Current standards for measuring the headphones, it's GOST 28728-89 (IEC 268-7 to replace 84 of 1984) - "Stereo Headphones - measurement methods", adopted in our country for the measurement of headphones in 1989. The most modern international standard is IEC 60268-7 "Sound system equipment - Part 7: Headphones and earphones (sound system equipment. Part 7: Headphones and earphones)."
The standard is constantly being updated.
Objective measurement - results of measurements made in doctorhead.ru