JPH03214999A - Acoustic reproducing device - Google Patents

Abstract

PURPOSE:To suppress leakage of sound and to attain reproduction pleasant not only to a listener itself but also to surrounding people by providing an attenuation filter attenuating a frequency band of external sound leakage while a headphone is put on and a control switch switching the operation of the attenuation filter. CONSTITUTION:The acoustic reproduction device consists of a magnetic head 6 extracting an audio electric signal, a preamplifier 7, a noise reduction circuit 8, an attenuation filter 9, a sound volume variable resistor 10, a power amplifier 11, an inner type headphone 12 and a control switch 13. The attenuation filter 9 is a notch filter whose maximum attenuation is caused at a frequency (6kHz) with a maximum level in the sound leakage frequency characteristic measures in advance. With the control switch 13 closed, a semiconductor inductor 16 is conductive and active, then the resonance circuit is active, and the attenuation filter 9 acts like a notch filter having a center frequency of 6kHz. With the control switch 13 closed conversely, since the semiconductor inductor 16 is not energized, the attenuation filter 9 does not act like a notch filter thereby has no notch characteristic in the frequency characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a sound reproduction device particularly suitable for listening through oven air type headphones.

BACKGROUND OF THE INVENTION In recent years, as the sound field has become more outdoor, many sound playback devices using open-air headphones have been seen in small, portable stereo cassette tape players, portable CD players, etc. It has become.

The above-mentioned oven air type headphones include bedphones with a so-called headband that covers the auricle, and inner-type headphones that are worn inside the auricle. These include a portable CD player, a Ratio receiver with FM stereo, or a combination thereof, all of which are small and convenient to carry. Even when listening outdoors, since it is an oven air type as mentioned above, you can still hear the sounds of cars, horns, signal sounds, etc.
It poses no danger and can be played back and listened to while walking outdoors.

Problems to be Solved by the Invention However, since the above configuration is an oven air type, there is a problem in that instead of being able to hear external sounds, the reproduced sound from the headphones leaks to the surroundings. In other words, there is no problem if there is no one around the listener, but in places where there are many people, such as on a train, there is a tendency to increase the volume due to the surrounding noise, so the sound leaking from the headphones can be heard by the surrounding people. There was a problem that the noise could be heard as a nuisance, causing a nuisance.

FIG. 6 is a diagram showing the sound leakage frequency characteristic 1 of a conventional oven air type headphone measured under the conditions shown in FIG. 7. That is, headphones 2
is attached to the ear 20a of the listener 20, and sound leakage is measured using a sound level meter 3 placed at a distance of L (approximately 30 cm) from the ear 20a. here,
The surrounding environment is a soundproof room, and the sound level meter 3 uses an eight-curve filter. As a result, as shown in Figure 6,
When the frequency is 1 kHz or more, the sound leakage becomes thick, resulting in a sound leakage frequency band characteristic 1a, and in a frequency band below 1 kHz, the background noise level of the soundproof room becomes a flat frequency characteristic 1b. In this way, it can be seen that a large amount of sound leakage occurs in the high frequency band.

In view of the above-mentioned problems, the present invention has been made with the object of providing a sound reproduction device that suppresses such sound leakage as much as possible and can reproduce music comfortably for both the listener and the surrounding people. .

Means for Solving the Problems In order to achieve the above object, the sound reproduction device of the present invention measures in advance the sound leakage frequency band to the outside when the headphones are worn, and uses an attenuation filter that attenuates the sound leakage frequency band. In addition, a control switch is provided to change the operation of the capital reduction filter, and by turning the changeover switch on and off, sound leakage from the headphones to the outside is controlled when the headphones are worn.

Effect of the Invention With the above-described configuration, the present invention attenuates the leakage of sound to the outside in the sound leakage frequency band of the headphones by turning the changeover switch on and off.

Embodiment Hereinafter, a sound reproducing apparatus according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic circuit block diagram of a sound reproduction device according to an embodiment of the present invention, and the embodiment shows a stereo type. In Fig. 1, 6 is a magnetic head that extracts audio electrical signals from a magnetic tape (not shown), 7 is a preamplifier with a built-in equalizer circuit, 8 is a noise reduction circuit, and 9 is an input signal for the output of the noise reduction circuit 8. 10 is a volume volume that receives the output of the attenuation filter, and 11 is a low impedance filter that includes a circuit that boosts the bass range. A power amplifier with a bass boost circuit capable of driving a load, 12 an inner-type headphone, and 13 a control switch capable of switching an attenuation filter between operation and non-operation (input and output have no frequency characteristics).

FIG. 2 is a circuit diagram showing details of the channels and control switch 13 on only one side of the attenuation filter 9. Second
In the figure, 14 and 15 are input and output terminals of the attenuation filter 9, respectively.

16 is a semiconductor inductor composed of one transistor; 17 is a resonant capacitor connected in series with the semiconductor inductor 16 to resonate in series. Note that 18 connects the output of the control switch 13 to the semiconductor inductor 16.
This is a switching circuit that supplies

The operation of the sound reproduction apparatus configured as described above will be explained below with reference to FIGS. 1, 2, and 3.

The attenuation filter 9 uses the frequency (6kHz) of the maximum level of the sound leakage frequency characteristics measured in advance as shown in FIG.
This is a notch filter that corresponds to this frequency (6 kHz) and has a maximum attenuation value.

Therefore, the constants of the series resonant circuit constituted by the semiconductor inductor 16 and the resonant capacitor 17 are determined so that its resonant frequency is 6 kHz.

As can be seen from FIG. 2, when the control switch 13 is on, the semiconductor inductor 16 is energized and operated, so a resonant circuit works, and the attenuation filter 9 works as a notch filter with a center frequency of 6 kHz. Conversely, when the control switch 13 is off, the semiconductor inductor 16 is not energized, so the attenuation filter 9 does not operate as a notch filter, and there is no frequency characteristic between the inputs and outputs 14 and 15. As a result of the above, the frequency characteristics of the entire circuit block in FIG. 1 are as shown in FIG. 3. In FIG. 3, 4a shows the frequency characteristics when the control switch 13 is off, and 4b shows the frequency characteristics when the control switch 13 is on. As can be seen in Figure 3, the characteristics of the attenuation filter 9 are such that the Q of the resonant circuit is adjusted to almost eliminate the effect on the vocal center frequency of 1 kHz and to maximize the attenuation effect at 6 kHz.
was made as large as possible. This achieved an attenuation level of 12 dB at 6 kHz.

As described above, according to this embodiment, by providing the attenuation filter 9 that attenuates the sound leakage frequency band and the control switch 13 that switches its operation, the control switch 13 can be turned on and off as shown in FIG. This makes it possible to reduce sound leakage when necessary. In Figure 4,
5a shows the frequency characteristics when the control switch 13 is off, and 5b shows the frequency characteristics when it is on.

Another effect will be explained using FIG. 5. Fifth
In the figure, 19 is the noise characteristic obtained by frequency analysis of the noise inside the train, and 4C is the reproduction frequency characteristic when the control switch 13 is turned on and the bass enhancement circuit of the power amplifier 11 is operated.

As can be seen from Figure 5, inside the train, the noise in the bass parts is large, but the noise in the treble parts is small. Therefore, for the listener, the low-pitched tone part of the output from the headphones 12 is buried in the noise and cannot be heard, whereas the high-pitched tone part is easy to hear because the S/N ratio with respect to the noise is large. Therefore, when the control switch 13 is turned on and the bass enhancement circuit is activated, it is possible to make it easier for the listeners on the train to hear the inaudible bass part, and attenuate the noisy treble part to an appropriate level. This makes it possible to provide a more natural sound quality that is easier to listen to. Furthermore, it is possible to prevent noise leakage from causing trouble to surrounding passengers on the train.

Note that the semiconductor inductor 16 in the embodiment may be a so-called inductor (coil) that is a passive element.

Effects of the Invention As described above, the present invention includes an attenuation filter that attenuates the sound leakage frequency band and a control switch that switches the operation of the attenuation filter, and by turning the control switch on and off, the sound is transmitted from the headphones to the outside while the headphones are being worn. It is possible to control sound leakage, and when necessary, reduce sound leakage to the outside when used in a noisy place such as inside a vehicle or in a crowded place.
This is a very effective invention that gives the listener a sense of security, avoids bothering people around them, and provides more natural sound quality in noisy environments.

[Brief explanation of drawings]

FIG. 1 is a schematic circuit block diagram of an audio reproduction device according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing one block in FIG. 1 in detail, and FIG. 3 is a frequency characteristic according to an embodiment of the present invention. 4 is a sound leakage frequency characteristic diagram showing the first effect of the embodiment of the present invention, FIG. 5 is a frequency characteristic diagram showing the second effect of the present invention, and FIG. 6 is a sound leakage frequency characteristic diagram showing the first effect of the present invention. A sound leakage frequency characteristic diagram of the reproducing device, FIG. 7 is an explanatory diagram showing the measurement state in obtaining the characteristics shown in FIG. 6.

Claims (4)

[Claims] (1) Measure in advance the sound leakage frequency band to the outside when the headphones are worn, provide an attenuation filter that attenuates the sound leakage frequency band, and provide a control switch to switch the operation of this attenuation filter, and install the above-mentioned changeover switch. 1. A sound reproducing device characterized in that the sound reproduction device is configured to control sound leakage from headphones to the outside while the headphones are being worn by turning on and off. (2) The sound reproducing device according to claim 1, wherein the frequency of the maximum attenuation level of the attenuation filter is made to match the frequency of the maximum level in a sound leakage frequency band measured in advance. (3) In claim 1, the attenuation filter has a frequency of 4 to 8 kHz.
1. A sound reproducing device characterized by being an attenuation filter having a steep attenuation characteristic in which z is the frequency with the maximum attenuation level and almost no attenuation at 1 kHz, which is the center frequency of vocals. (4) In claim 3, the attenuation characteristic of the attenuation filter is
A sound reproduction device characterized by having a damping characteristic that is steeper than a rise characteristic of a sound leakage frequency band.