Abstract:
A metallic drum shell has grooves which enhance its acoustical properties to provide a warmer and less harsh sound. The grooving can be a continuous spiral groove formed in the outside surface of the drum shell. The grooves can be formed with selected depths, widths, contours and frequencies in order to achieve the desired fundamental pitch, resonance and overtone suppression.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Not applicable. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable. 
   FIELD OF THE INVENTION 
   This invention relates generally to musical drums and more particularly to a drum having a cylindrical body or shell that is grooved in a manner to enhance its acoustical properties. 
   BACKGROUND OF THE INVENTION 
   Musical drums have a long history of development and have advanced significantly in recent years. For example, snare drums date back at least to the period of the American Civil War. Snare drums became integrated as parts of drum sets in the early 1900s and have been a principal component of drum kits ever since. 
   The snare drum has a unique characteristic that involves the use of “snares” which are currently constructed using metallic wire for the most part. The wires or snares are stretched across the bottom drum head to produce a raspy tone that gives the snare drum its unique sound which is different from the tom-toms or bass drum of the drum set. The snare drum is essentially a tom-tom with snares added. Snare drums are commonly considered to be an alternative sound source that defines the natural accents of a musical composition. 
   For many years, the snare drum construction was essentially standard. The drum shell was made of either wood or metal and had between six and ten tension rods for tuning the drum head. The nature of the sound (known as the “timbre”) that is provided by a metallic shell is distinctly different from that provided by a wood shell. Metallic shells are typically tin or galvanized steel that produces more volume and sound projection than a wooden shell. More recently, the design of snare drums has become more sophisticated as various enhancements have been developed to provide different sound effects. One example is a cast drum shell made of a bronze alloy that has achieved considerable popularity. Other efforts have been made to use various metals such as copper, brass and titanium to control the timbre of the metallic snare drum while preserving the projection in tone. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to a drum shell that is grooved in order to enhance its acoustical characteristics when used in a snare drum or other type of drum such as a bass drum or tom-tom. The provision of grooves that are strategically contoured and sized allows custom tailoring of various acoustical properties, including the fundamental resonating frequency, overtones and resonance of the drum shell. The grooves can effectively control excessive high frequency content (sibilance) that is inherent in a metallic shell. Consequently, upper harmonics and overtones are suppressed to expose the lower frequencies to a greater extent. The overall result is a consistent “warmer” tone with extended dynamic range and projection. 
   In accordance with the invention, the grooves are preferably formed in a spiral configuration around the outside surface of the drum shell. Alternatively, the grooves can be separate circles on the shell. Their depth, width, sectional contour and frequency or spacing can be varied widely in order to achieve the intended effect. For example, it has been found that the fundamental pitch is effected most significantly by the depth of the grooves, particularly the groove depth in comparison to the thickness of the drum shell. Resonance can be controlled by changing the width of the grooves. As the groove width increases, the resonance decreases. Overtone suppression and content can be controlled by changing the contour or shape of the groove. More inclined sides of the grooves generally results in less overtone suppression. By varying the angles, shapes and lengths of the groove walls and bass, the overtone suppression can be adjusted to meet virtually any requirements that are desired. The number and spacing of the grooves effects all tone elements, including pitch, resonance and overtones. 
   It is an important object of the invention to provide a drum shell that is strategically grooved in a manner to allow control over its acoustical qualities. 
   Another object of the invention is to provide a drum shell of the character described in which the depth, width, contour and spacing of the grooves can be widely adjusted in order to achieve virtually any desired combination of acoustical characteristics of the drum. 
   A further object of the invention is to provide a drum shell of the character described that can serve as the body of various types of drums, including snare drums, bass drums and tom-toms. 
   An additional object of the invention is to provide a drum shell of the character described that can be constructed in a simple and economical manner. 
   Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     In the accompanying drawings which form a part of the specification and are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views: 
       FIG. 1  is a perspective view of a musical drum having a grooved drum shell constructed according to one embodiment of the present invention; 
       FIG. 2  is a side elevational view, partially in cross-section, of the drum shown in  FIG. 1 ; 
       FIG. 3  is a fragmentary elevational view, partially in section, similar to  FIG. 2 , but showing a groove pattern in accordance with an alternative embodiment of the invention; 
       FIG. 4  is a fragmentary elevational view, partially in section, similar to  FIGS. 2-3 , but showing a groove pattern in accordance with another embodiment of the invention; 
       FIG. 5  is a fragmentary elevational view, partially in section, similar to  FIGS. 2-4 , but showing a groove pattern in accordance with yet another embodiment of the invention; 
       FIG. 6  is a fragmentary elevational view, partially in section, similar to  FIGS. 2-5 , but showing a groove pattern arranged according to still another embodiment of the invention; and 
       FIG. 7  is a fragmentary elevational view, partially in section, similar to  FIGS. 2-6 , but showing a groove pattern arranged according to another embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the drawings in more detail and initially to  FIGS. 1-2 , numeral  10  generally designates a musical drum constructed according to one embodiment of the present invention. The drum  10  has a body which is formed by a hollow cylindrical shell  12  preferably constructed of a suitable metal. An upper drumhead  14  is stretched across the top of the shell, while a lower drumhead  16  is stretched across the bottom of the shell. Upper and lower rims  18  and  20 , respectively, engage the peripheral edge portions of the upper and lower drumheads  14  and  16  and are provided with projecting lugs  22 . Tension rods  24  extend between the upper and lower lugs  22  and may be tightened to increase the tension of the drumheads and loosened to loosen the drumhead tension. The tensioning mechanism is conventional and is familiar to those having ordinary skill in musical drum technology. 
   The present invention is directed to the construction of the drum shell  12 . As best shown in  FIG. 2 , the shell  12  has a cylindrical wall which presents an outside surface  26  and an inside surface  28 . The thickness of the wall of shell  12  is identified by the dimension D in FIG.  2  and is the distance between the outside surface  26  and the inside surface  28 . In accordance with the invention, the shell  12  is provided with a grooved surface which is preferably the outer surface  26 . Thus, a plurality of grooves  30  may be formed in the outside surface  26 . The inside surface  28  may be smooth. Preferably, the adjacent grooves  30  are actually formed as a single continuous spiral groove that extends around the entire height of the drum shell  12 . Alternatively, the grooves  30  can be formed as individual circular grooves spaced apart on the drum shell. While the grooves are depicted as being in the outer surface of the drum shell, they may also be formed on its inside surface. 
   The grooves  30  shown in  FIG. 2  are continuously curved in their contour when viewed in section. Each groove  30  extends into the outside surface of the wall of shell  12  to present a concave configuration that occupies an arc of a circle. Adjacent grooves  30  preferably intersect with one another at lines  32  which extend around the body of the drum. Alternatively, the grooves  30  can be separated with a smooth angular band (not shown) extending around the drum shell between adjacent grooves. 
     FIG. 3  shows an alternative embodiment of the invention in which the outside surface of the wall of shell  12  is provided with grooves  130  that differ in their configuration from the grooves  30 . Each groove  130  has a pair of substantially flat opposite side surfaces  132  and  134  and a substantially flat base  136  at the depth of the groove that extends between the inner edges of each pair of side surfaces  132  and  134 . The base  136  is substantially parallel to a central longitudinal axis  150  of the drum shell  112 . The side surfaces  132  and  134  of each pair are inclined to the longitudinal axis  150 , with the surfaces  132  and  134  of each groove being inclined at different angles to the axis  150 . Each surface  134  is inclined less drastically than the corresponding surface  132 , although other configurations are possible. Flat circular bands  138  are formed between adjacent grooves  130  on the outside surface of the shell wall. 
     FIG. 4  depicts another alternative embodiment of the invention in which a cylindrical drum shell  212  is provided with grooves  230  extending into its outside surface. Each groove  230  has a pair of flat side surfaces  232  and  234  and a flat base  236 . The base  236  is inclined at an angle to the central longitudinal axis  250  of the drum shell  212 . The side surfaces  232  and  234  are inclined to the longitudinal axis of the drum shell and may be inclined at substantially the same angles but at different directions (or at different angles if desired). A generally flat band  238  is provided between each adjacent pair of grooves  230  on the outside surface of the shell wall. 
     FIG. 5  depicts still another embodiment of the invention in which a cylindrical drum shell  312  is provided on its outside wall surface with a plurality of grooves  330  which may be formed as a single spiral groove or as separate circumferential grooves. Each groove  330  has a pair of opposite side surfaces  332  and  334  which are curved in a concave configuration when viewed from within the groove  330 . The side surfaces  332  and  334  may be constructed as mirror images of one another and may intersect at a base of the groove forming a line  336 . Alternatively, the base of each groove  330  may take the form of a flat band. On the outside wall surface of the shell  312 , flat bands  338  may be formed between adjacent grooves  330 . 
     FIG. 6  illustrates still another embodiment of the invention in which a cylindrical drum shell  412  has a plurality of grooves  430  extending into its outside surface. Each of the grooves  430  has opposite flat side surfaces  432  and  434  and a flat base  436 . The side surfaces  432  and  434  may be parallel to one another and may be perpendicular to the base  436 . The surfaces  432  and  434  may be substantially perpendicular to the longitudinal axis of the drum shell, while the base  436  may be substantially parallel to the longitudinal axis  450  of the drum shell. The grooves  430  extend through a substantial portion of the thickness of the drum shell  412 . Flat bands  438  may be formed between each adjacent pair of grooves  430  on the outside surface of the shell wall. 
     FIG. 7  shows still another alternative embodiment of the invention in which a cylindrical drum shell  512  is provided with grooves  530  which may have substantially the same configuration but a lesser depth than the grooves  430 . Each groove  530  has opposite side surfaces  532  and  534  and a flat base  536 . The surfaces  532  and  534  may be parallel to one another and substantially perpendicular to the longitudinal axis  550  of the drum shell. Each base  536  may be substantially parallel to the longitudinal axis of the drum shell and thus substantially perpendicular to the side surfaces  532  and  534 . Flat bands  538  are formed between adjacent grooves  530  on the outside surface of the shell wall. 
   The relative depth, thickness, contour and frequency or spacing of the grooves can be varied in order to provide the drum shell with different acoustical characteristics. The depth of the grooves relative to the thickness D ( FIG. 2 ) of the wall of the drum shell has a significant effect on the fundamental pitch (the actual pitch produced by striking the drum shell without hardware mounted on it). In general, the lower the pitch, the warmer the tone. The thickness dimension D typically ranges generally from 0.050-500 inch. If a strong material such as titanium is used to construct the drum shell  12 , the depth of the groove can be up to 90% of the thickness dimension D of the drum shell. Conversely, if copper or another relatively soft metal is used, the maximum groove depth should not exceed about 60% in order to preserve the structural integrity and strength of the shell. It is generally preferred for the groove depth to be at least 10% of the overall shell thickness. Thus, the depth of the grooves can be in the range of approximately 10-90% of the shell wall thickness, depending largely upon the strength of the material used to construct the shell. Preferably, a groove depth in the range of about 10-25% of the shell thickness is used. 
   The width dimension of each groove (the maximum distance across the groove between its opposite sides) has a significant effect on the resonance of the drum. As the groove width increases, resonance decreases. 
   The contour or shape of the groove when viewed in section can be varied in order to vary the overtone suppression and content. The more inclined the sidewall surfaces of the grooves is, the less overtone suppression the grooves provide. For example, inclined sidewall surfaces such as the surfaces  132  and  134  in FIG.  3  and the surfaces  232  and  234  in  FIG. 4  provide less overtone suppression than the parallel surfaces  432  and  434  in  FIG. 6 and 532  and  534  in FIG.  7 . By using different inclinations for the two side surfaces  132  and  134 , a compromise effect can be provided. Similarly, by angling the base  236  to the longitudinal axis of the drum shell, the effect on the overtone suppression can be adjusted. 
   The frequency of the grooves (the number of grooves along the length or height of the drum shell (or the number of grooves per unit distance along the length of height of the drum shell) has an effect on all of the tone elements provided by the drum, including an effect on the fundamental pitch, the resonance and overtones. Thus, the frequency or spacing between the grooves can be adjusted to provide global control over all vibrational characteristics of the drum shell. 
   Grooves having a curved contour such as shown in  FIGS. 2 and 5  may be used for “fine tuning” of the acoustical properties of the drum, and the curvature may be varied as desired, depending upon the effect that is to be obtained. Similarly, providing the base of each groove with either a flat configuration or a simple line configuration controls the acoustical properties accordingly. 
   Thus, by utilizing grooves having the desired combination of depth, width, shape and frequency, virtually any desired acoustical properties of the drum shell can be obtained. In all cases, the upper harmonics and overtones are suppressed to provide more exposure for the low frequencies and a “warmer” tone of the drum with extended dynamic range and projection. At the same time, the grooving results in a drum shell vibration that provides a consistent and repeatable sound desirable to drummers and listeners. 
   The drum shell in accordance with the present invention can be constructed of a wide variety of materials. Preferably, the shell is constructed of a suitable metal, including metals such as copper, bronze, brass, titanium, various alloys and a wide variety of other metals that have been used in the past and may be developed in the future. The drum shell may also be a wood structure provided with grooves. 
   From the foregoing it will be seen that this invention is one well adapted to attain all ends and objects hereinabove set forth together with the other advantages which are obvious and which are inherent to the structure. 
   It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims. 
   Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative, and not in a limiting sense.