Micro-Hole Diameter Inspection Using Audible Sound

This paper presents a method for inspecting micro-holes with diameters of less than 100 μm using audible sound. The inspection system measures the micro-hole diameter by comparing two sound signals. Fluid flow through micro-holes affects the performance of products such as CO gas sensor parts, microphone filters and fuel injection plates. Therefore, if the flow rate of fluid passing through micro-holes is accurately assessed by an inspection system, the performance of a product can be guaranteed.