly tightening a hexagonal ring nut  68  onto threaded surface  67  of bushing  65 . 
     As shown in  FIGS. 11 and 12 , connector jack  62  has an outer electrically conductive, cylindrical shell-shaped ground conductor  68 . Jack  62  also has within a bore  62 B which extends coaxially inwards from the outer transverse end of shell  68  an internal center conductor  69  which consists of a conductive metal spring strip. Outer, ground conductor shell  68  and center conductor strip  69  are electrically connected to signal terminals  70 ,  71 , respectively, which protrude from rear wall  63 B connector body  63 . 
     As may be seen best by referring to  FIG. 12 , connector jack  62  also contains an internal switch which includes an electrically conductive spring strip  72 . Switch spring strip  72  is mechanically coupled by an insulating bar  73  to center conductor spring strip  69 . When center conductor spring strip  69  is pushed radially outwards by an audio signal plug inserted into connector jack  62 , conductive switch spring strip  72  is pivoted radially outwards, and brought into electrically conductive contact with a fixed normally open switch contact  74 . Pivotable switch spring strip conductor  72  and normally open switch contact  74  are electrically connected to switch terminals  75 ,  76 , respectively, that protrude from rear wall  63 B of connector body  63 . 
     As shown in  FIGS. 1 and 10-12 , electrical circuitry  61  of pickup device  20  includes a potentiometer  77  which is mounted to the upper panel wall  22  of housing  21 . Potentiometer  77  has a shaft  79  which protrudes outwards through a hole  80  in the upper panel wall. A knob  81  attached to potentiometer shaft  79  enables the shaft and a wiper  82  of potentiometer  77  to be turned to various angular positions to thereby adjust the value of electrical resistance between wiper output terminal  83  and input terminals  84  and  85  of the potentiometer. 
     As shown in  FIGS. 10-12 , pickup device  20  includes a battery holder  86  that includes a replaceable 3-volt lithium-ion, coin-cell type battery  87 . Battery holder  86  has a negative output terminal  88  which is connected to a common ground conductor of circuitry  61 , and a positive output terminal  89 . 
     As shown in  FIG. 12 , positive output terminal  89  of battery holder  86  is connected through a series current-limiting resistor  90  to transfer contact switch terminal  75  of connector jack  62 . Also, normally open switch terminal  76  of jack  62  is connected to the positive terminal  55  of electret microphone  45 . Consequently, when an audio plug is inserted into jack  82 , a 3-volt D.C. bias voltage is applied to electret microphone  45 . 
     As shown in  FIGS. 11 and 12 , circuitry  61  of pickup device  20  also includes a capacitor  91  connected in series with positive output terminal  55  of microphone  45 , and upper input terminal  84  of potentiometer  77 . Capacitor  91  isolates the D.C. bias voltage supplied by battery  87  to microphone  77  from potentiometer  77  and provides a low impedance path for conducting alternating frequency audio signals from the microphone to the potentiometer. 
     As can be readily understood by referring to  FIG. 12 , the amplitude of audio signals output from electret microphone and conducted to center output leaf conductor  69  of connector jack  62  can be varied between 0 and 100 percent by turning potentiometer knob  81  between counterclockwise and clockwise limit positions. 
       FIGS. 8 and 9  illustrate how acoustic pickup device  20  may be quickly and easily attached to and removed from various types of musical instruments, and how the sound directivity of the device may be readily adjusted. 
     In an example application of acoustic pickup device  20  according to the present invention shown in  FIG. 8 , the acoustic pickup device is attached to the soundboard B of a self-resonator type guitar A. Attachment of the device at a desired polar or azimuth angle on the to soundboard B, placing the suction cup fastener  36  in contact with the soundboard, and then applying a slight finger pressure downwards on the upper surface of upper panel wall  22  of the device housing. This pressure causes the base cup  37  of suction cup fastener  36  to be resiliently deformed into hermetically sealing contact with soundboard B, thus securing the device to the soundboard. 
     As may be understood by referring to  FIG. 8 , acoustic pickup device  20  may be positioned with rear wall  27  of device housing  21  and thus microphone support stalk  47  and microphone  45  at a desired position on soundboard B. For example, as shown in  FIG. 8 , the housing  21  of pickup device  20  is oriented to position the microphone  45  facing the strings C of guitar A. 
     As may also be understood by referring to  FIG. 8 , the proximity of microphone  45  to sound-producing elements such as strings C of a musical instrument may readily be adjusted by bending microphone stalk  47  into a desired shape. Moreover, the direction of maximum response to sounds produced by guitar A or other such musical instrument, which direction coincides with a perpendicular normal to microphone screen  53 , may be readily adjusted in inclination or elevation angle, and polar or azimuth angle, by bending stalk  47  into a desired contour. 
     As is shown in  FIG. 8 , with pickup device  20  adjustably mounted to soundboard B of guitar A, an input plug D at an input end of an audio signal cable E may be inserted into jack  62 . The output end of cable E would typically be connected to an audio amplifier (not shown). 
       FIG. 9  illustrates how acoustic pickup device  20  may be readily removed from a musical instrument such as the self-resonating guitar A shown in  FIG. 8 , and removably attached to a different instrument, such as the 12-string guitar a shown in  FIG. 9 . 
     Thus as shown in  FIG. 9 , the polar angle of housing  21  of acoustic pickup device  20  is oriented obliquely with respect to the longitudinal axis of 12-string guitar a., rather than parallel to the longitudinal axis of self-resonator guitar A, as shown in  FIG. 8 . Also, in the application shown in  FIG. 9 , microphone stalk  47  is bent to position microphone  45  at the outer end of the stalk near or actually within the sound hole or “rose” f of guitar a. 
     As those skilled in the art will recognize, the novel advantages of the acoustic pickup device described above will be retained in variations of the device. For example, the four side walls which form a rectangular ring shape may be replaced with a single continuous peripheral wall which has a circular, oval, or other shape.