Vibration characteristics of two types of piezoelectric transducers with whole-surface electrode and a partially electrode were driven in the thickness direction in air and water acoustic loading on the acoustic radiation surface. Partial electrode transducers had an acoustic loading on the side surface, which is called “siding”. Use of partial electrode transducer allowed the lateral vibration on the acoustic radiation surface to be flattened, and thickness vibration becomes almost uniform. Schlieren observation and wavenumber analysis indicate that lateral waves were identified as Lamb waves. An A1 mode Lamb wave is given as a sample to verify the usefulness of this method.