JPH0142855B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sound reproducing device used in a transport aircraft such as an automobile, a ship, or an aircraft, and the present invention relates to a sound reproducing device that can automatically eliminate the masking phenomenon in the auditory system due to noise during driving and noise generated from the engine. It provides equipment.

When playing a tape recorder or listening to the sound from a radio inside a transport vehicle, such as a car,
The reproduced sound is masked by driving noise such as the friction noise of the road surface and tires, wind noise, etc., and engine noise, making it difficult to hear the desired sound, as well as making it difficult to recognize information such as the pitch and loudness of the sound. interfere with or change the sound quality.

The present invention aims to automatically eliminate such masking phenomena in the auditory system caused by various noises.

Noise from a moving vehicle includes running noise such as friction noise between the road surface and tires and wind noise, and engine noise emitted from the engine.

Figure 1A shows the running noise spectrum of a 1976 model (1400c.c.) car while running at a constant speed.
Figure B shows the running noise spectrum of a 1974 model (2000c.c.) car while it was running at a constant speed. As is clear from Figure 1 A and B, constant speed (100, 80,
60, 40Km/h) -9dB/oct~
It shows a running noise spectrum of -10 dB/oct, and the noise when running at a constant speed has many low-frequency components.

FIG. 2 shows the relationship between the engine speed and the engine noise spectrum, and as the engine speed increases, the components of the engine noise from the middle range to the high range increase depending on the engine speed.

FIGS. 3A and 3B show compensation characteristics of loudness frequency characteristics. This compensation characteristic is based on the signal level
It shows the amount of correction at each frequency at each noise level when 75 dB (constant).
is a noise spectrum of −9 dB/oct, and B is −10.5 dB/oct.

As is clear from Figures 3A and B, when a car is running, the quality of the reproduced sound deteriorates due to noise, and the quality of the reproduced sound also changes due to changes in the noise spectrum. be.

The present invention provides a sound reproduction device that can automatically set the volume and sound quality to optimal values depending on the noise level.

An embodiment of the present invention will be described below with reference to FIG. In FIG. 4, 1 is a tape recorder, 2 is a low-pass filter, 3 is a middle-pass filter, and 4 is a high-pass filter.
It is divided into low frequency component, mid frequency component, and high frequency component.
Reference numerals 5, 6, and 7 are voltage gain adjusters that control the signal levels of the low-frequency component, mid-range component, and high-frequency component, respectively, and the voltage gain adjusters 5, 6, and 7 each control the signal level according to the control signal applied to the control terminals of the voltage gain adjusters 5, 6, and 7. As a result, the signal levels of the low-frequency component, middle-frequency component, and high-frequency component change. 8 is an adder that adds the output signals of the voltage gain adjusters 5, 6, and 7, and the output of this adder 8 is sent to the output terminal 9.
The reproduced sound is applied to a speaker (not shown) through the vehicle, and the reproduced sound is radiated into the vehicle. Reference numeral 10 is a microphone for detecting the noise inside the vehicle cabin, reference numeral 11 is a low frequency band amplifier for amplifying the low range of the noise detected by the microphone 10, and reference numeral 12 is a detection of the output of the low frequency band amplifier 11 and detecting the output according to the noise level. This is a detector that obtains a DC voltage, and the DC voltage from this detector 12 is applied to an adder 20 via a switch (analog switch) 18. 13 is a terminal to which pulses (for example, ignition pulses) are applied at intervals corresponding to the engine speed; 14 is an amplifier that amplifies the pulses; 15 is a frequency-voltage converter; A DC voltage corresponding to the engine speed is outputted from the switch 17, and this DC voltage is applied to the adder 20 via the switch 17. Further, the output of the frequency-voltage converter 15 is applied to a voltage comparator 16. When the output voltage of the frequency-voltage converter 15 is higher than the reference voltage of the reference voltage source 28, the output of the voltage comparator 16 causes the switch 1 to
7 becomes conductive. 19 is an inverter, and the output of the voltage comparator 16 is inverted by the inverter 19,
The switch 18 is controlled by this inverted output. That is, when switch 17 is in the ON state, switch 1
8 is OFF, and when switch 17 is OFF, switch 18 is ON. Reference numeral 21 denotes a weighting coefficient unit (such as an attenuator), and the output of the detector 12 is applied to the control terminal of the voltage gain regulator 5 via this weighting coefficient unit 21. The gain of the voltage gain regulator 5 changes depending on the noise level inside the vehicle detected by the microphone 9. When the noise level inside the vehicle increases, the gain of the voltage gain regulator 5 changes according to the increase in the noise level inside the vehicle. Gain increases. 22,2
2' is a weighting coefficient unit connected to the control terminal of the voltage gain regulator 6; 23, 23' is a weighting coefficient unit connected to the control terminal of the voltage gain regulator 7; these weighting coefficient units 22, 22' Switches 24, 2 are connected between the other ends of the adder 23, 23' and the output terminal of the adder 20.
5, 26, and 27 are connected. The switches 24 and 26 are controlled by the output of the voltage comparator 16.
The switches 25 and 27 are controlled ON and OFF by the output of the inverter 19. Switches 24 and 26 are OFF until the engine speed reaches the specified speed, and switches 25 and 26 are OFF.
27 is turned on, and a voltage corresponding to the immediate indoor noise level is applied to the control terminals of the voltage gain adjusters 6 and 7 via the weighting coefficient units 22' and 23'. On the other hand, when the engine speed exceeds the specified speed, the switches 24 and 26 become conductive, and a voltage corresponding to the engine speed is applied to the voltage gain regulators 6 and 7 via the weighting coefficient devices 22 and 23.

As described above, according to this embodiment, when the engine speed is lower than the specified speed, the low-frequency gain of the reproduced signal increases in accordance with the noise level, and the masking phenomenon caused by running noise inside the vehicle is prevented. is removed, and when the engine speed is higher than the specified speed, the gain in the middle and high ranges of the reproduced signal increases in accordance with the engine speed, thereby eliminating the masking phenomenon caused by engine noise.

The present invention has the above configuration, and has the advantage that the auditory masking phenomenon caused by running noise and engine noise can be automatically removed.

[Brief explanation of drawings]

Figures 1A and B are diagrams showing the running noise spectrum of a car, respectively, Figure 2 is a diagram showing the relationship between the engine speed of the car and the engine noise spectrum,
3A and 3B are compensation characteristic diagrams of loudness frequency characteristics, respectively, and FIG. 4 is a block diagram of a sound reproducing apparatus according to an embodiment of the present invention. 1... Tape recorder, 2... Low pass filter, 3... Middle pass filter, 4... High pass filter, 5, 6, 7... Voltage gain adjuster, 8...
Adder, 9...Output terminal, 10...Microphone, 11...Low frequency band amplifier, 12...Detector, 13...Terminal, 14...Amplifier, 15...Frequency-voltage converter, 16... Voltage comparator, 17...
...Switch, 18...Switch, 19...Inverter, 20...Adder, 21, 22, 22', 23,
23'... Weighting coefficient unit, 24, 25, 26, 27
...Switch.

Claims (1)

[Scope of Claims] 1. Sound reproducing means provided in a transport machine such as an automobile, a microphone for detecting running noise of the transport machine, and outputting a voltage according to engine noise or engine rotation speed of the transport machine. The rotation speed detected by the rotation speed detection means includes a rotation speed detection means and a control means for controlling the gains of low frequency components, middle frequency components, and high frequency components of the reproduction signal output from the sound reproduction means, and the rotation speed detected by the rotation speed detection means. The control means is controlled in accordance with the noise level detected by the microphone to increase the low-frequency gain of the reproduction signal output from the sound reproduction means until the number of rotations reaches a predetermined number of rotations. Sound reproduction characterized in that when the rotation speed exceeds the specified rotation speed, the control means is controlled by the output of the rotation speed detection means to increase the gain in the middle and high range of the reproduced signal output from the sound reproduction means. Device. 2. Control means including filter means for dividing the reproduction signal output from the sound reproduction means into low-frequency components, middle-frequency components, and high-frequency components, and voltage gain adjustment means for controlling the level of each of the divided band components. A sound reproduction device according to claim 1.