The RECD (Real Ear to Coupler Difference) measurement is most frequently used for hearing aid fittings with children. This type of procedure is used when real ear measurements are difficult to obtain or perform. For example, RECD can be performed with an active, restless child or an elderly woman with very sensitive ear canals. RECD requires only one measurement in the ear; the remainder of the measurements can be performed within the test box.

One of the disadvantages of RECD is working with difference values; in this case errors will be carried over throughout the entire fitting process. 

Frequent sources of error for RECD measurements:

• Incorrect/missing probe tube calibration
• Probe tube placed correctly, but it branched off
• Incorrect/missing test box calibration
• Background noise

Configuration and Procedure of the RECD Measurement (Figure 226)

Figure 226: RECD sub-tab screen shot

1. Prior to starting the measurement, the test box and real ear probe must be calibrated. If calibration is not completed, target curves will be incorrectly calculated. More specific calibration details are provided in the real ear and test box calibration sections.
2. Upon completion of the calibration, begin the measurement.
3. Select the input level for the first measurement (minimum of 20 dB louder than the environmental noise) and define the number of single measurements to be performed in the ACAM System. A more exact measurement will be obtained if more single measurements have been performed.
4. Correctly place the real ear measurement probe tube.
5. Click <Record in situ curve right/left> and the measurement will begin and save for the selected ear.