The REM-measurement equipment
There are several brands of REM equipment available on the market. E.g. Otometrics, Interacoustics Affinty and Callisto, Aurical Freefit, Auditdata Primus, Unity, Inventis Trompet and MedRx. Although they are all different in model and size, they all provide the same function; measuring the sound pressure close to the eardrum. Another similarity is the presence of two microphones which can be found on the measurement unit hanging close to the ear. The first microphone, the reference microphone, measures the reference sound outside the ear and the second microphone is connected to the probe tube, measuring the sound close to the eardrum.
By comparing these two sound measurements the hearing aid specialist can obtain a better view regarding the real sound waves send to the hearing impaired and how these sounds actually hit the eardrum.
The different measurement methods possible are discussed in the next chapters.