It has been known for many years that some listeners with normal hearing report difficulties in understanding speech in noisy environments. Currently, this syndrome cannot be diagnosed by conventional clinical test batteries and is called obscure auditory dysfunction. We are trying to elucidate its mechanism using various techniques; non-invasive physiological measurements, psychological measurements, and computational simulations. Further, we are developing auditory diagnostic tools based on knowledge and information obtained in the basic research on the mechanism of hearing disabilities.

Excessive noise exposure can cause temporary hearing deterioration as well as permanent hearing damage to the cochlear, which is known as noise induced hearing loss (NIHL). It has been known for many years that the susceptibility to noise induced hearing loss varies substantially between individuals; individuals with ‘tough’ ears are more resistant to acoustic overexposure, whilst individuals with ‘tender’ ears are more vulnerable. We have been investigating the effect of excessive noise exposure on auditory function and evaluated its inter-individual variations using various non-invasive physiological measurements.