JPH03247098A - Reproducing device and headphone device - Google Patents

Abstract

PURPOSE:To decrease leakage of sound and to allow the user to enjoy a music with the same sound quality as before at a usual sound volume by attenuating a signal of a frequency band with a large sound leakage for a headphone by means of variable electric filter. CONSTITUTION:A band attenuation means 2 attenuating a sound leakage band of an audio signal fed to a headphone 4 is provided and the attenuation quantity of the band attenuation means 2 is varied in response to the level of an audio signal. The band attenuation means 2 is provided in a headphone drive amplifier circuit of a small portable magnetic recording and reproducing device case 10. Thus, the sound leakage band is attenuated to improve the sound leakage and the output attenuation is varied in response to the sound volume of the headphone, then the audio signal not losing the sound quality is listened to at the usual output.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a portable playback device such as a small tape recorder or a portable CD player, and a headphone device suitable for use with this device.

[Summary of the invention]

The present invention relates to a portable playback device such as a small tape recorder or a portable CD player, and a headphone device suitable for use with this device. A playback device or headphones comprising a band attenuation means for attenuating a sound leakage band of an audio signal supplied to the headphones, and the amount of attenuation of the band attenuation means is varied according to the level of the audio signal. This device prevents sound leakage from being heard by people other than the person listening to music through headphones, and also reduces deterioration in sound quality.

[Conventional technology]

In recent years, an increasing number of people are enjoying music alone by listening to audio signals from small portable tape recorders, CD players, etc. through headphones or earphones in crowded places such as trains.

When using such a portable playback device or headphone device, the sound output level is raised to 100 dB or more. It also raises various problems.

A conventional structure for minimizing sound leakage from such headphones or earphones (hereinafter referred to as "headphones" including earphones in this example) will be described below. As shown in Fig. 7A, the conventional structure for preventing sound leakage of headphones is to connect a plug (8) inserted into the jack of the tape recorder body to one end of the cord (12).
Foam synthetic resin (for example, Maltbren (trademark)) is used to cover the housing including the sound emitting plate that emits the vibration sound from the diaphragm of the left and right headphones (4) connected to the other end of this cord. etc., so that the headphones (4) (4) fit into and are inserted into the entrance of the external auditory canal, and maintain a sealed state between the outer periphery of the housing of the headphones (4), that is, the cover and the entrance to the external ear. or use headphones (4) as shown in Figure 8A and B.
When attaching (4) to the left and right ears (18), adjust the housing of the bed phone (4) to match the positional relationship between the external auditory canal (20) inside the auricle (19) and the external auditory canal entrance (21). The outer periphery (22) and the sound emitting hole (23) of the diaphragm are arranged asymmetrically rather than concentrically, and the outer periphery (22) of the housing is made of a soft rubber material, etc., and is inserted into the ear canal (21) in a sealed state. It was configured in such a way that it could be escaped.

[Problem to be solved by the invention] As explained in the conventional example, the degree of sealing between the outer circumference of the housing of the headphone (4) and the entrance to the ear canal (21) is increased so that it fits into the entrance to the ear canal (21). When measuring the sound leakage characteristics of the headphones and headphones that do not have a high degree of sealing, the results are as shown in FIGS. 9 and 10. That is, in Figures 9 and 10, the vertical axis shows the sound pressure level (dB) and the horizontal axis shows the frequency (Hz).
4) This is the frequency characteristic curve when (4) is attached to the ear (1B) (1B) and the microphone is placed on the side of the listener's head to collect sound leakage. This is a frequency characteristic curve when a microphone is placed in front of the head to collect sound leakage. In FIGS. 9 and 10, the thin curve indicated by the symbol (24) is the characteristic curve when the input signal is 0.25V and the degree of sealing is not increased, and the thick curve indicated by the symbol (25) is the characteristic curve when the input signal is 0.16V. This is a characteristic curve for headphones with a high degree of sealing as shown in FIG. 8 at V.

As can be seen from both characteristic curves, even with the sound leakage prevention structure, the improvement is only about 6 to 10 dB. In such a mechanical sound leakage prevention mechanism, as mentioned above, the
If the improvement is not on the order of dB, and the sealing degree is particularly high, the shape of the area near the entrance of the ear canal will vary from listener to listener, and will also be greatly affected by the way the headphones are hung. Also, if you use a large headphone that completely covers the auricle with a load of cushioning material, the sound leakage will be considerably improved, but the large size will make it unsuitable for portable use. Inexpensive earphones in which the sound emitting hole introduction chamber is completely inserted have a problem in that satisfactory sound quality cannot be obtained.

In particular, the sound leakage band is 2 on the Fletcher-Munson characteristic curve.
Since the frequency is around ~5 kHz, there is a problem in that even a low level sounds loud to the human ear.

The present invention was made to solve the problem of ridges, and its purpose is to provide a playback device and headphones that prevent sound from leaking to people around the listener without impairing the sound quality. The aim is to provide equipment.

[Means for Solving the Problems] The playback device and headphone device of the present invention are examples of playback devices in which audio signals are listened to through headphones (4) as shown in FIGS. 1 and 2. In the device (10) or the headphone equipment W (4), (8), and (9), a band attenuating means (2) for attenuating the sound leakage band of the audio signal supplied to the headphones (4) is provided. Attenuation means (2)
The amount of attenuation can be varied according to the level of the audio signal.

[Effect]

According to the playback device and headphone device of the present invention, since the sound leakage band is attenuated, sound leakage is improved, and the output attenuation amount can be varied according to the volume of the headphones, so that the normal output With this, it is possible to hear audio signals without loss of sound quality.

[Example] Hereinafter, a playback device and a headphone device of the present invention will be described.

Before explaining the system diagram of the reproducing apparatus and headphone apparatus of the present invention with reference to FIG. 1, the portable compact magnetic recording/reproducing apparatus used in this example will be explained with reference to FIG.

In Fig. 2, (10) is the housing of a small portable magnetic recording and reproducing device, and the side wall of the housing has a playback and recording device.

Operation knob group (10a) such as the operation knob for fast forwarding and rewinding
, a microphone (10c), a headphone jack (10b), etc. are provided, and the lid (10) of the housing (10)
d) The tape cassette is opened and closed so that a tape cassette can be inserted and recorded or played back. When playing back the tape cassette, the user listens to the playback sound through headphones (4).

The headphones (4) are connected to one end of the remote control box via the cord (12), and the headphones (4) are connected to one end of the remote control box (9).
The playback output volume is adjusted with a volume knob (11) such as a variable resistor disposed in the. Remote control box (9)
The other end is connected to a cord (12), and one end of the coat page 12) is connected to a plug (8). By inserting the plug (8) into the headphone jack (10b), an audio signal or the like is emitted from the headphones (4).

Is it possible to provide the band attenuation means for preventing sound leakage in this example in the headphone drive amplifier circuit of the portable compact magnetic recording/reproducing device housing (10)? It may also be incorporated into the box (9) or into the housing of the headphones (4) (4). An embodiment of such band attenuation means will be explained with reference to FIG. In FIG. 1, an audio signal obtained by picking up a playback signal recorded on a tape cassette with a playback head is input to the input terminal (1). This audio signal is passed through a band prevention filter (hereinafter referred to as B).
(denoted as EF) (2).

The output of B E F (2) is amplified by the headphone drive amplifier (3) and supplied to the headphones (4) via the jack (10b), and the audio signal is emitted from the headphones (4). . In this example, the output of the headphone drive amplifier (3) is supplied to the detection circuit (7), and a control voltage is supplied to the base of the transistor (6) of the variable impedance means. The detection circuit (7) consists of a rectifier circuit and a smoothing circuit consisting of resistors R, RS, R, capacitors C4, C5, C6, and diodes CD, CDZ. It is also possible to rectify the entire frequency band of (8) and supply the control voltage to the transistor (6) via the base resistor R1, but for example, between the drive amplifier (3) and the detection circuit (7) By interposing a bandpass filter (hereinafter referred to as BPF) (5) with a center frequency between 4000 and 5000 Hz as necessary, BEF (2) eliminates only the high-frequency reproduced signal component with variable impedance. may be controlled. In this way, the variable filter can be controlled more reliably.

Furthermore, an external switch SW may be provided between the detection circuit (7) and the drive amplifier (3) to perform manual switching according to external ambient noise. This switch SW may be provided on the side wall of the magnetic recording/reproducing device housing (10), or may be provided on the remote control box (9).

In the above-mentioned detection circuit (7), when the rectified voltage of the reproduced audio signal is detected by the diode CD2, the diode CD becomes inactive when the voltage is below the dark value of 0.7V, and the control voltage is supplied to the base of the transistor (6). Therefore, the transistor (6) is in an open state, and the audio signal supplied to the input terminal (1) is eliminated only by the filter characteristic determined by the CR constant of B E F (2).

That is, B E F (2) is, for example, resistor R,,R,
, R3 and capacitors CI, Cz, and C3.
CR is a filter to vary the band characteristics as shown in Fig. 5A and B according to the level of the input reproduced signal.
Transistor (6) of variable impedance means is connected to the common connection terminal of resistor R1 and capacitor C3 that constitute the filter.
The variable impedance means is controlled by connecting the collector and grounding the emitter and supplying a control voltage to the base. When controlled according to the sound quality signal level by such variable impedance means, the result is shown in FIG. 5A.

An EF attenuation characteristic curve as shown in B is obtained. Figure 5A
The curves (26) to (30) indicated by thick lines are B E F (
FIG. 5B shows the frequency characteristic curves for each sound pressure when B E F (2) is not passed, and the frequency characteristic curve for each sound pressure when B E F (2) is passed. That is, BEF(
The center frequency branch of 2) is selected to be approximately 3,000 to 4,000 Hz, and the attenuation characteristic curve of the filter at each level is shown in Figure 5B.
curves (26a) to (30a).

When the input audio signal, that is, the power input to the headphones (4) becomes small, for example, about 0.628 mW, the transistor (6) becomes open as described above, and when the volume is below the normal volume, the fifth The curve in Figure B (30a
), B E F (2) does not operate, so there is no loss of sound quality. Furthermore, when the sound pressure level reaches a level that causes sound leakage, it is possible to cut out the harsh sound leakage band.

In the above embodiment, an example using B E F (2) was explained, but this filter may be a high frequency cut filter (hereinafter referred to as HCF) that cuts out the high frequency range of 3000 or more.

Figures 3A and 3B show the output sound pressure and frequency change characteristics of the conventional and this example with the above-described configurations, and Figure 4AB shows the output sound pressure and sound leakage characteristics of the conventional and this example. Figure 3 A (2
6b) to (30b) are B E F (
2) is a frequency characteristic curve that does not pass through (2) in Figure 3B.
6c) to (30c) show variable filter characteristic curves at each sound pressure level. In this way, the sound leakage characteristics obtained by placing the microphone on the side of the head of the headphones (4) for each sound pressure level when the EF (2) is not passed through are the curves (26d) in Figure 4A. (30d), whereas
The sound leakage characteristics for each sound pressure level when passing through B E F (2) are 4000-50, which is harsh as shown in Figure 4B.
The sound leakage band near 00Hz is cut by about 10dB to 20dB.

According to this example, the drive amplifier (3) of the headphones (4)
Since the amount of attenuation of B E F (2) is varied depending on the output of B E F (2), it is possible to listen to music at normal volume without losing sound quality. Furthermore, at high volumes, it is possible to improve sound leakage by 10 dB or more compared to headphones with mechanically improved sealing.

In the above embodiment, the case was explained in which the switch SW was changed manually, but in a small portable tape recorder capable of recording, rather than a playback-only tape recorder, a microphone is used as shown in Fig. 6. , an amplified output obtained by detecting external ambient noise from the microphone (17) and amplifying the detected output with an amplifier (13), and BEF or H
A comparator circuit (15) such as a microcomputer is used to compare the audio signal with a predetermined high band eliminated or cut through the CF (2) and the reproduced audio input after amplifying it with the drive amplifier (3).
), and the switch SW is automatically turned on depending on whether the external noise is louder than the predetermined playback audio input.

It may also be controlled to be "off". In other words, when a train or the like starts running and external noise becomes louder, the leakage sound is not noticeable, so HCF (2) is not activated, and when the ambient noise decreases, HCF (2) is activated, and the amount of attenuation is adjusted. may be selected appropriately. Conversely, when the switch SW has a manual operation function, the switch SW may be turned "off" if there are no people around and the sound leakage does not disturb others.

With the configuration of this example, sound leakage can be controlled according to the surrounding conditions.

It should be noted that the present invention is not limited to the embodiments on the ridges, and it is obvious that various changes can be made without departing from the gist of the present invention.

[Effects of the Invention] According to the playback device and headphone device of the present invention, the frequency band where the sound leakage of the headphones is large is attenuated by an electrically variable filter, so that at high volumes, the sound leakage is reduced compared to a device that mechanically increases the degree of airtightness. Not only can this greatly improve sound leakage, but you can also enjoy music at normal volume with the same sound quality as before.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an embodiment of the playback device and headphone device of the present invention, FIG. 2 is a block diagram showing an embodiment of the playback device and headphone device of the present invention, and FIG. 3 is a conventional example. and a sound pressure level-frequency characteristic curve diagram of the present invention, FIG. 4 is a sound pressure level-sound leakage characteristic curve diagram of the conventional example and the present invention, and FIG. 5 is a filter attenuation characteristic curve diagram of the conventional example and the present invention. FIG. 6 is a system diagram showing another embodiment of the playback device and headphone device of the present invention, FIGS. 7 and 8 are explanatory diagrams for explaining a method for preventing sound leakage in a conventional headphone device, and FIG. 1 and 1O are conventional sound pressure level-sound leakage characteristic curve diagrams. (2) is a BEF or HCF, (3) is an AMP, (4) is a headphone, (5) is a BPF, (6) is a transistor of variable impedance means, and (7) is a detection circuit.

Claims (1)

[Claims] 1. In a playback device in which an audio signal is listened to through headphones, a band attenuating means for attenuating a sound leakage band of the audio signal supplied to the headphones is provided, the band attenuating means A playback device characterized in that the amount of attenuation of the sound signal is varied according to the level of the audio signal. 2. In a headphone device in which audio signals are listened to through headphones, band attenuation means for attenuating the sound leakage band of the audio signal supplied to the headphones is provided, and the amount of attenuation of the band attenuation means is set as described above. A headphone device characterized by being variable in accordance with the level of an audio signal.