JPH09222895A - Muffler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a muffler capable of emitting canceling sound waves having coherence with noises in a wide frequency range. SOLUTION: This muffler generates canceling sound waves having the opposite phase to that of the noises from a noise source to suppress the noises, and it is constituted of the first speaker 5 having the first vibrating plate 52, the second speaker 6 having the second vibrating plate 62, and the third speaker 7 emitting sound waves to allow the first vibrating plate 52 and the second vibrating plate 62 to function as drawn cones respectively. The resonance frequency of the first speaker 5 and the resonance frequency of the second speaker 6 are set to values apart from each other by the prescribed frequency to effectively suppress the exhaust noises in a low-frequency range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a muffling device that suppresses noise by a canceling action of a canceling sound wave. In particular, it relates to an improvement of a muffler having a diaphragm that can operate as a drone cone.

[0002]

2. Description of the Related Art As a muffler of this type, a muffler has been developed which suppresses noise by causing a speaker to emit a canceling sound wave having a phase opposite to that of noise from a noise source (Japanese Patent Laid-Open No. 5-39712). Gazette). According to this silencer, a cancel sound wave of equal sound pressure is generated in a phase opposite to that of the noise, so that the noise is canceled and suppressed by the interference effect of the cancel sound wave.

However, according to this silencer, since resonance is utilized, the noise suppressing effect is obtained at the resonance frequency which is a single frequency, but the noise suppressing effect is not always sufficient at other frequencies. . Further, as a silencer, as shown in FIG. 8, a box body 200 is provided on the outlet 100a side of the exhaust pipe 100, and two speakers 300 and 400 are provided at substantially symmetrical positions with respect to the outlet 100a.
0, so that canceling sound waves K1 and K2 having coherence with the exhaust noise K1 are generated in the speakers 300 and 40.
It is disclosed that each substance is released from 0 (JP-A-5-46189). According to this, since the two speakers 300 and 400 are provided at substantially symmetrical positions with respect to the outlet 100a from which the exhaust noise K1 is emitted, it is advantageous to reduce the bias of the silencing effect.

Generally, in a sound wave generator such as a speaker,
In order to efficiently generate a canceling sound wave having a low frequency and a high sound pressure, it is necessary to vibrate the diaphragm with a large amplitude. According to the muffling device shown in FIG. 8, since the box body 200 has a closed structure, the air-stiffness is high, and the generation efficiency of generating the cancel sound wave of the low frequency range is not always sufficient. Therefore, it has been necessary to apply a large amount of power to the speaker or increase the size of the speaker in order to improve the generation efficiency. Note that stiffness is a concept that means a spring constant.

[0005]

By the way, a technique utilizing a drone cone based on a resonance phenomenon in a diaphragm such as a speaker has been developed in recent years. According to this technology,
Since the resonance phenomenon that increases the amplitude of the diaphragm is utilized, the diaphragm can be vibrated with a large amplitude while saving power consumption and reducing the size. Therefore, it is advantageous to emit a canceling sound wave having a high sound pressure in the low range. The drone cone does not vibrate based on an electromagnetic force acting on itself, but is driven by another vibration source and vibrates by a resonance phenomenon to generate a sound wave, and is also called a passive radiator.

The present invention is a further improvement of the above-described muffler having a diaphragm capable of operating as a drone cone, and is capable of emitting a canceling sound wave having coherence to noise in a wide frequency range. An object is to provide a silencer.

[0007]

According to a first aspect of the present invention, there is provided a sound deadening device which suppresses noise by generating a canceling sound wave having a reverse phase with respect to noise from a noise source, and which functions as a drone cone. A plurality of sound wave generators that emit a canceling sound wave having coherence to noise accompanying the vibration of the vibration plate, and a vibration drive source that causes each of the sound wave generator diaphragms to function as a drone cone. And at least two of the diaphragms of the plurality of sound wave generators have different resonance frequencies.

A sound deadening device according to a second aspect of the present invention is a sound deadening device for suppressing noise by generating a canceling sound wave having a reverse phase with respect to noise from a noise source, and a first diaphragm that functions as a drone cone. And a second diaphragm that functions as a drone cone and that emits a canceling sound wave that has a coherence to the noise as the first diaphragm vibrates. A second sound wave generator that emits a canceling sound wave having coherence to noise;
The first vibrating plate of the sound wave generator and the second vibrating plate of the second sound wave generator each include a third sound wave generator that emits a sound wave that functions as a drone cone. The resonant frequency of the vibrating plate and the resonant frequency of the second vibrating plate of the second sound wave generator are set to values separated from each other by a predetermined frequency.

A silencer according to a third aspect is a silencer for suppressing noise by generating a canceling sound wave having a reverse phase with respect to noise from a noise source, and is provided so as to be operable as a drone cone and a drive cone. The first diaphragm provided,
A first sound wave generator that emits a canceling sound wave having coherence to noise due to vibration of the first diaphragm, and a drone cone and a drive cone set to a resonance frequency different from the resonance frequency of the first diaphragm. A second sound wave generator which is provided so as to be capable of emitting a cancel sound wave having coherence to noise accompanying vibration of the second vibration plate;
It is composed of a first vibrating plate of the first sound wave generator and a third vibrating plate that emits sound waves for operating the second vibrating plate of the second sound wave generator as a drone cone, and operates as a drive cone. A first diaphragm of a first sound wave generator,
The second diaphragm of the second sound wave generator emits canceling sound waves in the high frequency range, suppresses the high frequency noise, and operates as a drone cone. The first diaphragm of the first sound wave generator and the second sound wave generator. The second vibrating plate emits a low-frequency canceling sound wave having a lower frequency than the high-frequency canceling sound wave, and suppresses the low-frequency noise.

According to the silencer of the fourth aspect, the sound wave generator according to any one of the first to third aspects is provided with a diaphragm that operates as a drone cone. The sound wave generator has a control circuit when the diaphragm operates as a drone cone. Is electrically connected to the control circuit, and cooperates as a drive cone by a drive signal from the control circuit, and has a suppressing means for suppressing an induced current based on an induced voltage generated in the sound wave generator when operating as a drone cone. It is characterized in that it is provided in the control circuit.

According to a silencer of a fifth aspect, in the first to fourth aspects, a box body provided with the first opening and the second opening arranged in parallel is provided, and the first sound wave generator is the first. A first speaker provided in the box body toward the opening, a second sound wave generator is a second speaker provided in the box body toward the second opening, and a third sound wave generator is the first sound wave. A third speaker provided in the space of the box located between the generator and the second sound wave generator, the first speaker being arranged on one side of the third speaker, and the other of the third speakers. Second on the side of
A speaker is arranged.

[0012]

According to the muffler of the present invention, when the cancel sound wave is emitted, the diaphragm of the sound wave generator is operated as a drone cone. Therefore, the amplitude of the diaphragm at a predetermined resonance frequency. Is large. Since the drone cone based on the resonance phenomenon is used as described above, it is advantageous to vibrate the diaphragm with a large amplitude. Therefore, it is advantageous to emit a canceling sound wave with high sound pressure while saving power consumption and reducing the size. In particular, it is advantageous to emit a canceling sound wave having a high sound pressure in a low frequency range. Since the canceling sound waves have a phase opposite to that of the noise, they cancel and interfere with each other.
As a result, noise can be suppressed. If the amplitude of the diaphragm increases due to resonance as described above, it is possible to obtain an effect that is advantageous in emitting canceling sound waves with high sound pressure while saving power consumption.

According to the silencer of each of the claims, since the resonance frequencies of the diaphragms of the sound wave generators that operate as drone cones are set to values separated from each other by a predetermined frequency, the above effects can be obtained. The resonance frequency range is expanded. Therefore, it is advantageous to emit a canceling sound wave having coherence to noise in a wide frequency range. Further, according to the muffler according to claim 3, the first silencer that operates as a drive cone
The first vibrating plate of the sound wave generator and the second vibrating plate of the second sound wave generator emit high-frequency canceling sound waves to suppress high-frequency noise. In addition, the first vibrating plate of the first sound wave generator and the second vibrating plate of the second sound wave generator, which operate as a drone cone, emit a low-frequency canceling sound wave having a lower frequency than a high-frequency canceling sound wave. , Suppress low frequency noise.
Therefore, it is possible to further widen the area of the canceling sound wave having the coherence to the noise.

When the diaphragm of the sound wave generator operates as a drone cone, if the sound wave generator is electrically connected to the control circuit, an induced voltage is generated, and the drone cone is generated based on the induced voltage. An induced current flows in a direction that hinders the operation of. That is, electromagnetic braking acts. In this case, the performance as a drone cone is reduced, and the generation efficiency of low-frequency cancel sound waves is reduced. In this regard, according to the silencer according to claim 4, the induction current based on the induction voltage is suppressed even though the diaphragm of the sound wave generator is electrically connected to the control circuit when operating as a drone cone. Since the control means for suppressing the electromagnetic braking is provided in the control circuit, it is advantageous to reduce or avoid electromagnetic braking.

According to the silencer of the fifth aspect, the first speaker is arranged on one side of the third speaker and the second speaker is arranged on the other side of the third speaker. Therefore, as will be described later, both the space on one side and the space on the other side of the third speaker can be effectively used as a sound wave propagation space, which is advantageous for downsizing the silencer.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram according to the present embodiment. The exhaust gas discharged from the internal combustion engine passes through the exhaust system muffler 1f and is discharged to the outside from the outlet 1c of the exhaust pipe 1. Exhaust noise K _p resulting from the explosion process of the internal combustion engine is emitted from the outlet 1c of the exhaust pipe 1 as a noise source together with the exhaust gas. Of the exhaust noise emitted from the exhaust pipe 1 of the internal combustion engine, generally, in addition to a large primary component of sound pressure energy and a low frequency range, it is smaller than the primary component in terms of sound pressure energy. There are secondary and tertiary components in the high frequency range, but exhibit harmonic states.

In order to secure a good silencing effect for exhaust noise, in addition to the interference with the primary component, the interference with the secondary component and the tertiary component cannot be ignored. As will be described later, the present embodiment suppresses not only exhaust noise related to the primary component in the low range, but also exhaust noise in the high range related to the secondary and tertiary components, which is emitted from the exhaust pipe 1. As shown in FIG. 1, a box 4 of a silencer is arranged near the exhaust pipe 1. The box body 4 includes a first small chamber 41 having an opening 41c,
A second small chamber 42 having an opening 42c and a large-volume large chamber 43 adjacent to the small chambers 41, 42 are provided.

As can be seen from FIG. 2, the opening 41c and the opening 42c are opened in the same direction, and are located substantially symmetrically on a virtual circle M centered on the central axis N of the outlet 1c of the exhaust pipe 1. It is arranged. The first speaker 5 as the first sound wave generator shown in FIG. 1 is installed in the first small chamber 41. The first speaker 5 is a cone that generates a canceling sound wave, and a first diaphragm 52 that faces the opening 41c,
A first voice coil 54 as a first drive source that vibrates the first diaphragm 52 with an electromagnetic force, and a magnet part (not shown) that forms a magnetic field are provided.

The second speaker 6 as the second sound wave generator is installed in the second small chamber 42. The second speaker 6 is composed of a cone that generates a canceling sound wave and faces the opening 42c, and a second voice coil 64 as a second drive source that vibrates the second diaphragm 62 with an electromagnetic force.
And a magnet portion (not shown) that forms a magnetic field.

The third speaker 7 is arranged at a substantially intermediate position of the large chamber 43. The third speaker 7 functions as a vibration drive source and a third sound wave generator. The third speaker 7 includes a third diaphragm 72 that is a cone that generates a canceling sound wave,
A third voice coil 74 as a third drive source that vibrates the third diaphragm 72 with an electromagnetic force, and a magnet part (not shown) that forms a magnetic field are provided.

As can be seen from FIG. 1, the third speaker 7
Is located approximately in the middle of the large chamber 43, so the box 4
The large chamber 43 is divided into a first divided chamber 43s and a second divided chamber 43t. In other words, the first divided chamber 43s and the first speaker 5 are arranged in front of (on one side of) the third speaker 7. The second divided chamber 43t and the second speaker 6 are disposed behind the third speaker 7 (on the other side).

According to this embodiment, in the first speaker 5, the first diaphragm 52 has a low frequency f ₁ (for example, 1
The resonance frequency of the first diaphragm 52 is set so as to resonate at 00 [Hz] and operate as a drone cone. A characteristic line B1 in FIG. 3 shows a relationship between frequency and sound pressure when the first diaphragm 52 operates as a drone cone. As can be understood from the characteristic line B1 in FIG. 3, when the first diaphragm 52 operates as a drone cone and resonates at the frequency f ₁ , the amplitude increases and the sound pressure level increases.

In the second speaker 6, the second diaphragm 6
The second vibrating plate 6 so that 2 resonates at a low frequency f ₂ (for example, 200 [Hz]) and operates as a drone cone.
A resonance frequency of 2 is set. Characteristic line B2 in FIG.
Shows the relationship between frequency and sound pressure when the second diaphragm 62 operates as a drone cone. As can be understood from the characteristic line B2 of FIG. 3, when the second diaphragm 62 operates as a drone cone and resonates at the frequency f ₂ , the amplitude increases and the sound pressure level increases.

According to the present embodiment, both the frequencies f ₁ and f ₂ are in the low frequency range, but as can be understood from FIG. 3, they are set to values separated from each other by a predetermined frequency Δf, and f
₁ <f ₂ is set. The characteristic line B4 in FIG.
The characteristic line B1 and the characteristic line B2 shown in FIG. Therefore, if the first diaphragm 52 operates as a drone cone near f ₁ and the second diaphragm 62 operates as a drone cone near f ₂ , the relationship between the frequency and the sound pressure indicated by the characteristic line B4 in FIG. 4 is obtained. can get. Therefore, the characteristic line B4 of FIG.
As can be understood from the above, the region where the sound pressure of the canceling sound wave can be increased is a wide region from around f _{1 to} around f ₂ ,
In other words, it can be made as wide as Δfa.

As can be understood from FIG. 3, the frequency f
_{In 1} , the sound pressure indicated by the characteristic line B1 is large, and the sound pressure indicated by the characteristic line B2 is small. Further, at the frequency f ₂ , the sound pressure indicated by the characteristic line B2 is large, and the sound pressure indicated by the characteristic line B1 is small. Although the sound pressure is biased in the low range as described above, the wavelength (sound velocity / frequency) of the sound wave in the low range is considerably long, whereas the distance between the exhaust pipe 1 and the speakers 5 and 6 is short. Therefore, inconvenience due to the deviation is not particularly practical, and good coherence due to the canceling sound wave in the low frequency band can be obtained.

The characteristic line B5 in FIG. 4 indicates the first speaker 5
5 shows the relationship between frequency and sound pressure when the first diaphragm 52 and the second diaphragm 62 of the second speaker 6 are vibrated not as a drone cone but as a drive cone. As can be understood from the characteristic line B5 of FIG. 4, when the first speaker 5 and the second speaker 6 operate as drive cones, the sound pressure is not sufficiently secured in the low frequency range, but the frequency becomes high. Along with this, the sound pressure gradually increases, and when the frequency exceeds the bass reproduction limit frequency f ₃ (for example, 250 [Hz]), a substantially constant high sound pressure is secured. The drive cone is different from the drone cone in that it vibrates based on the electromagnetic force acting on its own voice coil to generate a sound wave.

As shown in FIG. 1, the control circuit 8 includes a signal output circuit 80 for outputting a cancel signal P _m , a high pass filter (HPF) 81 connected to the signal output circuit 80,
A first amplifier 84 that amplifies the signal from the high-pass filter 81, a conductor 85 that connects the first amplifier 84 to the first voice coil 54, a second amplifier 88 that amplifies the signal from the high-pass filter 81, and a second amplifier 88. To the second voice coil 64, a low-pass filter (LPF) 90 connected to the signal output circuit 80, a third amplifier 93 for amplifying the signal from the low-pass filter 90, and a third
And a conducting wire 94 connecting the amplifier 93 to the third voice coil 74.

Further, as shown in FIG. 1, the control circuit 8 has a filter means 97 interposed between the conductor wire 94 and the conductor wire 85,
Filter means 98 interposed between the conductor 94 and the conductor 89
And an exhaust noise detection sensor 99 mounted on the exhaust pipe 1 or in the vicinity thereof. The exhaust noise detection sensor 99 detects the frequency of the pulsation of exhaust noise. The exhaust noise detection sensor 99 may be a sound sensor such as a microphone that detects exhaust noise, or a pressure sensor that detects pulsation of the pressure of the exhaust pipe 1. Based on the detection signal of the exhaust noise detection sensor 99, the signal output circuit 80 determines the frequency of the exhaust noise and outputs a cancel signal P _m for emitting a cancel sound wave corresponding thereto. As shown in FIG. 1, in the present embodiment, at the end of the outlet 1c of the exhaust pipe 1,
A confirmation sensor 69 is provided to detect whether or not the exhaust noise has been silenced as desired. The detection signal of the confirmation sensor 69 is input to the signal output circuit 80 via the signal line 69p,
Based on this, the cancellation signal P _m is modified.

The input terminal of the first voice coil 54 of the first speaker 5 is always connected to the first amplifier 84. The input terminal of the second voice coil 64 of the second speaker 6 is always connected to the second amplifier 88. The input terminal of the third voice coil 74 of the third speaker 7 is always connected to the third amplifier 93. The cutoff frequency of the high pass filter 81 can be set to 250 [Hz], and the cutoff frequency of the low pass filter 90 can be set to 250 [Hz], for example. Note that cutoff frequency> resonance frequency f ₂
> Resonance frequency f ₁ is established.

In the present embodiment, the cancel signal P _m generated by the signal output circuit 80 includes a high frequency signal having a high frequency and a low frequency signal having a low frequency. A high frequency signal having a high frequency in the cancel signal P _m passes through a high pass filter (HPF) 81, is amplified by the first amplifier 84, and is input to the input terminal of the first voice coil 54 of the first speaker 5. At the same time, it is amplified by the second amplifier 88 and input to the second voice coil 64 of the second speaker 6. Based on this, the first diaphragm 52 and the second diaphragm 52 of the first speaker 5 are
The second diaphragm 62 of the speaker 6 operates as a drive cone, and the first diaphragm 52 and the first diaphragm 62 vibrate at high frequencies. Therefore, the cancel sound wave having the sound pressure characteristic of the characteristic line B5 in FIG. 4 is emitted. Therefore, this canceling sound wave interferes with and cancels out exhaust noise having a high frequency range (a frequency higher than the low sound limit frequency), and the exhaust noise is suppressed.

The low-frequency signal having a low frequency in the cancel signal P _m passes through the low-pass filter (LPF) 90, is amplified by the third amplifier 93, and is supplied to the third speaker 7 of the third speaker 7.
It is input to the input terminal of the voice coil 74. Based on this, the third diaphragm 72 of the third speaker 7 vibrates. Then, the sound wave emitted from the third diaphragm 72 of the third speaker 7 propagates to the first divided chamber 43s, whereby the first diaphragm 52 of the first speaker 5 vibrates. Similarly, the third speaker 7
Sound waves emitted from the third vibrating plate 72 of the second dividing chamber 43
to the second diaphragm 6 of the second speaker 6.
2 also vibrates. At this time, if the frequency at which the first diaphragm 52 vibrates is the resonance frequency f ₁ , the first diaphragm 52 resonates with a large amplitude due to the resonance phenomenon, the first diaphragm 52 operates as a drone cone, and the first speaker A cancellation sound wave having a low sound pressure and a high sound pressure is emitted from 5.

If the frequency at which the second diaphragm 62 vibrates is the resonance frequency f ₂ , the second diaphragm 6 will be vibrated due to the resonance phenomenon.
2 resonates with a large amplitude, the first diaphragm 52 operates as a drone cone, and the second speaker 6 emits a canceling sound wave having a low sound pressure and a high sound pressure. Such canceling sound waves having a low frequency interfere with and cancel out the exhaust noise in the low range, and the exhaust noise in the low range is suppressed.

By the way, since a value apart Δf from each other and the resonance frequency f ₂ of the resonant frequency f ₁ and the second diaphragm 62 of the first diaphragm 52 as described above, the first of the first speaker 5
When the diaphragm 52 and the second diaphragm 62 of the second speaker 6 both vibrate, as a result, the characteristic line B4 as shown in FIG.
The sound pressure characteristic shown in (trapezoidal sound pressure characteristic) is obtained. Therefore, the region where the sound pressure of the cancel sound wave can be increased can be widened from around f _{1 to} around f ₂ , that is, Δfa.

As described above, according to the present embodiment, the cancel sound wave for suppressing the exhaust noise in the low frequency range, which is the primary component having the greatest influence on the exhaust noise from the internal combustion engine, increases the sound pressure. Since the range can be widened to Δfa, it is advantageous for suppressing exhaust noise in the low frequency range. As for the secondary component and the tertiary component of high frequency in the exhaust noise, as described above, the first component of the first speaker 5 is used.
The diaphragm 52 and the second diaphragm 62 of the second speaker 6 operate as a drive cone, and the first speaker 5 and the second speaker 6
Canceling sound waves having the same pressure and the same phase are emitted from each. The canceling sound waves interfere with the exhaust noise in the high frequency range and cancel each other, thereby suppressing the exhaust noise in the high frequency range.

A characteristic line B7 shown in FIG. 5 is a characteristic line B4 shown in FIG.
And the characteristic line B5 are superposed, and the frequency range where a high sound pressure level is obtained is widened to Δf _C (Δf _C > Δfa). Therefore, according to the present embodiment, a good silencing effect can be exerted from exhaust noise of the primary component in the low frequency range to exhaust noise of the secondary and tertiary components in the high frequency range.

By the way, according to this embodiment, the speakers 5 and 6 are considered in consideration of the frequency characteristic of the exhaust noise from the internal combustion engine.
When operating as a drone cone that emits low-frequency canceling sound waves, it also cooperates with the drive cone to emit mid-range and high-range canceling sound waves. Considering this point, as can be understood from FIG. 1, the first speaker 5
Is always electrically connected to the amplifier 84 side, and the second speaker 6 is always electrically connected to the amplifier 88 side. Therefore, when the first diaphragm 52 of the first speaker 5 operates as a drone cone, an induction voltage is generated in the first voice coil 54 of the first speaker 5 due to an electromagnetic induction phenomenon due to the resonance of the first diaphragm 52. , The induced current flows based on the induced voltage in the direction that restricts the operation of the drone cone. That is, the first speaker 5
Electromagnetic braking acts on the and reduces the operation as a drone cone.

In this respect, according to the present embodiment, the canceling signal P _t having the voltage waveform of substantially the same phase and the same voltage value as the phase and the voltage value of the induced voltage is generated by the filter means 97 operating as the suppressing means. Is generated and the cancellation signal P _t is applied to the input terminal of the first voice coil 54 of the first speaker 5.
Then, the potential difference between the voltage of the cancellation signal P _t and the induced voltage disappears or is reduced, whereby the flow of the induced current is suppressed. Therefore, electromagnetic braking in the first speaker 5 is suppressed, and operation as a drone cone is ensured.
Therefore, the sound pressure of the cancel sound wave in the low range is secured. Therefore, it is advantageous to increase the sound pressure of the cancel sound wave in the low frequency range while reducing the power consumption. Therefore, it is advantageous to effectively muffle low-frequency exhaust noise.

For example, when the third speaker 7 is driven, the first speaker
When the first diaphragm 52 of the speaker 5 operates as a drone cone, the input signal (IN signal) applied to the input terminal of the third voice coil 74 of the third speaker 7 is e
(t) = E.sin (ωt + φ ₁ ) and the induced voltage signal (OUT signal) generated in the first voice coil 54 is e ₀ (t) = E
_It is assumed that ₀ · sin (ωt + φ ₂ ). Here, if the Laplace transform of e (t) is E (S) and the Laplace transform of e ₀ (t) is E _O (S), the transfer function D (S) is
It is represented by D (S) = (output signal / input signal) = _EO (S) / E (S). Therefore, the transfer function D (S) satisfying this relationship is electrically formed by the filter means 97.

When the second speaker 6 also operates as a drone cone, the second speaker 6 operates as an amplifier 88.
Since it is always electrically connected to the side, there is a problem of electromagnetic braking due to an induced current as described above. Therefore, the second speaker 6 is activated by the filter means 98 that operates as a suppressing means.
Generates a cancellation signal P _k having a voltage waveform of substantially the same phase and same voltage value for in-phase and the voltage value of the induced voltage generated, a cancellation signal P _k second voice coil 64 of the second speaker 6 Apply to the input terminal of. Then, the potential difference between the voltage of the cancellation signal P _k and the induced voltage disappears or is reduced,
This suppresses the flow of induced current. Therefore, electromagnetic braking in the second speaker 6 is suppressed, and operation as a drone cone is ensured. Therefore, the sound pressure of the cancel sound wave in the low range is secured. Therefore, it is advantageous to increase the sound pressure of the cancel sound wave in the low frequency range while reducing the power consumption. Therefore, it is advantageous to effectively muffle low-frequency exhaust noise.

In the speaker, in order for the vibrating body, which is a cone, to vibrate well, not only a front space for vibrating the vibrating body to transmit sound waves to the front side but also a rear space behind the vibrating body is required. In this respect, according to the present embodiment, as shown in FIG. 1, the first divided chamber 43s and the first speaker 5 are arranged in front of the third speaker 7, and the second divided chamber 43t and the first speaker 5 are arranged behind the third speaker 7. Two speakers 6 are arranged.
Therefore, the second divided chamber 43t behind the third speaker 7 also serves as a sound wave propagation space for propagating a sound wave from the third speaker 7 to the second speaker 6, in addition to the above-mentioned role as the rear space. In other words, both the space on one side and the space on the other side of the third speaker can be effectively used as the sound wave propagation space. Therefore, it is advantageous in saving space, and is advantageous in reducing the size of the silencer.

(Second Embodiment) Next, a second embodiment will be described with reference to FIG. The second embodiment has basically the same configuration as the first embodiment. As shown in FIG. 6, the control circuit 8 outputs a cancel signal P _m as a digital signal, a signal output circuit 80, a digital high-pass filter (HPF) 81 connected to the signal output circuit 80,
A first D / A converter 83 for converting a digital signal output from the high-pass filter 81 via the conducting wire 82 into an analog signal; a first amplifier 84 for amplifying the analog signal from the first D / A converter 83; A conducting wire 85 connecting the amplifier 84 to the first voice coil 54, and a high pass filter 81.
Second D / A converter 87 for converting a digital signal output from the second conductor 86 into an analog signal, and a second amplifier 88 for amplifying the analog signal from the second D / A converter 87.
, A conductor 89 connecting the second amplifier 88 to the second voice coil 64, a digital low-pass filter (LPF) 90 connected to the signal output circuit 80, and a low-pass filter 9.
A third D / A converter 92 for converting a digital signal output from 0 through the conductor 91 into an analog signal; and a third D / A converter
Third amplifier 9 for amplifying analog signal from converter 92
3 and a conducting wire 94 connecting the third amplifier 93 to the third voice coil 74.

Further, as shown in FIG. 6, the control circuit 8 has a filter means 97 interposed between the conductor wire 91 and the conductor wire 82,
Filter means 98 interposed between the conductor wire 91 and the conductor wire 86.
And an exhaust noise detection sensor 99 mounted on the exhaust pipe 1 or in the vicinity thereof. In this embodiment also the resonance frequency f ₁ of the first speaker 5 as shown in FIG. 3 are both low frequency and the resonance frequency f ₂ of the second speaker 6, is set to a value apart sentence frequency Δf from each other , Therefore Figure 4
The sound pressure characteristics shown in and the sound pressure characteristics shown in FIG. 5 are obtained. Therefore, as in the case of the first embodiment described above, a good silencing effect can be exerted from exhaust noise of the primary component of the low frequency region to exhaust noise of the secondary component and the tertiary component of the high frequency region.

(Third Embodiment) Next, a third embodiment will be described with reference to FIG. The second embodiment has basically the same configuration as the first embodiment, and basically has the same operational effect. The third speaker 7 is installed in the large room 43. Both the first speaker 5 and the second speaker 6 are arranged in front of the third speaker 7, and the first speaker 5 and the second speaker 6 are arranged by sound waves emitted in front of the third speaker 7.
And the second speaker 6 both operate.

According to this embodiment, as the drone cone, as shown in FIG. 7, the first speaker 5 and the second speaker 6 which are arranged side by side are two in total, but not limited to this. The total number may be three or more. If the resonance frequencies of the speakers are set to different values, it is more advantageous for widening the noise suppression effect.

(Other Embodiments) According to the embodiment shown in FIG. 1 described above, the cancellation signal P is generated based on the signal from the exhaust noise detection sensor 77 for the frequency of the exhaust noise of the internal combustion engine.
_The method of generating _m is adopted, but not limited to this,
The cancel signal P _m may be generated based on a signal synchronized with an ignition signal of an ignition plug of the internal combustion engine or a drive signal of a crankshaft driven by the internal combustion engine.

According to the above embodiment, the exhaust noise leaking from the exhaust pipe of the internal combustion engine is applied, but the exhaust noise leaking from the exhaust pipe is not limited to the exhaust noise. Further, it is applicable not only to the internal combustion engine but also to the suppression of noise emitted from other noise sources.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a silencer according to a first embodiment.

FIG. 2 is a configuration diagram near an outlet of an exhaust pipe.

FIG. 3 is a graph schematically showing sound pressure characteristics when operating as a drone cone.

FIG. 4 is a graph schematically showing superimposed sound pressure characteristics when two speakers are operated as a drone cone.

FIG. 5 is a graph schematically showing sound pressure characteristics of canceling sound waves emitted by the muffling device.

FIG. 6 is a configuration diagram of a silencer according to a second embodiment.

FIG. 7 is a configuration diagram of a main part of a silencer according to a third embodiment.

FIG. 8 is a configuration diagram of a main part of a silencer according to a conventional technique.

[Explanation of reference numerals] In the figure, 4 is a box, 5 is a first speaker (first sound wave generator), 6 is a second speaker (second sound wave generator), and 7 is a third
A speaker (vibration drive source, third sound wave generator) 8 is a control circuit.

Claims (5)

[Claims] 1. A silencer for suppressing noise by generating a canceling sound wave having a reverse phase with respect to noise from a noise source, comprising a diaphragm functioning as a drone cone, and accompanying the vibration of the diaphragm. The sound wave generator is composed of a plurality of sound wave generators that emit canceling sound waves having coherence to noise, and a vibration drive source that causes the diaphragms of the sound wave generators to function as drone cones. A silencer, wherein at least two of the diaphragms of the generator have different resonance frequencies. 2. A silencer for suppressing noise by generating a canceling sound wave having a reverse phase with respect to noise from a noise source, comprising a first diaphragm that functions as a drone cone. With a first sound wave generator that emits a canceling sound wave having a coherence to the noise due to the vibration of the robot and a second diaphragm that functions as a drone cone, and interferes with the noise due to the vibration of the second diaphragm. A second sound wave generator for emitting a canceling sound wave having a property, a first diaphragm for the first sound wave generator, and a second sound wave for causing the second diaphragm of the second sound wave generator to function as drone cones, respectively. And a resonance frequency of the first diaphragm of the first sound wave generator and a resonance frequency of the second diaphragm of the second sound wave generator are separated from each other by a predetermined frequency. Characterized by being set to a value And silencer. 3. A sound deadening device for suppressing noise by generating a canceling sound wave having a reverse phase with respect to noise from a noise source, comprising a first diaphragm operably provided as a drone cone and a drive cone. A first sound wave generator that emits a canceling sound wave having coherence to noise accompanying vibration of the first diaphragm; a drone cone set to a resonance frequency different from the resonance frequency of the first diaphragm; A second vibrating plate operably provided as a drive cone, and a second sound wave generator that emits a canceling sound wave having coherence to noise accompanying vibration of the second vibrating plate; and the first sound wave generation Vibrating plate of the second wave generator and a third vibrating plate of the second sound wave generator for emitting a sound wave for operating the second vibrating plate of the second sound wave generator as a drone cone, respectively. 1 sound The first vibrating plate of the wave generator and the second vibrating plate of the second sound wave generator emit high-frequency canceling sound waves, suppress high-frequency noise, and operate as a drone cone. First of
The vibrating plate and the second vibrating plate of the second sound wave generator emit a low-frequency canceling sound wave having a lower frequency than a high-frequency canceling sound wave to suppress low-frequency noise. Characteristic silencer. 4. A sound wave generator having a diaphragm that operates as a drone cone according to any one of claims 1 to 3, when the diaphragm operates as a drone cone, it is electrically connected to a control circuit. The control circuit cooperates with a drive signal from the control circuit, and the control circuit is provided with a suppression unit that suppresses an induced current based on an induced voltage generated in the sound wave generator when operating as a drone cone. A silencer characterized by the above. 5. The first opening and the second opening according to claim 1.
A box body is provided in which the openings are provided in parallel, the first sound wave generator is a first speaker provided in the box body toward the first opening, and the second sound wave generator is the second opening. Towards the second speaker provided in the box body, the third sound wave generator is located between the first sound wave generator and the second sound wave generator, and is located in the space of the box body. A third speaker provided, wherein the first speaker is arranged on one side of the third speaker, and the second speaker is arranged on the other side of the third speaker. apparatus.