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0611 RM500SL User’s Guide Version 2.8 Page 60
15 RECD (real-ear to coupler difference)
15.1 Section overview
FastFacts 15.1: RECD (real-ear to coupler difference)
15.2 RECD facts
FastFacts 15.2: RECD facts
Individual RECD values are derived by comparing the real-ear SPL for a given test
signal to the 2cc coupler SPL for the same test signal. These RECD values are
used to: (1) convert HL threshold and UCL obtained using insert phones to SPL
values, (2) simulate real-ear measurements from 2cc coupler measures (S-REM);
and (3) derive 2cc coupler targets from real-ear aided targets.
If you use insert ear phones for audiometry OR if you verify using S-REM, you
should measure RECD (preferred) or use age-related average RECD.
If you use headphones or sound field for audiometry AND you use REM for
verification, RECD is not applied in any way and need not be measured.
If you use 2cc coupler targets, you should use measured or age-related RECD.
Insert phone audiometry with measured RECD and REM verification provides the
best fitting accuracy, with S-REM verification being slightly less accurate. Insert
phone HL data with age-related average RECD is next best.
This software provides average RECDs for 1 - 60 months, 6 - 10 years of age and
Adult. A sampling of age-related foam-tip HA-2 RECD values is shown below.
Age/Freq
250 500 750 1000
1500
2000
3000
4000
6000
1 month 3 8 9 12 15 15 16 20 23
12 months
3 6 8 10 10 11 11 15 17
24 months
3 5 7 9 9 10 10 14 15
36 months
3 5 7 9 8 9 9 13 14
60 months
3 5 7 9 7 8 8 13 13
8 yrs - Adult
3 4 6 8 7 7 8 13 13
Values are from DSL 5.0 but differ from DSL in that values for 119 months have
been used for ages >119 months. DSL 5.0 RECDs differ from DSL 4.1 RECDs.
The RECD measurement procedu
re may be accessed by selecting RECD from the
REM tests list or from the Audiometry poster within Speechmap. An optional
RECD transducer is required for RECD measurements.
This section covers the following
topics:
15.2: RECD facts
15.3: RECD coupler response
15.4: RECD real-ear response
15.5: RECD results