Patent ID: 7418102

Claim:
An echo sounder for radiating an acoustic wave, comprising: a front mass including a bending vibratory plate portion vibratory for radiating said acoustic wave and a remaining portion, wherein the bending vibratory plate portion has a lower surface and the remaining portion has an upper surface opposite to said lower surface of the bending vibratory plate and an inner side surface connecting said lower surface of the bending vibratory plate and said upper surface of the remaining portion, thereby defining a hollow space; a rear mass spaced from said front mass; a first vibrator sandwiched between said front mass and said rear mass, and giving rise to vibrations of said bending vibratory plate portion; and a second vibrator accommodated in said hollow space, and having at least one surface held in contact with said front mass without being fixed to said bending vibratory plate so as to enlarge said vibrations, said second vibrator being a ring-shaped piezoelectric ceramic plate, wherein said ring-shaped piezoelectric ceramic plate has an inner curved side surface defining an inner space, an outer curved side surface held in contact with the inner side surface of said remaining portion, and an upper flat major surface and an opposite lower flat major surface connecting said inner curved side surface and said outer curved side surface, said upper and lower flat major surfaces spaced from said lower surface of the bending vibratory plate portion and said upper surface of the remaining portion respectively.