The active earcanal.

In the past, the human earcanal has primarily been thought of as a passive conduit for sound. Several studies, reported here, explored evidence of how active the earcanal is. The "active earcanal" is conceptualized and aspects of it are viewed through three timeframes: jaw-induced canal change in seconds/minutes, cerumen production in weeks/months, and aging in years. The influence of each of these aspects on hearing aid performance and resulting patient satisfaction is explored. A new self-assessment tool, a Profile of Hearing Aid Physical Fit, is proposed that focuses on measuring patients' perceptions of those benefits that depend on the interface between earcanal and hearing aid.