Arthropods produce a variety of aposematic signals with their stridulatory organs. In most arthropods these organs have no resonant structures, so that the sound consists of a manifold of harmonics. Additionally, the ratio of dimension to wavelength is usually less than one, so that the fundamental frequency has a very low amplitude. The analysis of such signals was undertaken using two similar methods: 1. cepstrum analysis; and 2. autocorrelation. The cepstrum method (the spectrum of the logarithmic spectrum) proved to be better for evaluation of the fundamental frequency, but the autocorrelation is better for the characterization of mechanical properties such as attenuation and natural frequency. The use of these two methods is discussed. The practicability was investigated on mutillid wasps and on synthetic sound.