other conditions imposed on a speech at speakers' corner were that it had to take place only between 7:00 a.m. and 7:00 p.m. on the date notified by the person to the police, had to be in any of singapore's four official languages (english, malay, mandarin or tamil) or any related dialects, and the use of sound amplification devices was prohibited. the latter restriction was justified on the grounds that it would reduce noise pollution and prevent one speaker from drowning out another one, and that it also applied to speakers' corner in london.