Effects of ear canal occlusion on hearing sensitivity: A loudness experiment

Abstract

Over the last century, hearing research has repeatedly reported differences in loudness perception when different types of transducers are being used. One of the effects of using different transducers is that listening may be performed via an open ear (loudspeaker), a cushioned ear (headphones), or an occluded ear (hearing aid receivers, insert earphones). The question of whether varying the acoustic load applied to the ear canal might impact hearing sensitivity has therefore become essential given the need to establish realistic noise damage risk criteria in an attempt to prevent noise-induced hearing loss for any given listening condition. Although such loudness discrepancies in the cushioned ear have been recently proven to be caused by loudness measurement artifacts, currently available data do not exclude a possible impact of ear canal occlusion on loudness perception. This paper presents the results of a loudness balance test carried out on 18 normal-hearing listeners. Using an earplug to occlude the canal, in-ear sound pressure levels were compared between the occluded ear and the cushioned ear at equal loudness. The results show agreement within 1 dB between the two listening conditions, and support the conclusion that loudness does not depend on the type of acoustic load applied to the ear canal.

Towards a practical methodology for assessment of the objective occlusion effect induced by earplugs

“…This is achieved by using in-ear devices equipped with a designated probe tube for this purpose, such as the 3M E-A-RLink earplugs (3M, St. Paul, MN). Although the SPL is measured farther from the tympanic membrane, both approaches yield similar results when measuring OE obj (MacKenzie et al, 2004) as the OE is the largest at frequencies below 2000 Hz, frequencies for which the microphone location in the earcanal only slightly influences the measured SPL (Berger and Kerivan, 1983;Bonnet et al, 2018).…”

The “Missing 6 dB” Revisited: Influence of Room Acoustics and Binaural Parameters on the Loudness Mismatch Between Headphones and Loudspeakers

“…Altogether, we discard our hypothesis H1 and must conclude that small differences in the setup of the especially anechoic test conditions may lead to a considerable difference in obtained mismatch between diotic headphone and loudspeaker presentation. This might also explain the inconsistent reports from the literature about the (non-) observation of this mismatch since the experiments were all performed in somewhat different room conditions (Munson and Wiener, 1952;Rudmose, 1982;Fastl et al, 1985;Bonnet et al, 2018).…”

“…Contrary, experimental designs using individual dynamic binaural synthesis, where headphones remained in place during loudspeaker playback, such that the subject was not informed which source they were listening to, achieve an authentic headphone presentation where no mismatch appeared Brinkmann et al, 2017). In a similarly blinded comparison, Bonnet et al (2018) reported that an occlusion of the ear during stimulation by an external sound source did not result in a loudness mismatch to stimulation of the unoccluded ear with the same external sound source. Very recently, Meunier et al (2020) compared loudness growth functions for headphone and loudspeaker presentation without a direct comparison of both sources, and also found no loudness mismatch.…”

Effects of temporal fine structure preservation on spatial hearing in bilateral cochlear implant users

“…Before each test, the normal-hearing control group and the BiCI users adjusted the output volume to their most comfortable loudness level. 1 To ensure a proper fit and comparable loudness conditions with the in-ear headphones, individual ear tip sizes were chosen for each participant (Bonnet et al, 2018).…”