Violin chinrest acoustic boundary control device

Abstract

The application discloses a violin lower jaw support acoustic boundary control device and belongs to the technical field of musical instrument acoustics engineering. The device comprises a lower jaw support main body and an integrally formed elastic layer arranged on the contact surface of the lower jaw support main body and the lower jaw of a performer. The elastic layer is made of silica gel or microporous polyurethane, has a Shore A hardness of 30-50, a thickness of 1-3 mm, a loss factor tan delta of 0.1-0.3, and an arc surface with a curvature radius of 30-40 mm. The surface is provided with an array of solid hemispherical micro convexities (not less than 8, a diameter of 1.5-2.5 mm, a height of 0.3-0.8 mm, and a spacing of 3-5 mm). The dynamic stiffness change rate under a 10-20 N cyclic clamping force is not more than 20%. The low stiffness acoustic impedance mismatch of the elastic layer is used to reflect the medium and high frequency vibration energy of 2-8 kHz of the violin body back to the violin body, thereby reducing the dissipation through the human body. The actually measured sound pressure level in the 2-8 kHz frequency band is increased by 2.1 dB.

Description

Technical Field

[0001] This invention belongs to the field of acoustic engineering technology for musical instruments, specifically relating to an acoustic boundary control device for the chin rest of a violin. Background Technology

[0002] The acoustic energy transfer path of a violin is as follows: string vibration → bridge → top plate → back plate → sides → air radiation. The player holds the violin with a chin rest. The vibration of the violin is transmitted to the chin rest through the sides, and can be absorbed and dissipated by the human body through the contact interface between the chin rest and the chin, resulting in the attenuation of mid-to-high frequency overtones.

[0003] Traditional violin chin rests (such as those from brands like Kun and Wittner) are designed for ergonomic comfort, with contact surfaces typically made of maple, plastic, or hard rubber (Shore A hardness greater than 70), without any consideration for the acoustic performance of the contact surfaces.

[0004] US Patent 6,927,328 discloses a violin chin rest pad system for supporting a standard chin rest, designed to reduce damping of the violin's vibrations caused by the chin rest clamping. It should be noted that this solution addresses the clamping interface between the chin rest and the violin body, without incorporating any elastic reflective structures on the surface where the chin rest contacts the player's chin; it also does not specify acoustic parameters such as the hardness, thickness, and loss factor of the pad material, does not address the contact surface curvature design or micro-convex array structure, and does not establish parametric design specifications for frequency-domain selective reflection.

[0005] US Patent 7,476,789 discloses a custom-molded violin chin rest with a removable, flexible silicone top piece bonded to a rigid, flat base. The design aims to enhance comfort by conforming to the shape of the player's chin. While the silicone top piece is located on the surface of the chin rest that contacts the body, it is bonded to the base rather than being integrally molded. The contact surface is a custom-designed conformal surface without an array of micro-convex structures. Acoustic parameters such as the radius of curvature, material hardness, loss factor, and dynamic stiffness under cyclic loading are not defined. Its design purpose is comfort rather than acoustic boundary control.

[0006] US Patent 10,360,879 (ArcRest Shoulder Support) discloses a violin shoulder support with four silicone support points located between the shoulder support and the user's shoulder to distribute pressure. The shoulder support is rigidly connected to the violin body, and the silicone support points do not participate in the acoustic boundary control of the violin's vibration. The Swiss DOLFINOS support system uses EPDM or memory foam pads located between the shoulder support and the user, designed to reduce contact area and provide damping to prevent over-resonance. The elastic elements in the above solutions are not located at the chin rest contact interface with the chin, nor does the parametric structure of this invention disclose this invention.

[0007] In the field of audio engineering, there are flexible vibration-damping feet (such as ISO Acoustics OREA), designed to isolate the equipment enclosure from external vibrations, i.e., to achieve enclosure stillness. The resonating chamber of a musical instrument is the sound-producing body itself; therefore, applying the vibration isolation logic to the instrument's support interface has the opposite physical goal. Actual measurements show that when a speaker foot material with a Shore A hardness of 20 is bonded to the contact surface of a traditional chin rest, the sound pressure level of a violin in the 2-8kHz frequency range decreases by 0.9 dB compared to a traditional rigid chin rest (see Comparative Example 1 for details).

[0008] In summary, existing technologies have failed to provide a parameterized low-stiffness elastic reflective structure at the violin chin rest-human contact interface. Summary of the Invention

[0009] The technical problem to be solved by this invention is that existing violin chin rests only focus on ergonomic comfort, and a large amount of high-frequency vibration energy of the violin body is dissipated through the chin rest-human interface, resulting in damage to the integrity of overtones.

[0010] To address the aforementioned problems, this invention provides an acoustic boundary control device for a violin chin rest, comprising: a chin rest body for connecting to the tailstock side plate of the violin and providing chin support; an elastic layer disposed on the surface of the chin rest body that contacts the player's chin, made of silicone or microporous polyurethane, with a Shore A hardness of 30-50, a thickness of 1-3 mm, and a loss factor tanδ of 0.1-0.3; the contact surface of the elastic layer is arc-shaped with a radius of curvature R of 30-40 mm; the contact surface is provided with an array of solid hemispherical micro-protrusions, the number of which is not less than 8, with a diameter of 1.5-2.5 mm, a height of 0.3-0.8 mm, and a center-to-center distance of 3-5 mm between adjacent micro-protrusions; the elastic layer and the chin rest body are integrally formed; the dynamic stiffness change rate of the elastic layer under a cyclic clamping force of 10-20 N does not exceed 20%.

[0011] Preferably, the elastic layer has a Shore A hardness of 35-45; a thickness of 1.5-2.5 mm; a radius of curvature R of 35 mm; a compression rate of 15%-35% under a clamping force of 10-20 N; a thickness to radius of curvature ratio of 1:15 to 1:20; and a sound impedance ratio of the elastic layer to the sound impedance of the side panel of the instrument body of 1:4 to 1:18.

[0012] The technical principle of this invention is as follows: When a vibration wave originates from the side panel of the instrument body (maple / spruce, acoustic impedance Z3≈8.5×10⁻⁶), 6 The acoustic impedance Z1 of the chin rest (kg·m⁻²·s⁻¹) is transmitted through the chin support body to the elastic layer (Shore A 30-50 silicone, with an acoustic impedance Z1 of approximately 0.5-2.0×10⁻¹). 6 kg·m⁻²·s⁻¹ (measured value), then reaching human tissue (acoustic impedance Z2≈7.55×10⁻¹). 6When Z1 is much smaller than Z2 (kg·m⁻²·s⁻¹, as recorded in the literature), a significant acoustic impedance mismatch occurs at the interface between the elastic layer and the human body. According to the law of sound wave reflection R=[(Z2-Z1) / (Z2+Z1)]², for Shore A 40 silicone (Z1≈0.88×10⁻¹), the acoustic impedance mismatch is calculated as follows: 6 The corresponding reflection coefficient R≈0.63; R≈0.77 at Shore A30; R≈0.34 at Shore A50. A reflection coefficient of not less than 0.5 corresponds to a Shore A range of approximately 30-45. The ratio of acoustic impedance between the elastic layer and the side panels of the instrument body is approximately 1:4 to 1:18 in the Shore A 30-50 range (approximately 1:9.7 at Shore A40).

[0013] The function of the array of solid hemispherical micro-convexities is as follows: each micro-convexity forms an independent elastic contact point after being compressed, and the gaps between the micro-convexities prevent the lateral coupling propagation of vibration waves; the solid structure ensures that vibration energy propagates within the micro-convexities as a continuous elastic medium, avoiding dissipation in cavities. During performance, the jaw clamping force dynamically changes within the range of 10-20N with the movement. The geometric nonlinear elastic response of the micro-convex array (low stiffness in the initial stage of compression, and increased stiffness when approaching full compression) keeps the dynamic stiffness change rate within 20%, ensuring the stability of acoustic boundary performance throughout the performance.

[0014] The beneficial effects of this invention are as follows: measured sound pressure level in the 2-8kHz frequency band is increased by 1.8-2.1dB, and vibration velocity of the back plate of the instrument is increased by 37.5%; no modification to the instrument body is required, only replacement of accessories is needed; the one-piece molded structure eliminates sound energy loss at the bonding interface; and the acoustic performance is stable under cyclic load. Attached Figure Description

[0015] Figure 1 A schematic diagram of the overall structure of the acoustic boundary control device for the violin chin rest; Figure 2 This is a cross-sectional view of the assembly of the elastic layer and the chin support body; Figure 3 This is a diagram illustrating the principle of sound wave reflection. Figure 4 A magnified view of a portion of an array-type solid hemispherical micro-convex structure; Figure 5 A comparison diagram of vibration energy transfer paths; Figure 6 A comparison chart of measured sound pressure levels in the 2-8kHz frequency band; Figure 7 This is a comparison chart of the rate of change of dynamic stiffness under cyclic loading.

[0016] In the diagram: 1-Jaw support body; 2-Elastic layer; 3-Side panel of the instrument body; 4-Micro-convex; 5-Integrated molding interface. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the accompanying drawings.

[0018] [Example 1: Standard Performance-Grade Violin Chin Rest] like Figures 1 to 4 As shown, the main body 1 of the maple violin chin rest is polished with 400-grit sandpaper until Ra≤3.2μm. An elastic layer 2 (integrated bonding interface 5) with a thickness of 2mm and a contact surface radius of curvature R=35mm is integrally molded onto the contact surface using liquid silicone with a Shore A hardness of 40 through a molding process. The elastic layer has a loss factor tanδ=0.15 and 12 solid hemispherical micro-protrusions 4 (distributed within a 20mm×30mm contact area), each with a diameter of 2mm, a height of 0.5mm, and a center-to-center spacing of 4mm. The acoustic impedance of the elastic layer Z1≈0.88×10⁻⁶. 6 The ratio of kg·m⁻²·s⁻¹ to the acoustic impedance of the side panel of the instrument body is approximately 1:9.7; the ratio of thickness to radius of curvature is approximately 1:17.5. Under a clamping force of 15N, the micro-convex compression ratio is approximately 22%.

[0019] Cyclic load test: 10-20N cyclic loading, frequency 1Hz, after 1000 cycles, the dynamic stiffness changes from 45N / mm to 52N / mm, with a change rate of 15.6%, not exceeding 20%.

[0020] Acoustic verification: In an anechoic chamber, a laser Doppler vibration meter (Polytec PSV-500) measured the vibration velocity at the center of the back plate of the instrument, increasing it from 0.8 mm / s with a traditional rigid chin rest to 1.1 mm / s (+37.5%). A free-field measurement at a distance of 1 m from the instrument (using a B&K 4191 microphone) showed an increase of 2.1 dB in the average sound pressure level across the 2-8 kHz frequency band (see...). Figure 6 In a double-blind listening test with 20 participants (Bach's Unaccompanied Violin Sonata No. 1, Adagio, on a 1-5 scale), 15 participants correctly identified the timbre differences of the device, achieving an accuracy rate of 75% (chi-square test p<0.01). All participants applied clamping forces within the range of 10-20 N.

[0021] [Example 2: Professional Solo-Level Violin Chin Rest] The chin support body 1 is made of carbon fiber composite material. The elastic layer 2 is made of microporous polyurethane (60% porosity, Shore A hardness 35), 1.5mm thick, integrally molded. It features 10 micro-protrusions, 2mm in diameter, 0.5mm in height, and 4mm apart, with microgrooves (0.5mm wide, 0.3mm deep, 2mm apart) on the surface to enhance breathability. The acoustic impedance of the elastic layer is Z1≈0.65×10⁻⁶. 6kg·m⁻²·s⁻¹, with a sound impedance ratio of approximately 1:13 to the acoustic impedance of the side panels of the instrument. The dynamic stiffness change rate under cyclic load testing was 12.3%. In a concert hall performance of Paganini Capriccio No. 24, the sound pressure level in the 4-8kHz frequency band increased by 1.8dB.

[0022] [Example 2: Professional Solo-Level Violin Chin Rest] The chin support body 1 is made of carbon fiber composite material. The elastic layer 2 is made of microporous polyurethane (60% porosity, Shore A hardness 35), 1.5mm thick, integrally molded. It features 10 micro-protrusions, 2mm in diameter, 0.5mm in height, and 4mm apart, with microgrooves (0.5mm wide, 0.3mm deep, 2mm apart) on the surface to enhance breathability. The acoustic impedance of the elastic layer is Z1≈0.65×10⁻⁶. 6 The ratio of thickness to acoustic impedance of the instrument body side panels is approximately 1:13 (kg·m⁻²·s⁻¹). The dynamic stiffness change rate under cyclic load testing is 12.3%. In a concert hall performance of Paganini Capriccio No. 24, the sound pressure level in the 4-8kHz frequency band increased by 1.8 dB. In this example, the thickness-to-radius of curvature ratio is approximately 1:23.3, outside the 1:15 to 1:20 range defined in claim 8. As a boundary reference example, its performance (+1.8 dB) is lower than that of Example 1 (+2.1 dB), indicating that performance is better when this ratio is in the 1:15 to 1:20 range. Experiments show that when this ratio is relaxed to 1:12 to 1:25, the performance decreases by no more than 10%.

[0023] [Example 3: Violin Chin Rest for Children / Teenagers] The chin support body 1 is height adjustable (15-25mm). The elastic layer 2 is made of Shore A hardness 30 silicone, 3mm thick, integrally molded, with rounded edges R=2mm. It has 8 micro-convex features, each 2.5mm in diameter and 0.8mm in height, spaced 5mm apart. The acoustic impedance of the elastic layer Z1≈0.50×10⁻⁶. 6 The ratio of kg·m⁻²·s⁻¹ to the acoustic impedance of the side panels of the instrument body is approximately 1:17. The dynamic stiffness change rate under cyclic load testing is 18.7%. In a trial with 10 players aged 12-16, the comfort VAS score improved from 6.2 to 7.8, and the sound pressure level at 2-8kHz increased by 2.0dB. In this example, the thickness-to-radius of curvature ratio is approximately 1:13.3, and it serves as a boundary reference example.

[0024] [Comparative Example] Comparative Example 1: ISO Acoustics OREA speaker pads (Shore A hardness 20) were cut into 3mm thick pieces and bonded to the contact surface of a traditional maple chin rest. In an anechoic chamber, the measured sound pressure level in the 2-8kHz frequency band decreased by 0.9dB compared to the traditional rigid chin rest, and by 3.0dB compared to Example 1 (see Example 1). Figure 6 This indicates that the use of low-hardness acoustic vibration isolation materials at the chin support interface leads to acoustic degradation.

[0025] Comparative Example 2: A silicone elastic layer with a Shore A hardness of 60, with the rest of the structure the same as in Example 1. Actual measurements showed that the reflection coefficient in the 2-8kHz frequency band dropped below 0.25, resulting in a loss of acoustic improvement. This indicates that when the hardness exceeds the upper limit of 50, the interface approaches rigidity, leading to insufficient impedance mismatch.

[0026] Comparative Example 3: Elastic layers with curved surfaces having radii of curvature R=25mm and R=45mm, with the remaining structure the same as in Example 1. When R=25mm, the contact area is too small, the local pressure is too high, and the uneven edge thickness causes the reflection frequency band to drift; when R=45mm, the curved surface approaches a plane, the fit decreases, and the reflection consistency is reduced.

[0027] Comparative Example 4: The silicone pad with 4 support points (contact area accounts for about 45% of the total surface area of ​​the elastic layer) with the structure of US 10,360,879 has insufficient impedance mismatch and the reflection coefficient in the 2-8kHz frequency band is less than 0.5.

[0028] Comparative Example 5: An elastic layer with 4 micro-protrusions, the rest of the structure is the same as in Example 1. Insufficient contact point density and local pressure concentration lead to excessive compression of the micro-protrusions, resulting in decreased reflection uniformity.

[0029] Comparative Example 6: A conventional hard rubber (Shore A hardness greater than 70) contact surface, after 1000 cycles of 10-20N cyclic loading, exhibits a 47% change in dynamic stiffness, with continuous degradation of the contact condition (see...). Figure 7 ).

[0030]

Parameter Selection Basis

[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A violin chin rest acoustic boundary control device, characterized in that, include: The chin rest body (1) is used to connect with the side plate of the tail of the instrument and provide chin support; the elastic layer (2) is set on the surface of the chin rest body (1) that contacts the player's chin. The elastic layer (2) is made of silicone or microporous polyurethane with a Shore A hardness of 30-50, a thickness of 1-3 mm, and a loss factor tanδ of 0.1-0.3; the contact surface of the elastic layer (2) is an arc surface with a radius of curvature R of 30-40 mm; the contact surface is provided with an array of solid hemispherical micro-protrusions (4), with no less than 8 micro-protrusions (4), a diameter of 1.5-2.5 mm, a height of 0.3-0.8 mm, and a center-to-center distance of 3-5 mm between adjacent micro-protrusions (4); the elastic layer (2) and the chin rest body (1) are integrally formed; the dynamic stiffness change rate of the elastic layer (2) under a cyclic clamping force of 10-20 N does not exceed 20%.

2. The apparatus according to claim 1, characterized in that, The Shore A hardness of the elastic layer (2) is 35-45.

3. The apparatus according to claim 1, characterized in that, The thickness of the elastic layer (2) is 1.5-2.5 mm.

4. The apparatus according to claim 1, characterized in that, The elastic layer (2) is made of silicone.

5. The apparatus according to claim 1, characterized in that, The elastic layer (2) is a microporous polyurethane material with an open porosity of 50%-70%.

6. The apparatus according to claim 1, characterized in that, The radius of curvature R of the elastic layer (2) is 35 mm.

7. The apparatus according to claim 1, characterized in that, The elastic layer (2) has a compression rate of 15%-35% under a clamping force of 10-20N.

8. The apparatus according to claim 1, characterized in that, The ratio of the thickness of the elastic layer (2) to the radius of curvature of the arc surface is 1:15 to 1:

20.

9. The apparatus according to claim 1, characterized in that, The ratio of the acoustic impedance of the elastic layer (2) to the acoustic impedance of the side plate of the instrument body is 1:4 to 1:18; when the Shore A hardness of the elastic layer (2) is 30-45, the reflection coefficient of the elastic layer (2) in the 2-8kHz frequency band is not less than 0.

5.

10. The application of the device according to any one of claims 1-9 in increasing the sound pressure level of overtones in the 2-8kHz frequency band of a violin, characterized in that, The elastic layer (2) reflects the high-frequency vibration energy of the instrument body (2-8kHz) back to the instrument body at the interface between the elastic layer (2) and the human body.

Images