Much of the hospital's success in identifying and treating children with hearing loss is the result of the rapid transfer of research findings from laboratories to clinic and bedside.

Areas of Research - Clinical and Behavioral Studies of Human Communication - Hearing Aid Research Laboratory

Real-ear-to-coupler difference (RECD) Procedure: A Tutorial

It has been well established that real-ear measures of hearing aid gain and output are more accurate and reliable than functional gain measures. Furthermore, real-ear measures can provide an estimate of the maximum sound pressure level (SPL) that would be delivered to the ear after hearing-aid processing. This is particularly critical when fitting hearing aids to infants and young children because of the small size of their ear canals. If two hearing aids with identical electroacoustic characteristics were fitted on an adult and an infant, the SPL measured in the infant’s ear canal could be 10-20 dB higher than in the adult ear! It is important to account for these differences during the hearing aid selection and fitting process.

Unfortunately, probe-tube microphone procedures are difficult to implement with infants and young children. Due to poor head control, vocalizations, and random body movements, the test-retest reliability and the validity of traditional probe microphone measures may be poor in this population. Fortunately, there is an alternative!!

Moodie et al. (1994) described an alternative probe-microphone approach that can be used with children as young as a few days of age. This real-ear-coupler difference (RECD) procedure involves making 2 measurements. First, a stimulus is presented into a standard 2 cm 3 coupler via an insert earphone and the SPL is measured; this is the coupler response. Then, a probe microphone is placed in the child’s ear canal and the same insert phone (which has been coupled to the child’s earmold) is used to deliver the signal to the ear. The difference between the real-ear and coupler response is the RECD. These differences as a function of frequency then can be added to hearing aid responses measured in a coupler to predict the real-ear response.

This procedure can be completed in both ears in 5-10 minutes. All subsequent measures can be made in the test box. The attached tutorial provides a step-by-step description of this procedure. For additional information, a reference list is given.

Click here to view the tutorial online.

Click here to download the tutorial to view offline.

Click here to view References.