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Hearing Aid Verification

Advantages of RECD measurements with infants and young children

  • First, the measure is quick. Children may have a short window of cooperation for real ear testing procedures. With practice and with appropriate distraction for the child, RECD measures can be completed in less than 5 minutes per ear. All other electroacoustic measures and hearing instrument adjustments can be completed in the 2 cc3 coupler without the child present.

  • Second, the RECD measure is valid and repeatable (Sinclair et al, 1996, Seewald et al, 1999, Scollie, et al, 1998, Tharpe, et al, 2001). Using the RECD to predict the real ear hearing instrument response for a child is highly correlated with actual real ear probe-microphone measures. When the measurement is carefully completed, results are also highly repeatable.

  • Third, the measure can be used with any age child. Audiologists are at a particular disadvantage when fitting hearing instruments on infants younger than 6 months. Threshold information is typically limited to ABR responses and behavioral testing is not possible for either unamplified or amplified conditions. Using the RECD with 2cc coupler measures allows the audiologist to fit and evaluate the response of a hearing instrument before behavioral threshold testing can be completed.

Tricks Of the Trade

Bagatto (2001, Used with permission) reviewed 6 important tips for making more successful RECD measures.

  1. Proper Probe-Tube Placement
  2. Always Use Otoscopy
  3. Lubricate
  4. Coordinate
  5. Don't Hesitate
  6. Troubleshoot Your Measurement

Probe-Tube Replacement

Measure and mark the insert tube for the appropriate insertion depth (10-15 mm from ear canal entrance or 20-25 mm from intertragal notch)

Probe-Tube Replacement:


  • Determine shape and length of canal before placing probe-tube

  • Ensure appropriate insertion depth after placing probe tube.

  • Note any wax or drainage that may prevent making the RECD measure

  • Note the presence of PE tubes / TM perforations / Otitis Media. All of these conditions can have an acoustic effect on the RECD


  • Lubricate the probe tube

  • Lubricate the earmold


  • Pre-measure the 2cc coupler response before seeing the child

  • Pre-mark tubes to correct length

  • Stabilize the probe tube before inserting the earmold using FunTac, lubricant, tape or the strap of the probe microphone itself

Don't Hesitate:

  • Practicing on others before making the real measure will increase your comfort level

  • Have Toys, Bubbles or Mirror ready before testing starts

  • Use a second examiner or helpful parent to keep the child distracted. In the RECD procedure illustrated above, a second examiner was present, although out of camera range.

  • Using a least-restrictive hold generally makes for a happier baby and more reliable measures

Troubleshoot Your Measurement:

  • Know what to expect so you know when something isn't correct!

  • Look for high frequency roll-off or negative values in the low frequencies

What if I just can't measure the RECD?

  • Between-ear RECD values are highly correlated (Tharpe, et al, 2001, Munro & Buttfield, 2004). The measured RECD from one ear can be used to predict the second ear RECD, unless an obvious difference between ears is found. Differences may be related to ear malformations, middle ear effusions or TM perforations.

  • Average RECD values do exist, though individual variability from age-related averages is high

    • Using average values is better than ignoring the RECD completely

    • Using average values is better than using functional gain which has no estimate of output or audibility