Additively manufactured acoustic diffuser structures for ultrasonic measurement applications

To prevent errors in ultrasonic measurement systems (e.g. for sound velocity measurements), stray signals have to be absorbed or dispersed. While absorbers are commercially available, they are typically limited to a specific fluid, for example water, and to only a small temperature range. There are, however, some applications where more flexibility regarding the examined fluid (e.g. compatibility with gases and liquids) and the temperature is required. To achieve compatibility with a wide variety of fluids, structured diffusers are to be preferred over absorbers which require a matched acoustic impedance with the adjacent fluid. However, the structure of diffusers has to be in the scale of the wavelength of incident acoustic waves, which are often in the range of only a few millimeters, or below. We therefore propose using additive manufacturing techniques to create diffusive structures.Utilizing metals as materials for the diffuser allows for applicability over a wide temperature range. In an empirical study, different diffuser structures are manufactured by selective laser melting (SLM) of metallic powder. The diffusive properties of these structures are compared using ultrasonic pulse-echo and schlieren measurements.