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://www.bekindtopets.com/top-save-J-D-Manufacturing-Barnstormer-Basket-Fans-great-choice/