Ear and earmoulds.ppt

The acoustic properties of the ear and ear moulds The Ear Outer ear: : pinna Amplify sound A part of the human sound localization system Binaural sound perception App. 25 mm long, diameter app. 7 mm. Resonanse frequency @ app. 3,5 kHz. (more for children) The outer part is soft (cartilage), but it gets harder closer to the tympanic membrane (bone) Transmits sound from outer ear to tympanic membrane Cerumen Yellow or white matter, produced in glands in the ear canal The purpose of cerumen is to protect the tympanic membrane against water and dust particles, by picking up particles and transport them towards the entrance of the canal Too much cerumen in the ear canal can cause dissiness, hearing loss and tinnitus. Audiogram: cerumen Tympanic membrane oscillation in tympanic membrane of guinea pig Functional model of the middle ear Otosclerose deformity and sclerosis of the bones in the middle ear (most often stirrup). Can, in some cases, cause the round window to be pushed out of balance. causes conductive as well as preceptive hearing loss Audiogram: inflammation of the middle ear The ear mould Transfers sound from the hearing aid to the ear canal and eardrum Keeps the hearing aid in position Provides individual adjustment for maximum user comfort Ear mould technology: a craft Ear mould technology: a craft Types of ear mould Pocket hearing aid Closed mould (silhouette) Types of ear plug Wing Canal mould Types of ear plug Vented Open plug Types of ear mould Soft mould Horn Types of ear mould: in the ear hearing aids Modular Costum Ear mould acoustics Ear mould acoustics Ear mould acoustics Ear mould acoustics: occlusion effect Ear mould acoustics: occlusion effect Ear mould acoustics: venting Ear mould acoustics: venting Ear mould acoustics: damping Ear mould acoustics: damping Ear mould acoustics: damping Ear mould acoustics: sound bore Ear mould acoustics: canal length Ear mould acoustics: inserts Ear mould acoustics: posterior horn Ear mou