High intensity focused ultrasound (HIFU) is a noninvasive treatment technique to induce thermal or mechanical bioeffects. Characterising the wave field is essential for reliable and reproducible transducer operation in clinical use. This paper presents a schlieren technique to visualise and quantify transducer wave fields. https://safeersappliancers.shop/product-category/bosch-dwk98pr60b-serie-8-built-in-89cm-3-speeds-a-chimney-cooker-hood-black/