The telephone protection hood is an excellent aid to cut out extraneous noise and improve audibility in noisy surroundings when open telephones have to be installed for economic reasons. The special shape of the hood and its inner lining of sound-absorbing material optimally reduces noise in the area of the telephone. Eavesdropping is also made difficult. The best acoustic effect is achieved when the protection hood is mounted with its back facing the noise source or loudest noise source (see directional diagram of sound-level reduction). The protection hood is made of Synthetic material and lined on the inside with soundabsorbing mineral fibre boards behind a perforated plate cover.