JPH03297209A - Acoustic reproducing device - Google Patents

Abstract

PURPOSE:To suppress the influence of noise and to attenuate sound leakage when using a headphone by controlling the frequency characteristics of reproduced signals corresponding to the frequency characteristic of noise by changing over a control switch to change over a filtering operation. CONSTITUTION:Signals read out from a CD record 1 are converted to analog signals by a D/A converter 5 and reproduced by an openair type headphone 12. When turning a control switch 10 to a filter-on side terminal 10b, the reproduced output obtains the frequency characteristic reinforcing a low frequency band and attenuating a high frequency band in the ON operation of a filter 9. Therefore, since the low frequency band in the output from the headphone 12 is reinforced not so as to be drowned by the noise for a listener, the sounds are well balanced to be easily heard. Further, since the part of the high frequency band leaked from the headphone 12 is attenuated as well, any trouble caused by the sound leakage can be prevented from being given to people surrounding the listener in a train or a car.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a sound reproduction device for listening to reproduced sound in noise.

BACKGROUND OF THE INVENTION In recent years, as the sound field has become more outdoor, many sound playback devices using oven air type headphones have come to be seen in portable compact stereo cassette tape players, portable CD players, etc. It has become.

The open-air type headphones include headphones 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 radio receiver with FM stereo, or a combination of these devices, all of which are small and convenient to carry. Even when listening outdoors, since it is an open-air type as mentioned above, you can hear the sounds of cars, horns, signal sounds, etc., and you can listen to the playback without any danger while walking outdoors. It is something.

Problems to be Solved by the Invention However, with the above configuration, since it is an open-air type and external audio can be heard, it is affected by surrounding noise and the sound played from the headphones leaks into the surroundings. There was a problem.

In other words, when measuring the noise frequency characteristics under the listening environment inside a train or a car, as shown in Figure 5, the sound reproduction device has a flat frequency characteristic A, while the train noise frequency characteristic B and the inside car noise frequency characteristic It becomes C. Image frequency characteristic B
, C have a slight difference in frequency band, but both have a high noise level in the low frequency band and a low noise level in the high frequency band. Therefore, when trying to listen to the output of a playback device with frequency characteristic A, the low frequency band is buried in noise both on the train and inside the car, and the high frequency band is emphasized. There was a problem in that if you turned up the volume to hear the low frequencies well, the high frequencies would become even more emphasized. This is a problem in the same way, for example, when listening alone through headphones on a train, and when listening alone through headphones inside a car.

Furthermore, if the headphones are of the open-air type on a train, sound leakage to the surroundings becomes a problem. FIGS. 6 and 7 show the results of measuring the sound leakage.

FIG. 6 is a diagram showing the sound leakage frequency characteristics of a conventional open-air type headphone when measured under the conditions shown in FIG. That is, with the headphones H attached to the listener's ear La,
Sound level meter M placed at a position 1 (approximately 30-) away from a
This is used to measure sound leakage. Here, it is assumed that the surrounding environment is a soundproof room and that the sound level meter M uses an A-curve filter. As a result, as shown in Figure 6, the frequency is 1kHz.
Sound leakage increases above z, and sound leakage frequency band characteristics D
a, and in the frequency band below 1 kHz, the background noise level of the soundproof room has a flat frequency characteristic Db. As can be seen, it can be seen that a large amount of sound leakage occurs in the high frequency band, but this poses a problem as a cause of sound leakage when listening in the open air type.

Conventionally, when trying to listen to reproduced sound on a train or in a car, the noise in the area makes it very difficult to hear low frequencies, and raising the volume abnormally emphasizes high frequencies, making it difficult for the listener to hear the sounds. There was a problem with being overheard. Furthermore, when there are many people around, such as on a train, people tend to turn up the volume due to the noise from the surrounding trains, so the audio leaking from the headphones and headphones can be a nuisance to the people around them. There was a problem of being overheard and being disturbed.

In view of the above-mentioned problems, the present invention has been developed to provide a system that is not affected by the noise characteristics of trains or cars as described above, minimizes sound leakage, and enables comfortable playback for both the listener and the surrounding people. This was made for the purpose of providing a sound reproduction device.

Means for Solving the Problems In order to achieve the above object, the sound reproduction device of the present invention measures the noise frequency characteristics in advance by frequency-analyzing the amount of noise, and uses a filter set to correspond to the noise frequency characteristics. In addition, a control switch for switching the filter operation is provided, and the frequency characteristics of the reproduced signal are controlled to correspond to the noise frequency by switching the control switch.

According to the above-described configuration, the present invention performs a filter operation by switching the control switch, so that the frequency characteristics of the reproduced output are enhanced in the bass region and attenuated in the treble region, so that the frequency characteristics become the noise frequency characteristics. It is controlled accordingly, suppressing the influence of noise and attenuating sound leakage when using headphones as much as possible.

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 an audio reproduction device according to an embodiment of the present invention, and the embodiment is a portable C
One stereo type channel is shown on the D player. In FIG. 1, 1 is a CD (compact disc) record, 2 is a traverse mechanism including an optical pickup that reads signals from the CD record 1, 3 is a servo/drive circuit that accurately controls the traverse mechanism 2, and 4 is the traverse mechanism 2 A signal processing circuit 5 processes the signal read out by the signal processing circuit 4, and D converts the digital signal processed by the signal processing circuit 4 into an analog signal.
6 is a buffer amplifier 1' of the D/A converter 5, and T is a volume adjustment volume for controlling the output amount of the buffer amplifier 6. Reference numeral 8 denotes a headphone driving amplifier, which not only drives the headphones but also operates as an operational amplifier for filter 9, which will be described later. A filter 9 is inserted into the feedback circuit of the headphone drive amplifier 8. When inserted into the feedback circuit by a control switch 10, which will be described later, the input/output frequency characteristics of the headphone drive amplifier 8 are changed. 10 is an on/off control switch for filter operation; 11 is a headphone connection terminal to which eight of the headphone drive amplifiers 8 are connected; and 12 is one channel of the headphones connected to the headphone connection terminal 11. Reference numeral 13 denotes another channel, which is composed of the same circuit as that from the buffer amplifier 6 to the headphones 12.

FIG. 2 is a circuit diagram showing details of the filter 9 including the control switch 10 from the headphone drive amplifier 8.

In FIG. 2, 8 and 10 are the headphone drive amplifier and control switch described above, respectively. 10a is a filter off side terminal of the control switch 10, and 10b is a filter on side terminal of the control switch 10. 14.15
This resistor serves as a gain setting element that determines the input/output gain of the Hahe-Sodophone drive amplifier 8. Furthermore, when the control switch 10 is set to the filter off side 10a, the resistors 16 and 18 and the capacitor 17 operate as part of the gain setting element of the headphone drive amplifier 8, and the filter on side terminal 1
This is a low frequency enhancement filter element that enhances the low frequency band when set to 0b, and is a part of the filter 9 described above.

Further, the capacitor 19.22 and the resistor 20.21 are high frequency attenuation filter elements that attenuate the high frequency band only when the changeover switch 10 is set to the filter on side terminal 10b, and similarly, the capacitor 19.22 and the resistor 20.21 are high frequency attenuation filter elements that attenuate the high frequency band only when the changeover switch 10 is set to the filter on side terminal 10b. It has become a department. 23 is an input terminal of this circuit, and 24 is an output terminal thereof.

Figure 3 is a frequency characteristic diagram showing the relationship between the input/output frequency characteristics of the circuit shown in Figure 2 and the train noise frequency characteristics and car noise frequency characteristics shown in Figure 5 above. Noise frequency characteristics, 26 is car noise frequency characteristics,
Reference numeral 27 indicates the frequency characteristic of the reproduced output when the filter 9 is not operating, and 28 indicates the frequency characteristic of the reproduced output when the filter 9 is operating.

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

In FIG. 3, the train noise frequency characteristic 25. As can be seen from the car noise frequency characteristic 26 and the frequency characteristic 27 when the filter 9 is off, the noise in the low frequency band is large both inside the train and inside the car, but the noise in the high frequency band is small.

Therefore, for the listener, the low frequency band in the output from the headphones 12 is drowned out by the noise, making it difficult to listen.
On the other hand, high frequency bands are easy to hear because they have a large S/N ratio with respect to noise. Therefore, if the control switch 10 is set to the filter on side terminal 10b, the reproduced output will have the frequency characteristics 28 when the filter 9 is in operation, in which the low frequency band is enhanced and the high frequency band is attenuated. The low frequency band in the output from the system has been enhanced, making it easier to hear without being drowned out by noise, and conversely, the high frequency band, which used to be too loud, is attenuated, resulting in a well-balanced sound. Moreover, since the portion of the high frequency band Da leaking from the headphones shown in FIG. 6 is attenuated, it is possible to prevent the sound leakage from causing annoyance to surrounding people on the train or in the car.

As described above, according to this embodiment, the train noise frequency characteristic 2
5 and the vehicle noise frequency characteristic 26 are measured in advance, and a filter 9 is provided that attenuates the high frequency band and enhances the low frequency band so as to correspond to both of the above noise frequency characteristics, and a control switch 10 that switches the operation thereof. By turning the control switch 10 on and off as shown in FIG. 3, it is possible to provide well-balanced sound when it is necessary to listen to reproduced sound in a noisy environment.
It is possible to reduce sound leakage to the surroundings when using open air type headphones.

Next, a sound reproduction device according to a second embodiment of the present invention will be described.

FIG. 4 shows a schematic circuit block diagram of a sound reproducing apparatus according to a second embodiment of the present invention, which is a partial modification of the first embodiment. In the figure, reference numeral 29 is a volume adjustment volume for controlling the output amount from the previous stage. Reference numeral 30 denotes a headphone driving amplifier, which not only drives the headphones but also operates as an operational amplifier for a filter, which will be described later. 31 is a headphone drive amplifier 30
This is the first filter inserted into the feedback circuit of the train.The frequency characteristics of the train noise are measured in advance, and settings are made to attenuate the high frequency band and enhance the low frequency band to correspond to the noise frequency characteristics. When inserted into the feedback circuit by a control switch 33 to be described later, the input/output frequency characteristics of the headphone drive amplifier 30 change. A second filter 32 is inserted into the feedback circuit of the headphone drive amplifier 30, and has different characteristics from the first filter 31.
The vehicle noise frequency characteristics are measured in advance, and settings are made to attenuate the high frequency band and enhance the low frequency band to correspond to the noise frequency characteristics. When inserted, the input/output frequency characteristics of the headphone drive amplifier 30 change to have characteristics different from those of the first filter. 33 is an on/off control switch for filter operation, 34 is a headphone connection terminal to which the output of the headphone drive amplifier 30 is connected, and 35 is one channel of the headphones connected to the headphone connection terminal 34.

The operation of the sound reproducing apparatus configured as described above will be described below with reference to FIG. 4 and FIG. 3. In FIG. 3 above, the train noise frequency characteristic 25. As can be seen from the car noise frequency characteristics 26, there is a clear difference in the characteristics between the two noise frequency characteristics, and the most suitable first filter 31 and second filter 32 corresponding to the respective noise frequency characteristics are provided. Control switch 3 at the discretion of the listener
By switching between 3 and 3, a well-balanced sound suitable for the listener's surrounding environment can be obtained. Moreover, since the high frequency band leaking from the headphones is attenuated in accordance with the surrounding environment, it is possible to prevent the sound leakage from causing annoyance to surrounding people on the train or in the car.

As described above, according to the second embodiment, the train noise frequency characteristic 25 and the car noise frequency characteristic 26 are measured in advance, and the high frequency band is attenuated and the low frequency band is attenuated so as to correspond to each of the above noise frequency characteristics. By providing a first filter 31 and a second filter 32 that enhance the frequency band and a control switch 33 that switches their operation, it is possible to listen to reproduced sound in noise by switching the control switch 33. In some cases, it is possible to provide well-balanced sound, and when open-air type headphones are used, it is possible to reduce sound leakage to the surroundings.

Although the filter characteristics are limited to the train noise frequency characteristics and car noise frequency characteristics, it is important to note that the characteristics of the filter have been set only for train noise frequency characteristics and car noise frequency characteristics, but for example, in environments where specific noise is generated, such as trains and other vehicles such as airplanes, or environments where specific noise is generated, A similar effect can be obtained by measuring the noise frequency characteristics of the filter and setting the filter characteristics corresponding to the noise frequency characteristics.

Furthermore, in the above embodiment, the state of listening to the reproduced signal is as follows:
Although the case of listening in an open air type has been described, the case of listening with speakers may also be used. for example,
When listening inside the vehicle, the sound can be played back through the car stereo's speakers, but in this case, the player and the noise inside the car will be heard together. Therefore, if the above-mentioned device of the present invention is used to reproduce the sound, it is possible to obtain a well-balanced reproduced sound even when the sound is played back through the speaker in the presence of noise inside the car.

Effects of the Invention As described above, the present invention measures in advance the noise frequency characteristics obtained by frequency analysis of the amount of noise inside a train and the noise frequency characteristics obtained by frequency analysis of the amount of noise inside a car, A filter is provided that attenuates the high frequency band and enhances the low frequency band in order to correspond to the above-mentioned noise frequency, and a control switch is provided to change the operation of the filter. By adapting to the characteristics, the listener can obtain well-balanced sound suitable for the surrounding environment and avoid disturbing the people around them.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the present invention;
The figure is a circuit diagram of the main part, Figure 3 is a frequency characteristic diagram, Figure 4 is a block diagram showing the second embodiment, Figure 5 is a noise frequency characteristic diagram in trains and cars, and Figure 6 is a diagram of noise frequency characteristics in trains and cars. 7 is a diagram of sound leakage frequency characteristics from oven air type headphones of a conventional sound reproducing device, and FIG. 7 is a schematic diagram showing measurement conditions when obtaining the characteristics of FIG. 6. 9...Filter, 10...Control switch, 25...Noise frequency characteristics in the train, 26.
... Noise frequency characteristics in the car, 27 ... Frequency characteristics of the reproduction output when the filter is not operating, 28 ...
...Frequency characteristics of reproduction output during filter operation, 31...
. . . first filter, 32 . . . second filter, 33 . . . control switch.

Claims (3)

[Claims] (1) Measure in advance the noise frequency characteristics obtained by frequency analysis of the amount of noise inside the train and the noise frequency characteristics obtained by frequency analysis of the amount of noise inside the car, and set the high frequency characteristics to correspond to both of the above noise frequency characteristics. A filter is provided to attenuate the frequency band and enhance the low frequency band, and a control switch is provided to switch the operation of the filter, and by switching the control switch, the frequency characteristics of the reproduced signal are controlled to correspond to the noise frequency characteristics. A sound reproduction device characterized in that it is configured as follows. (2) In claim 1, the first and second filters are provided which attenuate the high frequency band and enhance the low frequency band so as to correspond to the train noise frequency characteristics and the car noise frequency characteristics, respectively. A control switch is provided to switch between operation of the first or second filter and non-operation of both filters, and by switching the control switch, control is performed to obtain the frequency characteristics of the reproduced signal corresponding to the noise frequency characteristics of the train or car. A sound reproduction device characterized in that it is configured to. (3) The sound reproduction device according to claim 1 or 2, characterized in that the noise frequency characteristics are measured in advance in a noisy environment other than a train or a car, and a filter is provided that corresponds to the noise frequency characteristics.