  The paper presents an electronic self-oscillation acoustic system (SAS)
destined to measure of stresses variations in the elastic media. The system
consists of piezoelectric detector, amplifier-limiter, pass-band filter,
piezoelectric exciter and the frequency meter. The mass rock plays a role of
delaying element, in which variations in stresses causing the variations of
acoustic wave velocity of propagation, and successive variation in frequency of
oscillations generated by system.
  The laboratory test permitted to estimate variations in frequency caused by
variations in stresses of elastic medium. The principles of selection of
frequency and other parameters of the electronic system in application to
stresses measurement in condition of the mine were presented.
