| 摘要 |
PURPOSE:To enable accurate detection for any running state of an engine, by changing the amplification factor of an amplifier of the noise level detection circuit according to the running state of the engine. CONSTITUTION:An amplifier 7 constituting a noise level detection circuit 4 consists, e.g., of a voltage control type amplifier (VCA), and the voltage signal VA and the amplification factor A which are output via an output interface 44 according to the result of judgement of the running state of the engine 9 from the detection signals of an air flow meter 12 or a crank angle sensor 18 or the two by a microcomputer 45, are varied. This voltage signal VA is stored in an ROM41 of the microcomputer 45 in advance by coding so that the amplification factor A of the amplifier 7 is made small and the voltage level is changed with increase of the number of revolutions N of the engine 9 as shown in figure. |
