JPH03149998A - Muffling device - Google Patents

Abstract

PURPOSE:To execute an operation in a quiet state by generating electrically a signal having all the same frequency component as an engine sound at its each time, and reproducing it by a loudspeaker after its phase inversion. CONSTITUTION:In accordance with the rotating speed of an engine detected by a detecting means 6, a read-out clock period of a memory 8 in which its engine sound is brought to sound recording in advance is controlled. Therefore, by varying a interval of the engine sound, the memory output of all the same interval as the engine sound in the course of its rotation is obtained. Subsequently, the memory output is brought to phase inversion, and reproduced by a loudspeaker 5. Accordingly, the reproduced sound A interferes with the engine sound N in the air, and since they are in an opposite phase relation, a noise level decreases in a place of a listener M. In such a way, the operation can be executed in a quiet state.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a silencer for reducing engine noise of automobiles, ships, airplanes, etc.

2. Description of the Related Art As a method of reducing the noise level in a vehicle interior, etc., interior materials and sound insulating materials are installed in the vehicle interior. or,
The engine, which is the source of the noise, is also surrounded by a sound insulating material such as metal or concrete.

Problems to be Solved by the Invention However, in the past, in order to reduce the noise level by a considerable amount in the passenger compartment, the engine room containing the engine that generates the noise has been surrounded with a considerable amount of sound insulating material. This increases the overall weight of the vehicle, which consumes more gasoline for driving, which goes against the trend of ``energy conservation.''

The present invention solves the above-mentioned problems, and reduces the overall weight of the vehicle by reducing noise by using an electroacoustic method rather than a physical method such as sound blowing materials or sound insulation materials. The purpose of this is to provide a device that can be implemented without increasing the number of devices.

Means for Solving the Problems In order to solve the above problems, the present invention provides a detection means for detecting the engine rotation speed of a vehicle, a memory in which the engine sound of the vehicle is recorded in advance, and an output signal of the detection means. The device is equipped with a memory control means that controls the read clock of the memory accordingly, a digital/analog converter that converts the digital output signal of the memory into an analog signal, and a phase inversion circuit.

According to the configuration of the present invention described above, the reading clock cycle of the memory in which the engine sound is recorded in advance is controlled according to the engine rotation speed detected by the detection means, and the pitch of the recorded engine sound is controlled. By changing the sound of the engine, you can obtain a memory output with exactly the same pitch as the engine sound while it is rotating. Then, by inverting the phase of this memory output and reproducing it through a speaker, it is possible to sufficiently suppress the sound of the rotating engine.

Example Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram of a silencing device of the present invention.

In FIG. 1, 6 is a rotation speed detection circuit as a detection means for detecting the engine rotation speed, and is configured to electrically detect the engine rotation speed from a distributor that controls the ignition timing of the engine. This circuit is the same as the rotation speed detection section found in general tachometers that display the engine rotation speed. Output signal S of rotation speed detection circuit 6
5 becomes an analog signal or a pulse signal proportional to the engine speed depending on the detection method, and is input to the pitch control circuit 7. The pitch control circuit 7 is a rotation speed detection circuit 6
This pitch control circuit 7 is a memory control means that controls the readout cycle of the memory 8 in which the engine sound of the vehicle is recorded in advance, according to the output signal S5 of the sound pitch control circuit 7.
The digital signal S7 read out from the memory 8 by the digital signal S6 output from the digital/
The analog output signal S2 is converted into an analog output signal S2 by the analog conversion circuit 3, and an engine sound controlled by the engine rotation speed having exactly the same pitch as the engine sound at each time, that is, the same frequency component is obtained. become.

Therefore, the analog output signal S2 is transferred to the phase inversion circuit 9.
After obtaining an antiphase signal S1, a signal S4 amplified by a power amplifier 4 is obtained, and the signal S4 is reproduced by a speaker 5 to obtain a reproduced sound A. This reproduced sound A interferes with the engine sound N in the air and is in an anti-phase relationship with each other, so that the noise level at the listener M's location is reduced.

The pitch control circuit 7 and memory 8 will be explained in detail below.

Figure 2 shows the waveform F0 of the engine sound recorded in memory 8.
The waveform F of this engine sound, which shows the period T, is the third
The waveform is simplified to a sine wave as shown in Figure (6), and the fourth
- N quantized signal sequences As that are sampled at a period Δt1 as shown in FIG.

A.・++ and AM-1 are recorded in the memory 8. Note that this recording work to the memory 8 is normally performed by the IC manufacturer, rather than recording a new sound for each product.

Next, I will explain how to deflect the pitch of the engine sound read out from the memory 8. When lowering the pitch as shown in FIG.
<Tt, as shown in FIG. 4(b), the data recorded in the memory 8 in the form of FIG. 4(a) is calculated from the period Δt when it was recorded. This can also be realized by reading out the data in the order in which it was recorded at a large period Δt2. On the other hand, as shown in Figure 3 (b), when raising the pitch, that is, the circumference urs of waveform F3 is
, as shown in Figure 4 (d),
Figure 4 (Data recorded in memory 8 in the form of grapes,
The period Δt is smaller than the period ΔL+ when it was recorded.
This can be achieved by reading out the recordings in the order they were recorded in step 3.

Figure 5 shows the engine speed and Figure 4 (3) to ((2)
This shows the relationship with the cycle shown in , that is, the readout clock cycle. The pitch control circuit 7 receives engine sound data A, , A+, - recorded in the memory 8.

In order to output AN- in proportion to the number of revolutions of the engine of the automobile, a digital signal S6 is output that controls the read clock cycle of the memory 8 in accordance with the number of revolutions of the engine. In this way, the engine sound of the vehicle recorded in advance in the memory 8 can be changed to exactly the same pitch according to the engine speed and then retrieved.

FIG. 6 shows another embodiment of the invention.

The arithmetic circuit 2 adds the signal S1 of the phase inversion circuit 9 shown in the embodiment of the present invention in FIG. You can enjoy traditional car audio while reducing noise.

Incidentally, a portion Z surrounded by a dotted line in FIG. 6 shows a conventional car audio device.

Effects of the Invention As described above, according to the present invention, a signal having exactly the same frequency component as the engine sound at each time is electrically generated, the phase is inverted, and then the signal is reproduced by a speaker. Due to the structure, it is possible to reduce or eliminate noise while minimizing the increase in weight, making it possible to enjoy driving in a quiet state.

[Brief explanation of the drawing]

1 and 6 are block diagrams of a silencer showing one embodiment of the present invention, FIG. 2 is a waveform diagram of engine sound, and FIG.
6) ~ ((2) is a simplified waveform diagram of the engine sound waveform, and Figures 4 (a) ~ (b) are schematic diagrams that quantized the waveforms of Figure 3 (6) ~ (2), respectively. , FIG. 5 is a characteristic diagram showing the relationship between engine rotation speed and memory read clock cycle. 1...Sound source reproduction device, 2...Arithmetic circuit, 3...・Digital/analog converter, 5...
... Speaker, 6 ... Rotation speed detection circuit, 7
...Pitch control circuit, 8...Memory, 9
・・・・・・Phase inversion circuit. Name of agent: Patent attorney Shigetaka Awano (1 person) Figure 2, Figure 3 B Tz 641□ □ 1G) Shi-Le-IAI > ) l=-, lA-,
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Claims (2)

[Claims] (1) A detection means for detecting engine rotation speed, a memory in which the engine sound is recorded in advance, a memory control means for controlling a read clock of the memory according to an output signal of the detection means, and a memory control means for controlling a read clock of the memory according to an output signal of the detection means; a digital/analog converter for converting a digital output signal into an analog signal; a phase inverter for inverting the phase of the output signal of the digital/analog converter; and reproducing sound based on the output signal of the phase inverter. A silencer comprising a speaker. (2) a reproduction means for reproducing and outputting the audio signal of the media;
2. The muffler according to claim 1, further comprising an arithmetic circuit that inputs the output of the reproducing means and the output of the phase inverting means and outputs an output signal to a speaker.