Signal averaging in real ear probe tube measurements

In this study, signal averaging measurements were performed using a broadband noise as the test signal in two acoustic environments typifying relatively noisy situations in which real ear probe tube measurements are made clinically. The minimum time-domain signal averaging required to reduce the degrading effects of background noise to levels acceptable for the production of valid real ear unaided responses (REURs) was established for three normal listeners at various signal-to-noise (S/N) ratios. Generally, averaging was not required at S/Ns of 20 dB or higher. Acceptable responses were obtained at S/Ns as low as -5 dB when the number of averages was increased to 256 and higher. The function derived from the data in the two acoustic environments was in good agreement with a theoretical rule. Findings suggest that averaging of only a few sweeps of the test signal is required to obtain reliable and valid real ear measurements, even in somewhat noisy test environments. With a knowledge of the levels of the test signal and the background noise, data from this study can be used to determine the requisite number of signal sweeps to be averaged in acquiring real ear responses in a minimum amount of time.