JPH02228196A - Headphone device - Google Patents

Abstract

PURPOSE:To reduce the signal level of noise from the external by variable setting the transfer function, namely, the gain of an amplifying circuit to a specific range with respect to the transfer function of a headphone unit, that of a microphone unit, and that of a feedback circuit. CONSTITUTION:The synthesized output signal from a signal synthesizer 2 is supplied to a headphone unit 4 through a variable gain amplifying circuit 3 whose gain A is freely variably set, and a noise signal N from the external is added to this acoustic output signal by a signal adder 15. This synthesized output is converted to an electric signal as the acoustic signal around the unit 4 by a microphone unit 6 and is supplied to the signal synthesizer 2 through a feedback circuit 7. In this headphone device, the transfer function, namely, the gain A of the amplifying circuit 13, a transfer function H of the unit 4, a transfer function M of the unit 6, and a transfer function beta of the feedback circuit 7 are variably set in the range of ¦AHMbeta¦>>1. Thus, a practical active noise reduction headphone is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a headphone device that converts an electrical signal into an acoustic signal and outputs it, and in particular, to an amplifier circuit that amplifies a human-powered electrical signal and supplies it to a headphone unit. The acoustic signal near the headphone unit is transmitted to the microphone unit.
The present invention relates to a so-called active noise reduction headphone device that has a function of reducing noise by converting it into an electrical signal and providing negative feedback.

B. Summary of the Invention The present invention eliminates noise by converting an acoustic signal near the microphone unit into an electrical signal and feeding it negative feedback to an amplifier circuit that amplifies an input electrical signal and supplies it to the microphone unit. In a so-called active noise reduction headphone device having a noise reduction function, the amount of reduction in external noise can be varied by variably setting the gain of the amplifier circuit.

C Conventional technology For example, JP-A-60-220698 and JP-A-62
As disclosed in Publication No. 2798, etc., in a headphone device that converts an electrical signal into an acoustic signal and outputs it, a microphone unit collects an acoustic signal near the headphone unit that converts the electrical signal into an acoustic signal and outputs it. So-called active noise reduction headphone devices have been used in the past that reduce noise in the vicinity of the headphone unit by converting it into an electrical signal and feeding it back in an opposite phase through a negative feedback loop.

The active noise reduction headphone device described above has a basic configuration shown in FIG.
A microphone unit (6) is provided near the headphone unit (4) to be attached to the signal source (
A signal synthesizer (2) is provided on the input side of an amplifier circuit (3) that amplifies the input electric signal S applied from the headphone unit (10) to the signal input terminal (1) and supplies the amplified signal S to the headphone unit (4). 4) The nearby acoustic signal is converted into an electrical signal by the microphone unit (6), supplied to the signal synthesizer (2) via the feedback circuit (7), and inputted by the signal synthesizer (2). The above feedback circuit (7
) outputs, that is, feedback signals, are synthesized and output to the amplifier circuit (3).
) is configured to perform negative feedback control of the amplifier circuit (3).

Like this active noise reduction headphone device, an acoustic signal obtained by adding the acoustic output signal from the headphone unit (4) and the external noise signal is obtained near the auditory canal entrance of the listener's ear (20). , the acoustic signal added with the external noise signal is converted into an electrical signal by the microphone unit (6), and the acoustic signal is sent to the feedback circuit (7).
) through the above amplification times! By providing negative feedback to the input side (3), the noise level of the acoustic signal input to the listener's ears (20) can be lowered.

D Invention tries to solve! By the way, with active noise reduction headphone devices that have a function to reduce external noise, if the amount of noise reduction is too large, for example, when listening to music with external noise reduced, it may cause noise from other people. You may not be able to hear someone calling out to you, and there is a risk that you may miss out on 9A emergency broadcasts, etc. Furthermore, if the amount of noise reduction is too small, it is not practical in factories, construction sites, etc. where the noise level is high.

In conventional active noise reduction headphone devices, the amount of noise reduction is fixed, so there is a problem in that the amount of noise reduction cannot be adjusted depending on the situation.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, the present invention aims to realize a practical active noise reduction headphone device that can be used with a noise reduction amount depending on the situation. The present invention provides a headphone device with a novel configuration in which the amount of noise reduction can be varied without affecting the signal level of an acoustic signal.

E Lli! Means for Solving II In order to achieve the above-mentioned object, a headphone device according to the present invention includes a headphone unit that converts an input electrical signal into an acoustic output signal, and amplifies the input electrical signal supplied to the headphone unit. an amplifier circuit whose gain can be freely set; a microphone unit arranged near the headphone unit to convert an acoustic signal into an electrical signal; and a signal obtained by the microphone unit that is negatively fed back to the input end of the amplifier circuit. a feedback circuit, and for the transfer function H1 of the headphone unit, the transfer function M of the microphone unit, and the transfer function β of the feedback circuit, l AHMβ
The present invention is characterized in that the gain A of the amplifier circuit can be freely set within the range of I)1.

F action In the headphone device according to the present invention, an acoustic signal with a sound pressure level P of 1+A summer IMβ 1+AHM β is obtained in the vicinity of the headphone unit, where the signal level of the input electric signal is S and the signal level of external noise is N. By variably setting the gain A of the amplifier circuit in the range of IAHMβI)1, external noise can be suppressed while maintaining a constant level of 1/Mβ with respect to the signal level S of the input electrical signal. The signal level N is reduced to 1/AHMβ.

G. Embodiment Hereinafter, an embodiment of the kM collection and processing 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 an example in which the present invention is applied to the conventional active noise reduction headphone device shown in FIG. The configuration is such that the signal is supplied to the headphone unit (4) via a variable gain amplifier circuit (13) whose gain A can be freely set.

The acoustic output signal from the headphone unit (4) is
In the acoustic space near the headphone unit (4), an equivalent signal adder (15) adds an external noise signal N, and the combined output of this signal adder (15) is sent to the headphone unit (4). It is converted into an electrical signal by the microphone unit (6) as an acoustic signal in the vicinity of , and is supplied to the signal synthesizer (2) via the feedback circuit (7).

In this headphone device, the variable gain amplification circuit (
13) The transfer function, that is, the gain A is the transfer function H of the headphone unit (4) and the microphone unit (6).
), the transfer function β of the feedback circuit (7), and the transfer function A of the variable gain amplifier circuit (13) are expressed in the frequency domain, and can be freely set within the range of AI (Mβl>1). .

In this headphone device, the signal adder ( An acoustic signal with a sound pressure level P of 1+AHMβ 1 +AHMβ as a composite output from 15) is output to the signal output terminal (19
) can be obtained.

The acoustic signal of the sound pressure level P obtained at the signal output terminal (19) is 1/1/1 with respect to the signal level S of the input electrical signal.
With the level of Mβ constant, the signal level N of external noise is reduced to 1/AHMθ, and l AHMβl
) The noise signal level N, that is, the amount of noise reduction, corresponds to the gain A of the variable gain amplifier circuit (13), which is variably set within the range of 1.

That is, in the headphone device of this embodiment, IAH
The above variable gain amplifier circuit (13) in the range of MβI>1
By variably setting the gain A of the variable gain amplifier circuit (13), an acoustic signal with a constant signal level relative to the signal level S of the input electrical signal and whose only noise level is reduced according to the gain A of the variable gain amplification circuit (13) is generated. The signal can be obtained at the signal output terminal (19).

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

H Effects of the Invention In the headphone device according to the present invention, the transfer function of the amplifier circuit, that is, the gain A is IAHMβ1)! with respect to the transfer function H1 of the headphone unit, the transfer function M of the microbon unit, and the transfer function β of the feedback circuit. By setting the signal level variably within the range of , the signal level of external noise can be reduced to 1/AHMβ while the signal level of the input electrical signal is kept at a constant level of 1/Mβ. By setting the gain A, it can be used for noise reduction according to the noise situation.

[Brief explanation of the drawing]

FIG. 1 is an equivalent block diagram showing an active noise reduction headphone device to which the present invention is applied. FIG. 2 is a schematic diagram showing the basic configuration of an active noise reduction headphone device commonly used in the present invention.

Claims (1)

[Scope of Claims] A headphone unit that converts an input electrical signal into an acoustic output signal; an amplification circuit with a variable gain that amplifies the input electrical signal supplied to the headphone unit; , a microphone unit that converts an acoustic signal into an electrical signal, and a feedback circuit that negatively feeds back the signal obtained by the microphone unit to the input terminal of the amplifier circuit, and the transfer function H of the headphone unit is A headphone device characterized in that the gain A of the amplifier circuit can be freely set in a range of |AHMβ|}1 with respect to the transfer function M and the transfer function β of the feedback circuit.