Vibrator comprising an outer carcass (2) intended to be fixed to a structure to be excited, which contains at least two rotary shafts (9), parallel and opposite, each of which is rotatably associated with two distinct supports (7, 8) fixedly connected to the carcass (2), and has two lateral portions (91, 92) projecting from them, on which a first and a second unbalancing mass (13b) are respectively fitted; and a transmission system (11, 12), suitable for transmitting the motion between said rotary shafts (9), so that they are suitable for rotating at the same speed, synchronous with each other and in a desired mutual phase. Said Vibrator comprises at least one drive motor (10) rigidly associated with the carcass (2), which is suitable for making one of said rotary shafts (9) rotate, coupling with an end thereof. Moreover, each rotary shaft (9) is provided with at least a third unbalancing mass (13a), which is fitted onto the central portion (90) between said supports (7, 8), through means (130, 131, 133) that allow its angular position on the shaft (9) itself to be adjusted.