Ultrasonic-wave delay element

An ultrasonic-wave delay element comprising:

• a pentagonal delay medium body formed by cutting at an angle of about 45.degree. a part of the major surface defined by a rectangular shape and a pair of input and output electro-mechanical transducers provided on a side A formed by cutting said major surface wherein said input and output electro-mechanical transducers are positioned and attached to said cut side A at positions near a longer side C contiguous to said cut side A with respect to the center of the cut side A;
• such that upon activation of one of said transducers a wave is produced which has a reflection point for said cut side A with no reflection point occurring in a shorter side B which is contiguous to said cut side A;
• wherein said wave reflects at two or more reflection points on said longer side C;
• further wherein said wave reflects at two reflection points are formed in the other shorter side D which is isolated from said cut side A;
• and wherein said wave reflects at four or more reflection points on the other longer side E isolated from said cut side A;
• and at least one sound-absorbing substance is attached to the major surface of said delay medium body so that a path for a sound-wave initiates from the lead-wire fitting part of said input or output electric-mechanic transducer to said output or input electric-mechanic transducer while the sound-wave is once reflected at said longer side E.