Anatomical studies have shown that the ossicular joints and tympanic membrane stiffen with age. Research attempting to quantify the acoustical ramifications of these changes using traditional clinical impedance tools has been inconclusive. However, the measurements used in these studies have been restricted to the frequency range of 200 to 2000 Hz due to technological limitations. The long-term objective of the proposed research is to characterize the effect of aging on the middle ear by expanding the assessment of middle ear function to an important frequency region for the perception of speech consonants: 2000 to 6000 Hz. New technology will be used to measure energy reflectance and impedance over a wider bandwidth than previously possible: 200 to 10,000 Hz.
The specific aims of the current proposal are 1) to examine the effect of age on static wide-band energy reflectance and impedance; and 2) to examine the effect of age on changes in wide-band energy reflectance and impedance produced by the contralateral acoustic reflex. Two specific hypotheses will be tested: 1) that high frequency energy reflectance of the middle ear measured at peak tympanometric pressure increases with age; and 2) that a change in wide-band energy reflectance and impedance patterns of the contralateral acoustic reflex will be observed with age. The first hypothesis is consistent with the developmental trend of increasing middle ear reflectance in the high frequencies. The second hypothesis is suggested in the data showing a stiffening of the incudostapedial joint with age which would alter the resonance characteristics of the reflex. Both of these hypotheses are supported by pilot data obtained from young and elderly subjects. A cross-sectional study is proposed in which both static and reflex-related measures of wide-band energy reflectance and impedance would be obtained. Three groups of 40 subjects will be used, with equal numbers of males and females aged 18-27,40-49 and greater than or equal to 60 years. A two- way analysis of variance will be used to assess differences in 1/3 octave band energy reflectance and impedance measures across age groups and gender. The data from these experiments will lay the groundwork for further studies to examine the development of middle ear function. Since the acoustic properties of the middle ear have been shown to have a dramatic effect on hearing aid performance, and since around one half of the 23,000,000 Americans over the age of 65 may be candidates for amplification this research has implications for the quality of health care for these individuals.
