Can we predict the altered subjective quality assessment of sound after ear canal surgery?

Abstract

Purpose To correlate the subjective quality assessment of ear canal acoustics of the participants to the objective measurement of the ear canal acoustics. The objective ear canal acoustics is the frequency-dependent modulation of soundwaves through the ear canal. Our second objective is to design a model to predict the subjective quality of sound based on the altered objective ear canal acoustics. Methods To determine the frequency-dependent modulation of the soundwaves the real-ear unaided gain (REUG) of the ear canal is measured. 40 participants with normal hearing were presented six simulated sound fragments representing the acoustic properties of six different ear canals (REUG). These six sound fragments were built based on the difference between these six REUGs and the average REUG of a normal adult ear canal. Subjective sound quality was evaluated using a VAS score and a paired comparison score. Results We found a strong correlation between the objective ear canal acoustics and the subjective assessment of the quality of sound (Spearman's rho-0.89). Our linear mixed VAS model for individual participants has an intercept of 95.6 and a slope of − 4.2 (p < 0.001). The paired comparison analysis endorsed our findings that an increased difference in REUG is predictive for a decreased quality assessment of ear canal acoustics. Conclusion There is a strong correlation between the subjective evaluation of ear canal acoustics and the objective quality assessment of ear canal acoustics. Our models show that an increased difference in REUG predicts a decreased quality of ear canal acoustics.

Habituation of changed acoustics properties after canal wall down mastoidectomy

“…Mean assessment of the naturalness of the sound fragment in the normal ear was in favour of the normal sound fragment. This is in line with our previous findings of quality assessment of the cavity acoustics presented to a normal ear [ 10 ]. Mean assessment of the naturalness of the sound fragment of the cavity ear presented to the cavity canal was close to baseline.…”

“…Our participants asses sharpness of the sound fragment of the normal ear canal as clearly sharper if presented to both the normal and the cavity ear canal. We have previously demonstrated that acoustics of cavity canals amplify low to mid frequencies and reduce the soundwaves of high frequencies [ 6 , 7 , 10 ]. We had one outlier assessing sharpness of the cavity acoustics as more clear than the acoustics of the normal ear canal.…”

“…Therefore, we use the difference between the RECD of the individuals normal ear canal and the RECD of the cavity ear canal, using the REM module of the Affinity 2.0 Hearing Aid Analyzer platform (Interacoustics, Denmark). For our participants, this filtering results in the same distribution of sound pressure (acoustics) at the eardrum as in the contralateral ear canal, mimicking the acoustic effect of the cavity in a normal ear, and mimicking the acoustic effect of the normal ear in the cavity ear [ 6 , 7 , 10 ].…”

“…The normal ear canal acts as a filter, to reduce low frequencies and enhance mid to high frequencies [ 9 ]. In case of a cavity condition, the acoustic properties shift toward an amplification of the soundwaves of low to mid frequencies, and a reduction in soundwaves of high frequencies [ 10 ]. Normal hearing subjects with normal ear canals are capable of accurately discriminating differences between the acoustic properties of different ear canals after surgical modulation [ 10 ].…”

“…In case of a cavity condition, the acoustic properties shift toward an amplification of the soundwaves of low to mid frequencies, and a reduction in soundwaves of high frequencies [ 10 ]. Normal hearing subjects with normal ear canals are capable of accurately discriminating differences between the acoustic properties of different ear canals after surgical modulation [ 10 ]. The possible effect of habituation to the altered acoustic properties of a radical cavity has never been studied.…”