JPH0314720Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a noise control device for a vehicle, and particularly to a noise control device for a vehicle that is characterized by lowering the identification sensitivity for high-frequency noise.

Various noises generated while a vehicle is running have a large effect on the comfort of the vehicle, and it is necessary to block out the noise as much as possible. Vehicle noise includes engine explosion noise, gear mesh noise, wind noise, and accompanying resonance noise, and various types of sound shielding are applied to each of these factors, but among these, gear mesh noise Even if the noise level itself is relatively low, such as noise, it is known from experience that noise that shows a single frequency peak in a relatively high frequency band of 500 Hz or higher is perceived as extremely harsh noise. It is being

Figure 1 shows an example of such high-frequency peak noise, where the hatched noise often forms a harsh noise compared to continuous noise at a higher level, such as the noise from an engine explosion. It has been experimentally confirmed that this is the case.

In practice, such noise causes various resonances in the car body and other parts, and in order to prevent such secondary resonance, measures such as asphalt sheets are required on the car body. No countermeasures were possible.

The present invention was developed in view of the above-mentioned conventional problems, and because such high-frequency peak noise only has a specific narrow frequency component that stands out from the background noise, it may cause noise to occupants even though the noise level is low. Unlike conventional noise countermeasures that reduce peak noise itself, it increases surrounding background noise within a predetermined level and thereby reduces peak noise. To provide a noise countermeasure device for a vehicle which lowers the hearing sensitivity of a passenger by burying noise in background noise, and thereby measures a perceptual noise reduction.

In order to achieve the above object, the present invention provides a microphone that electrically detects the sound pressure level of in-vehicle noise in a specific high frequency band, and a white microphone that has almost the same sound pressure level in the entire frequency range including the specific high frequency band. a white noise generator that generates noise; an arithmetic circuit that calculates the difference between the white noise and the in-vehicle noise; and a background noise having approximately the same sound pressure level as the in-vehicle noise detected by the microphone according to the output of the arithmetic circuit. and a speaker that generates noise inside the vehicle, and is characterized by lowering the noise identification sensitivity by burying the interior noise in the background noise within a predetermined level.

Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 2 shows a preferred layout of the noise control device according to the present invention in a vehicle, and FIG. 3 shows its specific circuit configuration.

In the present invention, a specific high frequency band, e.g.
A microphone 10 is mounted on the vehicle to detect in-vehicle noise in the band from 500Hz to 2KHz,
In the embodiment, this microphone 10 is provided near the ceiling of the vehicle interior.

Then, the noise signal electrically detected by the microphone 10 is supplied to a background noise signal generation circuit 12 to form a background signal that buries the peak noise within the band,
This is supplied to a speaker 14 installed in the vehicle to generate a predetermined low-level background noise in the vehicle interior, thereby making it possible to bury the peak noise in the background noise, thereby making it possible for the occupants to identify the noise level. power and, as a result, the impact of peak noise can be reduced.

The background noise generating circuit 12 is an IC.
It forms a circuit block integrated with circuits and the like and is fixed at a suitable location on the vehicle, and its internal structure is shown in detail in FIG. In order to generate a predetermined level of background noise in the vehicle interior, a white noise generator 16 is provided in the circuit 12, and as shown in FIG. 4, a constant low level noise signal is generated in a wide frequency band. is output.

The output of the white noise generator 16 is converted into a desired band signal by a filter 18, and in the embodiment, components below 500 Hz and above 2 KHz are removed, an example of which is shown in FIG.

Further, the output of the filter 18 is supplied to an arithmetic circuit 20, where the in-vehicle noise obtained from the microphone 10 is calculated. In the embodiment, the output of the microphone 10 is amplified by a predetermined amount by an amplifier 22, and then the arithmetic circuit At 20, a difference is calculated with the band white noise signal from the filter 18.

For example, when the in-vehicle noise obtained from the microphone 10 exhibits characteristics as shown in FIG. 6, the hatched portions form high-frequency peak noise. This in-vehicle noise is generated by the arithmetic circuit 20.
Then, the difference is calculated with the band white noise signal shown in FIG. 5, and the output becomes a noise signal with characteristics as shown in FIG. That is, the arithmetic circuit 20 outputs the signal from which the hatched high-frequency peak noise is removed from the band white noise signal shown in FIG.

Therefore, the output of this arithmetic circuit 20 is sent to the amplifier 24.
When the amplified signal is amplified by a predetermined amount and supplied to the speaker 14, the speaker 14 generates background noise in a frequency band other than the high-frequency peak noise in the vehicle interior. Being buried in the noise, the occupant's hearing sensitivity is significantly reduced, and even when peak noise occurs, it becomes impossible to distinguish it from others. In other words, the hearing of the occupants is significantly impaired by the continuous background noise in the vehicle interior, making it difficult for the occupants to actually hear the peak noise caused by gear meshing noise, etc. become unable to do so.

FIG. 8 shows the effect of the peak noise in the present invention being submerged into the background noise. By adding the background noise 200 described above to the original vehicle interior noise 100 shown by the solid line, the actual vehicle interior contains 300. The corrected noise shown in this figure will be filled, and the peak noise will disappear from this diagram, leaving almost only white noise in the cabin, so the actual hearing of the occupants will be significantly reduced within this level. It becomes possible to reduce the actual sensory noise.

In particular, the background noise in the present invention has a recess corresponding to the interior noise in its sound pressure level. Therefore, the sensitivity for identifying harsh noises can be lowered without increasing the sound pressure level for noises with frequencies corresponding to in-vehicle noises.

Of course, in the present invention, the background noise generated from the speaker 14 is kept at a low level to the extent that it does not itself create an unpleasant noise for the occupants.

In addition, in the embodiments, the white noise is always shown as a constant level, but in the present invention, it is also possible to arbitrarily change the white noise level to form background noise according to the driving conditions. It is also preferable to gradually increase the background noise level over a predetermined period of time from when the vehicle starts running, so that the occupant's hearing can become accustomed to the background noise without the occupant noticing.

As explained above, according to the present invention, it is possible to significantly improve the comfort of a vehicle by alleviating the harshness experienced by the occupants due to high-frequency peak noise.

[Brief explanation of the drawing]

Fig. 1 is a high-frequency peak noise characteristic diagram targeted by the present invention, Fig. 2 is a diagram showing a suitable arrangement of the noise countermeasure device according to the present invention in a vehicle, and Fig. 3 is an electrical diagram of the noise countermeasure device according to the present invention. Block circuit diagram, 4th, 5th,
Figures 6, 7, and 8 are characteristic diagrams showing the effects of the present invention. 10...Microphone, 12...Background noise signal generation circuit, 14...Speaker, 16
... White noise generator, 20 ... Arithmetic circuit.

Claims (1)

[Scope of utility model registration request] a microphone that electrically detects the sound pressure level of in-vehicle noise in a specific high frequency band; a white noise generator that generates white noise having approximately the same sound pressure level in the entire frequency range including the specific high frequency band; an arithmetic circuit that calculates the difference between the in-vehicle noise from white noise; and a speaker that generates background noise in the in-vehicle cabin at approximately the same sound pressure level as the in-vehicle noise detected by the microphone according to the output of the arithmetic circuit. A noise countermeasure device for a vehicle, characterized in that noise discrimination sensitivity is lowered by burying in-vehicle noise within background noise within a predetermined level.