| 1. | Nearly all engines are equipped with air cleaners , which help reduce the air inlet noise to a secondary sound source
一般发动机均装有空气滤清器，进气噪声即可有较大衰减，成为次要声源。 |
| 2. | Aerodynamic noises radiated directly to the atmosphere include the air inlet noise , the exhaust noise and the cooling fan noise
直接向大气辐射的空气动力噪声包括：进气噪声、排气噪声、冷却风扇噪声。 |
| 3. | The air inlet noise is related to designing factors like the air inlet mode , the inlet valve structure , the cylinder diameter as well as the cam curve
进气噪声与发动机的进气方式、进气门结构、缸径、凸轮型线等设计因素有关。 |
| 4. | For turbo - charged engines , due to the high rotating speed of the turbocharger , the air inlet noise is much higher than non - turbo - charged engines
对于采用涡轮增压的发动机，由于涡轮增压器的转速一般较高，因此其进气噪声明显高于非涡轮增压的发动机。 |
| 5. | For one same engine , the noise level is highly dependent on the rotation speed . when the rotation speed doubles , the air inlet noise can increase by 10 to l5db ( a )
对于同一台发动机来说，受转速的影响最大，转速提高一倍可导致进气噪声增加10 ~ l5db （ a ） 。 |
| 6. | The air inlet noise is one of the major aerodynamic noises of the diesel generator as a result of the pressure fluctuation caused by the periodic opening and closing of the inlet valve
进气噪声是柴油机的主要空气动力噪声之一，它是由进气门的周期性开启与闭合而产生的压力起伏变化而形成的。 |
| 7. | When the natural frequency of the gas column in the inlet valve is consistent with the main frequency of the periodic air inlet noise , the resonance noise of the gas column will also become prominent in the air inlet noise
进气管空气柱的固有频率与周期性进气噪声的主要频率相一致时，空气柱的共振噪声在进气噪声中也会较为突出。 |
| 8. | When the inlet valve opens , a pressure pulse is generated in the air inlet pipe , which is damped as the piston continues to move . when the inlet valve closes , another pressure pulse of certain duration is generated , thus giving rise to a periodic inlet noise
当进气门开启时，在进气管中产生一个压力脉冲，而随着活塞的继续运动，它受到阻尼；当进气门关闭时，同样产生一个有一定持续时间的压力脉冲。 |
| 9. | When other sound sources are under further control , the air inlet may become the primary sound source . under this situation it is proposed to apply good intake mufflers . usually the intake muffler needs to combine with the air cleaner in an integrated design to meet requirements of air admission and cleaning as well as perform an effective control over the air inlet noise
而当其它声源得到进一步控制后，进气噪声有可能成为主要声源，这时需考虑采用性能良好的进气消声器，通常进气消声器要和空气滤清器结合，进行一体化设计，既能满足进气和滤清方面的要求，又可使进气噪声得到有效的控制。 |
