The ossicle-softer-ligament design protects ears by dumping intense-sound energy.

Evidence

The middle ear also acts as a first line of defense against intense sounds. If the sound is not too sudden, muscles in the middle ear connected to the ossicles via ligaments contract in what is termed an acoustic reflex, desensitizing the response and restricting the energy flowing into the oval window, so as not to damage sensitive hair cells in the cochlea. For sudden loud sounds, the system is designed to dump energy before it can reach to oval window. A direct solid bone connection to the oval window would benefit from impedance transformation because of the ratio of the area of the tympanum to the oval window, but would likely invite damage from loud sounds. — Eric J. Heller, Why You Hear What You Hear- An…, 1945

Categorization

• DEFINE: Defines the acoustic reflex as the middle ear’s protective muscle response against loud sounds.
• XREF: Connects to the chapter’s earlier impedance-matching discussion and to why hearing evolution favored cushioning over rigid mechanical amplification.