What is an acoustic reflex measurement?
Just like tympanometry measurements, a probe is inserted into the ear canal. While playing a continues probe tone, short test signals (e.g. 0.5, 1 or 2kHz) are presented at levels of 70 - 100dB, triggering the stapes muscle to contract. Through this contraction, the ossicular chain and ear drum stiffens as well, leading to a measurable decrease of compliance in the ear canal. The acoustic reflex is measurable in both ears (ipsilateral and contralateral).
Why measure acoustic reflexes?
Acoustic reflex measurements are a regular used tool in audiological testing and provide feedback on:
• Type and degree of hearing loss (conductive, sensory, neural)
• Injury of the facial nerve or vestibulocochlear nerve
What is tympanometry?
Tympanometry is an objective measurement of the middle ear pressure, which was first developed in the 1950's (1Terkildsen et al.). Since then, the test technique was further developed and became a common part of the audiological test routine.
1Terkildsen, K. and K.A. Thomsen (1959). The influence of pressure variations on the impedance measuring bridge for clinical use. J. Laryngol. Otol. 73, 409-418.