Estimation of noise within signaling is contemplated. Barium titanate or lead zirconate titanate is used for a piezoelectric material constituting the ultrasonic transducer, and the thickness thereof is 0. The bucket restraining device has a lateral restraining wall and a rear restraining wall that cooperate to define a first restraining region and a second restraining region. A microprocessor-based control unit controls the water pump and foam pump.