The following general requirements shall be followed when conducting sound level measurement procedures:

(1) The measurements shall be conducted only by persons qualified by training to perform these procedures.

(2) Proper use of all test instrumentation is essential to obtain valid measurements. Operating manuals or other literature furnished by the instrument manufacturer should be consulted for both recommended operation of the instrument, and precautions to be observed.

(3) A measurement shall be invalid if changes in the background sound level affect the applicable reading.