PURPOSE: To remove an unnecessary sound wave effectively without using any baffle plate whose machining is complicated by providing a sound absorber at the rear part so that a sound wave from the rear is intercepted and setting the front surface part of the sound absorber at an acute angle to the fitting surface for a sonar dome.

CONSTITUTION: The sonar dome 12 is formed in a streamline lower-half shape and the reflection of a sound at the upper part of the dome is minimized by using a sound absorber. A sound absorber 3 is charged in the dome, the rear part slants gently as shown by 3a, and the side of a transmitter and receiver 2 is at an acute angle θ to the surface of a skirt part 4. Then when a ship body radiation noise 11 arrives from the rear, the sound absorber 3 absorbs the noise 11 and a noise reaching the transmitter and receiver 2 is extremely small. Further, a sound from the front reaches the front surface of the sound absorber 3 and the majority of it is absorbed, but the remainder is reflected. The reflected component is reflected toward the skirt part 4 because the front surface of the sound absorber 3 is at the acute angle to the skirt part 4, and absorbed by the skirt part 4. A component reflected by the skirt part 4 is extremely small and there is no influence upon the transmitter and receiver 2.