The CCIR, considering that it is necessary to establish a value for the protection ratio for sound broadcasting within the shared bands in the Tropical Zone; that the operation of sound broadcasting transmitters with 10 kHz separation makes it difficult to measure the protection ratio with a receiver having an audio-frequency cut-off in excess of 5 kHz; that more information concerning noise values in various parts of the Tropical Zone is necessary to arrive at a more accurate value of minimum field strength to which the protection ratio should be maintained; however, this minimum, field strength should provide satisfactory reception at the limit of the broadcast station coverage area, as provided by No.2666 of the Radio Regulations.