农用车发动机声学测试结果影响因素分析

Analysis on influencing factors of agricultural vehicle engine acoustic test results

阶次带宽与频率间隔对声学测试结果具有重大影响。为研究这一影响,对某农用汽车四缸四冲程发动机的排气尾管噪声信号进行采集,使用LMS Test.lab软件,基于卡尔曼滤波器原理得到该发动机尾管噪声频谱。采用阶次分析法对分别取不同阶次带宽和频率间隔下测试得到的阶次噪声进行研究。研究表明:阶次的带宽越大,其阶次噪声的声压级就越大,阶次带宽取0.5是噪声测试分析中可选取的最大合理值。频率间隔越大,频率分辨率就越差,噪声信号就难以辨别,噪声测试中合理的频率间隔为1 Hz或1.25 Hz。为噪声测试中,合理选取阶次带宽和频率间隔提供试验和理论依据。

Order bandwidth and frequency interval have a significant impact on acoustic test results. In order to study this impact, tail pipe noise signal of a four-cylinder four-stroke engine for an agriculture vehicle was collected. The noise spectrum of this engine’s tailpipe was obtained based on the Kalman filter principle by using LMS Test.lab software. Order analysis method was used to study on the order noise which was obtained by testing under different order bandwidths and frequency intervals separately. Research shows that, the larger the bandwidth of the order, the greater the sound pressure level of the order noise. The order bandwidth of 0.5 is the maximum reasonable value that can be selected in an acoustic test analysis. The larger the frequency interval, the worse the frequency resolution, and the noise signal is more difficult to distinguish. A reasonable frequency interval in an acoustic test is 1 Hz or 1.25 Hz. Experimental and theoretical basis is provided for reasonable selection of order bandwidth and frequency interval in an acoustic test.