To suppress a shock to the sense of hearing by arranging opening areas and providing them through a wall of a telephone set around a specified area named a closed area which is protected from sound at the time of transmission.

A hole having a diameter which is concentric with a loud speaker circle 3 and is, for example, larger than 25.4 mm, that is, an artificial or human ear diameter, does not exist inside a wall of a virtual circle of an alternate long and short dash line 21. An area 22 located inside a circle 21 is named a closed area of a baffle of the loud speaker 3 and, in fact, a closed area of tolerance of diameter 27 mm and of a circle shape is taken. An output opening 23 of the baffle of the loud speaker 3 is arranged nearby the closed area 22 virtually on the same plane of the rear side. When an artificial ear is precisely arranged against the wall of the rear side under the same condition, a sound pressure level of 12 dBPa (A) is obtained because a small part of the sound passes through the wall. When an ear is brought close to the area 22, the ear covers one-third of the hole 23 that maximally reaches the level of 30 dBPa (A) and still is permitted.