The invention relates to an additional device which controls the removal of sound indication when an elevator in a flat operates at night; an input and output circuit of a single-chip is connected in series with a former sound generation loop in a floor controlling system of the elevator; an input end of the single-chip is connected with a former floor controlling system of the elevator for receiving output signals of the controlling system; an output end of the single-chip is connected with a former sound generation device in the floor controlling system of the elevator for controlling the work of the sound generation device. To set the time for removing the sound indication during operation at night, the input end of the single-chip is provided with a time setting key comprising a clock setting key, a night operation setting key, and a resetting key. The output end of the single-chip is connected with a liquid crystal screen. The invention receives digital signals of the former floor controlling system of the elevator. The invention has the advantages of that the sound generated during the elevator going upward and downward in the floors within a set night operation time is controlled, and the sound indication is removed, so that no noise is brought to the residents of the floors in night environment. The night operation time can be adjusted according to seasons, and the floor controlling system of the elevator is not affected.