Meet the howler monkey – the loudest animal on land. Physical processes - Sound - Volume Learning Points Volume is a measure of the loudness of a sound. High-energy sounds are loud. Low-energy sounds are quiet. The larger the vibrations, the louder the sound. A Twig Curriculum Film. Delivering key learning points. Get straight to the facts in just three minutes – directly linked to core learning, Twig's curriculum films will fit neatly into your lesson plans.