Strategies of the auditory system

Sorry for the long delay, but I was really distracted by other activities.

In Nara, the ancient capital of Japan,  I had the honour to present a lecture at ICBEN2014. The facts presented indicate that the human auditory system has elaborate strategies to avoid noise-induced injury. Unfortunately these mechanisms are mostly not effective for impulses, particularly if they are extremely short and their pressure-time-history has the structure of a dagger. The pressure-time-history of acoustic impulses stimulate resonances of middle-ear structures, which in turn can permanently damage the organ of Corti in typical ways. – Masking effects are important, as well as training by the long-term acoustic environment. Middle-ear muscles have no protective functions, but they serve as an auditory equivalent of the visual task of accommodation.

It can be summarized that auditory training is very important for good sensitivity of hearing and that particularly very short impulses can be most harmful for hearing, and a cause for tinnitus.

Currently the ISO1999 is the basis for the protection of hearing, practically everywhere. It is based on the assumption that the acoustic energy received by the ear is the key parameter. However, the facts do not support this assumption. Orchestra musicians hear much better than nomadic people, and an extremely short impulse can permanently ruin the ear, even if it transmits only a small amount of energy. For effective auditory protection the basics of this standard should be replaced by principles derived from studies on human experience.

Here you can download the slides:

Fleischer-JP-Nara-ICBEN2014-short-(19Fig)

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