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JPH03297209

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DESCRIPTION JPH03297209
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sound reproducing apparatus for listening to reproduced sound in noise. 2. Description of the
Related Art In recent years, with the advent of the acoustic field outdoors, acoustic playback
devices using oven-air type headphones have come to be seen in large numbers in acoustic
playback devices such as portable stereo cassette tape players and portable CD players. It has
come. As the open air type headphones, there are so-called headphones with a headband that
covers the pinna and inner type headphones to be mounted in the pinna. The above-mentioned
sound reproducing apparatus using these is a cassette tape player, A portable CD player, a radio
receiver with FM stereo, or a combination of these devices, etc., are all small and convenient to
carry. And, even when listening outdoors, since it is an open air type as described above, you can
listen to car sounds, horns, signal sounds, etc., and there is no danger even while walking
outdoors and playback and listening is possible It is a thing. SUMMARY OF THE INVENTION
However, the above configuration is an open air type, and the external sound can be heard, so
the influence of the ambient noise is received and the reproduced sound from the headphone
leaks to the surroundings. It had the problem of. That is, when the noise frequency
characteristics under the listening environment in the train or in the vehicle are measured, as
shown in FIG. 5, the noise frequency characteristics B in the train and the noise frequency
characteristics in the car are compared with the flat frequency characteristics A of the sound
reproducing device. It becomes C. The image frequency characteristics B and C are high in noise
level in the low frequency band and low in noise level in the high frequency band although there
is a slight deviation of the frequency band. Therefore, when trying to listen to the output of the
playback device having the frequency characteristic A, the low frequency band is buried in the
noise both in the train and in the car, and the voice in the high frequency band is emphasized <<
for listening. There is a problem that if the volume is raised to try to listen well to the low band,
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the high band is further emphasized. This is also a problem, for example, when listening alone
with headphones in a train or when listening alone with headphones in a car. In the case of an
open air type headphone in a train, sound leakage to the surroundings becomes a problem. The
results of measurement of the sound leakage are shown in FIGS. FIG. 6 is a diagram showing
sound leakage frequency characteristics when measured under the conditions shown in FIG. 7 for
the conventional open air type headphones.
That is, in a state where the headphone H is attached to the ear portion La of the listener, the
sound leakage is measured by the sound level meter M placed at a position separated by 1 (about
30-) from the ear portion La. Here, the surrounding environment is a soundproof room, and the
sound level meter M uses an A-curve filter. As a result, as shown in FIG. 6, the sound leakage
increases when the frequency is 1 kHz or more, and the sound leakage frequency band
characteristic Da is obtained, and the flat noise characteristic of the background noise level Db of
the soundproof room is obtained in the frequency band 1 kHz or less. . As described above, it can
be seen that a large amount of sound leakage occurs in the high frequency band, which causes a
problem as a cause of the sound leakage when listening in the open air type. As described above,
conventionally, when trying to listen to the reproduced sound in a train or car, it is difficult to
hear the bass very much by the noise of the place, the high sound is abnormally emphasized by
raising the volume, and the listener himself There was a problem of being blinded. Furthermore,
when there are a lot of people around, as in the case of a train, the noise of the surrounding
trains also tends to increase the volume, so the sound leaked from the head and the phone
becomes a loud noise to the people around them I heard there was a problem that I was annoyed.
In view of the above problems, the present invention can minimize the sound leakage without
being affected by the noise characteristics of the train or car as described above, and can be
reproduced comfortably for the listener and the people around them. An object of the present
invention is to provide a sound reproduction device. Means for Solving the Problem In order to
achieve the above object, the sound reproducing apparatus of the present invention measures in
advance the noise frequency characteristic obtained by frequency analysis of the noise amount,
and sets a filter set to correspond to the noise frequency characteristic. A control switch is
provided to switch the filter operation, and the control switch is switched to control the
frequency characteristic of the reproduction signal to correspond to the noise frequency.
According to the configuration described above, the present invention causes the filter operation
to be performed by switching the control switch, the frequency characteristic of the reproduction
output is enhanced with the bass portion and the treble portion is attenuated and the frequency
characteristic is the noise frequency characteristic. It is controlled to correspond, and while
suppressing the influence of noise, it will attenuate the sound leak at the time of headphone use
as much as possible. Embodiment An audio reproduction 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 the sound reproduction apparatus in the embodiment of the
present invention, and the embodiment shows one channel of stereotype in the portable CD
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player.
In FIG. 1, 1 is a CD (compact disc) record, 2 is a traverse mechanism including an optical pickup
for reading out a signal from the CD record 1, 3 is a servo and drive circuit for accurately
controlling the traverse mechanism 2 and 4 is a traverse mechanism 2 A signal processing circuit
for processing the signal read out in step S. 5, a D / A conversion part for converting a digital
signal subjected to signal processing in the signal processing circuit 4 into an analog signal, 6 a
buffer of the D / A converter 5 Ann-1 ', T is a volume control volume for controlling the output
amount of the' 'signal 6. Reference numeral 8 denotes a sodophone drive amplifier, which not
only drives headphones but also operates as an operational amplifier of the filter 9 described
later. A filter 9 is inserted into the feedback circuit of the headphone drive amplifier 8. When the
filter 9 is inserted into the feedback circuit by the control switch 10 described later, the input /
output frequency characteristics of the headphone drive amplifier 8 change. 10 is an on / off
control switch for filter operation, 11 is a headphone connection terminal to which eight of
headphone drive amplifiers 8 are connected, and 12 is one channel of the headphone connected
to the headphone connection terminal 11. Reference numeral 13 denotes another channel, which
comprises the same circuit as the buffer amplifier 6 to the headphone 12. FIG. 2 is a circuit
diagram showing the details of the filter 9 including the headphone drive amplifier 8 and the
control switch 10. In FIG. 2, 8.10 are the above-mentioned headphone drive amplifier and control
switch Sochi. 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. A resistor 14.15 is a gain setting element that determines the
input / output gain of the sodophone drive amplifier 8. The resistor 16.18 and the capacitor 17
operate as part of the gain setting element of the headphone drive amplifier 8 when the control
switch 10 is on the filter off side 10a, and are low when the filter on side terminal 10b is used. It
is a low-pass enhancement filter element that enhances the high frequency band, and is a part of
the filter 9. The capacitor 19.22 and the resistor 20.21 are high-pass attenuation filter elements
that attenuate the high-pass band only when the changeover switch 10 is set to the filter on-side
terminal 10b. It is a part. Reference numeral 23 denotes an input terminal of the circuit, and
reference numeral 24 denotes an output terminal of the circuit. FIG. 3 is a frequency
characteristic diagram showing the relationship between the input / output frequency
characteristics of the circuit shown in FIG. 2 and the train noise frequency characteristics and car
noise frequency characteristics shown in FIG. 5. In FIG. The noise frequency characteristic, 26 is
a car noise frequency characteristic, 27 is a frequency characteristic of the reproduction output
when the operation of the filter 9 is off, and 28 is a frequency characteristic of the reproduction
output when the operation of the filter 9 is on.
The operation of the sound reproducing apparatus configured as described above will be
described below with reference to FIGS. 1, 2 and 3. In FIG. 3, train noise frequency characteristics
25. As seen from the car noise frequency characteristic 26 and the frequency characteristic 27
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when the operation of the filter 9 is off, the noise in the low frequency band is large but the noise
in the high frequency band is small both in the train and in the car. Therefore, for the listener,
the low frequency band in the output from the headphones 12 is scraped off by noise and << for
listening, conversely, the high frequency band is easy to hear because the S / N ratio with the
noise can be large. Therefore, if the control switch 10 is set to the filter on-side terminal 10b, the
reproduction output has the frequency characteristics 28 when the operation of the filter 9 in
which the low frequency band is enhanced and the high frequency band is attenuated. Since the
low frequency band at the output from is enhanced, it is easy to hear without being scraped by
the noise, and the high frequency band that was heard until it is too loud is attenuated and
balanced. 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 trouble due to the sound
leakage to the people in the train or in the car. As described above, according to this
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 to enhance
the low frequency band so as to correspond to the both noise frequency characteristics. When it
is necessary to listen to the reproduced sound in the noise by turning on / off the control switch
10 as shown in FIG. 3 by providing the filter 9 for switching and the control switch 10 for
switching the operation thereof. It is possible to provide a well-balanced sound and to reduce the
sound leakage to the surroundings when using an open air type headphone. Next, a sound
reproducing apparatus according to a second embodiment of the present invention will be
described. FIG. 4 is a schematic circuit block diagram of the sound reproducing apparatus in the
second embodiment of the present invention, in which a part of the first embodiment is changed.
In the figure, reference numeral 29 denotes a volume control volume for controlling the amount
of output from the previous stage. A headphone driving amplifier 30 not only drives the
headphones but also operates as an operational amplifier of a filter described later. Reference
numeral 31 denotes a first filter inserted in the feedback circuit of the headphone drive amplifier
30, which measures in advance the train noise frequency characteristic, attenuates the high
frequency band to correspond to the noise frequency characteristic, and reduces the low
frequency band The input / output frequency characteristic of the headphone drive amplifier 30
is changed when it is inserted into the feedback circuit by the control switch 33 described later.
Reference numeral 32 denotes a second filter inserted in the feedback circuit of the headphone
drive amplifier 30, which differs from the first filter 31 in characteristics, measures vehicle noise
frequency characteristics in advance, and is high to correspond to the noise frequency
characteristics It is set to attenuate the low frequency band and enhance the low frequency band,
and when it is inserted into the feedback circuit by the control switch 33 described later, the
input / output frequency characteristic of the headphone drive amplifier 30 is the first filter
Changes with different characteristics. Reference numeral 33 denotes a filter operation on / off
control switch, 34 denotes a headphone connection terminal to which the output of the
headphone drive amplifier 30 is connected, and 35 denotes one channel of the headphone
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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 FIGS. 4 and 3.
In FIG. 3 above, train noise frequency characteristics 25. As can be seen from the car noise
frequency characteristic 26, there is a clear difference between the two noise frequency
characteristics, and the most suitable first filter 31 and second filter 32 corresponding to each
noise frequency characteristic are provided. By switching the control switch 33 at the listener's
discretion, a balanced sound suitable for the environment around the listener is obtained.
Moreover, since the high frequency band leaked from the headphones is attenuated according to
the surrounding environment, it is possible to prevent the trouble due to the sound leakage to
the surrounding people in 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 so as to
correspond to each of the above noise frequency characteristics. By providing the first filter 31
and the second filter 32 for enhancing the frequency band and the control switch 33 for
switching the operation thereof, it is necessary to listen to the reproduced sound in the noise by
switching the control switch 33 A well-balanced sound can be provided in some cases, and it is
possible to reduce the sound leakage to the surroundings when using an open air type
headphone. Although the filter characteristics are set by limiting to the train noise frequency
characteristics and the car noise frequency characteristics, for example, the ambient environment
is set in advance in trains such as aircraft and vehicles outside the vehicle volume and in
environments where specific noise is generated. The same effect can be obtained by measuring
the noise frequency characteristic of and setting the filter characteristic corresponding to the
noise frequency characteristic. Moreover, although the above-mentioned Example demonstrated
the case where it listened by an open air type as a state of reproduction signal listening, it may be
a case where it listens with a speaker.
For example, when listening in a vehicle compartment, reproduction can be performed via a
speaker of a car stereo, but in this case, the reproduction person and the noise in the vehicle will
be mixedly heard. Therefore, if reproduction is performed by the above-described apparatus
according to the present invention, it is possible to make a well-balanced reproduction sound
even when listening in the in-vehicle noise is speaker reproduction. Effects of the Invention As
described above, the present invention measures in advance both the noise frequency
characteristics obtained by frequency analysis of noise in a train and the noise frequency
characteristics obtained by frequency analysis of noise in a car, and the above two noise
frequency characteristics To reduce the high frequency band and enhance the low frequency
band, and a control switch for switching the filter operation, and switching the control switch to
change the frequency characteristic of the reproduced signal to the noise frequency In order to
respond to the characteristics, the listener can obtain a well-balanced sound suitable for the
surrounding environment and avoid bothering other people.
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[0002]
Brief description of the drawings
[0003]
FIG. 1 is a block diagram showing a first embodiment of the present invention, FIG. 2 is a circuit
diagram of the main part, FIG. 3 is a frequency characteristic diagram and FIG. 4 is a block
diagram showing a second embodiment Fig. 5 is a noise frequency characteristic diagram in
trains and cars, Fig. 6 is a sound leakage frequency characteristic diagram from oven air type
headphones of the conventional sound reproducing apparatus, and Fig. 7 is for obtaining the
characteristics of Fig. 6 It is a schematic diagram which shows the measurement state of.
9 и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и filter и и и и и и control switch, 25 и и и и и и noise
frequency characteristics of the train, и и и и и и и и и noise frequency characteristics of the vehicle, 27
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и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и и. Second filter 33... Control
switch.
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