JPH0753119Y2 - Active noise canceller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an active noise canceller having a function of positively canceling external noise.

(Prior Art) Conventionally, as an active noise canceller, for example, one described in US Pat. No. 4,455,675 is known. This active noise canceller outputs a cancel sound having a phase opposite to that of an input sound from a monitor microphone from a muffling speaker, and cancels the external noise by canceling the external noise and the cancel sound.

However, according to this conventional technique, there is a problem that it is difficult to install the microphone for monitoring so as to input the cancel sound without bias and not disturb the sound field of the cancel sound.

Moreover, the monitoring microphone needs to be provided with some distance from the muffling speaker because external noise must also be input, which causes a phase delay and howling.

Therefore, the applicant of the present application, as a means for solving the above-mentioned conventional problems by a simple control circuit that does not require feedback control, is disclosed in Japanese Patent Application No. 1-44790.
We proposed a noise canceller (hereinafter referred to as prior art).

In this prior art, a sub-peaker that emits a sub-cancellation sound having the same phase as the cancellation sound is provided on the negative pressure surface of the muffling speaker, and a monitoring microphone is provided at a position where the cancellation sound and the sub-cancellation sound cancel each other. Only external noise is input to the microphone.

(Problems to be solved by the invention) However, in this prior art, only cancellation of external noise is considered, but no consideration is given to the case where it is not canceled. In other words, this prior art active noise canceller is a headphone type that is used by mounting it in the ear cavity, but when using it, sometimes you want to hear the necessary sound without canceling external noise. is there. In this case, if it covers the entire ear cavity like a headphone type, and in particular, if the soundproof speaker and the sub-speaker are completely cut off by a partition wall, the external sound that can be heard without canceling the noise is However, there is a problem that the external sound coming from the sub-speaker side is transmitted only to the external sound that has passed through the diaphragms of both speakers, and the external sound to be heard cannot be fully heard. In addition, in such a case, there is a problem that the air permeability is low and the ear cavity side feels a feeling of pressure and blockage.

The present invention has been made in view of the above-mentioned problems. When noise is not cancelled, an external sound can be fully heard, and an active / active sound that does not cause a feeling of pressure or blockage during use can be obtained. The task is to develop a noise canceller.

(Means for Solving the Problems) In the active noise canceller of the present invention, a support member fixed to a cover that covers the ear cavity and defining a space in the cover into two spaces, and the ear cavity of the support member. Side, and a muffling speaker that emits a canceling sound having a phase opposite to that of the sound to be muffled to the user's ear cavity, and the muffling speaker on the foreign sound side of the support member are supported in a facing arrangement, and the foreign sound A sub-speaker that emits a sub-cancellation sound that has a phase opposite to that of the cancellation sound with respect to the space and that is in the same phase as the cancellation sound with respect to the ear cavity of the user; A monitor microphone arranged on a target surface equidistant from both speakers to be cancelled, for inputting an external sound including a sound to be muted, and the muting speaker based on the input sound from the monitor microphone. A noise cancel circuit that outputs a cancel sound generation signal that causes the peaker to emit the cancel sound and outputs a sub cancel sound generation signal that causes the sub speaker to emit the sub cancel sound; and The silencer speaker side space, which is the ear cavity side space, and the sub speaker side space, which is the space opposite to the ear cavity of the sub speaker, communicate with each other, except for the support arm portion that supports both speakers on the outer circumference of both speakers. And a communication passage for connecting.

(Operation) In the active noise canceller of the present invention, the noise canceling speaker emits a canceling sound having a phase opposite to that of the noise to be muted and the sound is canceled by the canceling effect. Noise can be input without being affected by the sound being muted, howling can be prevented to improve sound deadening performance, and the monitoring microphone is placed close to the sound deadening speaker. With respect to the point that performance can be improved and the point that the monitoring microphone can be installed at a position removed from the radiation front of the vibration member pressure surface of the noise reduction speaker to improve the high frequency noise reduction performance, It is the same.

In addition, the active noise canceller of the present invention has a communication passage that connects the space of the muffler speaker (the space of the ear side) and the space of the sub-speaker side, so that the sound permeability of the muffler speaker in the ear cavity is improved. Is improved and there is no feeling of pressure or blockage.

In addition, the external sound transmitted to the sub-speaker side space through the cover and the like not only passes through the membrane surfaces of both speakers but also passes through the communication passages provided at the outer peripheral positions of both speakers to the silence speaker side space. When the noise is transmitted and the noise is not canceled, the external sound can be fully heard.

Therefore, it is preferable that the communication passage has a large cross-sectional area.

The communication passage also functions as an air vent hole for absorbing a change in space volume due to vibration of a vibration member such as a diaphragm of both speakers.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. still,
In describing the embodiments, a headphone type device that a person wears on the head to cancel noise will be described as an example. Further, in each drawing, the same reference numeral indicates the same object.

First, the configuration will be described.

FIG. 1 is an overall view showing the structure of an active noise canceller according to the first embodiment of the present invention.
Is a muffler speaker, 2 is a sub speaker, 3 is a monitor microphone, 4 is a noise canceling circuit, and 5 is a support member.

The muffling speaker 1 is for radiating a canceling sound toward the sound to be muffled, and includes the housing 1a,
It is composed of a diaphragm 1b, a coil 1c, and a magnet 1d. The diaphragm surface 1e serves as a positive pressure surface that emits a canceling sound, and the diaphragm back surface 1f serves as a negative pressure surface. The housing 1a is formed with an air vent hole 1g.

The sub-speaker 2 is the same speaker as the silencer speaker 1, that is, an acoustically equivalent speaker, and has a housing 2a, a diaphragm 2b, a coil 1c, and a magnet 2d, and the housing 2a is a housing of the silencer speaker 1. It is provided so as to face symmetrically with 1a, that is, the diaphragm back surface 2f which is the negative pressure surface of the sub-speaker 2 faces the diaphragm back surface 1f of the silence speaker 1. The alternate long and short dash line A indicates the plane of symmetry of both speakers 1 and 2. Further, in the sub speaker 2, the diaphragm surface 2e is a positive pressure surface,
The housing 2a is formed with an air vent hole 2g.

By the way, the muffler speaker 1 is mounted so as to face the ear cavity E of the user in the use state.
The space between the loudspeakers 1 and 2 and the ear cavity E is covered with a cover 6 having a shape like a so-called headphone, and the loudspeakers 1 and 2 have a support member inside the cover 6. It is fixed at 5. Therefore, the space inside the cover 6 is defined by the supporting member 5 such that the silencer speaker side space B facing the diaphragm surface 1e of the silencer speaker 1, the intermediate space C between the speakers 1 and 2, and the sub-speaker 2. It is defined in the sub speaker side space D facing the diaphragm surface 2e. Further, an opening 6a for inputting an external sound c is formed in a portion of the cover 6 on the side of the sub speaker side space D.

As shown in FIG. 3, the support member 5 is formed in an annular shape having a support arm 5d on the inside, and the support arm 5d
Both speakers 1 and 2 are attached to the tip of 5d. A communication path 5b is formed between the support arms 5d to connect the speaker side spaces B and D to each other, and the communication path 5b and the intermediate space C are communicated with each other.

Further, as shown in FIG. 1, the monitoring microphone 3 is installed with the tip protruding into the communication passage 5b.

The noise canceling circuit 4 includes a monitoring microphone 3
Based on the input sound of the
The cancel sound generation signal e is output from the 1e side to the muffler speaker 1 so as to generate a cancel sound (FIG. 2a) having a phase substantially opposite to the input sound of the monitor microphone 3, and the rear surface 2f of the diaphragm of the sub speaker 2f. Is a circuit for outputting a sub-canceling sound generation signal f to the sub-speaker 2 in order to generate a sub-canceling sound having the same phase as the canceling sound (a phase opposite to the canceling sound on the diaphragm surface 2e side of the sub-speaker 2). Preamplifier 4a to be amplified and filter circuit that removes unnecessary frequency range from cancel sound
4b, power amplifier 4c for main amplification, and input sound phase 18
It is formed to include an inverting circuit 4d that shifts by 0 degree.

Then, a canceling sound generation signal e having a phase opposite to that of the input signal from the monitoring microphone 3 is given to the muffler speaker 1 through the inverting circuit 4d.

On the other hand, the sub-speaker 2 is supplied with a sub-canceling sound generation signal f having the same phase as the input signal from the monitor microphone 3 without passing through an inverting circuit.

Next, the operation will be described.

The active noise canceller of this embodiment is applied to the ear cavity E as shown in the figure under external noise such as in the cockpit of an aircraft. In addition, in this embodiment, a case will be described in which all of the external sound is noise and all of the external sound is removed as the sound to be silenced.

In this case, the external sound (external noise) c is mainly input from the cover opening 6a through the sub-speaker side space D and the communication path 5b to the monitoring microphone 3. In addition to the above, the sound is also input from the muffler speaker side space B through the cover 6.

In the noise canceling circuit 4, a canceling sound generation signal e having a phase opposite to that of the input signal is formed, and based on this signal e, a canceling sound a as shown in FIG. The external sound c emitted and transmitted to the ear cavity E of the user is silenced by the canceling action of the cancel sound a having a phase opposite thereto.

When the canceling sound a is emitted from the muffling speaker 1, a negative canceling sound b having a phase opposite to that shown in FIG. 2 is emitted from the diaphragm back surface (negative pressure surface) 1f of the muffling speaker 1.

On the other hand, the sub-speaker 2 receives the sub-cancellation signal f having a phase opposite to that of the cancellation sound generation signal e, that is, the sub-cancellation sound (= a) having the same phase as the cancellation sound a is output from the rear surface 2f of the diaphragm. The diaphragm surface 2e emits a negative sub-canceling sound (= b) having a phase opposite to that of the sub-canceling sound.

Therefore, on the symmetry plane A of the speakers 1 and 2 where the monitor microphone 3 is provided, the canceling sound a from the diaphragm surface 1e of the muffling speaker 1 and the diaphragm surface 2e of the sub speaker 2 are generated. The negative sub-canceling sound (= b) is transmitted equivalently, and both sounds cancel each other out to 0.

Therefore, in the monitoring microphone 3, only the external noise c is input, which can prevent howling from occurring due to addition of the original signal and the feedback signal of an integral multiple of 360 °, and howling is generated. It is possible to obtain an effect that it is possible to prevent the deterioration of the silencing performance due to.

Moreover, since the monitoring microphone 3 is arranged on the side surface apart from the front surface of the cancel sound a emitted from the diaphragm 1b, it does not disturb the sound field of the muffling speaker 1, so that stable muffling performance is obtained even in a high frequency range. To be Also,
Since the monitor microphone 3 is installed in the input hole 5b close to the side surfaces of both speakers 1 and 2, only the same external noise that is transmitted to the ear cavity E close to the user's ear cavity E is input. be able to.

Therefore, stable muffling performance can be obtained, and the effect that the circuit and the microphone for feedback control are unnecessary and the configuration is simple is obtained.

Further, as the sub-speaker 2 for canceling the negative cancellation sound b radiated from the diaphragm back surface 1f of the muffling speaker 1, the same speaker as the muffling speaker 1 is acoustically equivalent. The input signal from the monitoring microphone 3 can be used as it is, and there is no need to make the output different with respect to the cancel sound generation signal e, and the configuration can be simplified.

Further, in addition to the above effects, in this embodiment, since the communication passage 5b is formed large in the support member 5, the air permeability is improved,
As a result, it is possible to obtain the effect of not feeling the oppression or the blockage.

When the emission of the cancel sound a is stopped in order to listen to the external sound c, the external sound c input from the opening 6a of the cover 6 into the sub speaker side space D passes through the communication passage 5b and the silence speaker. It is fully transmitted to the side space B and can be heard clearly and easily.

Although the embodiment has been described with reference to the drawings, the specific configuration is not limited to this embodiment, and even if there is a design change or the like within a range not departing from the gist of the invention, the invention is included in the invention. .

For example, in the embodiment, the example in which the communication passage is formed in the support member has been shown, but a small member such as a rod-shaped member may be used as the support member itself, and the remaining space may be used as the communication passage. Also, as the communication passage, if the cross-sectional area is larger than at least the air hole for allowing the displacement of the vibration member such as the diaphragm of both speakers, the external sound is more clearly heard than the one in which both speakers are blocked. The purpose of being audible can be achieved.

Further, since the present invention cancels the sound to be muted, the sound to be muted is not limited to the noise as described above. For example, for the purpose of harmony of the sound, only the arbitrary sound is selected. There is also a usage such as canceling.

(Effect of Device) As described above, in the active noise canceller of the present invention, the canceling sound and the sub-cancelling sound cancel each other, that is, on the target surface equidistant from the muffling speaker and the sub-speaker. Since a monitoring microphone is provided in the same manner as in the prior art, only the sound to be muted can be input, howling can be prevented, and the monitoring microphone cancels the emission of sound. The effect of improving the sound deadening performance can be obtained by disposing the sound deadening speaker close to the sound deadening speaker.

In addition, in the active noise canceller of the present invention, it is fixed to the cover that covers the ear cavity and is formed on the support member that defines the space inside the cover into two spaces. A communication passage that connects the muffler speaker side space that is a space with the sub speaker side space that is a space opposite to the ear cavity of the sub speaker except the support arm portion that supports both speakers on the outer circumference of both speakers. Since it is provided, the breathability is improved, and the effect that there is no feeling of pressure or blockage during use is obtained, and since external noise is sufficiently transmitted to the muffling speaker side space by the communication passage, noise is not canceled. Has the effect of being able to fully hear external sounds.

[Brief description of drawings]

FIG. 1 is an overall view showing the configuration of an active noise canceller according to a first embodiment of the present invention, and FIG. 2 is a characteristic diagram showing a canceling sound, a negative canceling sound and an external noise by the active noise canceller of the first embodiment. FIG. 3 is a perspective view showing a main part of the active noise canceller according to the first embodiment of the present invention. a …… Canceling sound B …… Silent speaker side space D …… Sub speaker side space 1 …… Silence speaker 2 …… Sub speaker 3 …… Monitor microphone 4 …… Noise canceling circuit 5b …… Communication path

Claims (1)

[Scope of utility model registration request] 1. A support member that is fixed to a cover that covers an ear cavity and defines a space inside the cover into two spaces, and a support member that is supported on the ear cavity side of the support member and that is to be silenced with respect to the ear cavity of the user. A muffling speaker that emits a canceling sound having a phase opposite to that of the sound, and the muffling speaker on the foreign sound side of the support member are supported in an opposing arrangement, and have a phase opposite to the canceling sound with respect to the foreign sound space. A sub-speaker that emits a sub-canceling sound in the same phase as the canceling sound to the ear cavity of the human body, and the sub-speaker that is provided on the support member and that cancels out the sounds emitted from both speakers Based on the input sound from the monitor microphone that receives the external sound including the sound to be silenced, the cancel sound generation signal that causes the cancel speaker to emit the cancel sound is output. A noise canceling circuit that outputs a sub-canceling sound generation signal that causes a sub-canceling sound to be emitted to the sub-speaker, and a muffling speaker-side space that is formed in the support member and is an ear cavity side space of the muffling speaker; A communication passage that communicates with the sub-speaker side space, which is a space opposite to the ear cavity of the speaker, except for a support arm portion that supports both speakers on the outer circumference of both speakers. Active noise canceller.