Abstract
In this paper we intend to treat the permissible values for the sound levels of loudspeaker for advertisements of street. The following researches have been performed: (1) measurements of attenuation of sound from a loudspeaker propagating in an open field and on a street; (2) the articulation of syllables produced by the loudspeaker; and (3) the decrease of the syllable articulation in the presence of the sound produced by the loudspeaker. Sound levels of loudspeaker in an open field and on a street were almost proportional to the reciprocal of the distance from it. The articulation of syllables produced by the loudspeaker was about 70% when the sound levels from it were 5-10db above the background noise level. In the presence of the loudspeaker-sound with a level of 80phons, conversations were masked and syllable articulation was decreased to about 70%. Our conclusions are followings: the permissible sound level of loudspeaker is fixed 80phons and has no need of exceeding 10phons above a background noise level at the place 10m distant from it. 10m corresponds to average value of distances between adjacent houses.
