A study about the synergistic interaction between noise and vibration in cochlear damage by means of Otoacoustic Emission analysis

Epidemiological and animal studies show how vibration exposure enhances hearing loss effects caused by noise only. Likewise, experimental studies on human subjects confirm hearing threshold shift after vibration and/or noise exposure. Cardiovascular effects have been hypothesized as causes of these hearing effects. An objective investigation of this phenomenon could be carried out by measuring otoacoustic emissions (OAEs) as biomarkers of early effects on hearing. The aim of our experiment was the study of the possible synergistic interaction between noise and vibration in three exposure conditions: 1) exposure to noise only, 2) exposure to hand-arm vibration only, 3) exposure to both hand-arm vibration and noise. Distortion Product OAEs were used as biomarkers of the exposure effect. As expected from literature results, the effect of noise combined with vibration is significantly larger than the effect induced by exposure only to noise or only to vibration. On the other hand, the comparison between combined noise and vibration and noise alone exposure gives no statistically significant result.