Written by Travis M. Moore
Last edited 31-Jan-2020
After visual inspection of the pinnae and otoscopy, our next assessment of the auditory system, immittance testing, gives us information about the middle ear. Acoustic immittance is a general term that refers to how well (or poorly) sound is moving through the middle ear.
Tympanometry, one type of immittance testing, gives us an idea of how the middle ear is functioning simply by measuring a physical quantity associated with immittance (usually admittance). If admittance is high, we can assume that sound is moving through the middle ear without any problems. If admittance is low, it is safe to assume sound is not traveling through the middle ear properly.
We can also measure the admittance of the middle ear in the presence of a loud sound. This is referred to as acoustic reflex testing). The acoustic reflex is triggered by loud sounds (especially low frequency) and activates a small muscle attached to the stapes. The acoustic reflex makes the ossicular chain temporarily less efficient in transmitting sound, and we can see that as a change in admittance (i.e., a change in how sound is moving through the middle ear).