Guqin bottom plate and improved guqin

Abstract

The purpose of this invention is to provide an improved guqin (a seven-stringed zither). The original two-slot structure (large and small) is modified into a three-slot structure with an added sound source slot. The aim is to further enhance the vibration frequency capability of the guqin's bottom plate, compensating for the limited audio function of the top plate caused by the physical pressure of the fingerboard. This invention uses an arched cross-section for the bottom plate, which improves its rigidity and fundamental frequency. Its relatively complex curvature makes the inherent frequencies of the structure more dispersed, improving the suitable frequency range. This invention replaces the dragon pool and phoenix pond with sound holes, ensuring the integrity of the antinode range of the bottom plate's vibration frequency and the smoothness of the transmission path. The adjustable position and diameter of the sound holes enrich the tuning methods. This invention bends the bottom plate with each tilt of the top plate, increasing the height of the head section and the formation of standing waves within the cavity. This invention also changes the string tension angle and the string tensioning and tuning methods, thus improving the stress on the instrument body, frequency transmission, and string tensioning and tuning.

Description

Technical Field

[0001] This utility model relates to the field of musical instruments, specifically to an improved guqin (a seven-stringed zither) with a different bottom plate and string tensioning method. Background Technology

[0002] Based on existing materials and surviving guqin (a seven-stringed zither) from various dynasties, many literati and scholars dedicated themselves to improving the guqin. For example, in the famous Song Dynasty painting "Listening to the Qin," the table under Emperor Huizong's guqin has a very thick surface, a typical resonant table. This reflects the guqin's inherent weakness of insufficient resonance and traces of how it was improved. In the 1950s, the Central Conservatory of Music's "Collection of Essays on the Improvement of National Musical Instruments" introduced the improvements made to the guqin by teachers Wu Jinglue and Guan Pinghu. Their improvements also targeted the insufficient resonance of the guqin. A careful study of the guqin reveals two main problems that limit its resonance.

[0003] Firstly, the guqin's soundboard is "same as the fingerboard," meaning it serves as both the resonating body and the fingerboard supporting the left fingers as they press the strings. The soundboard requires a loose, transparent, and resonant material, while the fingerboard requires a strong, solid, wear-resistant, and non-deforming material. We know that most wooden stringed instruments require a "loose top and solid bottom" in their soundboard and backboard selection. The soundboard needs to be resonant and easy to resonate, while the backboard needs to be relatively hard to facilitate sound wave reflection and resonance within the instrument's cavity. The guqin has always followed this principle. However, because the soundboard is both the resonating body and the fingerboard, the fingerboard's requirements are essential for guqin performance, while the soundboard's requirements are necessary for performance. Faced with this contradiction, the guqin employs a method of "covering the instrument with thick, heavy lacquer" to satisfy the fingerboard's physical requirements for rigidity and hardness. This results in a situation where, on one hand, the soundboard's rigidity and hardening limits its audio vibration performance, while on the other hand, the backboard's hardness makes it less suitable for matching the soundboard's audio vibration and transmission.

[0004] Second, the 90° tension of the strings (see...) Figure 6 The 90° string tension required slots to be cut into the soundboard for fixation, and the strings had to be replaced with loops instead of bends. One end of the string was tightly bound to the tuning pegs with loops, while the other end was bound with multiple overlapping loops on the bridge. The 90° string tension also created a resultant force in the 45° direction, which limited the transmission path of the string vibration frequency. The vertical loops also imposed a greater initial constraint on the instrument.

[0005] In addition, the guqin also has the following shortcomings:

[0006] 1. According to common sense, when playing gongs and drums, one should strike the gong surface and the center of the drumhead. However, in the existing technology, the dragon pool and phoenix pond are located in the center of the base plate, and the opening is relatively large, which is obviously not conducive to the vibration and transmission of the sound from the base plate.

[0007] 2. In the making of the guqin's headboard, there are primary and secondary dips (D11 and D12), resulting in uneven thickness of the internal space when the headboard is used as the soundbox. This is detrimental to sound wave vibration and the formation of standing waves (see...). Figure 6 ).

[0008] 3. The existing manufacturing process for the base plate involves heavy wrapping with hemp and binding, which affects the vibration frequency function of the instrument.

[0009] 4. 90° string tension has limitations such as difficulty in installing and changing strings, insufficient tuning sensitivity, and insufficient string locking.

[0010] A. Construction of the 90° tension angle and mechanical analysis around Yueshan:

[0011] Aa. The so-called 90° string tension refers to the fact that one end of the guqin string 3 extends to the tail of the instrument, bends twice around the dragon gum, and is tied to the base of the foot 7. Among them, the first to fourth strings are tied to the outer foot 7, and the fifth to seventh strings are tied to the inner foot 7. The other end of the string 3 extends to the top of the bridge 6 and is tied with a fly head knot. After being secured with a velvet knot, it bends 90° at point b of the bridge 6, passes down through the string eye on the dew-collecting 5, and connects to the tuning peg in the tuning peg pool inside the bottom board. Rotating the tuning peg changes the length of the velvet knot to tune the strings.

[0012] Ab. Verify the stability of Yueshan under static conditions (see...) Figure 7 ),

[0013] In the diagram, the horizontal string tension F1 and the buckle pull F2 at point b of the bridge rotate 90°. When static, F1 = F2. They form an overturning moment M1 and a balancing moment M2 at point a at the base of the bridge, respectively. The difference in moment is ΔM = M1 + M2.

[0014] Let the height of Yueshan be h1 = 15mm and its width be b1 = 10mm.

[0015] Since F1 = -86.83N and F2 = 8.83N (based on actual measurements of the Yuesheng neutral string),

[0016] ∴ΔM=M1+M2=-86.83*15+86.83*10=-86.83*5=-434.15Nmm.

[0017] In the diagram, the ae, ec, and cd surfaces of the Yueshan embedded in the soundboard are the adhesive surfaces with the soundboard. The stress torque generated by these surfaces, along with the compressive stress torque of the soundboard along the grain on the cd surface, forms four stress torques around point "a" in the groove. Among them, the stress torque generated by the adhesive force on the ae surface has a small torsional displacement because the ae surface is close to point a. The compressive stress torque of the soundboard along the grain on the cd surface must be considered because the plastic deformation of the adhesive on the adhesive surface must occur first before the relevant stress is generated. Therefore, only the torque m1 of the ec surface and the torque m2 of the cd surface are used for verification.

[0018] Calculation of torque m1: The bonding force f1 acting on the ec plane at the bottom of Yueshan is related to the horizontal distance of f1' at each point. That is, the stress diagram around point a is a triangle, and the arm length of the resultant torque should be the horizontal distance from the centroid of the triangle to point a. Assume the vertical tensile strength of the bonded surface is 0.5 N / mm². 2 b1 = 10, and the chord spacing width is k = 20mm.

[0019] Let x be the horizontal distance from the centroid of triangle f1 to point a, and let y be the magnitude of the cohesive force f1x at position x.

[0020] According to the rule that corresponding sides of similar triangles have equal ratios, we have x / 10 = y / 0.5

[0021] Therefore, y = x / 20

[0022] Since the areas on both sides of the centroid are equal, we have y*x / 2 = (y + 0.5)*(10 - x) / 2

[0023] ∴x 2 / 20 / 2=x / 2+5-x' / 20-x / 2

[0024] ∵x 2 / 20=5-x' / 20

[0025] Since x = √50

[0026] Since the stress moment m1 is equal to f1 * b1 * k * x / 2 = 0.5 * 10 * 20 * √50 / 2 = 353.55 N / mm,

[0027] The calculation of moment m2 is performed, and the stress diagram of surface f2 on the dc plane is rectangular. Similarly, the shear strength of the bonded surface under parallel conditions is assumed to be 0.5 N / mm. 2 The point of application and direction of force f2 overlap with the cemented surface. The size of m2 at this point is controlled by the embedding depth of h2. The required size of m2 to stabilize the bridge is actually determined by the depth of h2.

[0028] We get m2 = f2 * k * b1 * (h2 - 2) = 0.5 * 20 * 10 * (h2 - 2) (h2 minus 2 is to deduct unreliable bonded edges)

[0029] The torques around point a should be balanced, ∑Ma=0

[0030] Since M3 = m1 + m2

[0031] ∑Ma=M1+M2+M3=M1+M2+m1+m2=0

[0032] We get -434.15 + 353.55 + 0.5 * 10 * 20 * (h² - 2) = 0

[0033] Since h2 = 2.806mm, it is calculated that the Yueshan can maintain static stability when the embedding depth is about 3mm.

[0034] Ac, verify the stability of the bridge when tightening and loosening the string (see...). Figure 8 , 9 To discuss this issue, we must first quantify the static friction resistance between the top of the bridge and the string loop. Tuning the string involves rotating the tuning pegs to twist the loop. The tightening or loosening of the loop causes changes in the length of the loop, which in turn overcomes static friction to pull the string. In the diagram, the resultant force Fh is determined by the magnitudes of F1 and F2 and the string tension angle. When the static string tension angle is 90°, since F1 = F2, Fh = 1.414F1, and the angle is 45°. The static friction force between the loop and the top of the bridge is Fm = μFh, where μ is the coefficient of static friction between the loop and the bridge. At the instant the string is tightened, the string tension F1 and the string angle 90° remain unchanged. The tension of the loop increases, represented by F2'. The instantaneous resultant force becomes Fh' = √(F1² + F2'²), and the static friction increases, represented by Fm' = μFh'. For the loop to pull the string, the increment Δf of the loop tension F2' must be equal to or greater than Fm', i.e., F2' - F2 = Δf ≥ Fm', to force the tuning peg to move and tighten the string. Conversely, when loosening the string, the tension difference between the string and the loop, F2 - F2' = Δf ≥ Fm', needs to overcome the instantaneous static friction to allow the tuning peg to move and loosen the string. In other words, during the tuning process, the resultant force Fh' and the static friction Fm' change dynamically with the loop tension F2'.

[0035] The calculation of Δf when adjusting string tension using a loop fastener is as follows.

[0036] ∵Δf≥Fm'

[0037] Where: Δf is the instantaneous tension variable of the velvet buckle, with increments being positive and decrements being negative.

[0038] Fm' is the dynamic maximum static friction force Fm' = μFh'

[0039] F2' is the tension of the string adjusted by the loop, F2' = F2 + Δf

[0040] Fh' is the instantaneous resultant force of F1 and F2', Fh' = √(F1² + F2'²).

[0041] μ is the static friction coefficient between the velour button and the surface of the bridge, tentatively estimated at 0.25.

[0042] Therefore, Δf ≥ Fm' = μFh'

[0043] ∵Δf-μ√(F12+(F2+Δf)2)≥0

[0044] When the fleece tuck is properly tightened, Δf ≥ +0.4378509F1

[0045] When the fleece button is loosened, Δf ≥ -0.304518F1

[0046] The tension F2' when the string is tightened by the velvet buckle is greater than or equal to (1 + 0.43785)F2' = 124.85 N;

[0047] The tension F2' when loosening the strings is greater than (1-0.30452)F2'=0.69548F2=60.39N.

[0048] When tuning, the adjustment of the tension F2 of the string loop causes a change in the balancing torque M2 of the bridge.

[0049] M2'=(F2+Δf)*b1.

[0050] A positive increment of Δf is beneficial to the stability of Yueshan.

[0051] When the increment of Δf is negative, it is not conducive to the stability of the bridge. However, since the tuning is a single-string dynamic, the overturning moment ΔM' = -0.304518F1b1 = -264.397 Nmm generated when the string is loosened has a limited impact on the stability of the bridge under static conditions of the other six strings.

[0052] Since ∑Ma=M1+M2+M3=0

[0053] Since M1 = F1 * h1 * 7 = -105F1

[0054] ∵M2=F2*6*b1+(1-0.3045)F2*b1=66.955F2

[0055] ∵M3=m1+m2=353.55+0.5*10*20*(h2-2)

[0056] ∵-105F1+66.955F2+353.55*7+100*7(h2-2)=0

[0057] We get h = 0.82 mm

[0058] Because when the strings are loosened, the state of a single string is checked, the overall stability of the bridge is controlled by the check in the next section.

[0059] Ad, verify the stability of Yue Shan under string playing conditions (see Figure 10 When the strings are played, the string tension F1' = F1 + Δf. Assuming the maximum dynamic load increment coefficient is 0.25, and considering the extreme condition where all seven strings are plucked simultaneously, the increased overturning moment acting on point a of the bridge is M1'. The stabilizing moment M2 acting on point a by the buckle tension F2 remains unchanged. The calculations are as follows:

[0060] Since ∑Ma=M1'+M2+M3=0

[0061] ∵M1'=F1*h1=-1.25*15*F1*7=-1.25*15*7*86.83

[0062] ∵M2=F2*b1*7=10F2=10*7*86.83

[0063] ∵M3=7*m1+7*m2=7*353.55+7*0.5*10*20*(h2-2)

[0064] ∴(-18.75+10)*86.83+353.55+100(h2-2)=0

[0065] Therefore, h = 6.06 mm

[0066] When plucking the strings, the estimated overall embedding depth to maintain the stability of the bridge should be greater than approximately 6.06 mm.

[0067] Verify the magnitude and angle of F1': F1'=√(12+1.252)=1.601F1∠β=arctan(1 / 1.25)=51°

[0068] The calculations and results show that, under static tuning, the tension of the loops perpendicular to the soundboard and parallel to the bridge's vertical line is F2 = F1. The combined force of the string and loops is at a 45° angle, with a magnitude of 1.414F1, providing initial restraint to the instrument. When tightening the strings, the increase in tension required to pull the stationary string must exceed the static tension by approximately 44%. Without loops to replace the string tension, especially the seventh string, the string will yield at the point of maximum static friction on the bridge's corner, eventually breaking. Furthermore, the 90° tension method generates varying degrees of overturning torque on the bridge in both static and dynamic states. The guqin uses a grooved soundboard to secure the bridge. These simple methods, used for thousands of years, are ingenious, but we must also objectively acknowledge their inconveniences and limitations for further improvement.

[0069] B. Frequency propagation path under a 90° tensioned structure (see...) Figure 11 ):

[0070] As we know, the vibration of a simple string can create sound waves in the surrounding air. However, since the space of the surrounding air is infinite, it lacks the conditions to form standing waves, resulting in a faint sound perceived by the ear. Wooden stringed instruments transmit the vibration of the strings through the bridge and body to the air within the limited cavity, creating standing waves, i.e., resonance. To make this transmission more efficient, the physical characteristics of both vibration frequency and path need to be analyzed and discussed.

[0071] Bb, Main Conduction Path 32: From the perspective of vibration frequency, the string tension F1 and the tassel tension F2 act on the bridge, and their resultant force Fh = 1.414F1, with an angle ∠β = 45° between it and the perpendicular line of the bridge. When the string is plucked, the tassel tension F2 remains unchanged, and the string tension F1 will be between 1F1 and 1.25F1. At the same time, the magnitude of the resulting resultant force Fh' = (1.414 to 1.6)F1 and ∠β = 45° to 51° varies. This 6° range of conduction through the wooden medium into the air in the cavity is relatively narrow, and it is the main conduction path 32 of vibration frequency.

[0072] From the perspective of the instrument body, the resultant force of the vibration frequency enters the instrument body along the interval ∠β=45°∽51°. The instrument body bears the pressure along the diagonal grooves of the vibration frequency path, forming a dynamic pressure-bearing surface that is perpendicular to and symmetrical to the line of resultant force. The maximum area of ​​a single string is approximately 20b³ / cos45°mm. 2 The minimum value is approximately 20b3' / cos51°mm. 2 This generates shear stress in the solid medium, with the tangential shear force occurring in the plane along the longitudinal grain, and its shear-resistant surface is approximately 20b3mm. 2 ∽20b3'mm 2 (From the table, the shear strength of Chinese fir along the grain is fv = 1.4 N / mm) 2 The size, thickness, and shear resistance of the bearing surface are related to b2 and the embedding depth h2 in the diagram. Within this 6° range, multiple requirements for component strength, bridge stability, and efficient path must be balanced: a small b2 will result in a short and fast diagonal main conduction path 32, but will lead to insufficient strength of the instrument body; a large b2 will result in a long conduction path, which will increase the internal conduction resistance of the wood; at the same time, a small h2 will cause the bridge to be too shallow and the component to become unstable, while a large h2 will affect the narrowness of the vertical B secondary conduction path 34.

[0073] Bc represents the secondary transmission paths of the X and Y direction vibration frequencies. When the sound wave vibration frequency is transmitted from the bridge into the wooden medium, the frequency transmission will form a directional three-dimensional diffusion due to the restoring force of the tangential linkage between microparticles. Among them, the main transmission path 32 is obliquely transmitted through the "pressure bearing surface" along the resultant force interval and transmitted to the air medium in the cavity; the secondary part will be divided into two directions, horizontal and vertical, depending on the shape of the instrument, namely the horizontal x-direction along the grain and the vertical z-direction across the grain. When the strings are played, the tension F1 of the strings is dynamic, F1' = 1F1 ~ 1.25F1, and the 90° angle remains unchanged; the tension of the tassel is affected by the frictional resistance at the end of the bridge, and the angle and F2 = F1 remain static. From this, the order of the magnitude of the vibration frequency flux of each path can be determined. The horizontal direction of the X direction of the soundboard with the grain is the A-order transmission path 33, the vertical direction of the solid wood bridge with the grain in the Z direction is the B-order transmission path 34, and the oblique main transmission path 32 with the resultant force along the interval ∠β = 45° ~ 51°.

[0074] From a materials science perspective, the modulus of elasticity (Ed) is the ratio of stress to strain experienced by wood during its elastic deformation phase. The formula is E = ΔN / ΔL, and it measures the degree of elastic deformation in a material. For a given deformation, a lower required stress indicates a lower modulus of elasticity, lower density, and lower stiffness in the wood; conversely, a higher required stress reflects a higher modulus of elasticity, higher density, and higher stiffness. Like strength, the modulus of elasticity in wood varies. Taking Yangzhou guqin wood (Chinese fir) as an example, the modulus of elasticity parallel to the grain of fir is found to be EL = 9000 N / mm². 2 The transverse radial elastic modulus ER = 900 N / mm 2 The transverse tangential elastic modulus Er = 450 N / mm 2 Longitudinal tangential shear modulus Glt = 540 N / mm 2 That is, the transmission path of the A-order vibration frequency of the guqin analyzed above is along the grain direction, and the elastic modulus EL = 9000 N / mm. 2 The B-order vibration frequency propagation path is in the transverse direction, and the elastic modulus ER = 900 N / mm. 2 There is no table for the oblique elastic modulus of the main frequency transmission path. Referring to the longitudinal tangential shear modulus formed by it, Glt = 540 N / mm². 2 Adjusting the elastic modulus of different phase materials as the frequency transmission path directly affects the frequency transmission efficiency and the balance of frequency intensity within the bandwidth.

[0075] Be, the sound transmission characteristic index of wood is v. Looking up the data, the sound transmission velocity of cedar wood along the grain is v = 4500-5000 m / s, the radial sound transmission velocity across the grain is v = 1400-1800 m / s, and the tangential sound transmission velocity across the grain is v = 800-1200 m / s. These are closely related to the elastic transverse moment in their respective directions. Similarly, adjusting the phase of the vibration frequency transmission path will affect its sound transmission performance.

[0076] Therefore, in the manufacture of wooden stringed instruments, it is crucial to select materials with appropriate elastic modulus and sound transmission properties, and to make good use of the optimal phase of the material. Wooden stringed instruments generally have the bridge set perpendicular to the grain of the soundboard. This serves several purposes: first, it ensures that the vibration frequency is transmitted vertically through the thickness of the board into the soundbox, resulting in a simple path; second, it selects a moderate value for the radial phase elastic modulus and sound transmission velocity of the transverse grain, which is beneficial for a balanced response across the frequency range; and third, it utilizes the strong local transverse grain length of the wood to bear pressure.

[0077] Through the above analysis and discussion, we have gained a deeper understanding of "finger box on the same board" and 90-degree string tension, and propose the following utility model accordingly. Utility Model Content

[0078] The purpose of this invention is to provide an improvement to the bottom plate of the guqin and the string tension angle of 162°, which can effectively solve or mitigate the problems in the background technology.

[0079] This improvement to the bottom plate and string angle of the guqin is a development based on the following guqin improvement patents: Utility Model Patent No. ZL202010345407.3, entitled "An Improved Guqin Soundboard," which improves the two-soundboard structure of the guqin into a three-soundboard structure consisting of a large soundboard, a small soundboard, and a sound source soundboard; and Utility Model Patent No. ZL202222522730.0, entitled "An Improved Guqin," which sets the inner contour of the soundboard as a series of golden spirals and arcs, eliminates the soundpost, and extends the sound-absorbing elements in the large and small soundboards; a sound beam is installed between the second and third strings in the sound source soundboard; and the lower parts of the first and seventh strings of the bridge are suspended from the soundboard.

[0080] Key points for improving the bottom board of the guqin are detailed below:

[0081] A guqin baseboard has a groove, which includes a sound source groove, a large groove, and a small groove, arranged sequentially from the head to the tail. Several sound holes are provided on the baseboard at the middle and side edges of the large and small grooves, and between the large and small grooves, replacing the existing dragon pool and phoenix pond on the guqin baseboard.

[0082] Preferably, the seven tone holes in the middle of the large groove on the side of the player are arranged symmetrically with the seven tone holes on the side away from the player.

[0083] Preferably, the small soundbox has 5 pairs of sound holes in the middle, symmetrically arranged along the central axis. Each pair includes two sound holes symmetrically arranged on both sides of the center line in the width direction of the base plate. The center distance between the two sound holes in the first pair is 110mm, and the horizontal distance between the center of the two sound holes in the first pair and the end of the small soundbox located at the tail is 145mm. The second pair of sound holes is located on the side closer to the large soundbox, and the center distance between the two sound holes is 30mm. The horizontal distance between the center of the first pair of sound holes and the center of the second pair of sound holes is 20mm. The third pair of sound holes is also located on the side closer to the large soundbox. On the side closest to the large soundbox, the center distance between the two tone holes is 110mm, and the horizontal distance between the center of the third pair of tone holes and the center of the second pair of tone holes is 20mm. The fourth pair of tone holes is located on the side closest to the large soundbox, with a center distance of 30mm between the two tone holes, and the horizontal distance between the center of the fourth pair of tone holes and the center of the third pair of tone holes is 20mm. The fifth pair of tone holes is also located on the side closest to the large soundbox, with a center distance of 100mm between the two tone holes, and the horizontal distance between the center of the fifth pair of tone holes and the center of the fourth pair of tone holes is also 20mm. There are two tone holes between the large and small soundboxes, symmetrically positioned on both sides of the center line in the width direction of the base plate. The horizontal distance between the center of the two tone holes between the large and small soundboxes and the center of the two tone holes in the fifth pair in the middle of the small soundbox is 115mm, and the center distance between the two tone holes is 30mm. The large soundbox has seven pairs of tone holes in the middle. Seven tone holes are symmetrically arranged on each side of the center line of the width direction of the base plate. The seven tone holes on the side away from the player are spaced apart along the length direction of the base plate. The horizontal distance between the center of the first tone hole and the center of the tone hole between the large and small soundboxes is 146mm. The horizontal distance between the center of the second tone hole and the center of the first tone hole, and the center of the third tone hole and the center of the second tone hole are all 40mm. The horizontal distance between the center of the fourth tone hole and the center of the third tone hole, the fifth tone hole and the fourth tone hole, the sixth tone hole and the fifth tone hole, and the center of the seventh tone hole and the center of the sixth tone hole are all 20mm. The distance between the center of the first and fifth tone holes and the center line of the width direction of the base plate is 64mm. The distance between the center of the second and seventh tone holes and the center line of the width direction of the base plate is 73mm. The distance between the third tone hole and the center line of the width direction of the base plate is 70mm. The distance between the center of the fourth and sixth tone holes and the center line of the width direction of the base plate is 15mm.

[0084] Preferably, the transverse cross-section of the base plate is arched.

[0085] Preferably, the dividing line between the sound source groove and the large groove is located on the bottom plate on the side near the head of the guqin, which is inclined downwards.

[0086] Preferably, a reinforcing rib is fixed to the bottom plate at the middle of the width direction of the large and small grooves.

[0087] Preferably, the reinforcing rib has a width of 15mm and a thickness of 15mm.

[0088] An improved guqin includes a soundboard, a backboard, and strings mounted on the soundboard. A bridge for supporting the strings is installed on one side of the soundboard via a dew-collecting device. A string-hooking bracket for fixing the strings is installed on the goose feet of the backboard. The improved guqin has the aforementioned guqin backboard.

[0089] Preferably, the distance between the resting point of the string on the bridge and the inner edge of the groove on the side away from the head of the instrument is 80mm. The guqin has a string tension adjuster corresponding to each string installed at one end of the head panel. The winding shaft of the string tension adjuster extends upward from the panel. The string on the side of the head of the instrument rests on the bridge and its end is connected to the winding shaft of the corresponding tension adjuster. The string between the bridge and the string tension adjuster is inclined downward and forms a 72° angle with the vertical line of the bridge.

[0090] Preferably, the base plate and the front plate are made of the same material. When making the base plate, the board material is first processed into shape, then putty is used to fill and color is adjusted, and then paint is applied to obtain the product.

[0091] In order to avoid the dragon pool and phoenix swamp occupying or cutting off the antinode area of ​​the bottom plate and hindering the vibration and transmission of the antinodes, this utility model eliminates the dragon pool and phoenix swamp and instead uses small circular sound holes arranged in a dispersed manner.

[0092] How to determine the location of the tone holes: First, the vibration of audio frequencies will form nodes and antinodes in different areas of the bottom plate of the guqin. The tone holes should be placed in the common node area of ​​all audio frequencies in the guqin's range, while avoiding the antinode area as much as possible. The Chladni experiment involves scattering sand on a flat plate fixed around its perimeter (or center) and then vibrating the plate. The sand grains will be driven away by the larger vibration amplitude in the antinode area and gradually gather near the stationary node or line, forming a clear geometric pattern that vividly represents where the antinodes and nodes are. Since the positions of antinodes and nodes are different for different vibration frequencies, different vibration frequencies will form different geometric patterns. Combining relevant theories and the Chladni experiment diagram, it can be confirmed that the edge of the bottom plate is the common node area of ​​all audio frequencies of the guqin, therefore, the tone holes can be arranged along the edge of the bottom plate.

[0093] Secondly, when the vibration frequency of the strings is transmitted into the air inside the instrument cavity to form sound waves, air, being a fluid medium, exhibits elastic restoring force during the transmission of vibration frequency, but lacks tangential restoring force. This means that fluid particles only experience forward and backward pushing, not upward or sideways pulling. Consequently, the direction of sound wave propagation aligns with the direction of particle vibration, resulting in a well-directed, concentrated longitudinal sound wave. The changes in the medium within the tiny volume element during longitudinal sound wave propagation can be correlated with the small variable of the sound field pressure P and the square of the particle velocity v. 2 The relationship between the change in instantaneous density q' and the change in instantaneous density is expressed as P = v 2q', When sound waves are propagated, the three-dimensional standing wave formed in the air will have a significant acoustic impedance due to the large sound energy of some individual audio frequencies or the narrowing of some special propagation paths, which increases the sound field pressure and density at that location. The acoustic impedance ratio Zs is equal to the sound pressure p at that location divided by the velocity v of the proton at that location, Zs = p / v.

[0094] Acoustic impedance is unavoidable during sound wave conduction and resonance within the soundbox of the guqin. For example, at the foot pool spout where the large and small soundboxes meet, due to the definite directional nature of sound wave conduction, the sound waves in the center of the soundbox will travel straight downwards, while the conduction paths on the left and right sides will be bent by the sidewalls of the large soundbox and enter the small soundbox at an angle. This multi-path conduction forms a cross-shaped intersection at the spout, resulting in high sound pressure and density at that point, as indicated by P=v. 2 From q' and Zs = p / v, we can obtain the relationship between the acoustic impedance of Zs and the sound pressure and instantaneous density. Practice has also verified that the acoustic impedance at this point affects the individual notes pressed in the small groove. To address this, a sound hole can be opened at the boundary between the large and small grooves to adjust the sound pressure. Similarly, in the middle of the guqin, due to the removal of the Dragon Pool and Phoenix Pond, the sound waves in this area also face the problem of increased sound field pressure. To avoid the opening in the middle of the bottom plate affecting the antinode area, fewer or smaller holes can be opened in the middle of the large and small grooves for adjustment.

[0095] The beneficial effects of this utility model are:

[0096] This invention cuts the cross-section of each slot bottom plate into an arched cross-section, which is beneficial to improving its vibration performance and frequency coverage. Compared with the original planar bottom plate, the improved arched cross-section has greater plate stiffness and a higher fundamental frequency (lowest natural frequency). Its boundary forces are vertical tensile and compressive stresses and horizontal push-pull stresses (relative to vertical vibration). The equilibrium restoring force during the arch vibration process is its own elastic restoring force. Only elastic tensile or elastic compressive forces appear on the same cross-section, and the stress diagram is a uniform rectangle. The elastic deformation of the stretching is a "membrane" stress mode, which can significantly improve its suitable vibration frequency range. The curvature of the arched plate will disperse the vibration energy, which can easily excite more complex higher-order modes and easily form a relative dispersion of the structure's natural frequencies.

[0097] In order to avoid the dragon pool and phoenix swamp occupying or cutting off the antinode area of ​​the bottom plate and hindering the vibration and transmission of the antinodes, this utility model eliminates the dragon pool and phoenix swamp and instead uses small circular sound holes arranged in a dispersed manner.

[0098] This invention features an arched cross-section for the guqin's bottom plate, which enhances its rigidity and fundamental frequency. Its relatively complex curvature allows for a more dispersed natural frequency response, improving the optimal frequency range. The invention replaces the traditional sound holes (dragon pool and phoenix pond) with sound holes, ensuring the integrity of the antinode range and unobstructed transmission paths. The adjustable position and diameter of the sound holes enrich the tuning options. The bottom plate bends with each tilt of the top plate, increasing the height of the head section and improving the formation of standing waves within the sound cavity. Furthermore, this invention alters the string tension angle and tuning methods, improving the stress on the instrument, frequency transmission, and string tensioning and tuning. Attached Figure Description

[0099] Figure 1 This is a front view of the guqin (a seven-stringed zither) of this utility model;

[0100] Figure 2 This is a bottom view of the guqin (a seven-stringed zither) of this utility model;

[0101] Figure 3 This is a plan view of the inner surface of the base plate of this utility model;

[0102] Figure 4 This is a longitudinal sectional view of the guqin (a seven-stringed zither) of this utility model;

[0103] Figure 5 This is a detailed drawing of the arrangement of the sound holes on the bottom plate of the guqin (a seven-stringed zither) according to this utility model.

[0104] Figure 6 A simplified diagram of a 90° tensioning method and its construction;

[0105] Figure 7 A simplified diagram for verifying the stability of Yueshan under static conditions with a 90° tension angle;

[0106] Figure 8 A simplified diagram for verifying the stability of Yueshan under a 90° tensioned state;

[0107] Figure 9 A simplified diagram for verifying the stability of Yueshan under slack string conditions with a 90° tension angle;

[0108] Figure 10 A simplified diagram for verifying the stability of the Yueshan (a type of bridge) during performance at a 90° string tension angle.

[0109] Figure 11 A simplified diagram for analyzing the frequency transmission path of a 90° tensioned string.

[0110] Figure 12 This is a simplified diagram of the 162° tensioning method and structure of this utility model;

[0111] Figure 13 This is a simplified diagram for verifying the stability of a mountain bridge under static conditions at a tension angle of 162°, according to this utility model.

[0112] Figure 14 This is a simplified diagram for verifying the stability of a bridge under a 162° tension angle and tight string state according to this utility model.

[0113] Figure 15 This is a simplified diagram for verifying the stability of a bridge under slack conditions at a tension angle of 162° according to this utility model.

[0114] Figure 16 This is a simplified diagram for verifying the stability of the bridge in performance mode at a 162° string tension angle, as per the present invention.

[0115] Figure 17 This is a simplified diagram of the 162° tensioned string vibration frequency transmission path analysis of this utility model;

[0116] Figure 18 This is a flowchart illustrating the bending and low-head cutting process of the bottom plate of the sound source slot in this utility model.

[0117] Figure 19 This is a detailed drawing of the Yue Shan (mountain support) and Cheng Lu (dew-collecting structure) of this utility model;

[0118] Figure 20 Detailed structural drawings of the hook support and string tension adjuster of this utility model;

[0119] Figure 21 This is a flowchart illustrating the installation structure of the string tension adjuster and the manufacturing process of the instrument head of this utility model.

[0120] In the diagram: 1. Top plate; 2. Bottom plate; 3. Strings; 4. Soundbox; 4.1. Soundbox; 4.2. Large soundbox; 4.3. Small soundbox; 5. Drainage container; 6. Bridge; 7. Goose foot; 8. String tension adjuster; 9. Tuning pin; 10. Reinforcing rib; 11. Soundhole; 12. Triangle pad; 13. String hook support; 14. Velvet buckle; 15. Dragon's teeth; 16. Soundbox dividing line; 17. Cut the bottom plate along the 70° line; 18. Fold the bottom plate of the soundbox downwards by 3° with the "0" point as the center; 19. Attach vertically grained wood shavings to the beveled surface of the cut bottom plate, sand it to a 3° angle, and then glue the bottom plate on; 20. Arched soundbox cutting line; 21. 21. Glue the triangular pads to the edge of the soundbox according to the grain pattern; 22. Sand the pads into a 3° bevel to match the base plate; 23. Make a 3° dip at the top; 24. Make a second 18° dip starting from point "m"; 25. Make an 8° tilt at the top; 26. Carve out the string tension adjuster chamber at an 8° tilt; 27. Attach the tuning peg guard and make holes; 28. Temporarily fix the base plate; 29. ​​Install the inspection slot hole on the bottom surface; 30. After assembling the instrument and applying varnish, install the string tension adjuster; 31. Cover and fix the inspection slot hole cover; 32. Main frequency conduction path range; 33. Frequency A conduction path; 34. Frequency B conduction path. Detailed Implementation

[0121] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0122] like Figure 1 , 2 As shown in Figures 3 and 4, an improved guqin includes a soundboard 1, a baseboard 2, and seven strings 3 set on the soundboard 1. A soundbox 4 is provided between the soundboard 1 and the baseboard 2. The soundbox 4 includes a sound source soundbox 4.1, a large soundbox 4.2, and a small soundbox 4.3, which are arranged sequentially from the head of the instrument to the tail. A bridge 6 for supporting the strings 3 is installed on the soundboard 1 on one side of the head of the instrument through a dew-collecting 5. A goose foot 7 is provided at the bottom of the baseboard 2, and a string-hooking bracket 13 is provided at the handle of the goose foot. A string tension adjuster 8 corresponding to each string 3 is installed at one end of the guqin located at the head of the instrument. The bridge 6 is located inside the string tension adjuster 8.

[0123] The string 3 is set on the panel 1, and one end of the string is hooked to the back of the guqin at the tail end and connected to the string hook bracket 13 at the bottom of the base plate 2. The other end of the string 3 is supported on the bridge 6 and the end is connected to the winding shaft 9 of the corresponding string tension adjuster 8 protruding from the panel 1. The tuning knob in the string tension adjuster 8 may be, but is not limited to, the tuning knob combination device described in my patent: a guqin string tension fixing device (patent number: ZL201820578030.4).

[0124] The main improvements of this utility model include:

[0125] 1. The panel 1 and the base plate 2 of this utility model are made of the same paulownia wood or cedar wood. The base plate is made of paulownia wood or cedar wood instead of catalpa wood in order to improve the audio vibration of the base plate and make up for the limitation of the panel in generating audio vibration function due to the physical requirements of the finger plate.

[0126] II. In the production of the base plate 2 of this utility model, the board material is first processed into shape, then leveled and colored with putty, and finally painted to obtain the product. The minimalist painting process removes the initial constraints of the base plate, releases its vibration energy, and plays a supplementary role to the limited audio vibration of the front panel due to the physical requirements of the fingerboard.

[0127] III. In this utility model, a reinforcing rib 10 is provided at the center of the large soundbox 4.2 and the small soundbox 4.3 along the width direction of the guqin, connecting to the base plate 2. One end of the reinforcing rib 10 is flush with the left end of the large soundbox 4.2, and the other end is flush with the right end of the small soundbox 4.3. The reinforcing rib 10 is 15mm wide and 15mm thick. Since the base plate is generally 10mm thick, the thickest material currently available is 15mm. If thicker material is needed, it must be cut separately. This application uses 15mm thick material to make the arched base plate, with a 7mm thickness in the arch. After analyzing the overall structural stress of the guqin, the strength and stiffness of the large, small, and soundbox base plates meet the requirements under the tension of seven guqin strings. Considering the relatively thin arch plate and the frequent handling of the guqin, a reinforcing rib is provided to increase rigidity and safety (e.g., Figure 3 ).

[0128] IV. The arched shape of the base plate 2 along the width direction of this utility model is beneficial to improving its vibration performance and frequency coverage. Compared with the original flat base plate, the arched cross-section has greater stiffness than the flat plate. Its support stress consists of vertical tensile, compressive and horizontal push-pull stresses. The equilibrium restoring force during vibration is its own elastic restoring force. Only tensile or compressive stress appears in the same micro-unit cross-section, and the stress diagram is a uniform rectangle. The stretching of elastic deformation is a "membrane" stress form. From the perspective of the dynamic effect of the geometric shape, the curvature of the arched plate is easy to excite more complex higher-order modes. Its fundamental frequency (lowest natural frequency) is higher than that of the flat plate. At the same time, the complex curvature is easy to form a relative dispersion of the structure's natural frequencies. The arched structure improves its suitable vibration bandwidth through geometric shape, stiffness, fundamental frequency enhancement, and membrane effect.

[0129] exist Figure 3 In the cross-sectional diagram of the base plate, sections AA and CC represent the middle section of the large and small sound chambers; these are arched, ribbed sections. Section DD is the sound source sound chamber section, which is an arched, unribbed section. Section BB shows the boundary between the large and small sound chambers. The boundary between the large and sound source sound chambers is also similar; there is no arch at the junction of the two sound chambers. The arches on both sides gradually rise as they approach the boundary until the boundary is flush with the plate surface. This creates a bamboo tube effect connecting the sound chambers, enhancing rigidity.

[0130] V. The base plate of this utility model is as follows Figure 2 , 3 As shown in Figure 5, multiple sound holes 11 are respectively provided on the base plate 2 in the middle of the large sound hole 4.2, the middle of the small sound hole 4.3, and the area between the large sound hole 4.2 and the small sound hole 4.3. The sound holes 11 replace the existing dragon pool and phoenix pond on the base plate 2 of the guqin (as shown in Figure 5). Figure 5 ).

[0131] The small soundbox 4.3 has five pairs of tone holes 11 in the middle, symmetrically arranged along the central axis. Each pair includes two tone holes symmetrically arranged on both sides of the center line in the width direction of the base plate. Six tone holes 11A are arranged along the edge of the small soundbox, and four tone holes 11B are symmetrically arranged in the middle. The diameter of 11A1 is 8mm, and the center-to-center distance a is 110mm. The distance d between the center of the two tone holes 11A1 in the first pair and the end of the small soundbox 4.3 located at the tail is 145mm. The two tone holes 11B in the second pair are located on the side closer to the large soundbox 4.2, and the diameter of the two tone holes 11B in the second pair is 6mm, and the center-to-center distance c is 30mm. The horizontal distance b between the centers of the first pair of tone holes and the second pair of tone holes is 20mm. mm; the third pair of tone holes 11A2 are located on the side near the large soundbox, and the diameter of the two tone holes is 8-10 mm, the center distance a is 110 mm, and the horizontal distance b between the center of the second pair of tone holes and the center of the third pair of tone holes is 20 mm; the two tone holes 11B of the fourth pair are located on the side near the large soundbox 4.2, and the diameter of the two tone holes 11B of the fourth pair is 6 mm, the center distance c is 30 mm, and the horizontal distance b between the center of the third pair of tone holes and the center of the fourth pair of tone holes is 20 mm; the fifth pair of tone holes 11A3 are located on the side near the large soundbox, and the diameter of the two tone holes is 8 mm, the center distance a is 100 mm, and the horizontal distance b between the center of the fourth pair of tone holes and the center of the fifth pair of tone holes is 20 mm.

[0132] The tone holes 11C between the large groove 4.2 and the small groove 4.3 are a pair, specifically two tone holes symmetrically arranged on both sides of the center line in the width direction of the base plate 2. The diameter of the tone holes 11C is 6mm. The horizontal distance e between the center of the two tone holes 11C and the center of the fifth pair of tone holes 11A3 in the middle of the small groove 4.3 is 115mm, and the center distance between them is 30mm.

[0133] The large soundbox has seven pairs of tone holes in its center. Seven tone holes are symmetrically arranged on each side of the center line along the width of the base plate. The seven tone holes on the side furthest from the player are arranged along the length of the base plate, arranged from left to right as follows: tone holes 11D, 11E, 11F, 11G, 11H, 11J, and 11k. The diameters of 11D and 11K are 6-8mm, 11G and 11J are 6mm, 11E and 11H are 8mm, and 11F is 8-10mm. The horizontal distance m between the center of the first tone hole 11D and the centers of the tone holes in the large and small soundboxes is 146mm. The horizontal distance g between the centers of the first tone hole 11D, the second tone hole 11E, and the third tone hole 11F is 40mm. The horizontal distance k between the centers of the holes 11F and 11G, 11G and 11H, 11H and 11J, and 11J and 11k is 20mm. The distance f between the center of the holes 11D and 11H and the center line of the width direction of the base plate is 64mm. The distance t between the center of the holes 11E and 11K and the center line of the width direction of the base plate is 73mm. The distance n between the center of the hole 11F and the center line of the width direction of the base plate is 70mm. The distance c / 2 between the center of the holes 11G and 11J and the center line of the width direction of the base plate is 15mm.

[0134] The seven tone holes in the middle of the large soundbox, located on the side of the performer, are arranged symmetrically with the aforementioned tone holes.

[0135] The design principle behind the position and diameter of the aforementioned tone hole 11 is as follows: When a string is plucked, it creates a wave-like oscillation. The node with the largest oscillation displacement is called an antinode; the node whose displacement remains zero is called a node. The fixed points at both ends of the string are always nodes. When the wave-like oscillation is transmitted to the ends of the string, it is reflected back. The reflected wave superimposes with the wave that is being transmitted, causing the antinode to increase in size due to the superposition. This process repeats, forming a standing wave (a bounded string will always form a standing wave). The standing wave is the basic physical phenomenon of resonance. The 18th-century Chladni experiment involved scattering sand grains on a flat plate fixed at its perimeter or center and vibrating it—a two-dimensional wave-like vibration. The sand grains were driven away by the large amplitude vibration of the antinodes and gradually gathered at the stationary nodes, forming geometric patterns. Different vibration frequencies resulted in different positions of the antinodes and nodes, creating different geometric patterns. Historically, the Chladni experiment was used to study the audio vibration characteristics of the violin to optimize the design of the soundbox shape, tone hole position, and size. When we add sound holes to the bottom plate of the guqin, we must consider placing them in the common node region of all its frequencies. Based on the Chladni experiment, we can confirm that the edge of each groove on the bottom plate is definitely the common node region of all the frequencies of the guqin, and placing the sound holes there will not affect the vibration frequency function of the bottom plate.

[0136] Secondly, the vibration of the strings is conducted through the soundbox and enters the air cavity, forming a three-dimensional standing wave. Air is a fluid medium, and its particles exhibit elastic restoring force during vibration, but not tangential restoring force. This means that fluid particles only push and shove forward and backward, without pulling or stretching left or right. This causes the direction of sound wave propagation to align with the direction of particle vibration, resulting in a more focused and concentrated sound energy, characteristic of longitudinal sound wave propagation. The changes in density of its tiny volume elements can be described by sound pressure, density, and particle velocity. The linear acoustic equation of state for the amplitude sound wave of tiny particles is P = v. 2 q'. Additionally, during sound wave propagation, the air medium can experience significant acoustic impedance due to abrupt changes in sound pressure and density at certain locations caused by the relatively high sound energy of individual audio frequencies or spatial variations in the propagation path. The acoustic impedance ratio Zs is equal to the sound pressure p at that location divided by the velocity v of the protons at that location, Zs = p / v. These characteristics require attention during sound wave propagation and resonance within the sound chamber. For example, at the footwell outlet at the junction of the large and small sound chambers, due to the definite directional nature of sound wave propagation, the sound waves in the central path of the sound chamber will travel straight downwards, while the propagation paths on the left and right sides will be bent by the sidewalls of the large sound chamber and enter the small sound chamber obliquely. Multiple paths form a cross-shaped intersection at this outlet, and the superposition of antinodes of multiple phases increases the sound pressure p and slows down the velocity v at that point, thus increasing the acoustic impedance ratio Zs. This affects individual notes within the small sound chamber. To address this, adjusting the sound by opening a sound hole at the junction of the large and small sound chambers can be considered.

[0137] In addition, in order to ensure the integrity of the antinode region of the base plate and the smooth conduction path, the Dragon Pool and Phoenix Swamp were removed, which changed the local audio of the third, fourth and fifth strings from the original transparent to the muffled. Fewer and smaller sound holes can be opened in the middle of the base plate groove to adjust the sound field pressure.

[0138] Finally, from the perspective of wooden stringed instrument making, while theoretical guidance is certainly important, due to the vast differences in wood properties, different materials will have different acoustic and physical properties. The soundholes must be "positioned according to the tone and adjusted according to the sound." For different types of wood, different numbers and sizes of soundholes can be determined. Using soundholes allows for a certain degree of adjustment space and reversibility. The soundhole diameter can be reduced by using plugs or sleeves to assess the changes in the sound. Plugs and sleeves can be used for tuning during the initial wood preparation, after assembly, and during the lacquer application. Even after the instrument is finished, plugs and sleeves can be used for further adjustments. This adds another tuning method to the existing methods of selecting good materials, crafting the instrument, carving the wood, and applying the lacquer.

[0139] VI. This utility model adopts a bending and lowering design of the base plate (e.g., Figure 12 ).

[0140] The bottom plate 2 on the right side of the dividing line between the sound source cavity 4.1 and the large cavity 4.2 is tilted downward at an angle of 3°, which increases the spatial height of the instrument head inside the sound source cavity and forms a complete and equal-height golden spiral sidewall, which enhances the sidewall reflection of sound waves and the formation of standing waves inside the sound source cavity.

[0141] The specific bending process is as follows: At the boundary line between the sound source cavity 4.1 and the large cavity 4.2 base plate 2, cut the base plate at approximately 70°; fold the sound source cavity base plate 3° with the "0" point as the center; attach a vertically grained wood sliver to the beveled surface of the cut base plate, sand it to a 3° angle, and then glue the base plate on; glue the triangular pads to the edge of the sound source cavity according to the grain requirements, sand the pads to a 3° bevel, and glue them firmly to the base plate; finally, sand and finish to form a sealed structure between the panel 1 and the base plate 2. This process is used because the strength of a simple vertical cross-section connection is often lower than the strength of a uniform cross-section, so a 70° beveled overlap is generally used to avoid future joint cracks.

[0142] Explanation of the arrangement of the first and second bowing movements during violin making (e.g.) Figure 6In traditional guqin, to ensure comfortable fingering and reliable string contact for the left hand, and to prevent strings from rubbing against the soundboard outside the pressing points, specific requirements were established for the height of each string from the soundboard and the curvature of the soundboard itself – known as the "string path." However, on the left side of the bridge, the right-hand plucking area needs to maintain sufficient plucking space, requiring the strings to maintain a certain height from the soundboard. Therefore, the strings typically begin to bend downwards from the second and a half frets, decreasing by about 9-10mm at the bridge, equivalent to approximately 3°, known as the "first bow." The second bow occurs at the head of the guqin, specifically the area from the edge of the bridge towards the end of the head. Traditionally, the head is mostly solid; the second bow is for aesthetic purposes, and its height varies depending on the guqin style.

[0143] This utility model incorporates a sound source groove, as described in the previous patent. The horizontal peak line at the highest point of the panel is defined as the dividing line between the sound source groove and the large groove. The sound source groove is 275mm long. The horizontal line of the string rest on the bridge is 195mm away from the peak line (the position of the second fret is one-sixth of the effective string length of 1100mm, which is 185mm, i.e., 10mm outside the second fret). The head is lowered by 10mm, and the head-down angle is approximately 3°. Calculating with a height h1 = 15mm at the string rest point b on the fourth string bridge, draw a string tension line at a 72° angle to the vertical line of the bridge through point b. This is the 18° line required for the second bow dip. The 18° line intersects the 3° line at point m, which is approximately 66mm from the string rest point on the bridge and approximately 14mm from the inner wall of the soundbox. Starting from point m, bow downwards at an 18° angle, accompanied by a 3° bow dip of the soundbox bottom plate. The bottom plate is parallel to the first bow dip line of the soundboard, thus achieving a roughly equal height in the soundbox space (e.g., Figure 12 ).

[0144] VII. The horizontal distance between the resting point b of the string 3 and the bridge 6 and the left side of the top of the bridge 6, after dynamic stability calculation of the bridge, is adjusted to 5.2mm. The string 3 on the right side of the bridge is tilted downwards to form an inclined section 3.1, which forms a 72° angle with the vertical line of the bridge 6 (i.e., an 18° second-downward line) and a 162° tension angle with the string 3 on the left side of the bridge 6 (e.g., as shown in the figure). Figure 13 ).

[0145] This invention changes the corner angle of string tensioning, significantly reducing the resultant force of string tensioning, the static friction force at the end of the bridge 6, and the overturning moment. It eliminates the string tensioning mode of the velour buckle and the tuning peg. Because the direction of the resultant force is closer to vertical, the transmission of the main vibration frequency is more focused on the radial phase of the horizontal grooves on the soundboard, making the path simpler and the structure more reasonable.

[0146] C. Mechanical analysis and verification of the stability of the bridge with a 162° tensioned cable of this utility model:

[0147] Verification of the stability of the bridge under static state with a tension of 162° (e.g., Ca, 162° tension) Figure 14 In the diagram, the position of point b, the chord resting point at the top of the mountain, is determined to be 5.2 mm to the right. The distance between F1 and point a at the base of the mountain is h1 = 15 mm, therefore the overturning moment M1 of F1 about point a is M1 = h1M1. The distance h3 between F2 and point a requires connecting point a and endpoint j of F2, and drawing a circle with aj as its diameter intersecting the extension of the b-end of F2 at point f. Connecting af forms the distance line from F2 to point a (the inscribed angle of the diameter is a right angle). af intersects the top of the mountain kb at g, resulting in two similar right triangles with acute angles of 18°, fbg and akg.

[0148] Where: ag = ak / cos(18°) = 15 / cos(18°)

[0149] kg=ak tan18°=15tan18°=4.874,

[0150] gb = 5.2 kg

[0151] fg = bg sin(18°)

[0152] h3=af=ag+gf=15 / cos(18°)+(5.2-15tan(18°))=15.873

[0153] Then the stabilizing torque M2 = h3F2 = 15.873F2

[0154] The torque M around point a is balanced as follows: Torque balance around point a

[0155] Torque balance around point a: ∑Ma=M1+M2≥0

[0156] The overturning moment M1 generated by string F1 is M1 = F1 * h1

[0157] The stabilizing torque generated by string F2 is M2 = F2 * h3

[0158] We get M1 + M2 = (-15 + 15.873)F1 = 0.873F1 ≥ 0, which gives us the stability of Yueshan.

[0159] Find the resultant force Fh of F1 and F2.

[0160] Since the ∠bjc of an equilateral rhombus is 18°

[0161] Therefore, the resultant force on the strings Fh = 2F1sin(18° / 2) = 0.3129F1∠β = 90° - 72° - 9° = 9°

[0162] The stability of the bridge under Cb, with the string tension and slack states at 162° is verified as follows (e.g., ...). Figure 15 , 16 ):

[0163] Since Δf ≥ Fm' (see the previous calculation for the 90° string tension angle),

[0164] Therefore, Δf ≥ Fm' = μFh'

[0165] In triangle bcj, bc = (F² + Δf) * cos72° and cj = (F² + Δf) * sin72°.

[0166] cd = cj - F1 and F1 = F2

[0167] Therefore, Fh' = √(bc² + cd) 2 )=√(((F2+Δf)cos72°)2+((F2+Δf)sin72°-F1)2)

[0168] Let F2 = 1

[0169] ∵Δf≥μ√(((1+Δf)cos72)2+((1+Δf)sin72-1)2)

[0170] Where: Δf is the increase in string tension when tuning F2, Fm' is the instantaneous static friction force, μ is the static friction coefficient, and Fh' is the instantaneous resultant force generated when the string tension F1 remains constant and the tuning force F2 increases by Δf.

[0171] Therefore, when the loop fastener is tightened, Δf ≥ +0.08411F2.

[0172] When the fleece button is loosened, Δf ≥ -0.07758F2

[0173] That is, tightening F2 increases the stability of the bridge; loosening F2 reduces the stabilizing torque. However, since the Δf of loosening a single string is very small, the stability risk is less than the overturning torque increment when all seven strings are plucked simultaneously in the next section. Therefore, the verification is shown in the next section.

[0174] Cc, Verification of the stability of the bridge when the string is stretched to 162° (e.g.) Figure 17 Because the improved bridge uses a design where the bottom of the first and seventh strings are suspended from the soundboard, the stability is verified by using the overturning torque of plucking all seven strings simultaneously at F1' to balance the balancing torque formed by the bonding of the bottom of the bridge to the soundboard with the seven 72° tensioned strings plus the five strings.

[0175] Since ∑Ma=7*(M1+M2)+5*M3≥0

[0176] ∵M1=(F1+Δf)*h1=1.25*15F1=-18,75F1=-1628.06Nmm

[0177] M2=F2*h3=15.873F2=1378.25Nmm

[0178] M3=0.5*10*20*√50 / 2=353.55Nmm

[0179] Substituting ∑M=7*(1378.25-1628.06)+5*353.55=19.08Nmm≥0, Yueshan is stable.

[0180] Where: ∑Ma is the sum of all moments around point a of the bridge, M1 is the dynamic overturning moment of the horizontal string, M2 is the balancing moment of the static tension of the string at 72°, M3 is the balancing moment generated by the bonding force of the five strings at the bottom of the bridge (see the 90° string tension verification section for detailed calculation), and Δf is the maximum increase in string tension when the horizontal string is plucked, calculated as 0.25F1.

[0181] The string rest point is usually set in the center. Here, the string rest point is set at 5.2mm to meet the theoretical calculations for the stability adjustment of the bridge. The 0.2mm shift increases the distance from the 72° string to point a on the bridge, so that when all seven strings are plucked at maximum tension, the bonding force at the bottom of the bridge of only five strings can work together with M2 to achieve a stable balance of the bridge.

[0182] Additionally: Assuming F1 = 1, find the maximum instantaneous resultant force of a single string during playing.

[0183] maxFh=F1*√((sin18°)2+(1.25-cos18°)2)

[0184] maxFh=0.43F1

[0185] Find the angle of maximum resultant force at instantaneous moment.

[0186] ∠β=arctan(dc / bc)=arctan(1.25-cos(18°)) / (sin18°))=44.05°

[0187] Bd, the frequency transmission path of a 162° tensioned string (e.g.) Figure 18 ):

[0188] When the string is at rest, the resultant force between the string and the string loop is Fh = 0.3129F1, and the angle between the string and the vertical line of the bridge is 9°. When the string is plucked, the maximum resultant force is maxFh = 0.43F1, ∠β = 44.05°, and the dynamic range of the resultant force is 35°. Under normal string plucking frequency and playing intensity, the magnitude of Fh and ∠β will tend to be smaller. Therefore, the 162° string tension reduces the initial pressure on the bridge and makes the main transmission path simpler, closer to vertical, wider in area, and with increased throughput.

[0189] Ce, the following is a comparison table of various data between the 162° tension of this utility model and the existing 90° tension:

[0190] Static resultant force Fh 1.414F1 0.3129F1 The maximum resultant force Fh' of plucking 1.601F1 0.43F1 ∠β' interval 51°-45°＝6° 44.05°-9°＝35° Static ΔM = M1 + M2 -5F1 0.876F1 Pluck ΔM=M1+M2 -8.75F1 -2.877F1 M3 value is needed to obtain stability in Yueshan. 7(m1+m2) requires Yueshan embedding. 5m1 The maximum Δf of tightening the string +0.4378509F2 +0.08411F2

[0191] Analysis of the data in the table shows that: In the existing technology, point b of the 90° string tension is located at the corner of the bridge top. It is necessary to use the method of using a velvet peg to tension and tune the string. The resultant force generated is large in value, has a large directional tilt, and a small dynamic resultant force variation range. The overturning moment of the static and dynamic bridge stability balance ΔM = M1 + M2 is large. It is necessary to fix the m2 generated by the bridge to ensure the stability of the bridge. The string tension increment Δf is large when tightening the string, reaching +0.4378509F2. Therefore, a velvet peg must be used instead of a peg in the section where the string bears the greatest frictional resistance.

[0192] Point b, with a 162° string tension, is located slightly off-center at the top of the bridge. It generates a small resultant force, a small directional tilt, and a large dynamic range of force variation. The overturning moment of the static and dynamic bridge stability balance ΔM = M1 + M2 is small; only the m1 generated by the bonding force at the bottom of the five strings is needed to ensure bridge stability. The increase in string tension Δf is small, only +0.08411F2. These results create favorable conditions for improving the soundbox design, refining the string tensioning method, maintaining the integrity of the soundboard, and optimizing bridge stability. This series of improvements further makes the stress distribution on the body structure surrounding the bridge more rational, and the vibration frequency transmission path more optimized and simplified.

[0193] The structural design of the 162° tensioned bridge section of this utility model (as shown in the figure) Figure 19 In addition to the suspension of the first and seventh strings as described in the previous patent, this utility model determines that the string resting point at the top of the cross-section of the Yueshan is located in the middle of the direction of the qin's head. Specifically, the Yueshan is 10mm wide, and the string resting point is 5.2mm horizontally from the top corner of the qin's tail towards the qin's head. That is, the distance from the string resting point to the corner of the Yueshan in the direction of the qin's head is 4.8mm. The string resting width is 1mm wide on each side of the resting point b as the center, forming a resting band with a width of 2mm. The horizontal line of the resting center is 80mm away from the inner wall of the qin's head end of the sound source groove. The resting band is connected by a 1.5mm drop from the top corners of the Yueshan cross-section to form a slope of more than 20° to prevent the strings from rubbing against each other when tensioned.

[0194] The lower part of the bridge is embedded in the diaphragm, with each side of the diaphragm extending 6mm beyond the bridge, for a total width of 22mm and a horizontal length of 123mm. The diaphragm is positioned horizontally based on the horizontal line of the bridge and the four strings as the longitudinal center positioning reference. The positioning is glued to the soundboard. After the glue has solidified, a groove is cut into the bridge to embed it. The groove depth is only 2.5mm of the thickness of the diaphragm board. After cutting the groove, the bridge is glued into the groove. Since the projected area of ​​the diaphragm on the soundboard is much smaller than that of the existing method, the initial constraint on the soundboard of the sound source groove is reduced.

[0195] The setting of the hook-string bracket at the goose foot of this utility model (such as...) Figure 20The string hook bracket is a U-shaped bracket with seven string hooking slots at the bottom. The upper part of each slot is a circular hole for threading the string, and the lower part contains slots of varying widths depending on the string diameter. When using the instrument, adjust the direction according to the string order. Place both ends of the bracket against the goose-foot handle, using the fourth string position as the center point. Align the bracket with both ends of the base plate. Due to the arched shape of the base plate, place a thick rubber pad underneath. After positioning, use small screws to pass through the small holes at both ends of the bracket to secure it to the goose-foot handle. Stringing begins with the fourth string, then strings are symmetrically attached. Before hooking the string, tie a small knot at an appropriate position at the end of the string. Thread the string through the string hole and pull it to the knot position, securing it in the string hooking slot. Then, wind the string through the bridge to the soundboard, and after passing the nut, wind it clockwise around the corresponding winding peg. Generally, three or four turns are sufficient to thread the string through the string hooking hole and secure it.

[0196] This utility model relates to a winding shaft, which is a string winding component (such as a worm gear screw knob) mounted on the bridge of a violin. Figure 20 The seven tuning pegs are assembled on a tuning peg bracket, which is installed within a 25mm range at the head of the instrument. In order to squeeze out 25mm for the tuning peg bracket, the length of the head and tail of the guqin was adjusted. The tail was shortened from the original 55mm to 35mm (the dragon teeth are limited to within 10mm). The width around the sound source cavity is left 10mm according to the "narrow edge" requirement, and 5mm is squeezed out to leave a total of 25mm, keeping the total length of the instrument unchanged at 1235mm. The effective string length after verification is 1110mm.

[0197] The installation of the knob assembly in this utility model (such as...) Figure 21 Because the string angle on the instrument's head is 72°, which corresponds to the second 18° tilt, the tuning pegs are installed at an 8° angle to reduce the angle between the strings and the tuning pegs. A hardwood protective plate is attached to the protruding part of the tuning pegs on the head. For the specific instrument-making sequence, see [link to instrument-making instructions]. Figure 21 The first step in installing the tuning pegs is to cut the first 3° dip of the headboard. The second step is to cut the second 18° dip of the headboard along the horizontal line m, the starting point of the second dip, and then trim the headboard end at an 8° angle. The third step is to carve the tuning peg chamber at an 8° angle, attach the hardwood tuning peg headboard guard, and drill seven tuning peg holes at an 8° angle. The fourth step is to temporarily fix the base plate and drill the installation and maintenance slot holes in the base plate. The fifth step is to assemble the body with the base plate, apply varnish, install the turbine screw assembly, install the slot hole cover plate, and the entire piano is now made and installed.

[0198] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0199] Finally, it should be noted that the above description is only a preferred embodiment of this utility model and is not intended to limit this utility model. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A guqin bottom plate, the bottom plate is provided with a slot abdomen, the slot abdomen includes a sound source slot abdomen, a large slot abdomen and a small slot abdomen, and is arranged in the order of guqin forehead to guqin tail direction, characterized in that: The base plate is provided with several sound holes located in the middle and on both sides of the large and small grooves, and between the large and small grooves, replacing the existing dragon pool and phoenix pond on the base plate of the guqin.

2. The bottom plate of a Chinese zither according to claim 1, characterized in that: The seven tone holes in the middle of the large soundbox, located on the side of the player, are arranged symmetrically with the seven tone holes on the side away from the player.

3. The bottom plate of a Chinese zither according to claim 1, characterized in that: The small soundbox has five pairs of tone holes, symmetrically arranged along its central axis. Each pair includes two tone holes symmetrically positioned on either side of the center line of the baseboard's width direction. The center-to-center distance of the first pair of tone holes is 110mm, and the horizontal distance between the centers of the two tone holes in the first pair and the end of the small soundbox located at the tailpiece is 145mm. The second pair of tone holes is located on the side closer to the large soundbox, with a center-to-center distance of 30mm, and a horizontal distance of 20mm between the centers of the first and second pair of tone holes. The third pair of tone holes is also located on the side closer to the large soundbox, with a center-to-center distance of 110mm. The horizontal distance between the center of the third pair of tone holes and the center of the second pair of tone holes is also 20mm; the fourth pair of tone holes is located on the side closer to the large soundbox, with a center-to-center distance of 30mm between the two tone holes, and the horizontal distance between the center of the fourth pair of tone holes and the center of the third pair of tone holes is 20mm; the fifth pair of tone holes is also located on the side closer to the large soundbox, with a center-to-center distance of 100mm between the two tone holes, and the horizontal distance between the center of the fifth pair of tone holes and the center of the fourth pair of tone holes is also 20mm; there are two tone holes between the large and small soundboxes, symmetrically arranged on both sides of the center line in the width direction of the base plate, with the center of the two tone holes between the large and small soundboxes... The horizontal distance between the centers of the five pairs of tone holes in the middle of the small soundbox is 115mm, and the center distance between the two tone holes is 30mm. The middle of the large soundbox has seven pairs of tone holes, symmetrically arranged on both sides of the center line in the width direction of the base plate. The seven tone holes on the side furthest from the player are spaced apart along the length of the base plate. The horizontal distance between the center of the first tone hole and the centers of the tone holes in the large and small soundboxes is 146mm. The horizontal distance between the center of the second tone hole and the center of the first tone hole, and between the center of the third tone hole and the center of the second tone hole, is 40mm. The fourth tone hole... The horizontal distance between the center of the first tone hole and the center of the third tone hole, the center of the fifth tone hole and the center of the fourth tone hole, the center of the sixth tone hole and the center of the seventh tone hole is 20mm. The distance between the center of the first tone hole and the fifth tone hole and the center line of the width direction of the base plate is 64mm. The distance between the center of the second tone hole and the seventh tone hole and the center line of the width direction of the base plate is 73mm. The distance between the third tone hole and the center line of the width direction of the base plate is 70mm. The distance between the center of the fourth tone hole and the sixth tone hole and the center line of the width direction of the base plate is 15mm.

4. The bottom plate of a Chinese zither according to claim 1, characterized in that: The base plate has an arched cross-section.

5. The bottom plate of a Chinese zither according to claim 1, characterized in that: The dividing line between the sound source groove and the large groove is located on the bottom plate, which is tilted downwards on the side near the head of the guqin.

6. The bottom plate of a Chinese zither according to claim 1, characterized in that: A reinforcing rib is fixed to the middle of the base plate in the width direction of both the large and small grooves.

7. The bottom plate of a Chinese zither according to claim 6, characterized in that: The reinforcing rib has a width of 15mm and a thickness of 15mm.

8. A modified guqin, comprising a face plate, a bottom plate, strings arranged on the face plate, Yue mountains arranged on one side of the face plate through Chenglu for supporting the strings, and hook string supports arranged on the Yan feet of the bottom plate for fixing the strings, characterized in that: The improved guqin has a guqin baseboard as described in any one of claims 1-7.

9. The improved Chinese zither according to claim 8, characterized in that: The distance between the resting point of the string on the bridge and the inner edge of the groove on the side away from the head of the guqin is 80mm. At one end of the guqin's head panel, there is a string tension adjuster corresponding to each string. The winding shaft of the string tension adjuster extends upward from the panel. The string on the side of the head of the guqin rests on the bridge and its end is connected to the winding shaft of the corresponding tension adjuster. The string between the bridge and the string tension adjuster is tilted downward and forms a 72° angle with the vertical line of the bridge.

10. The improved Chinese zither according to claim 8, characterized in that: The base plate and the front plate are made of the same material. When making the base plate, the board material is first processed into shape, then putty is used to fill and color is adjusted, and finally paint is applied to obtain the product.

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