Final answer:
The semicircular canals detect angular acceleration, not sound waves or linear acceleration. They contain hair cells that respond to head rotation by sending signals to the brain.
Step-by-step explanation:
The semicircular canals are part of the inner ear's vestibular system, which is responsible for detecting head motion and maintaining body balance. Specifically, they detect angular acceleration, which occurs when turning the head or rotating the body. Each canal is filled with fluid and has a base called the ampulla, where hair cells with stereocilia are located.
As the head rotates, the fluid moves within the canals, deflecting the stereocilia within the cupula, and sending signals to the brain to interpret this motion. The semicircular canals do not respond to sound waves, nor do they detect linear acceleration, which is the role of different structures within the vestibular system: the utricle and saccule. Therefore, the correct answer to the question is that the semicircular canals detect angular acceleration.