9/9/2023 0 Comments Auditory nerve earTwo of thechambers are separated by the basilar membrane, on which sits the organ of Corti. Appropriate amplification at differentfrequencies compensates for the conductive loss.īack to Main Index 1.3 Inner ear: cochlea The snail-shaped cochlea, unwound, is a three-chambered tube. These thresholds are measured in an audiologicaltest and shown in an audiogram. In a conductive hearing loss, absolutethresholds are elevated. The reflex is triggered by loud sounds it also reducesthe extent of upward spread of masking from intense low-frequency sounds(see hearing lecture 3).ĭamage to the middle ear causes a Conductive Hearing Loss which canusually be corrected by a hearing aid. The middle ear offers some protection bythe stapedius reflex, which tenses muscles that stiffen the vibrationof the ossicles, thus reducing the extent to which low frequency soundsare transmitted. (ii) Protection against loud low frequency sounds - the cochlea is susceptibleto damage from intense sounds. The large area of the ear-drum compared with the small area of thestapes helps to achieve this, together with the lever action of the threemiddle ear bones or ossicles (malleus, incus, stapes). The middle ear helps turn a large amplitudevibration in air into a small amplitude vibration (of the same energy) influid. If there were no middle ear most of the soundwould just bounce off the cochlea. (i) Impedance matching - vibrations in air must be transmitted efficientlyinto the fluid of the cochlea. This frequency region is particularly importantin speech.īack to Main Index 1.2 Middle ear: tympanic membrane, malleus, incusand stapes The middle ear transmits the vibrations of the ear drum (tympanic membrance)to the cochlea. It resonatesat around 2kHz so that frequencies in that region are transmitted more efficientlyto the cochlea than others. The meatus is the tube that links the pinna to the eardrum. The brain interprets these changes as direction. Differenthigh frequencies are amplified by different amounts depending on the directionof the sound. Only frequencies that have a wavelength comparable tothe dimensions of the pinna are influenced by it (> 3kHz). The human pinna is not mobile, but servesto colour high frequency sounds by interference between the echoes reflectedoff its different structures (like the colours of light produced by reflectionfrom an oil slick). Those with mobilepinnae (donkey, cat) use it to amplify sound coming from a particular direction,at the expense of other sounds. 1.1 Pinna and meatus The pinna serves different functions in different animals. Hearing Lecture Notes (2): Ear and Auditory Nerve 1 THE EARġ.1 Pinna and meatus 1.2 Middle ear: tympanic membrane, malleus,incus and stapes 1.3 Inner ear: cochleaġ.3.1 Non-linearity 1.3.2 Sensori-neural hearing loss (SNHL) 1.3.3 Forms of deafness 1.3.4 Role of outer hair cells 2 AUDITORY NERVEĢ.1 Response to single pure tones 2.2 Frequency threshold curves (FTCs) 2.3 Characteristic frequency (CF) 2.4 Phase locking 2.5 Coding frequency 2.6 Coding intensity 2.7 Two-tone suppression 2.8 Cochlear implants 3 WHAT YOU SHOULD KNOW.īack to Main Index 1 THE EAR There are three main parts of the ear: the pinna (or external ear)and meatus, the middle ear, and the cochlea (innerear).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |