The purpose of this work is to offer a contribution to network modelling of the human middle ear. The model proposed has been successfully adapted to the following empirical frequency characteristics: 1) stapes displacement per unit sound pressure at the eardrum, 2) sound pressure increase from ear canal entrance to the tympanic membrane, 3) acoustic impedance at the eardrum for a normal ear, an otosclerotic ear, and an ear with interrupted incudo-stapedial joint. The acoustical energy reflectance at the eardrum, as calculated from a model of the ear canal when terminated by the middle ear model, agrees reasonably well with experimental data up to about 12 kHz. Satisfactory agreement between model results and experimental data has also been achieved for the sound pressure transformation in the middle ear. Stapedius muscle contraction is simulated by changing a single parameter. It is concluded that further progress in middle ear model development requires a strengthening of the empirical basis.
The equality of volume displacements in the inner ear windows is commonly assumed. In the present work this assumption is experimentally verified. The stapes is given a known displacement. The volume displacement of the round window is determined by measuring the sound pressure set up in a tube cemented to the round window. Inner ears of pigs have been used in the investigation. Supplementary measurements on one human temporal bone have been performed. The equality of the volume flows in the inner ear windows is also supported through an analysis of earlier measurements of the round window displacement for a given sound-pressure level at the eardrum.
For 68 temporal bones, frequency curves for the round window volume displacement have been measured for a constant sound pressure at the eardrum. Phase curves were measured for 33 of the specimens. The levels averaged amplitude curve is approximately flat below 1 kHz, where the round window volume displacement per unit sound pressure at the eardrum is 6.8 X 10(-5) mm3/Pa, and falls off by about 15 dB/oct at higher frequencies. For the 20 ears having the largest sound transmission magnitude at low frequencies, the corresponding amplitude curve is displaced about 5 dB towards higher levels. The phase of the round window volume displacement lags the eardrum sound pressure phase. In average for 33 temporal bones, the phase lag increases from zero at the lowest frequencies to pi near 2 kHz and to about 1.5 pi at 10 kHz.
The speech intelligibility index (SII) is interpreted as the proportion of total speech information available to the listener's ear for a given speech material. Consequently, SII varies in the range 0-1. A simple graphical method for determining SII for monaural listening at 1 m distance from a talker producing "average speech" (or PB-words) at normal speech effort is described. The speech area is visualized by 10 x 10 = 100 points in the audiogram form, each point contributing 0.01 to the SII. The SII thus equals 0.01 times the number of points in the audible range. A sensorineural hearing loss gives rise to an additional loss in speech recognition due to reduced frequency discrimination and time resolving ability. This suprathreshold deficit is corrected for, if the SII contribution in each frequency band is multiplied with a hearing threshold level dependent "desensitization factor". The SII is related to the intelligibility of speech, and may be used to evaluate a hearing disability.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.