本文给出海上实验数据表明舰船噪声在几十赫以下频段有着很强的低频线谱,这些线谱与螺旋桨转速等工作特征紧密联系在一起.所以螺旋桨识别特征的提取除了从解调制谱线谱来得到外,还可直接从低频线谱来得到,本文讨论了在噪声中低频线谱和解调制谱线谱的检测性能,在噪声掩盖下,低频线谱的信号高度与信噪比成正比,而解调制谱线谱的信号高度随信噪比下降是非线性的,当信噪比大时下降得很慢,当信噪比小时下降得很快. In this paper, the experimental data at sea shows that the ship noise has a strong low frequency spectrum in the frequency band below tens of hertz, which are closely linked with the operating characteristics such as propeller speed, etc. Therefore, Spectrum can be obtained, but also can be obtained directly from the low-frequency line spectrum, this paper discusses the detection of low-frequency line spectrum and demodulation spectral line noise detection performance, under the noise cover, low frequency line spectrum signal height and signal to noise ratio is proportional to , While the signal height of the demodulation spectrum spectrum is non-linear with the signal-to-noise ratio decrease. When the signal-to-noise ratio is large, the signal level drops slowly, and decreases rapidly when the signal-to-noise ratio is small.