Abstract: An acoustic reflectometry instrument and method for ascertaining fluid presence in an ear. Drive side normalization involves normalizing the speaker to adjust its output to compensate for non-linearity over a frequency range used for acoustic reflectometry measurement of the ear. The microphone is normalized to compensate for system non-linearity. Measurement involves repetition a selected number of times until the spectral gradient angle is within a specified range for each repetition to provide validation of the measurement. For enhanced reliability, various sources of error are tested.