Occlusion effect is a known phenomenon affecting hearing protection device (HPD) wearers. Objectively, it is an amplification of low frequency sounds resulting from bone conduction that can be induced by different types of excitations internal or external to the human body. A common or standard occlusion effect indicator (OE) is defined as the difference between sound pressure levels (SPL) measured inside the occluded ear and the unoccluded ear. Two factors may cause this indicator to be sensitive to the type of excitation: (i) the repeatability of the excitation, because occluded and unoccluded noise levels are commonly measured at two different moments, (ii) the contribution of airborne noise emitted during the excitation process and mainly captured during unoccluded ear measurements. To investigate the impact of these factors, SPL are measured in the ears of 30 participants subjected to different excitations, namely physiological noises (chewing, breathing, heart beats), vocal effort and bone oscillator. Miniature microphones are placed outside and inside both ears using microphonic earpieces ensuring a constant positioning of the microphones for both ear conditions and for all the participants. Measurements are done in three ear configurations: (i) both ears unoccluded, (ii) one ear occluded and contralateral ear unoccluded, (iii) both ears occluded. This allows for the calculation of the aforementioned OE but also a new indicator called Real Time Occlusion Effect (RTOE) calculated as the difference between the SPL measured simultaneously in both ears, one being occluded and the other one unoccluded, for a given excitation. Results are presented and discussed to compare the OE induced by the three excitations and the OE and RTOE respectively.
