Comparison of acoustic immittance measures obtained with different commercial instruments.

Three acoustic admittance measurements (tympanometric peak pressure, peak compensated static acoustic admittance, and tympanometric width) were compared across seven commercially available acoustic immittance systems. Forty-nine adult subjects (45 females and 4 males), 16 to 50 years of age (mean = 27.7 years), with normal middle ear function participated in this investigation. Small but statistically significant differences were observed for each of the tympanometric variables for several of the instruments evaluated. In most instances, the differences were small enough that the same normative data could be applied across the instrumentation employed in this study; however, there were two measurement conditions, peak compensated static acoustic admittance and tympanometric width, where, for selected instruments, the range in values differed by an amount great enough to warrant consideration in clinical decision making.