JP2893701B2 - Headphone equipment - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a headphone device that converts an electric signal into an acoustic signal and outputs the signal, and more particularly, to an amplifier circuit that amplifies an input electric signal and supplies the amplified signal to a headphone unit. The present invention relates to a so-called active noise reduction headphone device having a function of reducing noise by converting an acoustic signal in the vicinity of the headphone unit into an electric signal by a microphone unit and performing negative feedback.

B SUMMARY OF THE INVENTION The present invention relates to a so-called active noise reduction headphone device, in which a pair of microphone units arranged such that respective diaphragms are close to each other and oppose each other to convert an acoustic signal near the headphone unit into an electric signal. By negatively feeding back the sum signal of the signals obtained by the pair of microphone units to the input terminal of the amplifier circuit, the external noise can be reliably reduced in a state where the influence of the mechanical vibration is reduced. It can be reduced to the following.

C Prior Art In general, in a passive headphone device, external noise is input to a listener's ear together with its sound output. For example, Japanese Patent Application Laid-Open No. 60-220698 and Japanese Patent Application Laid-Open No. 62-2798 As disclosed in, the headphone unit converts the acoustic signal in the vicinity of the headphone unit that converts the electric signal into an acoustic signal and outputs the electric signal in the microphone unit, and the negative feedback loop that performs feedback in opposite phase. 2. Description of the Related Art A so-called active noise reduction headphone device that reduces nearby noise has been conventionally proposed.

As shown in FIG. 4, the active noise reduction headphone device has a microphone unit (6) near a headphone unit (4) attached to a listener's ear (20). A signal synthesizer (2) is provided on the input side of an amplifier circuit (3) for amplifying an input electric signal S supplied from a signal source (10) to a signal input terminal (1) and supplying the amplified signal to a headphone unit (4). The microphone unit (6) converts an acoustic signal in the vicinity of the headphone unit (4) into an electric signal, and supplies the electric signal to the signal synthesizer (2) via a feedback circuit (7). (2) A configuration in which the output of the feedback circuit (7), that is, the feedback signal is combined with the input electric signal S and supplied to the amplifier circuit (3), thereby performing the negative feedback control of the amplifier circuit (3). Becomes ing.

Like this active noise reduction headphone device,
Near the entrance of the ear canal of the listener's ear (20), a sound signal is obtained by adding the sound output signal from the headphone unit (4) and a noise signal from the outside, and the sound signal from the outside is added. The microphone unit (6) converts the acoustic signal into an electric signal and feeds it back to the input side of the amplifier circuit (3) via the feedback circuit (7) to thereby provide the listener's ear (20). Can reduce the noise level of the acoustic signal input to the device.

D Problems to be Solved by the Invention As described above, in the active noise reduction headphone device, an acoustic signal in the vicinity of a headphone unit that converts an electric signal into an acoustic signal and outputs the acoustic signal is converted into an electric signal by a microphone unit. External noise near the headphone unit can be reduced by a negative feedback loop that returns in opposite phase. However, mechanical vibrations such as shock vibration applied to the housing and frictional vibration of the connection cord are reduced by the microphone unit. When transmitted to the microphone, the microphone unit converts the vibration noise due to the mechanical vibration into an electric signal, which causes a problem that external noise cannot be reduced normally. The microphone converts sound pressure into an electric signal, but also responds to mechanical vibration, and converts vibration noise due to the mechanical vibration into an electric signal and outputs it.

Therefore, an object of the present invention is to solve the problems in the conventional active noise reduction headphone device as described above, and to always reduce external noise normally without being affected by vibration noise due to mechanical vibration. It is intended to provide a headphone device having a novel configuration capable of performing the following.

E Means for Solving the Problems In order to achieve the above object, a headphone device according to the present invention provides a headphone unit, an amplifier circuit for amplifying an input electric signal supplied to the headphone unit, and a vicinity of the headphone unit. And a non-directional first and second microphone unit, and the first and second microphone units are connected to a front portion of each of the first and second microphone units by a coupling member. The arranged diaphragms are arranged coaxially so as to face each other, and a sound incidence portion for emitting sound from outside is provided in a gap between the first and second microphone units facing each other. A microphone and a feedback circuit for negatively feeding back a sum signal of the electric signals obtained by the microphone to an input terminal of the amplifier circuit; It is characterized by comprising a circuit.

F Function In the headphone device according to the present invention, a pair of microphone units arranged such that the respective diaphragms are close to and opposed to each other converts an acoustic signal near the headphone unit into an electric signal having the same phase as each other. Vibration noise due to vibration is converted into electric signals having phases opposite to each other. The sum signal of the electric signals obtained by the pair of microphone units is a signal obtained by canceling the vibration noise component and converting only the acoustic signal near the headphone unit into the signal. The sum signal of the electric signals obtained by the pair of microphone units is negatively fed back to the amplifier circuit that amplifies the input electric signal supplied to the headphone unit via a feedback circuit.

G Embodiment Hereinafter, an embodiment of a headphone device according to the present invention will be described in detail with reference to the drawings.

The embodiment shown in the equivalent block diagram of FIG. 1 is one in which the present invention is applied to the conventional active noise reduction headphone device shown in FIG. 4 described above, and converts an acoustic signal near the headphone unit (4) into an electric signal. As the microphone unit (6) for converting into a signal, each of the diaphragms (16a) and (16b) obtained by a pair of microphone units (16A) and (16B) arranged so as to be opposed to each other is provided. A microphone device (16) that adds and outputs an electric signal by a signal adder (16C) is provided on an input side of an amplifier circuit (3) that amplifies an input electric signal supplied to the headphone unit (4). The addition signal obtained by the microphone device (16) is supplied to the signal synthesizer (2) via a feedback circuit (7).

The sound output signal from the headphone unit (4) is added with an external noise signal N by an equivalent signal adder (15) in an acoustic space near the headphone unit (4), and this signal adder ( The combined output of 15) is converted into an electric signal by the microphone unit (16) as an acoustic signal near the headphone unit (4) and supplied to the signal combiner (2) via the feedback circuit (7). ing.

As shown in FIG. 2, the microphone device (16) includes, for example, a pair of omni-directional condenser microphone units (16A) and (16
B), and the microphone units (16A) and (16B) are connected to the highly rigid connector (23) in a state where the diaphragms (16a) and (16b) are close to each other so as to face each other. Combined. The diaphragms (16a), (16) of the microphone units (16A) and (16B) are attached to the connector (23).
A plurality of through holes (24) for guiding an acoustic signal are formed in b). As shown in FIG. 3, the microphone device (16) includes output terminals (20A), (2) that connect signal output terminals of the same polarity of the microphone units (16A) and (16B) to each other.
0B) is provided.

In the microphone device (16) having such a configuration, the microphone unit (16A), the microphone unit (16A), Electric signals obtained by pressing and deforming each of the diaphragms (16a) and (16b) of (16B) are added and synthesized in phase and output from the output terminals (20A) and (20B). Further, in the microphone device (16), since the microphone units (16A) and (16B) are connected to each other by the connector (23), the impact vibration applied to the housing and the frictional vibration of the connection cord are provided. The noise and vibration components due to mechanical vibration such as
A) and (16B) are converted into electric signals of opposite phases,
The electric signals having the opposite phases are added and synthesized to cancel each other, and only electric signals corresponding to the sound pressure P of the acoustic signal are obtained at the output terminals (20A) and (20B).

Therefore, in this headphone device, only the sound signal in the vicinity of the headphone unit (4) is converted into an electric signal by the microphone device (16), and the signal synthesizer (2) is converted via the feedback circuit (7). Supplied to

Here, in the headphone device, each transfer function of the amplifier circuit (3), the headphone unit (4), the microphone device (16), and the feedback circuit (7).
A, H, M, β are shown in the frequency domain Is set in a range that satisfies the condition of Assuming that the signal level of the input electric signal given to the signal input terminal (1) is S and the signal level N of the external noise signal given to the signal input terminal (18) is the combining by the signal adder (15). As output The sound signal of the sound pressure level P, that is, the input electric signal S is given a conversion characteristic of 1 / Mβ, so that the frequency characteristic and the distortion are corrected, and the signal level N of the external noise is reduced to 1 / M. An acoustic signal with reduced AHMβ is obtained at a signal output terminal (19) which is at the entrance of the ear canal of a listener wearing the headphone device.

In order to adjust the volume of the acoustic signal obtained at the signal output terminal (19), a volume adjuster may be provided at a stage preceding the signal input terminal (1), that is, at the sound source side.

H Effects of the Invention In the headphone device according to the present invention, the first microphone unit and the second microphone unit arranged coaxially so that the diaphragms of the microphones face each other, the sound incident from the sound input unit, that is, the vicinity of the headphone unit Is converted into an electric signal in phase with each other, and vibration noise due to mechanical vibration is converted into an electric signal in phase opposite to each other, and a sum signal of electric signals obtained by the first and second microphone units As a result, an electric signal corresponding to only the acoustic signal in the vicinity of the headphone unit is obtained by canceling the vibration noise component, and a negative input terminal of an amplifier circuit for amplifying an input electric signal supplied to the headphone unit via a feedback circuit The sound signal near the headphone unit can be converted to an electric signal by a microphone and returned in opposite phase. By the negative feedback loop which, without suffering the influence of vibration noise due to mechanical vibrations, can always be successfully reduced external noise.

[Brief description of the drawings]

FIG. 1 is an equivalent block diagram showing an active noise reduction headphone device to which the present invention is applied, and FIG. 2 shows a specific example of a microphone device having a pair of microphone units constituting a headphone device according to the present invention. FIG. 3 is a connection diagram of a pair of microphone units in the microphone device. FIG. 4 is a schematic diagram showing a principle configuration of an active noise reduction headphone device to which the present invention is applied. (1) Signal input terminal (2) Signal synthesizer (3) Amplifier circuit (4) Headphone unit (7) Feedback circuit (16) Microphone device (16A), (16B) ) Microphone unit (16a), (16b)… diaphragm (16C)… signal synthesizer (20A), (20B)… output terminal of microphone device

Continuation of the front page (56) References JP-A-55-120300 (JP, A) JP-A-61-196698 (JP, A) JP-A-60-220698 (JP, A) JP-A-59-200599 (JP) JP-A-62-2798 (JP, A) JP-A-52-133206 (JP, A) JP-A-1-142295 (JP, U) JP-A 55-179481 (JP, U) JP-A 61-70486 (JP, U) Patent 2638838 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04R 3/00 H04R 1/10

Claims (1)

(57) [Claims] A headphone unit; an amplifier circuit for amplifying an input electric signal supplied to the headphone unit; and an amplifier circuit provided near the headphone unit;
It comprises omnidirectional first and second microphone units, and the first and second microphone units are connected to each other by a coupling member. A microphone in which the plates are coaxially arranged so as to face each other, and wherein a sound incident portion for receiving an external sound is provided in a gap between the first and second microphone units, and the microphone And a feedback circuit for negatively feeding back the sum signal of the electric signals obtained at step (1) to the input terminal of the amplifier circuit.