Dr. Helen Czerski investigates the extraordinary science behind the sounds we're familiar with and the sounds that we normally can't hear. She begins by exploring the simplest of ideas: what is a sound? At the Palace of Westminster, Helen teams up with scientists from the University of Leicester to carry out state-of-the-art measurements using lasers to reveal how the most famous bell in the world - Big Ben - vibrates to create pressure waves in the air at particular frequencies. This is how Big Ben produces its distinct sound. It's the first time that these laser measurements have been done on Big Ben.

Dr. Helen Czerski examines the extraordinary messages sound waves carry and how they help us understand the world around us.