Patent Publication Number: US-7582820-B2

Title: Method and apparatus for optimizing sound output characteristics of a bass drum

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of and priority from U.S. provisional application Ser. No. 60/904,619 filed Mar. 2, 2007. 
    
    
     INTRODUCTION AND OVERVIEW OF INVENTION 
     The present invention pertains generally to techniques for optimizing the sound output of a bass kick-drum. The sound output is a factor of the batter head membrane, resonant membrane and space between them, and the resonant characteristics of said components both individually and the interaction of all components combined. As described below, the system of the present invention for the first time adjustably lowers the fundamental resonant frequency of the resonant membrane, increases the amplitude of the fundamental resonant frequency which enhances the bass kick-drum&#39;s tonal characteristics, reduces unpleasant or dissonant overtones and undesirable continuation of sound waves, also known as “ringing,” by providing an improved dampening feature and dynamically compressing the sound output; all of which are highly desirable improvements over the prior art. Furthermore, the present invention is novel due to its easily removable and portable design in one embodiment, allowing the user the opportunity to use the device by inserting it directly into the resonant chamber through an opening in the resonant membrane of the bass kick-drum without opening the drum. 
     The present invention, having mass and being coupled to the resonant membrane, increases the mass of the resonant membrane, thereby lowers the resonant membrane&#39;s fundamental resonant frequency, and due to its innovative coupling, simultaneously dampens the vibrations known as “ringing,” all of which are desirable improvements. Additionally, the invention, constituting a tuned port attached to the resonant membrane and extending into the resonant chamber, furthermore adjustably boosts and enhances the desired frequency characteristics of the bass drum. Furthermore, the invention momentarily restricts the propagation of the sound wave through the opening in the resonant membrane, and, we believe, adds a sonically warm dynamic compression. The result of the foregoing is increased low frequencies, better definition, clarity, a more consistent sound in varying acoustical environments, and increased dynamic impact. 
     BACKGROUND 
     Description of Invention 
     The output sound of a bass drum is inherently much more difficult to optimize than that of a simple string. A vibrating string used in all string instruments is a one dimensional body that vibrates in a second dimension. A vibrating string produces harmonic, pleasant sounding overtones that are integral multiples of the fundamental frequency of the string. “Tuning” or “adjusting the pitch” of the string&#39;s fundamental frequency is a simple matter of loosening or tightening the string tension. 
     In contrast to the vibrating string, a circular bass kick-drum membrane is a two dimensional body that vibrates in a complex fashion described by Bessel function equations in a third dimension. A drum cannot be “tuned” like a vibrating string. As described below, the subject invention allows the user to “tune” or adjust the desired fundamental resonant frequency while concurrently minimizing the undesirable overtones known as “ringing.” 
     When the batter head membrane is struck by the foot pedal, the resonant membrane vibrates and the vibrations include the desired fundamental resonant frequency along with non-harmonic, unpleasant and/or dissonant ringing overtones. These unpleasant overtones are inherent in any circular drum membrane and cannot be removed or reduced by simply adjusting the resonant drumhead tension. The primary dissonant overtone is approximately 2.4 times the fundamental frequency of the drumhead membrane, regardless of the tension applied to the membrane. The above-described dissonant overtones are also produced in bass drums having two drumheads—the resonant and batter head membranes. 
     If the resonant membrane is allowed to vibrate in an undampened manner, we believe the dissonant undesirable frequency continues which is not only noticeable, but actually interferes with the next sound wave and likely often subsequent sound waves produced when the foot pedal beater strikes the batter head membrane. We also believe that “ringing” moreover occurs as a result of the combination of the inherent, dissonant overtones and an undampened vibration of the resonant membrane. The present invention minimizes “ringing” by quickly dampening the vibration of the resonant membrane. 
     It is desirable to increase what the percussion industry commonly describes as the “punch” of the bass drum sound output. As used herein and in the claims, the word “punch” is defined to include the following three features: (1) the lowering of the fundamental resonant frequency of the resonant membrane, (2) increasing the amplitude of the fundamental resonant frequency, and (3) increasing the damping of the resonant membrane which reduces undesirable continuation of tone which interferes with subsequent sound waves. These three features can be scientifically measured as described below. In addition to these three measurable features, we believe the invention dynamically compresses the sound output via restriction of sound waves in their exit from the resonant chamber through the resonant membrane. 
     Lowering the fundamental frequency of the resonant membrane produces a deeper, fuller sound output which is one of the elements of “punch.” As is known from Bessel function equations, the fundamental resonant frequency of a circular drum membrane is governed by three variables. The first variable is the diameter of the membrane—the greater the diameter, the lower the fundamental resonant frequency. The second variable is the mass of the vibrating membrane—the greater the mass, the lower the fundamental resonant frequency. The third variable is the tension applied to the drumhead membrane—the greater the tension, the higher the fundamental resonant frequency. 
     Various prior art techniques have attempted to optimize the bass drum output sound, i.e., reduce the “ringing” and/or increase the “punch” of the bass kick-drum. These techniques generally address either the “ringing” or the “punch” problems individually. For example, the Billings U.S. Pat. No. 4,805,514 requires that the dual membrane bass kick-drum be opened, the device placed inside the drum, adhesively attached and the drum then closed. This prior art device does not have a frequency adjusting capability. Furthermore, it is inconvenient to the drummer who is forced to abandon tuning and other adjustments to open the drum, in addition to the time necessary to accomplish installing the device and then retightening/tuning the drumhead(s). 
     A further disadvantage of Billings is that the design utilizes a tapered inlet inserted into the resonant chamber which is larger than the circular opening or outlet formed in the resonant membrane. This design projects a large degree of the beater attack on the batter membrane which contains what we believe to be an undesirable increase of high frequencies. As described in more detail below, the present invention utilizes an insert with a cylindrical body that extends into the resonant chamber and which is flared in the opposite direction of Billings and as such focuses and projects the sound output from the resonant chamber into a microphone or acoustical environment. 
     The present invention provides a novel method and apparatus for lowering the fundamental resonant frequency of a circular bass kick-drum. The drummer is now, for the first time, able to easily maximize the “punch” or a bass kick-drum by adjustably lowering the fundamental resonant frequency. By adding “mass” or “weight” to an insert described below, the user can adjustably lower the fundamental resonant frequency of the resonant membrane. 
     Additionally, the design of the present invention constitutes a “tuned port” which when inserted provides a novel method of increasing the amplitude of fundamental resonant frequencies of the resonant membrane. 
     A primary object of the invention is to simultaneously provide dampening which minimizes “ringing,” which is the combination of the inherent, dissonant or unpleasant overtones and vibrations of the resonant membrane that otherwise continue to occur and interfere with subsequent sound waves. 
     A further object of the invention is to provide a novel insert constituting a “tuned port” for a bass kick-drum which simultaneously and adjustably increases the amplitude of the desired fundamental resonant frequency permitting the user to “tune” the sound output while preserving the natural and original acoustic qualities of the bass kick-drum. 
     A further object of the invention is to provide a novel insert which through the momentary restriction of sound waves in their exit from the resonant chamber, we believe, dynamically compresses the output, which results in a more consistent sound in varying acoustical environments. 
     A further object of the invention is to provide a novel insert that focuses sound out of the resonant chamber into a microphone. 
     A further object is to provide a method for adjustably optimizing the output sound of a bass kick-drum by maximizing the “punch” and simultaneously minimizing the “ringing” of the drum. 
     A final object of the invention is to provide a novel insert that offers a clean, powerful and purposeful aesthetically pleasing look rather than industry standard five inch resonant drum hole opening. 
     Other objects and advantages will become apparent from the following description of the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic representation of a first embodiment of the invention; 
         FIGS. 2A and 2B  are front and rear views of the insert utilized in  FIG. 1  illustrating the insert before it is connected to the drum; 
         FIG. 3  is a schematic representation of a second embodiment of the invention; 
         FIGS. 4A ,  4 B and  4 C are graphical representations comparing the output of a single drum wherein  FIG. 4A  illustrates the output of the drum without the invention applied,  FIG. 4B  illustrates the output with one embodiment of the invention applied and  FIG. 4C  illustrates the output sound with a second embodiment of the invention applied; 
         FIGS. 5A ,  5 B and  5 C are tables that correspond to the graphs of  FIGS. 4A-4C , the tables illustrating decibel levels of various frequencies produced by the vibrating drum head; 
         FIG. 6  is a schematic representation of a third embodiment of the invention; and 
         FIG. 7  is a schematic representation of a fourth embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic drawing of a first embodiment of the invention. A bass drum shown generally as  10  includes two circular membranes  11  and  12 . Membrane  11  is commonly referred to as the batter head membrane and is struck by a conventional base drum pedal  14  and striker or beater  15 . The second membrane  12  is commonly referred to as the drum head or resonant membrane and typically has a circular opening  12   a  formed in membrane  12  as is known in the prior art. Opening  12   a , as is known in the art, is provided to help optimize the sound output of the drum  10 . 
     According to the present invention, a novel removable insert  20  is simply slid into opening  12   a  of membrane  12 , and in the first embodiment shown in  FIG. 1 , slightly rotated and the slight rotation causes a plurality of rubber fins or mounting means  30  to extend outwardly against the inner surface of resonant membrane  12  to attach insert  20  firmly to resonant membrane  12 . Other means of attachment are described below. 
     The insert  20  includes a cylindrical body  25  on which a plurality of fins  30  is mounted. The outer diameter “d” of cylinder  25  is adapted to allow it and fins  30  to slide through opening  12   a  in resonant membrane  12 . Insert  20  has a flared flange  40  at its outer end which extends outwardly through membrane  12  and which is outwardly flared in the direction shown by arrows  99 . It is significant to note that the weight of insert  20  is carried entirely by resonant membrane  12 . As noted above, the weight or mass of insert  20  is added to the mass of membrane  12  and directly reduces the fundamental frequency of membrane  12 . 
     The present invention provides increased “punch” of the drum  10  after each time the pedal  14  is actuated to cause striker  15  to impact the batter head or attack membrane  11  of the drum. The increased “punch” is imparted to the drum by a combination of optimizing the weight of insert  20  for the particular drum and by sizing and shaping the cylindrical body  25  of insert  20  to maximize the amplitude of movement of resonant membrane  12  in response to the striking of attack membrane  11 . The insert of the present invention utilizes a cylindrical body  25  in which the inner end  26  of body  25  is the same diameter as the entire portion of the body  25  which is positioned between the resonant membrane  12  and batter head membrane  11 . This is in sharp contrast to the bell-shaped or heavily flared bell  10  used in the Billings &#39;514 patent referred to above. The use of the Billings bell  10  tends to direct much of the energy created by the attack membrane through the opening in the resonant membrane. In contrast, the insert of the present invention maximizes the percentage of energy generated by the batter head membrane that is transmitted directly to the resonant membrane  12 . The cylindrical body  25  of insert  20  tends to direct all but a small portion of the energy generated by the batter head membrane directly to resonant membrane  12 . The length “L” of cylindrical body  20  exceeds its diameter “d.” This geometry momentarily restricts sound waves passing through opening  12   a  after the batter head membrane is struck. By sizing the weight, diameter and length of insert  20 , adjustment is made to the “punch” of the drum. 
     If the insert  20  is removed from the drum illustrated in  FIG. 1 , the “punch” of the drum is reduced for two reasons: First, the mass of the resonant membrane has been reduced significantly by removing the insert and, secondly, the energy generated by striking the batter head membrane passes easily through opening  12   a  in the resonant membrane  12 . 
     The ringing of the drum is minimized by adding the weight of insert  20  to resonant membrane  12 . We believe this weight combined with viscous characteristics of insert  20  quickly dampens the sound output which reduces the ringing. 
       FIGS. 2A and 2B  are front and rear views respectively of insert  20  before it is inserted into opening  12   a  of membrane  12 . As shown in the front view ( FIG. 2A ), the flared outer end is a flange  40  which is circular and extends outwardly from cylindrical body  25 . The tips of rubber fins  30  are visible extending beyond the outer diameter of flange  40 . In the embodiment shown in  FIGS. 2A and 2B , the cylindrical body  25  has an inner diameter of four inches and a length of six inches. 
     As shown in the rear view ( FIG. 2B ), fins  30  are tangentially attached to cylindrical body  25  at points  30   a  by adhesive. A foam gasket  60  is carried adjacent the flared outer end  40 . Foam gasket  60  bears against resonant membrane  12  when insert  20  is attached to membrane  12 . Insert  20  is slid into opening  12   a  by simply rotating in a counterclockwise direction, as shown in  FIG. 2B , so that the resilient fins  30  can pass through opening  12   a . Once the insert  20  is slid all the way into opening  12   a  so that gasket  60  bears against resonant membrane  20 , insert  20  is simply rotated in a clockwise direction, as shown in  FIG. 2B , to cause fins  30  to move outwardly and to grasp membrane  12 . Removal of insert  20  is achieved by simply rotating insert  20  in the counterclockwise direction, as shown in  FIG. 2B , and sliding it outwardly through opening  12   a . Fins  30  have a truncated bell-shape so that insert  20  is easily slid into and out of opening  12   a . Fins  30  are made of rubber having a durometer level of 50 to 55 and having a thickness of 0.125 inch. 
       FIG. 3  shows an alternate embodiment of the invention in which bass drum  10  with membranes  11  and  12 , as shown in  FIG. 1 , has an alternate insert  120  installed. Insert  120  differs from insert  20 , shown in  FIG. 1 , in one significant aspect. Insert  120  includes weights  151  and  152 , each weighing one ounce, which have been added to the body  125  of insert  120  to increase the overall weight or mass of insert  120 . 
       FIGS. 4A ,  4 B and  4 C are graphical representations of sound outputs achieved during laboratory trials.  FIGS. 4A-4C  illustrate the amplitude of the drum output on the vertical scale as against time in seconds illustrated by the horizontal scale. 
       FIG. 4A  was generated by striking a 22 inch bass kick drum without any insert connected to the resonant membrane. The prolonged vibration of the drum extending for 2 seconds or more illustrates the phenomenon of “ringing.” 
       FIG. 4B  illustrates the output of a first embodiment  20  of the present invention ( FIG. 1 ) applied to the same 22 inch drum wherein insert  20  has a weight of 7.35 ounces. As can be seen by  FIG. 4B , the output is quickly dampened and the ringing effect, illustrated in  FIG. 4A , is quickly ended in less than approximately one-half second. 
       FIG. 4C  illustrates the damping of the second embodiment of the invention (shown in  FIG. 3 ) wherein one ounce was added to insert  120  increasing its weight to 8.35 ounces. The ringing effect is again quickly ended. 
     The tables shown in  FIGS. 5A ,  5 B and  5 C were generated in the laboratory along with graphs shown in  FIGS. 4A ,  4 B and  4 C. 
     The fundamental resonant frequency and amplitudes are represented in  FIGS. 5A-5C  by taking an average of the two frequencies having the greatest decibel levels and averaging their respective decibels. In  FIG. 5A , the two frequencies having the largest amplitudes are 45.75 Hz and 43.06 Hz. The fundamental resonant frequency is therefore approximately 44.4 Hz and the amplitude is the average of 7.17 Db and 6.43 Db, or about 6.8 Db. 
       FIG. 5A  corresponds to  FIG. 4A  wherein the drum had no insert installed. 
     The table of  FIG. 5B  shows that with a first embodiment ( FIG. 1 ) of insert  20  installed, the fundamental frequency of the resonant membrane dropped from 44.4 Hz to approximately 28.3 Hz. This represents more than a 33% lowering of the fundamental frequency of the resonant membrane! It is also significant to note that the output level in decibels increased from 6.8 decibels to about 10.5 decibels which is approximately a 50% increase in the amplitude of vibration of the fundamental frequency at resonant membrane  12 . This significantly increases the “punch” of the sound output. 
     The table of  FIG. 5C  corresponds to  FIG. 4C  and illustrates the sound output of insert  120  of  FIG. 3  with the addition of one ounce to increase the overall weight of insert  120  to 8.35 ounces. The addition of this weight to insert  120  lowered the fundamental frequency to about 25.6 Hz (about 10%) and slightly decreased the amplitude from about 10.5 decibels to about 10.2 decibels. 
     The drum utilized to produce the graphs in  4 A- 4 C and tables  5 A- 5 C was a 22 inch diameter bass kick drum. The resonant membrane was made of Mylar film and had an overall weight of 14 ounces. The inserts  20 ,  120  utilized to produce graphs  4 B, 4 C and tables  5 B, 5 C utilized  8  rubber fins  30 . The cylindrical bodies  25 ,  125  each had an inner diameter of 4 inches and a length of 6 inches. Each rubber fin was made of rubber having a durometer rating of 50-55. The extra weight used in insert  120  ( FIG. 3 ) was added by simply attaching it to cylindrical body  125  with adhesive. 
       FIG. 6  shows a third embodiment wherein insert  220  has a cylindrical body  225  and a flared outer end with flange  240 . A rubber sleeve  270  slides over cylindrical body  225 . The forward end of sleeve  270  is flared outwardly to form a peripheral flange  271 . Flange  271  contacts resonant membrane  12  so that resonant membrane  12  is engaged firmly between outer flange  240  and peripheral flange  271 . Rubber sleeve  270  is held in position by a stop ring  275 . The insert  220  must be applied either by opening the drum  10  or by applying it to membrane  12  before membrane  12  is attached to the drum. 
       FIG. 7  shows a fourth embodiment wherein insert  320  has a cylindrical body  325  and a flared outer end with flange  340 . Adhesive  345  is applied between flange  340  and resonant membrane  12  to mount insert  320  to membrane  12 . In this embodiment, adhesive  345  connects insert  320  to membrane  12  without any mechanical connector. 
     Other mounting means may be utilized to attach the cylindrical body and flange of the insert of this invention to the resonant membrane, including any mechanical connecting device and/or adhesive which securely attaches the insert and/or flange of the insert to the resonant membrane. 
     The foregoing description of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teaching. The embodiments were chosen and described to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best use the invention in various embodiments and with various modifications suited to the particular use contemplated. The scope of the invention is to be defined by the following claims.