JPH0241955A - Device for reducing sound confined in vehicle - Google Patents

Abstract

PURPOSE:To reduce confined sounds originating from the vibration of an engine by processing to generate additional sounds of opposite phases with a phase converter and putting them out from a speaker, after pulse-like ignition signals are converted into sinusoidal wave signals and processed with filters. CONSTITUTION:Pulse-like ignition signals of an engine 2 are converted into sinusoidal wave signals with a waveform shaper 3. Sinusoidal signals are put into a band pass filter 5 for filter processing which has, as its pass band, a frequency domain corresponding to the engine speed which generates confined sound due to resonance. Sinusoidal waves passed through the filter are put into a phase converter 6 for processing to generate additional sounds of opposite phases. The additional sounds are put out from a speaker 1 inside a vehicle cabin after amplification process, etc. The confined sounds originating from engine vibration are set off by the additional sounds to reduce the confined sounds.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides a vehicle muffler system that reduces muffled noise in a vehicle interior caused by engine vibration by interfering with additional sound. This relates to a reduction device.

(Prior Art) Is it well known that this type of device generates an additional sound with the same amplitude and opposite phase as the sweat from the speaker at the listening point based on the detection signal from the microphone? 1
51150), and a device that generates an additional sound source based on the ignition signal in order to further enhance the reduction effect is also known (Actual Opening/Closing 62-127052).

[Invention or problem to be solved]

However, in either case, the overall circuit configuration becomes complicated because the detection signal is processed and a separately prepared oscillator is controlled.

Therefore, an object of the present invention is to provide a muffled sound reduction device that can reliably reduce muffled sound with a simpler circuit configuration based on an ignition signal.

(Means for Solving the Problems) In order to achieve this object, the present invention focuses on the fact that muffled noise is particularly problematic in the resonance frequency head area in the vehicle interior, and adds an additional feature to counteract the muffled sound. ff! 1 (a speaker that outputs into the room, a waveform shaper that receives a pulsed ignition signal as input and converts this ignition signal into a sine wave signal, and a sine wave signal that inputs the ignition signal and converts it to a muffled sound that occurs at a specific engine speed. A bandpass filter whose passband is in the frequency domain, and a predetermined phase angle so that the output signal of this bandpass filter is in the opposite phase to the scratchy sound at a predetermined listening λ. Take phase i1j
1' which amplifies the sine wave signal at a predetermined listening point with a gain that outputs an additional sound at a level corresponding to the muffled sound from the speaker. ? It is equipped with a width gauge.

In order to simplify the adjustment at the time of construction or afterward, the phase converter and amplifier can be set to J/Q function using a control signal, and function as a microphone instead of generating additional sound from the speaker when setting the operating conditions. A changeover switch inputs the output signal of the speaker to a bandpass filter having the same pass band as the frequency range and outputs a muffled sound signal, and a switch that outputs an additional sound at a level corresponding to the muffled sound at a predetermined listening point when setting operating conditions. a gain control value 1) that generates a gain control value 1) according to the level of the muffled sound signal so as to output it from the muffled sound signal, and stores this gain control signal during normal operation; A phase control signal is generated according to the phase difference between the output signal of the waveform shaper and the muffled sound signal so that the phase of the additional sound is in reverse phase with respect to the muffled sweat at the point, and this phase control signal is generated during normal operation. Write tα
A phase setting fO is provided.

[Effect]

The ignition signal is converted into a sine wave by a waveform shaper, and if the engine speed is not high enough to cause muffled noise due to resonance, the sine wave signal is attenuated by a bandpass filter, and virtually no additional sound is generated.

On the other hand, a large muffled sound due to resonance is generated ((When the a rotation number is reached, the ignition signal passes through the bandpass filter as a sine wave, and the phase converter generates an additional a whose phase is delayed by 18a degrees from the muffled sound at the listening point. The phase of the sine wave that has passed through the band-pass filter is then amplified in an amplifier so that the additional sound is at the same level as the muffled sound at the listening point. Additional sound of the same level and opposite phase as the muffled sound at the listening point is generated, and the muffled sound is reduced by mutual interference.

If the phase converter and amplifier can be set using control signals, the selector switch is switched to the operating condition setting side at the time of manufacture or during subsequent adjustment, and the output signal of the speaker functioning as a microphone is passed through a bandpass filter and the gain setting means and A muffled sound signal is input to the phase setting means. This results in
A gain control signal that generates an additional sound at a level corresponding to the muffled sound at a predetermined listening point and a phase control signal that reverses the phase are detected and held, and are automatically adjusted according to the muffled sound that actually occurs during normal operation. An additional sound is generated.

[Embodiments of the invention]

Next, the muffled sound reduction device of the present invention will be explained based on an embodiment with illustrations.

In FIG. 1, a speaker 1 is attached to the roof at the rear of the vehicle interior, and generates additional sound to a listening point A at the driver's seat, for example. 3 is a waveform shaper that inputs a pulsed ignition signal supplied from the engine 2 and converts it into a sine wave of that frequency; 4 is a waveform shaper that converts the sine wave signal output from the waveform shaper 3 into a muffled sound from a speaker l; This is an amplifier that amplifies the level of additional sound by setting the gain to output it to the listening point A. Reference numeral 5 designates a bandpass filter, which receives an amplified sine wave signal as an input, and has a pass band of, for example, 45±5Hz in a frequency range corresponding to a specific engine rotation speed that causes a loud muffled sound due to resonance in the vehicle interior. A phase converter 6 controls the phase of the output signal of the bandpass filter 5 by a predetermined phase angle so that the phase of the additional sound is opposite to the muffled sound at the listening point A. The delay phase angle in this phase converter is set to 180' + 0-α so as to generate an additional sound delayed by 180 degrees with respect to the muffle a (dotted line in Figure 2), that is, in the opposite phase. . In other words, 0 is the waveform shaper 3 at a specific engine speed.
α is the phase shift of the muffled sound with respect to the output signal of the speaker l (solid line in FIG. 2), and α is the phase shift of the additional sound, which is the output signal, with respect to the input signal of the speaker l.

The operation of the muffled sound reduction device configured as described above is as follows.

When the engine is running, its ignition signal (FIG. 2a) is converted into a sine wave by a waveform shaper 3. However, when the engine speed is not high enough to generate muffled sound due to resonance, the sine wave signal is attenuated by the bandpass filter 5, and no additional sound is substantially generated.

On the other hand, when the rotational speed reaches a speed that generates a large muffled sound due to resonance, the ignition signal passes through the bandpass filter 5 as a sine wave, and is sent to the phase converter 6 at a phase angle of +8".
+0−α and further delayed by α at speaker l. This sine wave signal is amplified with a predetermined gain in an amplifier 4, so that the speaker l
The same level as the muffled sound at listening point A is 180''.
Additional sounds with a phase delay are generated and mutual interference reduces the muffled sound. Incidentally, it is also conceivable that the amplifier be replaced with the amplifier 4 or separately followed by the phase converter 6.

FIG. 3 shows a muffled sound reduction device according to another embodiment of the present invention.

In this case, corresponding to the above-described embodiment, a waveform shaper 13 is provided between the speaker l and the engine 2 for converting the pulsed ignition signal into a sine wave signal, and the output signal is adjusted to a level corresponding to sweat. An amplifier 14 amplifies with a gain set in response to a gain control signal so as to be output from a speaker l as an additional sound, and a sine wave signal which is the output of a waveform shaper 13 is input, and corresponds to a specific engine rotation speed. Bandpass filter 1 whose passband is the muffled sound frequency region
5 is connected to a phase converter 16 which controls the phase of the output signal of the bandpass filter in response to a phase control signal so that the output signal of the bandpass filter has a phase opposite to the phase of the additional sound or the muffled sound.

Further, a changeover switch 17 that is operated externally when setting operating conditions for amplification and phase characteristics is inserted on the input/output side of the bandpass filter 15.

21 is a gain setting means, which detects the level of the muffled sound signal taken in from the speaker l functioning as a microphone through the bandpass filter 15, and outputs a gain control signal to generate an additional sound of the same level at the listening point A. The gain control signal is generated and stored in the memory 21a. That is, in a standard muffled state of a certain vehicle type, the amplifier 14
Let the amplitude of the input signal be P. , the amplitude of the muffled sound signal taken from speaker l is Pl, and the gain at that time is G. Then, if a vehicle of the same type or the same vehicle changes to P or P2 after aging, the gain is G. X
Set to P2/P.

22 is a phase setting means, which passes the muffled sound signal taken in from the speaker l through the bandpass filter 15, detects the phase difference between the filter signal and the output signal of the waveform shaper 13, and sets the muffled sound exactly opposite to the muffled sound. A phase control signal is generated to generate a phase-added sound and is stored in the memory 22a. That is, similarly, the phase difference β of the muffled sound signal taken in from the speaker l with respect to the input signal of the amplifier 14 in the standard muffled row state. , if the phase difference of a certain vehicle of the same model or the same vehicle after aging is β, then β - β. The control phase angle of the phase converter 16 is set to be corrected accordingly.

The operation is as follows.

When the device is installed at the vehicle manufacturing stage, or when the muffled sound level increases due to aging, the changeover switch 17
When switched to the operating condition setting side, the muffled sound signal taken in from the speaker l and passed through the bandpass filter 15 is supplied to the gain setting means 21 and the phase setting means 22.As a result, the gain setting means 21 and phase setting means 22
generates and holds a gain control signal and a phase control signal for the amplifier 14 and phase converter 16 based on the muffled sound signal taken in from the speaker l. Then, when the changeover switch 17 is returned to the normal operating position, an additional sound with an amplitude and phase matching the actual muffled sound of the vehicle is generated from the speaker l based on these gain control signals and phase control signals. Ru.

FIG. 4 shows a microcomputer 30 constituting the gain setting means and phase setting means in FIG. 3, which includes an input/output interface 31, a CPU 32, and a reference gain G.
. , a ROM 33 storing amplitude data P1, control phase angle data for the detected phase β, and a program, and a RAM 14 including a non-volatile area. cpu
: +z takes in the muffled sound signal input through the bandpass filter 15 and generates G. A gain control signal corresponding to XP2/P+ and a phase control signal corresponding to phase difference β are stored in RAM:
14 non-volatile areas. As a result, during normal operation, the amplifier 14 and phase converter 16 have RAM3.
The held data of 4 is supplied from the input/output interface 31.

In addition, the muffled sound signal filter may not be shared but may be prepared separately, and the circuit configuration of the changeover switch may be modified in various ways.

〔Effect of the invention〕

Second, according to the present invention, it is possible to significantly reduce the muffled sound, which is a substantial problem, by using a small circuit configuration that simply performs waveform shaping, amplitude #AyJ adjustment, and phase adjustment of one ignition signal.

Furthermore, by allowing the phase shifter and amplifier to be controlled by detecting the actual muffled sound, the device can be easily adjusted during manufacturing and easily matched over time.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the configuration of a muffled sound reduction device according to an embodiment of the present invention, Fig. 2 is a diagram showing waveforms of various parts of the circuit of the same embodiment, and Figs. 3 and 4 are diagrams according to another embodiment. FIG. 3 is a diagram showing the configuration. l...Speaker, 2...Engine.

Claims (1)

[Scope of Claims] 1) A speaker that outputs additional sound to cancel muffled noise into the vehicle interior; a waveform shaper that receives a pulsed ignition signal and converts the ignition signal into a sine wave signal; and the sine wave signal. a bandpass filter whose pass band is the frequency region of the muffled sound generated at a specific engine speed; a phase converter that controls the phase by a predetermined phase angle so that the sine wave signal is in reverse phase with respect to the sine wave signal; and outputting the additional sound at a level corresponding to the muffled sound from the speaker at the predetermined listening point. A muffled sound reduction device for a vehicle, comprising: an amplifier that amplifies with a gain of 2) a speaker that outputs additional sound into the vehicle interior to cancel muffled sounds; a waveform shaper that receives a pulsed ignition signal as input and converts the ignition signal into a sine wave signal; a bandpass filter whose passband is the frequency region of the muffled sound generated at the engine speed; a phase converter that controls the phase of the output signal of the bandpass filter in response to a phase control signal; an amplifier that amplifies in response to a gain control signal; and an output signal of the speaker that functions as a microphone instead of generating the additional sound from the speaker when setting operating conditions is input to a bandpass filter having the same passband as the frequency domain. a changeover switch that causes the muffled sound signal to be output by changing the level of the muffled sound signal so that the additional sound having a level corresponding to the muffled sound is output from the speaker at the predetermined listening point when the operating condition is set; gain setting means for generating the gain control signal corresponding to the muffled sound and storing the gain control signal during normal operation; phase setting means for generating a phase control signal according to a phase difference between the output signal of the waveform shaper and the muffled sound signal so that the output signal and the muffled sound signal are in opposite phase, and storing this phase control signal during normal operation; A muffled sound reduction device for a vehicle, comprising: