Sakeb,: Application of self – excited acoustical system for stress changes measurement in sandstone bar

A self-excited acoustical system is suggested for monitoring of the chan-ge of stress in a sandstone bar. Stress changes manifest themselves in small but detectable variations of frequency in the self-excited system. The suggested system can be applied for the continuous stress changes monitoring in elastic constructions and rock masses. Tests on a single sample of sandstone were performed. They examined the impact on the stress measurement such parameters as: position of sensors and the ac-tuator as well as the influence of geometrical shape and dimensions of the sample. A theoretical model whose parameters have been confirmed by performed experiments is also developed. Key words: self-excited system, stress monitoring 1. SAS system in stress change measurement 1.1. Introduction to self-excited systems By bringing a speaker closer to a microphone, the system is excited and it produces a hum. This effect also occurs in the radiotechnics. The autodyn