Sound-dampening silencer with variable frequency

Abstract

We provide a silencer with a variable silencer frequency that allows the user to change the frequency at which sound is silenced according to their preference. [Solution] The silencer with variable silencer frequency (silencer 100) comprises a plurality of resonant tubes (first resonant tube 11 to fifth resonant tube 15) having different silencer frequencies, a sound guide path 20 provided so as to be surrounded by the plurality of resonant tubes, openings (first opening 11a to fifth opening 15a) provided in each of the plurality of resonant tubes and connected to the sound guide path 20, and operating parts (first operating part 11c to fifth operating part 15c) for operating plugs (first plug 11b to fifth plug 15b) that can open and close the openings.

Description

Technical Field

[0001] The present invention relates to a silencer with variable silencing frequency.

Background Art

[0002] Conventionally, a silencer using a resonance tube has been disclosed to reduce noise (see Patent Document 1 below).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in order to reduce the influence of noise on the human body, the use of earplugs or earmuffs having a silencing effect can be considered. An earmuff is a type of soundproof protective gear that covers the entire ear. However, although earplugs are the most convenient noise countermeasure, there is a possibility that if the earplugs do not fit the ears, they may hurt the ear canal or cause inflammation. Also, both earplugs and earmuffs block sound by covering the ears, and for example, there is a problem that it is difficult to make only the human voice audible while silencing the noise.

[0005] The present invention has been made in view of such problems, and an object thereof is to provide a silencer with variable silencing frequency that can change the frequency to be silenced according to the preference of the user.

Means for Solving the Problems

[0006] To solve the above problems, the sound-dampening frequency variable silencer according to the present invention comprises a plurality of resonant tubes having different sound-dampening frequencies, a sound guide path provided so as to be surrounded by the plurality of resonant tubes, an opening provided in each of the plurality of resonant tubes and connected to the sound guide path, and an operating part for operating a plug that can open and close the opening. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a silencer with a variable silencer frequency that can change the frequency at which sound is silenced according to the user's preference. [Brief explanation of the drawing]

[0008] [Figure 1] This is a plan view showing an example of the silencer according to this embodiment. [Figure 2] This is a perspective view showing an example of the silencer according to this embodiment. [Figure 3] This is a perspective view showing the inside of a resonant tube. [Figure 4] This is a plan view showing an example of a silencer. [Figure 5] This is a plan view showing the first resonant tube in its open state. [Figure 6] This is a perspective view showing an example of multiple silencers connected in series. [Figure 7] This diagram shows a method for evaluating the noise reduction effect of a silencer. [Figure 8] This diagram shows the sound-reducing effect of a silencer. [Figure 9] This is a schematic diagram showing noise-canceling earmuffs. [Figure 10] This diagram shows the noise-canceling effect of noise-canceling earmuffs. [Figure 11] This is a perspective view showing another example of a silencer. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. The silencer 100 as a variable-frequency silencer according to this embodiment has a substantially cylindrical external shape and comprises a first to fifth resonance tube 11 to 15 connected in an annular manner, as shown in Figures 1 to 3. As a result, a sound guide path 20 surrounded by the first to fifth resonance tubes 11 to 15 is formed in the silencer 100. Hereinafter, the first to fifth resonance tubes 11 to 15 connected in an annular manner will also be referred to as the resonance section 10. Note that the number of resonance tubes provided in the silencer 100 is not limited to the above, and at least two or more are sufficient.

[0010] The first to fifth resonant tubes 11 to 15 each have internal air chambers 11A to 15A, which are air chambers with different capacities. In this embodiment, the capacity of the first air chamber 11A, second air chamber 12A, third air chamber 13A, fourth air chamber 14A, and fifth air chamber 15A increases in that order.

[0011] Furthermore, the inner circumferential surface of the resonant section 10 has first openings 11a to fifth openings 15a that connect the first air chambers 11A to fifth air chambers 15A to the sound guide path 20, respectively. The silencer 100 also includes first plugs 11b to fifth plugs 15b that close the first openings 11a to fifth openings 15a, respectively. In other words, the first plugs 11b to fifth plugs 15b are provided on the inner circumferential surface side of the resonant section 10. Note that the first plugs 11b to fifth plugs 15b are omitted in Figures 2 and 3. As shown in Figure 4, the first plug 11b has a first outer member 111b whose diameter is larger than the diameter of the first opening 11a, and a first inner member 112b whose diameter is approximately the same as the diameter of the first opening 11a and closes the first opening 11a. The second plug 12b has a second outer member 121b whose diameter is larger than the diameter of the second opening 12a, and a second inner member 122b whose diameter is approximately the same as the diameter of the second opening 12a and closes the second opening 12a. The third plug 13b has a third outer member 131b whose diameter is larger than the diameter of the third opening 13a, and a third inner member 132b whose diameter is approximately the same as the diameter of the third opening 13a and closes the third opening 13a. The fourth plug 14b has a fourth outer member 141b whose diameter is larger than the diameter of the fourth opening 14a, and a fourth inner member 142b whose diameter is approximately the same as the diameter of the fourth opening 14a and closes the fourth opening 14a. The fifth plug 15b has a fifth outer member 151b whose diameter is larger than the diameter of the fifth opening 15a, and a fifth inner member 152b whose diameter is approximately the same as the diameter of the fifth opening 15a and which closes the fifth opening 15a.

[0012] Furthermore, the silencer 100 includes first to fifth operating sections 11c to 15c for operating the first to fifth openings 11a to 15a to be opened and closed by the first to fifth plugs 11b to 15b, respectively. Note that the first to fifth operating sections 11c to 15c are omitted in Figures 2 and 3. The first to fifth operating sections 11c to 15c are located on the opposite side from the first to fifth plugs 11b to 15b, which correspond to the first to fifth operating sections 11c to 15c, with the first to fifth resonant tubes 11 to 15c, respectively, in between. In other words, the first to fifth operating sections 11c to 15c are located on the outer circumferential surface side of the resonant section 10. Therefore, the first to fifth operating sections 11c to 15c can be easily operated from the outer circumferential surface side of the resonant section 10.

[0013] The first stopper 11b and the first operating part 11c are connected by, for example, a round rod-shaped first connecting part 11d, as shown in Figure 4. A first hole 11e is formed on the outer surface of the first resonant tube 11, with a diameter approximately the same as the diameter of the first connecting part 11d. The first hole 11e is closed when the first connecting part 11d is inserted through it. The second stopper 12b and the second operating part 12c are connected by, for example, a round rod-shaped second connecting part 12d. A second hole 12e is formed on the outer surface of the second resonant tube 12, with a diameter approximately the same as the diameter of the second connecting part 12d. The second hole 12e is closed when the second connecting part 12d is inserted through it. The third stopper 13b and the third operating part 13c are connected by, for example, a round rod-shaped third connecting part 13d. A third hole 13e is formed on the outer surface of the third resonance tube 13, with a diameter approximately the same as the diameter of the third connecting portion 13d. The third hole 13e is closed when the third connecting portion 13d is inserted through it. The fourth plug 14b and the fourth operating portion 14c are connected by, for example, a round rod-shaped fourth connecting portion 14d. A fourth hole 14e is formed on the outer surface of the fourth resonance tube 14, with a diameter approximately the same as the diameter of the fourth connecting portion 14d. The fourth hole 14e is closed when the fourth connecting portion 14d is inserted through it. The fifth plug 15b and the fifth operating portion 15c are connected by, for example, a round rod-shaped fifth connecting portion 15d. A fifth hole 15e is formed on the outer surface of the fifth resonance tube 15, with a diameter approximately the same as the diameter of the fifth connecting portion 15d. The fifth hole 15e is closed when the fifth connecting portion 15d is inserted through it.

[0014] The state shown in Figures 1 and 4 is a closed state in which the first opening 11a to the fifth opening 15a are closed by the first plugs 11b to the fifth plugs 15b, respectively. The first operating parts 11c to the fifth operating parts 15c can each be operated individually. From the closed state of the first opening 11a, as shown in Figure 5, for example, if the first operating part 11c is pushed a predetermined distance toward the center of the resonance section 10, the first plug 11b moves a predetermined distance toward the center of the resonance section 10. As a result, the first opening 11a becomes open, not closed by the first internal member 112b of the first plug 11b. Note that the second resonance tubes 12 to the fifth resonance tubes 15 are omitted in Figure 5. Similarly, from the closed state of the second opening 12a, if the second operating part 12c is pushed a predetermined distance toward the center of the resonance section 10, the second plug 12b moves a predetermined distance toward the center of the resonance section 10. As a result, the second opening 12a becomes open, not blocked by the second internal member 122b of the second stopper 12b. Similarly, when the third operating part 13c is pushed a predetermined distance toward the center of the resonance part 10 from the closed state of the third opening 13a, the third stopper 13b moves a predetermined distance toward the center of the resonance part 10. As a result, the third opening 13a becomes open, not blocked by the third internal member 132b of the third stopper 13b. Similarly, when the fourth operating part 14c is pushed a predetermined distance toward the center of the resonance part 10 from the closed state of the fourth opening 14a, the fourth stopper 14b moves a predetermined distance toward the center of the resonance part 10. As a result, the fourth opening 14a becomes open, not blocked by the fourth internal member 142b of the fourth stopper 14b. Similarly, when the fifth operating part 15c is pushed a predetermined distance toward the center of the resonance part 10 from the closed state of the fifth opening 15a, the fifth stopper 15b moves a predetermined distance toward the center of the resonance part 10. As a result, the fifth opening 15a is left open and not blocked by the fifth internal member 152b of the fifth plug 15b.

[0015] Also, when the first operation part 11c is pulled by a predetermined distance toward the radially outer side of the resonance part 10 from the open state of the first opening part 11a, the first plug 11b moves by a predetermined distance toward the radially outer side of the resonance part 10. As a result, the first opening part 11a becomes a closed state blocked by the first internal member 112b of the first plug 11b. Similarly, when the second operation part 12c is pulled by a predetermined distance toward the radially outer side of the resonance part 10 from the open state of the second opening part 12a, the second plug 12b moves by a predetermined distance toward the radially outer side of the resonance part 10. As a result, the second opening part 12a becomes a closed state blocked by the second internal member 122b of the second plug 12b. Similarly, when the third operation part 13c is pulled by a predetermined distance toward the radially outer side of the resonance part 10 from the open state of the third opening part 13a, the third plug 13b moves by a predetermined distance toward the radially outer side of the resonance part 10. As a result, the third opening part 13a becomes a closed state blocked by the third internal member 132b of the third plug 13b. Similarly, when the fourth operation part 14c is pulled by a predetermined distance toward the radially outer side of the resonance part 10 from the open state of the fourth opening part 14a, the fourth plug 14b moves by a predetermined distance toward the radially outer side of the resonance part 10. As a result, the fourth opening part 14a becomes a closed state blocked by the fourth internal member 142b of the fourth plug 14b. Similarly, when the fifth operation part 15c is pulled by a predetermined distance toward the radially outer side of the resonance part 10 from the open state of the fifth opening part 15a, the fifth plug 15b moves by a predetermined distance toward the radially outer side of the resonance part 10. As a result, the fifth opening part 15a becomes a closed state blocked by the fifth internal member 152b of the fifth plug 15b.

[0016] Note that the silencer 100 may include a drive part such as a motor that drives the first operation part 11c to the fifth operation part 15c to individually switch the first opening part 11a to the fifth opening part 15a between the closed state and the open state, and a control part that controls the drive part. In this case, the control part may control the drive part based on a preset combination of the closed state and the open state in the first opening part 11a to the fifth opening part 15a.

[0017] In the open state of the first opening 11a, when a sound wave is incident into the sound guide path 20 from one end which is the entrance of the sound guide path 20, a resonance sound corresponding to a wavelength according to the volume of the first air chamber 11A occurs in the first air chamber 11A. At the end of the first opening 11a on the side of the sound guide path 20, the sound (incident sound) incident from the sound guide path 20 to the first opening 11a and the resonance sound (emitted sound) generated in the first air chamber 11A interfere with each other, and the frequency sound according to the volume of the first air chamber 11A is canceled. That is, the first opening 11a and the first resonance tube 11 constitute a Helmholtz resonator. As a result, at the other end which is the exit of the sound guide path 20, the frequency (resonance frequency) sound according to the volume of the first air chamber 11A is silenced and emitted. The frequency according to the volume of the first air chamber 11A is the silencing frequency of the first resonance tube 11.

[0018] Similarly, in the open state of the second opening 12a, when a sound wave is incident into the sound guide path 20 from one end which is the entrance of the sound guide path 20, a resonance sound corresponding to a wavelength according to the volume of the second air chamber 12A occurs in the second air chamber 12A. At the end of the second opening 12a on the side of the sound guide path 20, the sound (incident sound) incident from the sound guide path 20 to the second opening 12a and the resonance sound (emitted sound) generated in the second air chamber 12A interfere with each other, and the frequency sound according to the volume of the second air chamber 12A is canceled. That is, the second opening 12a and the second resonance tube 12 constitute a Helmholtz resonator. As a result, at the other end which is the exit of the sound guide path 20, the frequency (resonance frequency) sound according to the volume of the second air chamber 12A is silenced and emitted. The frequency according to the volume of the second air chamber 12A is the silencing frequency of the second resonance tube 12.

[0019] Similarly, when the third opening 13a is open and sound waves are incident on the sound guide 20 from one end, which is the entrance to the sound guide 20, a resonant sound corresponding to a wavelength corresponding to the volume of the third chamber 13A is generated in the third chamber 13A. At the end of the third opening 13a on the sound guide 20 side, the sound incident on the third opening 13a from the sound guide 20 (incident sound) and the resonant sound generated in the third chamber 13A (emitted sound) interfere with each other, and a sound with a frequency corresponding to the volume of the third chamber 13A is canceled out. In other words, the third opening 13a and the third resonant tube 13 constitute a Helmholtz resonator. As a result, at the other end, which is the exit of the sound guide 20, a sound with a frequency corresponding to the volume of the third chamber 13A (resonant frequency) is attenuated and emitted. The frequency corresponding to the volume of the third chamber 13A is the attenuation frequency of the third resonant tube 13.

[0020] Similarly, when the fourth opening 14a is open and sound waves are incident on the sound guide 20 from one end, which is the entrance to the sound guide 20, a resonant sound corresponding to a wavelength corresponding to the volume of the fourth chamber 14A is generated in the fourth chamber 14A. At the end of the fourth opening 14a on the sound guide 20 side, the sound incident on the fourth opening 14a from the sound guide 20 (incident sound) and the resonant sound generated in the fourth chamber 14A (emitted sound) interfere with each other, and a sound with a frequency corresponding to the volume of the fourth chamber 14A is canceled out. In other words, the fourth opening 14a and the fourth resonant tube 14 constitute a Helmholtz resonator. As a result, at the other end, which is the exit of the sound guide 20, a sound with a frequency corresponding to the volume of the fourth chamber 14A (resonant frequency) is attenuated and emitted. The frequency corresponding to the volume of the fourth chamber 14A is the attenuation frequency of the fourth resonant tube 14.

[0021] Similarly, when the fifth opening 15a is open and sound waves are incident on the sound guide 20 from one end, which is the entrance to the sound guide 20, a resonant sound corresponding to a wavelength corresponding to the volume of the fifth chamber 15A is generated in the fifth chamber 15A. At the end of the fifth opening 15a on the sound guide 20 side, the sound incident on the fifth opening 15a from the sound guide 20 (incident sound) and the resonant sound generated in the fifth chamber 15A (emitted sound) interfere with each other, and a sound with a frequency corresponding to the volume of the fifth chamber 15A is canceled out. In other words, the fifth opening 15a and the fifth resonant tube 15 constitute a Helmholtz resonator. As a result, at the other end, which is the exit of the sound guide 20, a sound with a frequency corresponding to the volume of the fifth chamber 15A (resonant frequency) is emitted at a reduced volume. The frequency corresponding to the volume of the fifth chamber 15A is the silencer frequency of the fifth resonant tube 15.

[0022] The respective silencer frequencies f of the first to fifth resonant tubes 11 to 15 can be determined by the following formula (1).

number

[0023] The shape of the resonant section 10 in this embodiment is, for example, an inner diameter of 100 mm, an outer diameter of 184 mm, a length of 40 mm from one end to the other of the sound guide path 20, a diameter of 10 mm for the first opening 11a to the fifth opening 15a, and a plate thickness of 2 mm for the inner surface of the first to fifth resonant tubes 11 to 5. In this case, the silencer frequency of the first resonant tube 11 is 345 Hz, the silencer frequency of the second resonant tube 12 is 488 Hz, the silencer frequency of the third resonant tube 13 is 690 Hz, the silencer frequency of the fourth resonant tube 14 is 976 Hz, and the silencer frequency of the fifth resonant tube 15 is 1382 Hz.

[0024] As described above, by operating the first operation unit 11c to the fifth operation unit 15c respectively to open or close the first opening 11a to the fifth opening 15a, the frequency at which the silencer 100 will silence can be selected.

[0025] Furthermore, as shown in Figure 6, a silencer 100A may be constructed by connecting multiple silencers 100 in series along the length of the sound guide path 20. In the example shown in Figure 6, silencer 100A comprises three silencers 100, but the number of silencers 100 is not limited to this. Also, the inner diameters of the resonant sections 10 of the multiple silencers 100 may be the same or different from each other. Also, the silencer frequencies of the first to fifth resonant tubes 11 to 15 of the multiple silencers 100 may be the same or different from each other. When the silencer frequencies of the first to fifth resonant tubes 11 to 15 are the same in the multiple silencers 100, the silencer effect can be improved at the same silencer frequency. On the other hand, when the silencer frequencies of the first to fifth resonant tubes 11 to 15 are different in the multiple silencers 100, the frequency range silenced by silencer 100A can be widened compared to when the silencer frequencies are the same.

[0026] Next, the sound-dampening effect of the silencer 100A of this embodiment will be described. The method for evaluating the sound-dampening effect of the silencer 100A of this embodiment is shown below. First, as shown in Figure 7, a speaker 202 is placed inside a soundproof box 201 made of sound-absorbing material and sound-insulating material, with the speaker 202 oriented to emit sound upwards. Next, the silencer 100A is placed on top of the soundproof box 201 so that the centers of the silencer 100A and the speaker 202 are aligned. Here, the sound-dampening frequencies of the first resonant tube 11 to the fifth resonant tube 15 are the same in the three silencers 100 that the silencer 100A is equipped with. Next, a microphone 203 is placed 30 cm above the speaker 202. Next, white noise of 100 to 2000 Hz is emitted from the speaker 202, and the sound that has passed through the sound guide path 20 of the silencer 100A is received and observed by the microphone 203.

[0027] In Figure 8, the observed results when all of the first openings 11a to the fifth openings 15a of each silencer 100A are closed are shown by solid lines. Furthermore, the observed results for the first state, where the first openings 11a to the fifth openings 15a of one silencer 100 are open and the first openings 11a to the fifth openings 15a of the other two silencers 100 are closed, are shown by dashed lines. Furthermore, the observed results for the second state, where the first openings 11a to the fifth openings 15a of two silencers 100 are open and the first openings 11a to the fifth openings 15a of the other silencer 100 are closed, are shown by dashed lines. Furthermore, the observed results for the third state, where all of the first openings 11a to the fifth openings 15a of each silencer 100A are open, are shown by double-dashed lines. In the graph in Figure 8, the horizontal axis represents sound frequency, and the vertical axis represents decibels (dB).

[0028] As shown in Figure 8, in the observation results for the first, second, and third states, a sound-dampening effect is observed around the mute frequency of the first resonant tube 11 (345 Hz), the mute frequency of the second resonant tube 12 (488 Hz), the mute frequency of the third resonant tube 13 (690 Hz), the mute frequency of the fourth resonant tube 14 (976 Hz), and the mute frequency of the fifth resonant tube 15 (1382 Hz). Furthermore, the sound-dampening effect is higher around the above mute frequencies in the order of the third, second, and first states. Therefore, the sound-dampening effect can be improved by connecting multiple muters 100 in series along the length of the sound guide path 20.

[0029] Next, a noise-canceling earmuff 300 utilizing the noise-canceling device 100A of this embodiment will be described. The noise-canceling earmuff 300 is an earmuff designed to reduce ambient noise and background noise around the user wearing the earmuff 300, thereby suppressing the impact of noise on the user.

[0030] As shown in Figure 9, the noise-canceling earmuffs 300 include a silencer 100A positioned so that the user's left ear is located at the other end of the sound guide 20, which is the exit point; another silencer 100A positioned so that the user's right ear is located at the other end of the sound guide 20, which is the exit point; and a headband 310 that connects the silencer 100A for the left ear and the silencer 100A for the right ear and is worn over the top of the user's head. Note that instead of a three-stage silencer 100 with three silencers 100 connected in series, the noise-canceling earmuffs 300 may also include a two-stage silencer 100 with two silencers 100 connected in series, or a single-stage silencer 100 without overlapping silencers 100.

[0031] In Figure 10, the observed results when all of the first openings 11a to the fifth openings 15a of the silencer 100A are open are shown by a dashed line. Furthermore, the observed results when the first operating parts 11c to the fifth operating parts 15c of the silencer earmuff 300 are operated to open all of the first openings 11a and all of the fifth openings 15a of the silencer 100A, and to close all of the second openings 12a to the fourth openings 14a are shown by a solid line. In this case, as shown by the solid line in Figure 10, it is possible to silence only the noise around 345 Hz, which is the silencer frequency of the first resonant tube 11, and around 1382 Hz, which is the silencer frequency of the fifth resonant tube 15. This makes it possible to silence low-frequency noise around the silencer frequency of the first resonant tube 11 and high-frequency noise around the silencer frequency of the fifth resonant tube 15, while making human voices, which are in the frequency band between low and high frequencies, easier to hear.

[0032] As shown in Figure 11, a single-stage silencer 100B may be constructed with a height equal to that of silencer 100A (the length of the sound guide path 20). By configuring silencer 100B to have more resonant tubes with different silencer frequencies than silencer 100, the frequency range silenced by silencer 100B can be widened compared to silencer 100.

[0033] As described above, the variable-frequency silencer (silencer 100) of this embodiment comprises a plurality of resonant tubes (first resonant tube 11 to fifth resonant tube 15) having different silencer frequencies, a sound guide path 20 provided so as to be surrounded by the plurality of resonant tubes, openings (first opening 11a to fifth opening 15a) provided in each of the plurality of resonant tubes and connected to the sound guide path 20, and operating parts (first operating parts 11c to fifth operating parts 15c) for operating plugs (first plugs 11b to fifth plugs 15b) that can open and close the openings. Therefore, by operating each of the operating parts (first operating parts 11c to fifth operating parts 15c), the openings (first opening 11a to fifth opening 15a) can be opened and closed individually, thereby changing the silencer frequency according to the user's preference. As a result, in noisy places such as construction sites, airports, shooting ranges, and motorsports venues, wearing the silencer 100 makes it possible to reduce noise while making human voices and sounds of specific frequencies easier to hear. Therefore, it becomes easier to communicate even in noisy places. In addition, since the multiple resonant tubes (first resonant tube 11 to fifth resonant tube 15) are configured to surround the sound guide path 20, the silencer 100 can be made into an earmuff type suitable for covering the ears. By using the silencer 100 as an earmuff type silencer, the effects of noise on the human body can be suppressed without damaging the wearer's ear canal, unlike earplugs.

[0034] Furthermore, in the variable-frequency silencer (silencer 100) of this embodiment, the operating sections (first operating section 11c to fifth operating section 15c) are located on the opposite side of the corresponding plugs (first plug 11b to fifth plug 15b) from the corresponding resonance tubes (first resonance tube 11 to fifth resonance tube 15) that are in between the operating sections. Therefore, the user can easily operate the first operating section 11c to fifth operating section 15c from the outer circumferential surface side of the resonance section 10. This allows the user to easily change the frequency at which the silencer 100 silences the sound.

[0035] Furthermore, in the variable-frequency silencer (silencer 100) of this embodiment, the multiple resonant tubes (first resonant tube 11 to fifth resonant tube 15) are connected in a ring shape to form a cylindrical shape. Therefore, the silencer 100 can be made into a shape that is easy to apply to earmuffs.

[0036] Furthermore, the variable-frequency silencer (silencer 100) of this embodiment includes a plurality of resonant tubes (first resonant tube 11 to fifth resonant tube 15) connected in series in multiple stages along the length of the sound guide path 20. Therefore, when the silencer frequencies of the first resonant tube 11 to fifth resonant tube 15 are the same in the silencer 100 connected in series in multiple stages, the silencer effect can be improved at the same silencer frequency. Also, when the silencer frequencies of the first resonant tube 11 to fifth resonant tube 15 are different from each other in the silencer 100 connected in series in multiple stages, the frequency range over which sound is silenced can be widened compared to when the silencer frequencies are the same.

[0037] Although the present invention has been described in detail based on embodiments above, the present invention is not limited to the above embodiments and can be modified without departing from the spirit of the invention. For example, in the above embodiment, a noise-canceling earmuff 300 is given as an example of how the silencer 100 can be used, but this is merely one example. The silencer 100 may also be used by installing it so as to surround the source of the noise. In this case, for example, it is possible to silence noises other than abnormal sounds, alarm sounds, and other sounds that the user would like to hear more easily, using the silencer 100. [Explanation of symbols]

[0038] 100, 100A Silencer (Variable Silencer Frequency Type), 11 First Resonant Tube, 11a First Opening, 11b First Plug, 11c First Operating Section, 12 Second Resonant Tube, 12a Second Opening, 12b Second Plug, 12c Second Operating Section, 13 Third Resonant Tube, 13a Third Opening, 13b Third Plug, 13c Third Operating Section, 14 Fourth Resonant Tube, 14a Fourth Opening, 14b Fourth Plug, 14c Fourth Operating Section, 15 Fifth Resonant Tube, 15a Fifth Opening, 15b Fifth Plug, 15c Fifth Operating Section, 20 Sound Conductor

Claims

1. Multiple resonant tubes with different sound-dampening frequencies, A sound guide path is provided so as to be surrounded by the aforementioned plurality of resonant tubes, Each of the plurality of resonant tubes is provided with an opening connected to the sound guide path, An operating section for operating a stopper that can open and close the aforementioned opening, A silencer with a variable silencer frequency.

2. The sound-dampening frequency variable silencer according to claim 1, wherein the operating section is located on the opposite side of the stopper corresponding to the operating section, with the resonant tube corresponding to the operating section in between.

3. The sound-dampening frequency variable silencer according to claim 1, wherein the plurality of resonant tubes are connected in a ring shape to form a cylindrical shape.

4. The sound-dampening frequency variable silencer according to claim 1, comprising a plurality of resonant tubes connected in series in a plurality of stages along the length of the sound guide path.

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