Sound Pressure Generated in an External-Ear Replica and Real Human Ears by a Nearby Point Source

TLDR

A rubber ear replica with realistic pinna, concha, and meatus was mounted on a rigid plane and exposed to a point source 8 cm away, while sound pressure was measured at the eardrum and canal positions using a probe‑tube microphone under both open‑canal and meatus‑blocked conditions, and pressure distributions for several resonant modes were recorded. The replica’s open‑canal and meatus‑blocked responses were nearly identical up to 12 kHz, with substantial acoustic gain between 2–7 kHz from canal and concha resonances, and real‑ear measurements matched the replica up to 7 kHz but revealed a sharp on‑axis minimum at 8 kHz that disappears or shifts when the source is above the axis.

Abstract

A rubber replica has a pinna, concha, and auditory meatus with dimensions comparable with those of real human ears. At the eardrum position, there is provision for a totally reflecting termination (hard wall) or for various eardrum impedance networks. The replica is mounted in a rigid plane, and a point source at a distance of 8 cm provides sound with various angles of incidence over the frequency range 1–15 kHz. The sound pressure is measured with a probe-tube microphone at selected positions in the open canal and at the center of a plug closing the ear-canal entrance (“meatus-blocked” condition). The response with open canal and the response with blocked meatus have virtually identical angular dependence up to 12 kHz. From 2–7 kHz, there is substantial acoustic gain at the eardrum position associated with a fundamental canal resonance (M1) and a second mode largely controlled by a depth resonance of the concha (M2). Pressure distributions in the canal and concha are given for M1, M2, and three other modes. Limited data for six real ears with open and blocked canal are in good agreement with replica measurements up to 7 kHz. At 8 kHz, however, the on-axis response of real ears passes through a sharp minimum that is either removed to a higher frequency or is largely absent with the sound source above the axis.