浮石検知に関する各種坑内騒音の影響について

抄録

In this paper the improvement of the drummy rock detector analyzing an impact sound of rock acoustically and its application test under the underground noise are described.
For the measurement in field as well as in laboratory the circuit set in the detector was improved to have two parallel routes devided from Microphone-Amplifier route. In both routes the signal with original wave form and the signal with filtered wave form of the impact sound of rock were integrated and logarithmically amplified respectively, and then the difference between both signals could be read on voltmeter.
The characteristics of many kind of noises were investigated to know how each of them would disturb to the detection of drummy rock. From this, it was considered that the disturbance by over-all sound pressurel evel is greater than that by the level-difference between the component level of frequency band and the former level. Thus, the disturbance of noises from air-driven machines, i. e. rock drill, is known as the greater one rather than that from the leakage of compressed air and water flow. It was found that the impact sound of rock is not affected by the acoustic characteristic of the underground drift where this investigation was done.
And the detection of drummy rock could be carried out successfully by use of the highly-directional microphone even in trie noise circumstance of 91d B.