JP2007101720A - Silencer for brass instrument and silencing system for brass instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silencer for a brass instrument possibly having a variety of pipe lengths with which a blow sound having the same interval and timbre as those when the silencer is not mounted in a sound radiation part can be obtained while the blow sound is cut off and not radiated to the outside. <P>SOLUTION: The silencer 10 is provided with a microphone 21 placed at a position where sound pressure at a position a specified distance Δx spaced backward from an open end P of a bell 3 can be detected while a primary silencer body 11 is mounted in the bell 3, and provided with a speaker 22 at a position a distance Δx spaced forward from the open end P. The output signal of the microphone 21 is made opposite in phase through a microphone amplifier 31 and a power amplifier 32 and supplied to the speaker 22. Further, a plurality of air holes 12 are formed in an outer peripheral part of the primary silencer body 11 which faces a front end of the bell 3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a device for performing silencing when playing a brass instrument such as a trumpet.

This type of silencer has a hollow body with a hollow inside, the front end is closed, and the rear end has an opening leading to the cavity. In general, it is used by inserting it from the rear end side. In general, this type of silencer has a microphone provided in a hollow of a cylindrical body, and sends the output signal of the microphone to a headphone outside the silencer via a cable, and the wind sound is monitored by the headphone. To be able to. However, in a state where the silencer is mounted on the morning glory, the sound wave propagating from the mouthpiece side of the brass instrument toward the outside of the morning glory is reflected to the mouthpiece side on the front end wall of the silencer. For this reason, the position of the end of the standing wave of the sound pressure generated in the morning glory to which the silencer is attached deviates from the position of the end of the standing wave of the sound pressure generated in the morning glory to which the silencer is not attached. . Therefore, even if the same playing is performed, the wind sound obtained in the state where the muffler is mounted is deviated from the sound of the wind sound obtained in the state where the muffler is not mounted, and the tone is also different. There was a problem. In order to solve such a problem, the silencer disclosed in Patent Document 1 has a shape in which the inner diameter of the cylindrical body becomes the maximum diameter in the middle portion in the axial direction and becomes smaller toward the front and rear ends. According to the silencer having such a shape, the inner surface of the front end portion is not a single plane perpendicular to the axis, but is inclined, so that a reflection surface (point) corresponding to each is formed by the sound range. For this reason, even if the silencer is attached, the position of the end of the standing wave effective for generating the pitch of each overtone does not move significantly (see paragraph 0021 of Patent Document 1).
Japanese Patent No. 2865030

  By the way, in a brass instrument, a tubular body which is an acoustic resonance portion has a relatively high Q value indicating the sharpness of resonance of acoustic characteristics and a relatively large acoustic impedance. In such a brass instrument, it is the tubular body that determines the pitch of the wind sound. Therefore, when a silencer is attached to a brass instrument, if the resonance characteristics of the tube with the silencer attached are not appropriate, the tone and volume of the wind sound will not be appropriate at the time of blowing. I can't even get the pitch. According to the technique described in the above-mentioned Patent Document 1, since the displacement of the position of the standing wave end when the silencer is attached is reduced, the silencer is attached to the tone and pitch when the silencer is attached. It can be brought close to the timbre and pitch in a state that is not. However, as described above, the influence of the resonance characteristics of the tube on the pitch and tone color of the wind sound in a brass instrument is extremely large. For this reason, in order to obtain the same tone and pitch when the silencer is installed, it is necessary to closely match the resonance characteristics of the tube when the silencer is installed with the resonance characteristics when the silencer is not installed. is there. In addition, in the case of brass instruments having pipe length changing devices such as pistons and valves, the brass instruments can have various pipe lengths. Therefore, in all those pipe lengths, the resonance characteristics of the pipes when the silencer is installed are not resonant. It is necessary to closely match the characteristics. Even if the shape of the silencer is optimized as disclosed in Patent Document 1, the effect is limited, and the requirement regarding the resonance characteristics of the tube when such a silencer is mounted is satisfied. It is extremely difficult.

  The present invention has been made in view of the circumstances described above, and when mounted on a brass instrument that can take various tube lengths, while blocking the radiation of the wind sound to the outside, inside the acoustic radiation section An object of the present invention is to provide a brass silencer capable of obtaining a wind sound having the same pitch and tone as when not worn.

In this invention, the brass silencer has a cavity inside, the front end is closed, the rear end has an opening communicating with the cavity, and the sound radiating portion of the brass instrument from the rear end side. A silencer body mounted on the sound radiating unit, and in a state where the silencer body is mounted on the sound radiating unit, at a position within the cavity of the muffler body that is separated from the open end of the sound radiating unit by a predetermined distance Δx backward. In the cavity of the muffler body such that the microphone and the muffler body are located at a point a predetermined distance Δx forward from the open end of the sound radiating unit when the muffler body is mounted on the sound radiating unit. And a speaker provided at the position.
In a state where the silencer body of the brass instrument silencer is mounted on the sound radiating portion of the brass instrument, the microphone and the speaker face each other with the open end of the sound radiating portion sandwiched between the respective intermediate positions. Therefore, by supplying the output signal of the microphone to the speaker and adjusting the phase of the signal supplied to the speaker so that the sound pressure waveform opposite in phase to the sound pressure waveform detected by the microphone is output from the speaker. , The boundary condition of the sound pressure waveform at the open end of the sound radiating part is matched with the boundary condition in the state where the silencer body is not mounted, and the same resonance state as occurs in the state where the silencer body is not mounted It can be generated in the sound radiating part to which the silencer body is mounted. Therefore, when mounted on a brass instrument that can take various tube lengths, it is possible to produce a wind sound with a pitch and tone that is the same as when the sound is not mounted inside the sound radiating section while blocking the radiation of the wind sound to the outside. Obtainable.

<First Embodiment>
First, with reference to FIG. 1, the operation principle of the silencer system for brass instruments according to the first embodiment of the present invention will be described. In general, a brass instrument generates sound using the resonance of an open / close tube, that is, the tip of an acoustic radiation portion (for example, morning glory) is in an open state and the wind end (for example, a mouthpiece) is in a closed state. Is. More specifically, when a brass instrument is played, a sound wave is generated in the morning glory tube from the end of the morning glory toward the tip of the morning glory. Sound waves are returned. In the morning glory tube, the sound wave from the playing end to the open end overlaps with the sound wave returning from the open end to the playing end side, and the sound pressure has a belly at the playing end and a node at the open end. A wave (resonant sound wave) is generated, and a loud sound is emitted from the open end to the outside.

  What should be done to prevent leakage of sound to the outside of the brass instrument without hindering the generation of standing waves in the morning glory tube of such a brass instrument? For this purpose, the inventors have adopted the following idea. That is, as shown in FIG. 1, a state in which the open end P ′ of the dummy tube 1 ′ having the same shape and resonance characteristics as the brass instrument 1 is abutted with the open end P of the brass instrument 1 is virtually created. If possible, the sound can be contained in the brass instrument 1 and the dummy tube 1 'without leaking outside without changing the state of occurrence of standing waves in the brass instrument 1. is there. Here, the brass instrument 1 and the dummy tube 1 ′ whose open ends are butted together are both closed ends (winding ends), and constitute a closed tube having a pipe length twice that of the original brass instrument 1. . How to create such a closed tube will be described later.

  In the closed tube as shown in FIG. 1, when the brass instrument 1 and the dummy tube 1 ′ are played by blowing simultaneously from the left and right mouthpieces 2 and 2 ′ in exactly the same manner, A sound pressure wave from the left mouthpiece 2 to the right mouthpiece 2 ′ and a sound pressure wave from the right mouthpiece 2 ′ to the left mouthpiece 2 are generated. Here, since the brass instrument 1 and the dummy tube 1 ′ have exactly the same resonance characteristics and share the open ends of the brass instrument 1 and the dummy tube 1 ′, the shared open ends have a node 4A, and the left and right wind instruments. A standing wave 4 having a belly 4B at the end is generated in the brass instrument 1 and the dummy tube 1 ′. At this time, the standing wave 4 generated in the brass instrument 1 is the same as that generated in the state where the dummy tube 1 'is not present. This is because, in the absence of the dummy tube 1 ′, a reflected wave returning from the open end P to the mouthpiece 2 side is generated by reflection at the open end P of the brass instrument 1, but in a state where the dummy tube 1 ′ is mounted. This is because a sound wave having the same phase as this reflected wave propagates from the dummy tube 1 ′ into the brass instrument 1. In this case, since both ends of the closed tube composed of the brass instrument 1 and the dummy tube 1 'are closed ends, the standing wave generated in the inside thereof does not leak to the outside as sound. If the sound pressure of the standing wave generated in the closed tube can be detected and reproduced as a sound outside the closed tube, the wind sound of the brass instrument 1 can be monitored. In the brass instrument 1 and the dummy tube 1 ′, the positions of the open ends P and P ′ at which standing wave nodes occur substantially coincide with the tip positions of the morning glory, but strictly speaking, as shown in the figure, the resonance mode Varies by However, since these errors are about 2% at the maximum, there is no practical problem even if the open end is considered to be the same between the resonance modes.

  Now, in FIG. 1, the acoustic vibration in the closed tube is generated by blowing in from the left and right mouthpieces 2 and 2 '. Therefore, in order to continue this acoustic vibration, it is necessary to exhaust the air by the breath pressure from both mouthpieces from the inside of the pipe. Here, if the exhausted air contains an alternating current component, it causes sound leakage. Therefore, in the present embodiment, the velocity of the air particles is at a portion where the sound pressure with the outside world is equal in all resonance modes, that is, at the position of the virtual open end shared by the brass instrument 1 and the dummy tube 1 ′ in the closed tube. A vent hole for guiding air in a direction perpendicular to the direction is provided, and air containing only a direct current component is exhausted outside the closed tube through the vent hole. The above is the operation principle of the muffler system in the present embodiment.

  Next, with reference to FIG. 2, a muffler system that operates according to the operation principle described above will be described. In FIG. 2, a silencer 10 according to an embodiment of the present invention is attached to the morning glory 3 of the brass instrument 1. The silencer 10 has a silencer body 11. The silencer body 11 is a cylindrical body having a cavity 11A therein, a front end portion closed, and an opening communicating with the cavity 11A at the rear end portion, and inserted into the morning glory 3 from the rear end side. It is attached to morning glory 3. The silencer body 11 is increased in thickness as it proceeds from the front end and the rear end toward the center. The outer peripheral surface of the rear half of the silencer body 11 is inclined with a gentle concave surface, and the outer peripheral surface of the rear half of the silencer body 11 is the inner peripheral surface of the morning glory 3 when mounted on the morning glory 3. It is in close contact with.

  A microphone 21 and a speaker 22 are provided in the cavity 11 </ b> A of the silencer body 11. Here, the positions of the microphone 21 and the speaker 22 in the silencer body 11 are as follows. First, let P be the open end of the morning glory 3 of the brass instrument 1, that is, the position near the tip of the morning glory where a node of a standing wave occurs in each resonance mode when the brass instrument 1 is played. In this case, the microphone 21 detects the sound pressure at the position returned by the predetermined distance Δx from the open end P of the morning glory 3 to the mouthpiece 2 side on the inner wall of the cavity 11 </ b> A of the silencer body 11 attached to the morning glory 3. It is fixed in a position where it can. On the other hand, when the silencer 10 is mounted on the morning glory 3, the speaker 22 can silence the sound wave so that it can radiate sound waves toward the mouthpiece 2 at a position advanced forward from the open end P by a distance Δx. It is fixed to the inner wall of the main body 11. The speaker 22 is fixed with a frame or the like, and the back surface thereof is covered with a cushioning material 22A such as glass wool.

  The output signal of the microphone 21 is taken out of the silencer 10 via the cable 23. This output signal is amplified by the microphone amplifier 31 and the power amplifier 32 and supplied to the speaker 22 in the silencer 10 via the cable 24. The output signal of the microphone amplifier 31 is amplified by the headphone amplifier 33 and output from the headphones 34 as sound. By playing this headphone 34 and listening to the output sound, the wind player can monitor the wind sound in the morning glory 3 detected by the microphone 21. Note that a loudspeaker may be used instead of the headphones 34.

  The gain of the closed loop including the microphone 21, the microphone amplifier 31, the power amplifier 32, and the speaker 22 is 1 or less. In addition, the phase characteristics of the signal transmission system from the microphone 21 to the speaker 22 are adjusted so that the sound wave detected by the microphone 21 and the sound wave radiated from the speaker 22 are exactly in reverse phase.

  According to the above configuration, the microphone 21 and the speaker 22 are located at an equal distance Δx across the open end P, and the speaker 22 transmits sound waves having a phase opposite to that detected by the microphone 21 to the mouthpiece 2 side. , The standing wave 4 in which the sound pressure becomes a node is generated at the open end P, which is the midpoint between the microphone 21 and the speaker 22. The positions of the nodes and antinodes of the standing wave 4 coincide with the positions of the nodes and antinodes of the standing wave generated in the brass instrument 1 when the silencer 10 is not attached. Therefore, according to this embodiment, when the silencer 10 is attached and the brass instrument 1 is played, a wind sound similar to that when the silencer 10 is not attached is generated in the brass instrument 1, and this is the microphone. 21 and output from the headphone 34.

  In the present embodiment, the microphone 21 may be of any type as long as it has a wide frequency band, but a condenser microphone is usually preferable. The speaker 22 needs to have a frequency characteristic suitable for the frequency band of the sound generated by the target brass instrument 1. For example, when configuring the silencer 10 for trumpet, the speaker 22 needs to have a flat amplitude characteristic in a frequency band of 150 to 4000 Hz. Furthermore, as illustrated in FIG. 3, the speaker 22 needs to have a phase characteristic close to 0 degrees in a frequency band of 150 to 4000 Hz. This is because the role of the speaker 22 in this embodiment is such that when the phase characteristic of the speaker 22 deviates from 0 degrees, a sound pressure wave having a phase opposite to the sound pressure wave reaching from the mouthpiece 2 side is supplied at the open end P. This is because it cannot be performed normally.

  In order to obtain the effect of the present embodiment in which a standing wave similar to that in the case where the silencer 10 is not installed is generated in the tube, the sound pressure of the portion other than the node in the standing wave in the morning glory 3 is set to the microphone. It is necessary to output from the speaker 22 a sound that is detected by 21 and reversed in phase. In view of this point, in this embodiment, the distance Δx between the open end P and the microphone 21 (speaker 22) is viewed from the open end P of the morning glory 3 in the standing wave node of the eighth resonance mode of the brass instrument 1. When the distance between the first node and the open end P is L8 (see FIG. 1), the value is in the range of L8> Δx> 0. As described above, when L8> Δx> 0, the effect aimed by the present embodiment can be obtained for each resonance mode up to the eighth resonance mode which is important in terms of acoustic effect.

  In the present embodiment, the outer peripheral portion of the silencer main body 11 has a maximum diameter at a position facing the tip of the morning glory 3 when the silencer 10 is mounted on the morning glory 3. In the silencer body 11, a plurality of small-diameter vent holes 12 are provided on the outer periphery of the maximum diameter at intervals that divide this into 4 to 16 equal parts. These ventilation holes 12 are holes for exhausting the air in the morning glory 3 to the outside of the silencer body 11. Here, each ventilation hole 12 is in a position facing the open end P of the morning glory 3 in a state where the silencer body 11 is mounted on the morning glory 3, and the air in the morning glory 3 is piped to the morning glory 3 near the open end P. It is guided in a direction perpendicular to the axis (center axis of the tube) and exhausted to the outside of the silencer body 11. Moreover, the sum total of the opening area of the several ventilation hole 12 is an area required in order to discharge | emit the average amount of air generated by blowing.

  According to the present embodiment, since the direction of each air vent 12 is orthogonal to the particle velocity direction of sound waves at the open end P (the direction of propagation of air density), the AC component of the air pressure generated in the morning glory 3 is the air vent. The possibility of going in and out through 12 is very low. Further, a standing wave node of sound pressure always occurs at the open end P, and only a direct-current atmospheric pressure difference occurs between the open end P and the outside. Therefore, only the direct current component of the air pressure passes through the vent hole 12 to the outside, and no sound leaks through the vent hole 12. Therefore, according to the present embodiment, it is possible to prevent the sound of the wind sound from leaking to the outside while giving the wind feeling similar to that when the silencer 10 is not mounted.

  As described above, according to the present embodiment, in the state in which the silencer 10 is mounted, the silencer 10 reliably performs silencing while the morning glory 3 whose opening end is blocked by the silencer 10 The sound wave at the position returned from the open end P to the mouthpiece 2 side by a predetermined distance Δx is reversed in phase, and emitted toward the mouthpiece 2 side at a position advanced forward from the open end P by the distance Δx. The same resonance state as that in the open state can be generated in the morning glory 3. Therefore, according to the present embodiment, there is an effect that it is possible to obtain the same wind sound from the brass instrument 1 as in the case where the silencer 10 is not mounted while the sound is silenced. Further, according to the present embodiment, the silencer body 11 penetrates in the direction perpendicular to the tube axis 3A of the morning glory 3 and passes through the plurality of ventilation holes 12 provided toward the open end P in the morning glory 3. Since the air is exhausted, there is no effect that an AC component of air pressure does not enter and exit between the morning glory 3 and the outside, and sound leakage can be reliably prevented.

Second Embodiment
FIG. 4 is a diagram showing a configuration of a silencing system according to the second embodiment of the present invention. In this silencing system, a filter 35 is interposed between the microphone amplifier 31 and the power amplifier 32 in the first embodiment. The filter 35 is a filter having a variable frequency characteristic. After the analog signal output from the microphone amplifier 31 is converted into a digital signal, a filter coefficient prepared according to the target frequency characteristic is applied to the digital signal. The used filter calculation processing is performed, and the resulting digital signal is converted into an analog signal and supplied to the power amplifier 32. The filter control unit 36 is connected to a plurality of piston sensors 42 that detect ON / OFF of a plurality of pistons 41 that are pipe length adjustment units of the brass instrument 1, and based on output signals of the plurality of piston sensors 42, the filter 35. Switches the filter coefficients used for the filter operation.

  In this embodiment, when the filter control unit 36 detects the ON / OFF pattern of the plurality of pistons 41 based on the output signals of the plurality of piston sensors 42, the filter control unit 36 determines the tube length of the brass instrument 1 determined by the ON / OFF pattern. A plurality of appropriate resonance frequencies corresponding to each other are detected, and the frequency characteristics of the filter 35 are adjusted so that the audio signals having the resonance frequencies are passed with priority over the audio signals having other frequencies. For this reason, when the silencer 10 is mounted, resonance at a resonance frequency not intended by the blower is avoided, and resonance in an appropriate resonance mode corresponding to the ON / OFF pattern of the plurality of pistons 41 is stably generated. Can do.

  Although the first embodiment and the second embodiment of the present invention have been described above, these are merely examples, and the present invention can be implemented in various modified modes. For example, in each of the above embodiments, an amplifier outside the silencer 10 is used as the microphone amplifier 31 and the power amplifier 32. However, the microphone amplifier 31 and the power amplifier 32 may be provided in the silencer body 11.

It is a figure explaining the principle of operation of the silence system which is a 1st embodiment of this invention. It is a figure which shows the structure of the muffling system in the embodiment. It is a figure which shows the example of the phase characteristic of the speaker 22 in the silencing system. It is a figure which shows the structure of the silencing system which is 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Brass instrument, 2 ... Mouthpiece, 3 ... Morning glory, 3A ... Tube axis, 10 ... Silencer, 11 ... Silencer body, 11A ... Cavity, 12 ... Vent, 21 ... Microphone, 22 ... Speaker, 22A ... Cushion material, 31 ... Microphone amplifier, 32 ... Power amplifier, 33 ... Headphone amplifier, 34 ... Headphone, 35 ... Filter, 36 ... Filter control unit, 41 ... ... Piston, 42 ... Piston sensor.

Claims (5)

A silencer body that has a cavity inside, has a front end closed, has an opening that communicates with the cavity at a rear end, and is mounted on a sound radiating part of a brass instrument from the rear end side;
A microphone provided at a position in the cavity of the silencer body that is separated from the open end of the acoustic radiation part by a predetermined distance Δx in a state where the silencer body is attached to the acoustic radiation part;
The silencer body is provided at a position in the cavity of the silencer body such that the silencer body is located at a point separated by a predetermined distance Δx forward from the open end of the acoustic radiation unit in a state where the silencer body is mounted on the acoustic radiation unit. A silencer for brass instruments, comprising: a speaker.   Of the nodes of the sound pressure standing wave in the eighth resonance mode generated in the brass instrument, the distance between the position of the first node viewed from the open end of the sound radiating portion and the open end of the sound radiating portion is L8 The silencer for brass instruments according to claim 1, wherein the distance Δx is in a range of L8> Δx> 0.   In the silencer body mounted on the sound radiating unit, the sound radiating unit is located at a position facing the open end of the sound radiating unit, and guides air in the sound radiating unit of the brass instrument in a direction perpendicular to the tube axis of the sound radiating unit. The silencer for a brass instrument according to claim 1 or 2, wherein a vent hole is provided in the silencer main body to escape to the outside of the silencer main body. A silencer for brass instruments according to any one of claims 1 to 3,
An electric circuit that adjusts the phase of the output signal of the microphone so that a sound wave having a phase opposite to that of the sound wave detected by the microphone is output from the speaker;
A silencer system for brass instruments, wherein a gain of a closed loop including the microphone, the electric circuit, and the speaker is 1 or less. The brass instrument is
A tube length adjusting unit for adjusting the tube length of the brass instrument;
A sensor for detecting an operation state of the tube length adjusting unit;
The electrical circuit is
A filter having a variable frequency characteristic interposed between the microphone and the speaker;
Based on the operation state of the tube length adjusting unit detected by the sensor, the resonance frequency of the resonance mode generated in the brass instrument is determined, and the frequency characteristic of the filter is set so that the signal of the resonance frequency can easily pass. The silencer system for brass instruments according to claim 4, further comprising: a filter control unit for controlling the filter.

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