Predictability of Speech-In-Noise Performance from Real Ear Measures of Directional Hearing Aids Sumitrajit Dhar, Larry E. Humes, Lauren Calandruccio, Nancy N. Barlow, and Nicholas Hipskind Objective: Inability to understand speech in noise has been cited repeatedly as the principal com- plaint of hearing aid users. While data exist docu- menting the benefit provided by hearing aids with directional microphones when listening to speech in noise, little work has been done to develop a standard clinical protocol for fitting these hearing aids. Our goal was to evaluate a clinical measure of the acoustic directivity of a directional hearing aid, including its association with a test of speech per- ception in noise. Design: The performance of two commercially avail- able directional behind-the-ear (BTE) hearing aids was evaluated using the Hearing in Noise Test (HINT) and the Real Ear Aided Response (REAR) on 24 adult participants with symmetric, mild to mod- erately severe, sensorineural hearing loss. The HINT was conducted with the speech signal pre- sented from 0° and the noise from 180° and either 135° or 225° degrees, depending on the ear tested. REAR was measured at the above three angles using swept pure tones, and these measures were used to compute in situ directivity for each subject and hearing aid. Conclusions: Directional benefit for the HINT was greatest when noise was presented from the azi- muth of the published polar diagram null of a given hearing aid in its directional mode (180 or 135/225°). The only significant correlation between HINT and REAR results, however, was found when the noise source was at 180°. These results confirm the valid- ity of using real ear measures as a way to assess directionality in situ, but also indicate the complex- ity of predicting perceptual benefit from them. These data suggest that factors beyond acoustic directionality may contribute to improvement in speech perception in noise when such improve- ments are found. (Ear & Hearing 2004;25;147–158) Inability to understand speech in noise remains one of the most common complaints among hearing aid wearers today (Kochkin, 1996; Ricketts & Dhar, 1999; Schum, 2000; Smriga, 2000; Voll, 2000). Pro- vision of effective amplification in the presence of background noise is indeed one of the greatest chal- lenges to researchers and audiologists (Preves, 2000). Although normal-hearing individuals experi- ence difficulty in speech perception in the presence of background noise, many hearing-impaired listen- ers often need an even greater signal-to-noise ratio (SNR) to successfully perceive speech in noise (Kil- lion, 1997). Directional microphones, which have been imple- mented in hearing aids since the early 1970s (Agnew & Block, 1997; Lentz, 1972; Valente, Fabry, & Potts, 1995), appear to provide the most effective solution to the problem of reduced speech perception in noise. Recent revival of interest in directional microphones has resulted in increased research focus and com- mercial implementation of this technology (Chris- tensen, 2000; Preves, Sammeth, & Wynne, 1999; Valente et al., 1995). The rekindled interest in directional microphones is based on three factors: increased directivity available today [as measured by the Directivity Index (DI)]; the ability to imple- ment directional microphones in in-the-ear and in- the-canal style hearing aids; and the ability of the wearer to switch between omni and directional mi- crophones (Christensen, 2000). Voll (2000) provides a detailed discussion on design aspects of directional microphones and the differences between earlier and present-day implementations. Several researchers have recently documented the improvement in SNR due to directional micro- phones (Agnew, 1997; Christensen, 2000; Killion, 1997). Killion (1997) reported that directional micro- phones can improve SNR by 3 to 5 dB in noisy, reverberant environments, and up to 5 to 10 dB in nonreverberant listening environments. This small increase in SNR may not appear significant. How- ever, a change in SNR as small as 1 dB can result in a 10% increase in speech understanding for mean- ingful sentences (Venema, 1999), thereby making even minimal improvements in SNR highly desirable. With the benefits of directional hearing aids es- tablished, research focus has shifted to the quanti- fication and prediction of directional benefit in the end user. The directivity of a hearing aid can be quantified using either acoustical or behavioral Department of Speech and Hearing Sciences, Indiana Univers- ity, Bloomington, Indiana. DOI: 10.1097/01.AUD.0000121236.56217.8F 0196/0202/04/2502-0147/0 • Ear & Hearing • Copyright © 2004 by Lippincott Williams & Wilkins • Printed in the U.S.A. 147