A complete ear-canal seal improves low-frequency transmission while feeling physically intrusive

Evidence

The passive types are somewhat intrusive, as their presence in the ear canal is felt physically, since the seal has to be complete to enable them to function well. One advantage of a good seal with the ear canal is that transmission of the low-frequency components is significantly improved. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2569

Categorization

• QUESTION: Why does occlusion improve low-frequency transmission? Worth chasing the acoustic reasoning and its relevance to in-ear monitoring.
• XREF: Connects to the reader’s interest in how seal/fit shapes what one actually hears during listening.