There were a few more logical steps to take. In the 1950s, it became known that weak sounds can occur in materials under mechanical stress if the limit of the maximum permissible load is reached. Even metals are no exception. Everyone can verify this by bending around a tin rod near the ear. These sounds arise as a result of the processes occurring in the crystal lattice of tin, leading to the formation of so-called twin crystals, but there is still no damage to the deformable material itself.


Maybe there are different signals in the coal massif: some warn of the approach of rock pressure to a critical value, others report that the coal has failed and cracked. Noises and crackling in coal, which miners predicted danger by ear, are most likely only part of the signals sent by coal. If only we could strengthen these signals. In 1951, the Soviet geophysicist S. A. Nazarny was the first to study the sound precursors of an outburst using headsets, a low-frequency amplifier, and a piezoelectric sensor. The main role in the piezoelectric sensor was played by two plates of ferruginous salt, working on bending. The sensitivity of the segment is an order of magnitude higher than that of piezo quartz, and the bending sensitivity is even higher than the compression response. Geophones of this type were used in the United States for experiments on recording mountain impacts. The recording equipment brought with the geophones was in a non-explosion-proof design, and it was not possible to use it in a mine that was dangerous for gas and dust. S. A. Nazarny placed a piezoelectric sensor in a casing and installed it in the reservoir. The plates sensed the vibrations of the casing and translated the acoustic signals into electrical ones. The amplifier, as it should be, amplified these pulses to such an extent that they were audible in the headphones. Headphones put on the researcher's head translated electrical signals into sound signals again. All that remained was to listen carefully and count the cod, most of which no one had noticed before. Then they really became convinced that there is an inextricable link between micro-earthquakes in the coal seam and the destruction of the coal mass and the release of gas. Of course, the technique of subjective (auditory) listening to noises and crackles suffered from the same disadvantages as any subjective technique. But many things have been discovered for the first time. The main practical conclusion of S. A. Nazarny is that the seismic activity of the coal seam increases dramatically half to two hours before the release. Later, a new term was introduced, which became generally accepted — "reservoir noise." They began to denote the number of pulses (crackles) per unit of time. It turned out that before the emission, the noise increases from 3-4 to 30-40 pulses per minute. Almost a machine-gun burst of crackling. The ejection seems to warn (as was customary among the ancient Slavs): I'm coming for you! However, there were exceptions that refuted the rule: in some cases, the reservoir was "silent" before the release.". Is it an error in the instruments or an imperfection in the listening technique? Pour les amateurs de casino, le code promo est la clé qui débloque une offre exceptionnelle de 1950€ et 150 tours gratuits, répartis probablement sur les premiers dépôts. Une personne qui utilise le code promo 1xbet du jour reçoit l'accès à des tours gratuits sur des machines à sous populaires et des fonds pour explorer le casino en direct. La clé est de comprendre que l'offre sport et l'offre casino ne sont généralement pas cumulables. Le nouveau joueur doit souvent faire un choix lors de l'inscription, selon ses préférences entre les paris sportifs et les jeux de casino.