New ANSI RECD Standard: Why Your RECD May Contain Errors and What You Can Do About It

Carolyn Smaka:  Jim, thanks for your time today.  What was the reason that ANSI recently updated the real-ear-to-coupler-difference (RECD) standard?

Jim Jonkman:  The new update to the real ear standard includes an annex for guidance in making accurate RECD measurements.  In the past, there was no official guidance; there was research completed by various people who came up with methods for RECD.  We have published the methods that we use with our equipment at Audioscan.  However, for clinicians conducting RECD, it was never really completely understood where you might run into problems, or situations where you might have inaccuracies that could become significant.  ANSI has now provided that guidance via an annex in the standard that presents the results of their studies and explains these potential situations.

Carolyn: Do the new findings change the general procedure for RECD?

Jim:  The RECD procedure does not change.  You still do an ear level measurement and a coupler measurement. It is the equipment that you use to make that measurement, i.e. the transducer, the plumbing, etc. to couple to the ear and to couple to the coupler, that could introduce error.  There are a lot of practical considerations, especially with pediatric fittings, where you might want to conduct the measurement with tubing and an ear mold; that can present some potential for errors in the measurement. 

There are two main error sources.  The first is when there is a difference in the coupling path between the transducer and either the ear or the coupler.  In other words, you use a different length of tubing or you think one piece of tubing is equivalent to another.  Every section of tubing has an acoustic response that you have to factor into your measurement.  When ANSI did the simulations and the measurements, they discovered that it was causing some significant errors.  The other error source is more subtle; it is an error due to the acoustic impedance.  We are getting into a little more detail on the properties of the transducer and the coupling.  You want to make your measurement with a high impedance sound source.  It if is not high impedance, and there are certain situations where that occurs, then you will also get a significant error. 

When performing RECD, you want to ensure that your measurement has minimized those errors as much as possible.  

Carolyn:  How significant are these errors, should they occur?

Jim: They found that they could get errors of 10 to 15 dB.  It might not be for the entire measurement, but for certain regions, there could be a fairly significant bump or dip in the RECD.  For pediatrics, because you are not able to do real ear, and instead are doing simulated real ear on a coupler, it can be significant.

Carolyn:  It is great that you have provided further detail in the Audioscan Expert Insight paper.

Jim:  The ANSI update has just been published.  I think it will take a while for the information to get out there, which is why we published the Insight document.  For our equipment, we have explained the matrix of measurement options, if you will, that can be done to ensure that you are complying with the ANSI recommendation. The bottom line is that it is actually pretty simple.  ANSI has done really good work in teasing out exactly what the error sources are.  That is why we were able to do our summary document in just two pages to explain what it means for clinicians, and what they need to do to ensure accurate results.

Carolyn:  How are things going with the new Verifit 2? 

Jim:  Very well – there is a lot of interest and we are now ramping up production.  People are excited about the binaural capability, and some of the other new features. 

We have implemented the new ANSI RECD in Verifit 2, and it is also offered as a free software update for other Audioscan fitting systems including the original Verifit, Axiom, and RM500SL.

Carolyn:  How does the software upgrade work?    

Jim:  It’s a very simple download from Audioscan.com, just click the software update link near the top of the home page and follow the instructions. If your ability to download is restricted, just give us a call and we can arrange to have the software shipped to your door. All of our system software is free — by removing barriers like the high cost of upgrades we figure more patients will receive cutting-edge hearing care, and that aligns perfectly with our mission at Audioscan.

Carolyn:  That sounds easy enough.

I know clinicians appreciate this kind of support from Audioscan in regards to the Expert Insight document that you have made available, and I thank you for your time in giving us the opportunity to help spread the word.  

Jim:  It’s my pleasure – thanks, Carolyn.

For more information about Audioscan, visit www.audioscan.com or the Audioscan Expo Page on AudiologyOnline.