Ultrasonic inspection of extents of voids or the like in heated material using fluid blowing

An inspection method for confirming voids, peeling, foreign matter contamination, unintended uneven distribution of constituent components in a material to be inspected using ultrasound waves, comprising following processes 201 and 301:

• process 201:
• blowing a fluid through a blowing port onto a part of a surface of the material to be inspected, wherein an angle of a direction of the fluid blown onto the part of the surface of the material to be inspected is within ±45° but not within ±3° with reference to the surface of the material to be inspected, and then a flow of the fluid is deflected to be a substantially parallel flow in which the fluid flows in a direction within ±3° with reference to the surface;
• and
• process 301:
• inspecting the material to be inspected using the ultrasound waves after the process 201 or at a same time as the process 201,
• wherein
• the process 201 is performed in a condition where:
• a surface temperature of a material to be inspected—an ambient temperature>2° C., and
• inspection using ultrasound waves in the process 301 is a non-contact air coupled inspection in which the ultrasound waves propagate in the fluid in the substantially parallel flow to a portion on the surface of the material to be inspected, the portion being away from a position of the part where the fluid is blown in the process 201, and the inspection satisfies:
• a refractive attenuation rate in echo intensity measurement≤1.5%.