Comparison of different excitations to assess the objective occlusion effect measured on human subjects

Occlusion effect is a known phenomenon affecting in-ear device (e.g., hearing protection devices HPD, hearing aids) wearers. This psychoacoustical annoyance felt when the ears are occluded is perceived under various types of natural excitations such as physiological noises (chewing, breathing, heart beats) and one's own voice or under an artificial excitation such as a bone oscillator. A common objective measurement of this occlusion effect (denoted 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 SPLs are commonly measured at two different moments and (ii) the contribution of airborne sound emitted during the excitation process and mainly captured during unoccluded ear measurements. To investigate the impact of these factors, SPLs are measured with miniature microphones placed in occluded and unoccluded ears of various participants subjected to 5 different excitations, namely chewing, bone oscillator and speech at three intensities. 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 much less common indicator called the Real-Time Occlusion Effect (RTOE).