JP3553059B1 - guitar - Google Patents

Abstract

PROBLEM TO BE SOLVED: It is a common theory in acoustic physics that, even though it is currently evaluated as a good instrument, only a few percent of the vibration energy of the strings is converted into sound. An object of the present invention is to provide a practical means for increasing the transmission efficiency when transmitting the vibration energy of a string to a surface plate to enrich the sound volume.
SOLUTION: As shown in FIG. 1, the present invention provides a lever mechanism 13 having a small lever ratio of 1 to 3 between a string 12 and a bridge 14 to match the mechanical impedance between the string 12 and the surface plate 15. By transmitting the vibration energy of the strings 12 to the surface plate 15 efficiently, a rich sound volume can be obtained.
[Selection diagram] Fig. 1

Description

  Some stringed instruments use an electric amplifier to convert string vibration into acoustic vibration, and others do not. The present invention relates to an acoustic guitar belonging to the latter type.

  In stringed instruments, various researches have been conducted historically to find the secret of good sounding instruments. The meaning of "good sound" has two aspects: "the volume is rich" and "the sound is beautiful". Among them, the beauty of the tone depends on the personal preference and the objective judgment criteria are not clear, but the rich sound can be judged objectively. The present invention realizes the latter rich volume.

Currently, methods widely used to produce musical instruments with good sound include (1) evaluation / selection of wood (tone wood) to be used, (2) examination of the shape of the surface board (sound board) and body, (3) Examining the arrangement method of the brace (riki) on the back surface of the front plate (for example, see Patent Document 1), (4) Examining the material / shape of the bridge (piece) (for example, see Patent Document 2), (5) Sound hole Examination of the shape of the (acoustic hole) (for example, see Patent Document 3).
Patent 2864013 Tuning structure of rod vibration and piece vibration by stringed instrument Japanese Patent Laid-Open No. 2002 278542 String vibration transmission method using three-layer plywood piece for stringed musical instrument Patent No.2903041 Stringed instrument with sound hole

However, the causal relationship of these methods is not clear enough to be theoretically clarified, so they rely solely on trial and error. Even if they are manufactured using the same method using the same expensive materials, the expected sound quality cannot be reproduced. Is the current situation.

  It is a common theory in acoustic physics that at present, only a few percent of the vibrational energy of a string is converted into sound, even though it is currently regarded as a good instrument. An object of the present invention is to provide a practical means for increasing the transmission efficiency when transmitting the vibration energy of a string to a surface plate to enrich the sound volume.

The following is a brief discussion of vibration energy transfer efficiency.
Fig. 4 (a) shows the mechanism by which the vibration energy of the string is transmitted to the surface plate via the bridge (piece) by an equivalent circuit. In the figure, Fs [N] is the force due to string vibration, Z1 [Ns / m] is the mechanical impedance from the bridge to the string side, and Z2 [Ns / m] is the mechanical impedance from the bridge to the face plate side. Here, the mechanical impedance means the ratio of the speed obtained as a result of applying a force to the applied force. (Hereinafter, mechanical impedance is simply referred to as impedance.) In general, impedance is a complex number and further changes with frequency. However, for simplicity of explanation, it is assumed that this is a real number and does not change with frequency. The instantaneous energy E2 [W] transmitted from the vibration source Fs to the surface plate in the circuit is expressed by Eq.

R (Z2 / Z1) in the equation represents the change in transmission efficiency due to the change in impedance ratio Z2 / Z1 when Z1 is constant. Fig. 4 (b) is a schematic diagram of this R (Z2 / Z1). Is shown. Examination of this equation shows that the instantaneous energy transmitted from the strings to the surface plate is maximized when Z2 / Z1 = 1. In other words, the instantaneous energy transfer efficiency is maximized when the impedances on the string side and the (bridge + surface plate) side are matched.
Z1 is determined by the string material and tension. Z2 varies depending on the material of the surface plate and the arrangement of braces, but in general, Z2 is considerably larger than Z1, and it is difficult to achieve Z2 / Z1 = 1.

  According to the present invention, the instantaneous lever mechanism is applied to a guitar whose string tension is as low as about 10 [kg] at the maximum and whose maximum sound frequency is as low as about 1000 [Hz], thereby realizing the instantaneous lever. It is intended to improve energy transfer efficiency.

Specifically, as shown in FIGS. 1 and 2, a beam 10 made of a lightweight and highly rigid material (for example, an aluminum alloy) is attached to a body 16 of a guitar, and a pin 11 provided on the upper portion is fixed without vibration. As a fulcrum, a lever mechanism 13 is provided between the string 12 and the bridge (piece) 14 to perform the impedance matching described above.
This fixed fulcrum beam 10 may be mounted either outside (Fig. 1 (a)) or inside (Fig. 1 (b)) of the fuselage 16, taking into account the structure and appearance of the instrument. Also, it is necessary to support from the side plates (Fig. 7 (a) 16a) on both sides of the body so as not to hinder the vibration of the surface plate 15.
When mounting the beam 10 inside the fuselage, make a small hole in the surface plate 15 and fix the pin plate 10b for mounting the pins 11 on the top of the surface plate with stud bolts 10a.

Although the effect is slightly reduced, as another method, the rigidity of the back plate may be increased and the beam 10 may be substituted with the back plate.
The bridge (piece) 14 may be fixed to the surface plate like a general guitar, or may be movable like a violin. If it is a movable type, the lever ratio can be made variable, and the sound quality can be adjusted to the taste of the player, as described in (Effects of the Invention) below.

The following describes the impedance matching function of this lever mechanism.
Figures 5 (a) and 5 (b) are equivalent circuits when a lever with a lever ratio of N: 1 is inserted. As can be seen from the lever principle shown in Fig. 3, the force applied to this lever from the string is increased N times at the bridge, while the displacement and velocity are reduced to 1 / N. In other words, the value of force / velocity on the primary side (string side) of the lever is equivalent to N ^ 2 (= N × N) times on the secondary side (face plate side) of the lever. Conversely, when the secondary side (surface plate side) impedance Z2 is converted to the primary side (string side), it will be reduced to 1 / N ^ 2.
Therefore, ideally, perfect impedance matching is performed by selecting the lever ratio so that Z2 / Z1 = N ^ 2.

The above discussion is based on the ideal condition that the lever mass is zero and the rigidity is infinite, and the principle itself has been known for a long time. (For example, the function of the ossicles connecting the eardrum and the cochlea is the same principle as this lever.) However, it is impossible to satisfy the ideal condition with materials that can be used in practice, The range and effects are limited.

For example, there is an example of applying this known lever element to a silencer piano (Patent Literature: Japanese Patent Publication No. 56-28271, piano). No embodiments or experimental results are shown. Also, such a piano is not found in the market to the knowledge of the present applicant, for the following reasons.

If the string tension is extremely high (approximately 300 [kg] = 100 [kg] x 3) like a piano, it is necessary to increase the rigidity of the lever accordingly. growing. This lever mass acts as a brake as the frequency increases, impeding the ability of the lever to follow. For a musical instrument with a wide range such as a piano, the substantial effect as a lever decreases in the treble range (maximum frequency: 4186 [Hz] x higher harmonics), and in some cases, the braking effect exceeds the impedance matching effect. This has a negative effect.
In other words, it is possible in principle, but not actually applicable to some instruments.

In the following, it is explained that in the actual lever mechanism, even if the lever ratio is increased, the overall efficiency does not improve at a lever ratio above a certain level.
First, it is necessary to understand that the length between the fixed fulcrum and the bridge shown in Fig. 3 cannot be reduced arbitrarily, but has a minimum limit. It is self-evident that it cannot be set to zero in an extreme case, but it is necessary to keep the lever rotation angle at the maximum vibration amplitude of the bridge to a small value, and it is considered that the limit is about 10 [mm] in the case of a guitar . Therefore, if the lever ratio is increased, the length of the lever, that is, the mass, will increase in proportion to this.

FIGS. 6 (a) and 6 (b) show changes in transmission loss (decrease in transmission efficiency) with respect to lever ratio. When the lever ratio N is gradually increased from 1, the transmission loss decreases due to the impedance matching effect (curve A), while the loss due to the increase in lever mass increases (curve B). Therefore, the total loss has a minimum value as shown by the curve C.

In addition, as shown in FIG. 6B, the loss of the curve B increases as the frequency becomes higher, so that the loss as a whole increases as compared with the lower frequency region. At the same time, the lever ratio at which the total loss of the curve C becomes the minimum moves to the smaller one, and at the same time, the lever ratio at which the curve C becomes the same level as when there is no lever also moves to the smaller one. Since the lever ratio at which this substantial effect disappears cannot be calculated, it must be confirmed by experiments.

Since the high frequency region is critical, using the first open string of the guitar (approximately 330 [Hz]), if there is no lever (equivalent to lever ratio N = 1), lever ratios N = 2 and N = 3 Experiments were performed for the case of N = 4 and N = 4. The results for N = 3 and below are shown in FIGS. 11 to 15 and Tables 1 and 2.
From this experimental result, it is understood that the effect when increasing from N = 1 to N = 2 is effective in almost all frequency regions (Figs. 11, 12, and 14). When increasing to N = 3, the fundamental frequency and lower harmonics (Table 1) are only as effective as N = 2 or slightly larger than N = 2. Then, on the contrary, the effect is lower than when N = 2 (10 points out of 12 points in Table 2), and it can be seen that there is almost no difference from the case without the lever (FIGS. 11, 13, and 15).
It is clear from the explanation in Fig. 6 (b) that increasing the lever ratio further has no effect, but it has also been confirmed in the experimental results at N = 4.
From these experimental results, it can be said that the lever ratio at which the substantial effect in the high frequency region disappears is between N = 2 and N = 3. However, since the impedance of each instrument varies, specific values may be required. Has some width.

In the low-frequency region, the problem caused by the lever mass is not critical, but for confirmation, the experimental results with the sixth string open string (approximately 82 [Hz]) and a lever ratio N = 2 are shown in FIG. 18 and Tables 3 and 4. From these, it can be clearly seen that there is a volume improvement effect.

Independently of the experiment, the improvement effect at lever ratio N = 2 is examined from Equation 1 as follows. The value of Z2 / Z1 varies with frequency. For example, when Z2 / Z1 = 10, the value of R (Z2 / Z1), which represents the transmission efficiency in Equation 1, increases from 0.083 to 0.204, which is about 2.5 times. Similarly, when Z2 / Z1 = 20, the value of R (Z2 / Z1) increases from 0.045 to 0.139, about 3.1 times. When Z2 / Z1 = 30, the value of R (Z2 / Z1) improves from 0.031 to 0.104, about 3.3 times.

From the above experimental results and numerical calculation results, if the selection range of the lever ratio is greater than 1 and less than or equal to 3, preferably 1.5 to 2.5, the overall improvement effect can be achieved while suppressing the lever mass. It can be said that a rich sound volume can be obtained compared to a guitar of the same material, shape and structure, except for the members such as levers and beams added in the present invention.

In summary, the only materials currently available that can increase the volume are musical instruments with low tension strings (at most 10 kg for guitars) and low maximum sound frequencies (about 1000 Hz for guitars). This is limited to the case where a small lever mechanism with a small lever ratio is applied.

In the present invention, by providing a lever mechanism 13 having a small lever ratio (1 to 3) between a string 12 and a bridge (piece) 14, a guitar having the same material, shape, and structure manufactured by a conventional method is compared with a guitar manufactured by a conventional method. Therefore, it is possible to realize a guitar with "rich volume". Furthermore, since the method according to the present invention is theoretically supported, there is no problem of "poor reproducibility", which is common in the conventional trial and error method.

If the total vibration energy applied from the finger to the string is the same, the duration will be reduced by the increase in volume (Fig. 19). The lever ratio can be changed, and the volume and duration, that is, the sound quality can be adjusted according to the player's preference. For example, if the lever ratio is increased, the volume will increase, but the sound will attenuate in a short time, so-called sharp sound. Conversely, if the lever ratio is reduced, the sound will be less attenuated and soft.

Hereinafter, embodiments of the present invention in a guitar will be described, but all changes within the scope of the present invention are within the scope of the present invention. For example, the present invention is applicable to musical instruments such as mandolin and ukulele.
Guitars can be broadly classified into flat-top guitars with a flat surface plate and arch-top guitars with a convex surface plate (similar to the appearance of a violin). Is taken up.

  Since the distance between the strings 12 and the surface plate 15 of the flat-top guitar is narrow, it is natural to adopt the style shown in FIG. 1B in which the beam 10 for forming a fixed fulcrum that does not vibrate is housed inside the body 16. The beam 10 is required to have high rigidity, but it is desirable to have a light weight in consideration of the carrying of the musical instrument. Therefore, the material is mainly made of a light alloy represented by aluminum and has a channel or box shape. Use. From the experience with the experimental equipment, it can be said that it is sufficient to use an aluminum box material with a thickness of 2 [mm] and a size of 30 x 20 [mm], with the direction of high rigidity up and down. As shown in FIG. 7 (a), both ends of the beam 10 are fixed to a solid wood block 18 adhered to the body side plate 16a. The gap between the beam 10 and the surface plate 15 is determined in consideration of the sinking of the surface plate 15 under the force of the string 12, but usually about 10 [mm] is sufficient.

Two stud bolts 10a having a diameter of 5 [mm] are attached to the beam 10 at intervals of about 100 [mm] (the width of six strings + a margin). Drill two holes of the order. Attach an aluminum pin plate 10b with a thickness of 5 [mm] and a size of 120 x 15 [mm] to the stud bolt protruding above the surface plate. The pin support (11a in Fig. 2) of the lever 13 is fixed on this plate. When it is necessary to make the height from the surface plate 15 as low as possible, the thickness of the pin plate 10b can be reduced by using a rigid stainless steel material instead of the aluminum material.

The shape of the lever body 13 may be the simple one shown in FIG. 2, but by adopting a shape that is as light and rigid as possible as the manufacturing technology allows, the characteristics in the high frequency range can be improved. In the case of the shape shown in Fig. 2, the length is 20 [mm] using an aluminum channel material with a thickness of 1 [mm], a width of 5 [mm], and a height of 8 [mm]. Place the bridge at this intermediate position and set the lever ratio to 2.
The height of the string receiving part 13a is adjusted in consideration of the fretboard (fingerboard). It is natural that the pin 11 can be freely rotated, but the gap is minimized to eliminate chatter and suppress the reduction in transmission efficiency in the high-frequency region.

The position at which the lever 13 receives the string (Fig. 2 (a) 13a) has an important meaning in determining the pitch at which the position of the bridge 14 was carried in the conventional method. Conversely, it is necessary to recognize that the position of the bridge 14 in the present invention is not related to the pitch determination. In this sense, in order to fine-tune the pitch, it is preferable to adopt a structure in which the position of the pin portion of the lever 13 can be adjusted. As the simplest method, it is sufficient to make the screw holes for mounting the pin supports 11a elliptical as shown in Fig. 2 (b).
In the configuration of FIGS. 1A and 1B, the position of the bridge 14 is closer to the sound hole 16b than the string receiving portion of the lever 13 (FIG. 213a). If you want to avoid this, adopt a configuration as shown in FIG.
The bridge 14 is easier to maintain, such as changing the strings, if it is fixed to the surface plate, but it has no problem in terms of function even if it is movable.

The tailpiece that holds the string 12 (Fig. 1 (c) 17) may be one commonly used in arch-top guitars and the like. However, if the height of the lever 13 with respect to the surface plate 15 is low and the force of the string 12 to press the lever 13 against the surface plate 15 is insufficient, use a string stopper similar to an ordinary guitar bridge (Fig. 9 (a) 19). It may be retained directly on the surface plate.
Alternatively, a method of reducing the horizontal force applied to the surface plate 15 by using the tail piece 17 together as shown in FIG. 9B may be used.

Next, the case where the present invention is applied to an arch-top type guitar will be described.
The arch-top guitar bridge is relatively tall, similar to a violin bridge, and has the function of converting string vibration parallel to the face plate into a direction perpendicular to the face plate. Therefore, it is possible to insert a lever mechanism between the string and the bridge, but it is easier to insert the lever mechanism between the legs (Fig. 10 (b) 14c) and the surface plate 15 of the bridge.
FIGS. 10A and 10B illustrate this method. The main bridge 14a represents a conventional bridge part, and the auxiliary bridge 14b is an additional bridge part accompanying the insertion of the lever mechanism. The other parts are the same as those described in the section on the flat top guitar, so the explanation is omitted.
This method can be considered as a combination of "string + lever + bridge" if "main bridge 14a + lever 13" is regarded as a lever in a large meaning.

Lever mechanism installation between the string and bridge (piece) (a) When the fixed fulcrum forming beam is installed outside the guitar body (side view) (b) When the fixed fulcrum forming beam is installed inside the guitar body (Side view) (c) Overall arrangement example of beam and lever mechanism Lever mechanism for impedance matching (a) Overall perspective view When lever 13 is directly mounted on beam 10 mounted as shown in Fig. 1 (a), black dots in the figure mean that similar levers are lined up I do. (b) Lever mounting plan view Illustration of lever ratio for impedance matching Instantaneous energy transfer equivalent circuit between string and face plate (without lever) (a) Circuit diagram (b) Schematic diagram of transfer efficiency Instantaneous energy transfer equivalent circuit between string and face plate (with lever) (a) Circuit before converting the secondary side of lever mechanism to primary side (b) After converting secondary side of lever mechanism to primary side Circuit Illustration of transmission loss with respect to lever ratio (a) Low frequency region (b) High frequency region: Loss is larger than low frequency region. Schematic diagram of beam for forming fixed fulcrum (a) Diagram of how to attach beam to fuselage side plate (b) Diagram of relative relationship between beam, pin plate and surface plate Modification of the lever mechanism arrangement for impedance matching Example of string retention method (a) When not using tailpiece (b) When using tailpiece together Example of lever mechanism inserted between bridge and surface plate (a) Side view (b) Perspective view Power spectrum experiment result of the first string of guitar (330 [Hz]) When there is no lever for impedance matching Power spectrum experiment result of the first string of guitar (330 [Hz]) In case of lever ratio N = 2 for impedance matching Power spectrum experiment result of the first string of guitar (330 [Hz]) In case of lever ratio N = 3 for impedance matching Power spectrum experiment result of the first string of the guitar (330 [Hz]) For ease of comparison, a graph in which FIGS. 11 and 12 are drawn on one sheet Power spectrum experiment result of the first string of the guitar (330 [Hz]) For ease of comparison, graphs of FIGS. 11 and 13 drawn on a single sheet Power spectrum experiment result of the 6th string of guitar (82 [Hz]) Without lever for impedance matching Power spectrum experiment result of guitar 6th string (82 [Hz]) In case of lever ratio N = 2 for impedance matching Power spectrum experiment result of the 6th string of guitar (82 [Hz]) Graph for drawing Fig. 16 and Fig. 17 on one sheet for easy comparison Time change of sound volume with respect to transmission efficiency

Explanation of reference numerals

10 Beam Fs String Vibration Force
10a Mechanical impedance of stud bolt Z1 string
10b Pin plate Z2 bridge + mechanical impedance of surface plate
10c Nut R Function representing transmission efficiency
10d pin plate N lever ratio
11 pin
11a Pin support
12 strings
13 lever
13a String receiving groove
14 bridge
14a main bridge
14b Auxiliary bridge
14c legs
15 Surface plate
16 torso
16a fuselage side plate
16b sound hole
17 Tailpiece
18 wood blocks
19 String stop
20 columns
21 fixed fulcrum

Claims (4)

  A vibrating string, a sound board (surface plate) for converting mechanical vibration energy of the string into acoustic vibration of air, a bridge (piece) for transmitting mechanical vibration energy of the string to a sound board, A guitar having a body side plate that supports the sound board at an outer peripheral edge of the board, a high rigidity fixed between the left and right body side plates inside the surface plate and facing along the direction orthogonal to the strings. A support member having one end supported by the beam and the other end penetrating the surface plate, a pin serving as a fulcrum supported by the other end of the support member, and one end supported by the pin serving as a fulcrum. A lever mechanism for receiving vibration of the string at an end thereof and supported by the bridge at an intermediate portion, and the bridge is disposed outside a face plate.   2. The guitar according to claim 1, wherein a lever ratio of said lever mechanism is made variable by making said bridge movable.   2. The guitar according to claim 1, wherein a lever ratio of the lever is in a range of 1.5 to 2.5. 2. The guitar according to claim 1, wherein a mounting position of a pin for supporting the lever with respect to the support member is adjustable.
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