Abstract: A method capable of accurately evaluating a reflected wave by properly evaluating an attenuation rate of an elastic wave without being influenced by a transmission loss in each of transmission and reception. In an evaluation method of a reflected wave for evaluating, in a long object, the presence or absence and the size of a defect of the long object by transmitting an elastic wave propagating in a longitudinal direction of the long object and receiving a reflected wave of the elastic wave, the size of the defect is evaluated by determining an attenuation rate ?1 of the elastic wave based on an environment in which the long object is installed from a transmission wave amplitude At of the elastic wave and a first reflected wave amplitude Ar from a specific portion of the long object serving as a reference, creating a distance-amplitude characteristic curve of the reflected wave by using the attenuation rate ?1, and comparing the distance-amplitude characteristic curve with the reflected wave amplitude.

Abstract: A transmission probe for transmitting guided waves propagating in the longitudinal direction of a long member and a reception probe for receiving guided waves derived from the guided waves reflected from a predetermined portion of the long member are set on the long member. The guided waves received by the reception probe include a guided wave serving as a second signal that is noise of a desired first signal. The guided wave serving as the second signal having nodes in a circumferential direction distribution of displacement in a specific direction in the circumferential surface of the long member, and the guided waves transmitted by the transmission probe are formed such that the displacement of the guided wave serving as the second signal in the specific direction becomes zero at a specific circumferential surface position of the long member.

Abstract: A transmission probe for transmitting guided waves propagating in the longitudinal direction of a long member and a reception probe for receiving guided waves derived from the guided waves reflected from a predetermined portion of the long member are set on the long member. The guided waves received by the reception probe include a guided wave serving as a second signal that is noise of a desired first signal. The guided wave serving as the second signal having nodes in a circumferential direction distribution of displacement in a specific direction in the circumferential surface of the long member, and the guided waves transmitted by the transmission probe are formed such that the displacement of the guided wave serving as the second signal in the specific direction becomes zero at a specific circumferential surface position of the long member.