Index I. Introduction 92 II. Terminology.. 93 III. Literature review 94 A. Historical notes 94 B. Acute acoustic trauma 98 1. Pathophysiology and clinical facts 98 2. Biochemistry......... 103 3. Morphology......... 106 4. The origin of specific noise-induced dips. 111 5. Prophylaxis and treatment 114 C. Cochlear microcirculation 115 1. Vascular anatomy of the cochlea. 115 2. Pathophysiology of the cochlear blood supply 121 3. Metabolic supply to the organ of Corti... 125 D. Microcirculation and low molecular weight dextran. 128 1. Physiology and pathophysiology of microcirculation 128 2. Chemistry and pharmacology of low molecular weight dextran. 132 3. The rheological effects of low molecular weight dextran in microcirculation.. 134 IV. Present investigations.. 136

A. Aim........ 136 B. Experimental findings. 138 1. Materials and methods 138 2. Results..... 143 3. Discussion... 151 C. Clinical investigations 152 V. General discussion 155 VI. Summary. 158 VII. References.... 159 KELLERHALS 92 I. Introduction Noise appears to be an inevitable side effect of human civilization. In modern times, the sources of noise have changed and multiplied; at all times, however, noise has been considered an embittering nuisance. Thus, the fight against noise pollution emotionally aims rather at the diminution of