Numerical Simulation of Acoustically Driven Flows in the Inner Ear

Chris­ti­an Gers­ten­ber­ger, Leib­niz Uni­ver­si­tät Han­no­ver

An acousti­cal­ly dri­ven flow (also cal­led as acoustic strea­m­ing) is a mean mo­ti­on ge­ne­ra­ted by sound waves. So, also the sound field in the inner ear is ca­pa­ble of in­du­cing mean mo­ti­ons. But the exis­tence and re­le­van­ce of acousti­cal­ly dri­ven flows for the me­cha­ni­cal pro­ces­ses in the co­ch­lea has re­mai­ned con­tro­ver­si­al. No­wa­days, it is com­mon­ly as­su­med that the re­le­van­ce of acoustic strea­m­ing is only si­gni­fi­cant for very high sound pres­su­re le­vels lar­ger than 120dB. An ex­pe­ri­men­tal ex­ami­na­ti­on of the in­flu­ence of acoustic strea­m­ing in the inner ear (and es­pe­cial­ly in the organ of corti) has not yet been pos­si­ble, since on the one hand the co­ch­lea is not di­rect­ly ac­ces­si­ble and on the other hand the in­du­ced mean mo­ti­on is com­pa­ra­tive­ly slow.

To in­ves­ti­ga­te the in­flu­ence of acousti­cal­ly dri­ven flows in the inner ear, the ob­ject of re­se­arch is to de­ve­lop an ap­pro­pria­te com­pu­ta­tio­nal model, which can be stu­di­ed in a si­mu­la­ti­on pro­cess. The model is in­ten­ded to ve­ri­fy, whe­ther a si­gni­fi­cant mean flow oc­curs and the si­mu­la­ti­on should esti­ma­te and eva­lua­te the order of ma­gni­tu­de of such mean mo­ti­ons. The pur­po­se of such in­ves­ti­ga­ti­on is mo­ti­va­ted by the fact that (even small) de­flec­tions of the ste­reo­ci­li­as of the hair cells – which can also be cau­sed by mean strea­m­ing mo­ti­ons – are re­s­pon­si­ble eit­her for the neu­ral sti­mu­la­ti­on pro­cess (inner hair cells), or for the ac­tive am­pli­fi­ca­ti­on pro­cess of the ba­si­lar mem­bra­ne mo­ti­ons (outer hair cells).

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