Wideband reflectance tympanometry in normal adults

Acoustic impedance/reflectance measurements were made at various ear-canal pressures in 20 subjects with a clinical acoustic immittance instrument and an experimental impedance/reflectance system. Measurements were made over a frequency range of 226-2000 Hz with the clinical system and 125-11310 Hz with the experimental system.. For frequencies less than or equal to 2.0 kH z, tympanograms obtained with the two systems are similar, with patterns th at progress through the same orderly sequence with increasing frequency. Ea rdrum impedance measurements were also similar. There are small gender diff erences in middle-ear impedance. Reflectance patterns (reflectance versus f requency) at ambient ear-canal air pressure are characterized by high refle ctance at low frequencies, two distict minima at 1.2 and 3.5 kHz, increasin g reflectance to 8.0 kHz, and decreasing reflectance above that frequency. Ear-canal pressure increases reflectance at low frequencies, decreases refl ectance in the region of the minimum, and increases reflectance slightly at high frequencies. Reflectance tympanograms (reflectance versus ear-canal p ressure) progress through a sequence of three patterns. At low frequencies, reflectance tympanograms are "V" shaped, indicating that pressure increase s reflectance. At frequencies near the minimum reflectance, the pattern inv erts, indicating that pressure decreases reflectance. At high frequencies, the patterns are flat, indicating that ear-canal pressure has little effect . Results presented for one patient suggest that reflectance tympanometry m ay be useful for detecting middle-ear pathology. (C) 1999 Acoustical Societ y of America. [S0001-4966(99)04706-2].