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DESCRIPTION JPH08116600

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DESCRIPTION JPH08116600
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sound reproducing apparatus for use in a transport vehicle such as a car, a ship, or an aircraft,
which detects a noise level while traveling and adjusts the volume of reproduced signals
according to the noise level Audio reproduction apparatus.
[0002]
2. Description of the Related Art FIG. 2 is a block diagram showing an example of a conventional
sound reproducing apparatus of this type, which is applied to an on-vehicle audio apparatus. In
FIG. 2, a music signal from a sound source 201 such as a tape or a radio is adjusted in level by a
volume adjustment unit 202 and a power amplifier 203 and reproduced by a speaker 204. The
traveling noise is detected by the microphone 205 placed in the vehicle compartment, and the
detection band is limited by the low pass filter 207. The microphone signal, the vehicle speed
signal 208, and the engine speed signal 209 are input to the microcomputer 210, and the noise
level in the passenger compartment is estimated. The microcomputer 210 controls the volume
adjustment means 202 in accordance with the estimated noise level to increase the volume of the
reproduction signal.
[0003]
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SUMMARY OF THE INVENTION However, in the above-mentioned conventional sound
reproducing apparatus, what is detected by the microphone 205 includes not only traveling noise
but also reproduced music signals. Therefore, the vehicle speed signal 208 and the engine speed
signal 209 are used for accurate estimation of the traveling noise. However, with the method of
centering the vehicle speed signal or engine speed signal, the volume can not be increased unless
the actual speed is increased, and the window can be opened or closed during constant speed
driving, or the running noise can be changed due to road conditions. There was a problem that it
was impossible.
[0004]
The present invention solves such conventional problems, and aims to provide an excellent sound
reproducing apparatus capable of obtaining a comfortable listening environment under any noise
condition.
[0005]
SUMMARY OF THE INVENTION In order to achieve the above object, sound reproducing means
provided in a transporter such as a car, a microphone for detecting noise in the transporter, and
microphones detected by the microphone A first rectifying means for obtaining a first level of the
signal, a second rectifying means for obtaining a second level of the reproduction signal output
from the sound reproducing means, and Noise level detection means constituted by gain
adjustment means for making substantially equal; arithmetic circuit for reducing the second level
from the first level; volume adjustment means for controlling the volume of the reproduction
signal output from the sound reproduction means Is provided.
[0006]
Therefore, according to the present invention, the noise detection means detects only traveling
noise by subtracting the level of the reproduction signal output from the sound reproduction
means from the level of the signal detected by the microphone. By increasing the volume of the
reproduction signal output from the sound reproduction means according to the noise level, it is
possible to perform natural sound volume control corresponding to the actual noise level without
depending on the vehicle speed or the engine rotational speed.
[0007]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows the configuration of
an embodiment of the present invention, and this figure shows the case where it is applied to an
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on-vehicle audio apparatus.
Reference numeral 101 denotes a sound source such as a tape or a radio, 102 denotes a
reference signal generation unit, and 103 denotes volume adjustment means, and the volume
adjustment means 103 adjusts the volume of the reproduced music signal from the sound source
101.
Reference numeral 104 denotes a power amplifier, and reference numeral 105 denotes a
speaker. A reproduction signal is emitted from the speaker 105 into the vehicle.
Reference numeral 106 denotes a microphone placed in the vehicle compartment, and reference
numeral 107 denotes a microphone amplifier for amplifying a signal from the microphone 106.
Reference numerals 108 and 109 denote low pass filters, which respectively limit the detection
band frequency. Reference numerals 110 and 111 denote rectifying means, which obtain the
absolute value (magnitude) of the signal. Reference numeral 112 denotes a gain adjustment unit,
113 denotes an adder, and 114 denotes a noise level detection unit. The volume adjustment unit
103 is adjusted by the signal from the noise level detection unit 114.
[0008]
The operation of the above embodiment will now be described. In the state where the reproduced
music signal from the sound source 101 is not output, the traveling noise is detected by the
microphone 106 placed in the vehicle compartment, and the detection band is limited by the low
pass filter 108 through the microphone amplifier 107. , Find the absolute value (magnitude) A of
the signal.
[0009]
Further, when the reproduced music signal from the sound source 101 is output, the volume is
adjusted by the volume adjusting means 103 and reproduced into the vehicle interior by the
speaker 105 through the power amplifier 104. Also for this reproduced music signal, the output
of the volume adjustment means 103 is input to the low pass filter 109 to limit the detection
band, and the rectification means 111 obtains the absolute value (size) B of the signal.
Thereafter, the adder 113 performs the processing of A-B. The sound volume of the volume
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adjusting means 103 is adjusted by the gain adjusting means 112 so that A ≒ B when the
passenger compartment is noiseless. Although this gain adjustment can be performed with a
normal music signal from the sound source 101, a reference signal generating means 102 such
as white noise is used to perform adjustment with higher accuracy. Further, inter-station noise of
the radio may be used to easily obtain pseudo white noise.
[0010]
Here, when noise is generated after the adjustment, an actual noise level can be obtained by
performing the processing of A-B in the adder 113. This result is averaged for a fixed time by the
noise level detection means 114, and the noise level is graded later. The volume adjustment
means 103 is controlled according to the stage obtained here, and the volume of the
reproduction signal is increased. In addition, at the time of staging, voice control can be made to
act acoustically smoothly by defining the maximum variation of temporally adjacent stages.
[0011]
The processing up to the rectifying means 110 and 111, the gain adjusting means 112, the adder
113 and the noise level detecting means 114 can also be digitally processed by a microcomputer
or the like.
[0012]
Further, by providing a high-pass filtering circuit in the front stage of the rectifying means 110
and limiting the frequency band of the noise to be detected, the actual noise level can be detected
more reliably.
[0013]
Further, in addition to the volume control in accordance with the detected noise level, sound
control with less discomfort can be performed by enhancing the low frequency range and the
high frequency range, and according to the value of the volume by the volume adjustment means
103. Thus, the maximum increase in volume is changed.
In addition, the noise level detected by the noise level detection means 114 is averaged at fixed
time intervals, and after the stage is performed, the volume is increased according to the stage,
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and the maximum change amount of one stage is defined. By redetermining the stage of the
volume increase, the volume adjustment can be made smoother in hearing.
[0014]
As apparent from the above embodiment, the present invention detects the level of the traveling
noise only by subtracting the level of the reproduction signal output from the sound reproducing
means from the level of the signal detected by the microphone. This has the effect of being able
to perform volume control corresponding to the actual noise level without depending on the
vehicle speed or the engine speed.
In addition, since the gain adjustment of the signal detected by the microphone is performed,
even if the sound pressure of the reproduced music signal changes due to the change of the
power amplifier or the speaker, only the noise level can be detected at all times.
[0015]
Brief description of the drawings
[0016]
1 is a schematic block diagram of a sound reproduction apparatus according to an embodiment
of the present invention.
[0017]
Fig. 2 A schematic block diagram of a conventional sound reproducing apparatus
[0018]
Explanation of sign
[0019]
101 sound source 102 reference signal generation means 103 volume 104 power amplifier 105
speaker 106 microphone 107 microphone amplifier 108 low pass filter 109 low pass filter 110
rectification means 111 rectification means 112 gain adjustment means 113 adder 114 noise
level detection means
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