For real-ear measurements, where should the probe tube be placed to measure the SPL at the tympanic membrane most accurately?

• A. Deep in the Ear Canal Away From the Tympanic Membrane
• B. Near the Tympanic Membrane
• C. At the Entrance of the Ear Canal
• D. Outside the Ear

Answer: (B)

Real-ear measurements aim to capture the sound pressure that actually reaches the eardrum. To get an accurate read of SPL at the tympanic membrane, the probe tube must sit just inside the ear canal, very close to the tympanic membrane—typically about 5 millimeters away and not touching it. This proximity ensures the microphone samples the pressure at the point where it matters for hearing aid output, taking into account the ear canal’s acoustics. If the probe is placed deeper away from the eardrum, at the entrance, or outside the ear, the reading will be influenced by canal resonances or lack the necessary ear-canal contribution, misrepresenting what the eardrum experiences. So, near the tympanic membrane provides the most accurate measurement of SPL at that critical location.