Reflectance measurements can be affected by an acoustic leak. This occurs when there is an incomplete seal between the eartip and the ear canal, which lets stimulus sound out and noise in. This shows up at low frequencies as low reflectance and also as a high equivalent volume. In a normal ear, reflectance is high at low frequencies and equivalent volume is usually much less than 2cc. For certain pathologies such as TM perforation, reflectance will be low at low frequencies. We recommend that when you see this pattern, to reinsert the probe tip, possibly with a wider tip, and repeat the measurement. The results will be very repeatable if it is a true pathology, but first you need to ensure there is no leak.