State system for ensuring the uniformity of measurements. Acoustics. Reference zero for the calibration of audiometric equipment. Part 7. Reference threshold of hearing under free-field and diffuse-field listening conditions
State system for ensuring the uniformity of measurements. State special standard and all-union verification schedule for means measuring instruments of variable temperature of water medium in the range of pulsation amplitudes of temperatures within 0,01 - 3 K at the pulsation frequencies from 0,005 to 50 Hz, at background temperature from 270,15 to 380,15 K and at water flow velocity from 0,5 to 20 m/s
