Real-Ear Measures: Status Quo 2015
Sanders et al (2015) report that not only are real-ear measures (REMs) an important part of all hearing aid best practice guidelines, REMs are simply a necessary part of each fitting. They note, as a result of acquiring REMs, it is likely “considerable subsequent adjustments” would need to be made to bring the hearing aid fitting into compliance with the prescription selected, such as NAL-NL2 or DSL v5.0. Unfortunately, Sanders et al indicate that it appears the majority of hearing care professionals (HCPs) do not verify that the prescribed gain and output are present in the actual fitting.
Many authors have previously reported the inaccuracy and variability associated with “first fits.” Beck and Duffey (2007) report that previous estimates indicate REMs appear to be used in fewer than 25 percent of all fittings yet “real-ear probe-microphone measures are important because they represent the only objective analysis of sound between the hearing aid and the tympanic membrane.” Aarts and Caffee (2005) report that less than 12 percent of predicted real-ear aided responses (REARs) are comparable to actual REARs. Aazh, Moore, and Prasher (2012) reported on 51 hearing aid fittings programmed to NAL-NL1 via manufacturer’s software. Unfortunately, only 29 percent of resultant fittings were within 10 dB (+/-) of target., that is, 71 percent were not within +/- 10 dB.
Sanders et al desired to compare real-ear output between multiple manufacturer’s versions of NAL-NL2, to the Audioscan Verifit version. The authors report that in general, the NAL-NL2 software the manufacturer’s provided offered less speech audibility than NAL-NL2. Four general deviations appear to be mostly true when using the manufacturer’s versions of NAL-NL2—(1) reduced gain for soft inputs, (2) roll-off of high frequencies (above 2000 Hz), (3) gain boost in mid-tones (above NAL-NL2 prescription), and (4) more linear fittings than NAL-NL2. The authors state that “if the intended goal of the fitting is to provide the patient with the gain and output of a validated prescriptive measure, such as NAL-NL2, the dispensing professional cannot rely on the manufacturer’s version of thus algorithm….”
For More Information, References, and Recommendations
Aarts NL, Caffee CS. (2005) The Accuracy and Clinical Usefulness of Manufacturer-predicted REAR Values in Adult Hearing Aid Fittings. Hearing Review 12(12):16-22.
Aazh H, Moore BC, Prasher D. (2012) The Accuracy of Matching Target Insertion Gains with Open-Fit Hearing Aids. The American Journal of Audiology 21(2):175-180.
Beck DL, Duffey J. (2007) Visible Speech: A Patient-Centered Clinical Tool. Hearing Review January 3.
Sanders J, Stoody TM, Webver JA, Mueller HG. (2015) Manufacturer’s NAL-NL2 Fittings Fail Real- Ear Verification. Hearing Review. March.