Earl E. Johnson

Effects of degree and configuration of hearing loss on the contribution of high- and low-frequency speech information to bilateral speech understanding.

Objectives:The purpose of this study was to examine the effects of degree and configuration of hearing loss on the use of, and benefit from, information in amplified high- and low-frequency speech presented in background noise. Design:Sixty-two adults with a wide range of high- and low-frequency sensorineural hearing loss (5 to 115+ dB HL) participated in the study. To examine the contribution of speech information in different frequency regions, speech understanding in noise was assessed in multiple low- and high-pass filter conditions, as well as a band-pass (713 to 3534 Hz) and wideband (143 to 8976 Hz) condition. To increase audibility over a wide frequency range, speech and noise were amplified based on each individuals hearing loss. A stepwise multiple linear regression approach was used to examine the contribution of several factors to (1) absolute performance in each filter condition and (2) the change in performance with the addition of amplified high- and low-frequency speech components. Results:Results from the regression analysis showed that degree of hearing loss was the strongest predictor of absolute performance for low- and high-pass filtered speech materials. In addition, configuration of hearing loss affected both absolute performance for severely low-pass filtered speech and benefit from extending high-frequency (3534 to 8976 Hz) bandwidth. Specifically, individuals with steeply sloping high-frequency losses made better use of low-pass filtered speech information than individuals with similar low-frequency thresholds but less high-frequency loss. In contrast, given similar high-frequency thresholds, individuals with flat hearing losses received more benefit from extending high-frequency bandwidth than individuals with more sloping losses. Conclusions:Consistent with previous work, benefit from speech information in a given frequency region generally decreases as degree of hearing loss in that frequency region increases. However, given a similar degree of loss, the configuration of hearing loss also affects the ability to use speech information in different frequency regions. Except for individuals with steeply sloping high-frequency losses, providing high-frequency amplification (3534 to 8976 Hz) had either a beneficial effect on, or did not significantly degrade, speech understanding. These findings highlight the importance of extended high-frequency amplification for listeners with a wide range of high-frequency hearing losses, when seeking to maximize intelligibility.

The Effect of Extending High-Frequency Bandwidth on the Acceptable Noise Level (anl) of Hearing-Impaired Listeners

This study examined the effects of extending high-frequency bandwidth, for both a speech signal and a background noise, on the acceptable signal-to-noise ratio (SNR) of listeners with mild sensorineural hearing loss through utilization of the Acceptable Noise Level (ANL) procedure. In addition to extending high-frequency bandwidth, the effects of reverberation time and background noise type and shape were also examined. The study results showed a significant increase in the mean ANL (i.e. participants requested a better SNR for an acceptable listening situation) when high-frequency bandwidth was extended from 3 to 9 kHz and from 6 to 9 kHz. No change in the ANL of study participants was observed as a result of isolated modification to reverberation time or background noise stimulus. An interaction effect, however, of reverberation time and background noise stimulus was demonstrated. These findings may have implications for future design of hearing aid memory programs for listening to speech in the presence of broadband background noise.

A comparison of NAL and DSL prescriptive methods for paediatric hearing-aid fitting: Predicted speech intelligibility and loudness

Abstract Objective: To examine the impact of prescription on predicted speech intelligibility and loudness for children. Design: A between-group comparison of speech intelligibility index (SII) and loudness, based on hearing aids fitted according to NAL-NL1, DSL v4.1, or DSL m[i/o] prescriptions. A within-group comparison of gains prescribed by DSL m[i/o] and NAL-NL2 for children in terms of SII and loudness. Study sample: Participants were 200 children, who were randomly assigned to first hearing-aid fitting with either NAL-NL1, DSL v4.1, or DSL m[i/o]. Audiometric data and hearing-aid data at 3 years of age were used. Results: On average, SII calculated on the basis of hearing-aid gains were higher for DSL than for NAL-NL1 at low input level, equivalent at medium input level, and higher for NAL-NL1 than DSL at high input level. Greater loudness was associated with DSL than with NAL-NL1, across a range of input levels. Comparing NAL-NL2 and DSL m[i/o] target gains revealed higher SII for the latter at low input level. SII was higher for NAL-NL2 than for DSL m[i/o] at medium- and high-input levels despite greater loudness for gains prescribed by DSL m[i/o] than by NAL-NL2. Conclusion: The choice of prescription has minimal effects on speech intelligibility predictions but marked effects on loudness predictions.

Segmenting dispensers: Factors in selecting open-canal fittings

The trend is clear. More clinicians and patients are choosing open-canal (OC) fitting hearing aids as a treatment option for hearing impairments. Now, just a few years after GN ReSound’s launch of an OC device called the ReSoundAIR, nearly every manufacturer has a similar product. In a very real sense, an OC is more or less a small behind-the-ear (BTE) device with a tube fitting, although some products classified as “open” have the receiver in the ear canal and use a wire rather than a tube to connect with the ear canal. Last year, BTE sales in the USA increased significantly (no doubt largely because of the OC product), jumping to 33% of all hearing aid sales. In the second quarter of 2006, BTEs accounted for 44% of the domestic market and a large portion of these were OC devices. Based on OC products’ cosmetic appeal and their use in fitting mild to moderate high-frequency hearing losses, one might assume that the OC aid’s closest competitor would be the completely-in-the canal (CIC) style. However, according to the Hearing Industries Association (HIA) data,1 the surge in BTE sales is coming at the expense of all three custom hearing aid styles. Sales for the in-the-ear (ITE) styles have fallen from 41% of the market in 2003 to 32% this year, while the in-the-canal (ITC) and CIC styles have fallen from 21% and 14% of the total market, respectively, in 2003 to 15% and 11% in 2006. The OC device is clearly shaking up the hearing aid market.

Hearing-aid safety: A comparison of estimated threshold shifts for gains recommended by NAL-NL2 and DSL m(i/o) prescriptions for children

Abstract Objective: To investigate the predicted threshold shift associated with the use of nonlinear hearing aids fitted to the NAL-NL2 or the DSL m[i/o] prescription for children with the same audiograms. For medium and high input levels, we asked: (1) How does predicted asymptotic threshold shifts (ATS) differ according to the choice of prescription? (2) How does predicted ATS vary with hearing level for gains prescribed by the two prescriptions? Design: A mathematical model consisting of the modified power law combined with equations for predicting temporary threshold shift (Macrae, 1994b) was used to predict ATS. Study sample: Predicted threshold shift were determined for 57 audiograms at medium and high input levels. Results: For the 57 audiograms, DSL m[i/o] gains for high input levels were associated with increased risk relative to NAL-NL2. The variation of ATS with hearing level suggests that NAL-NL2 gains became unsafe when hearing loss > 90 dB HL. The gains prescribed by DSL m[i/o] became unsafe when hearing loss > 80 dB HL at a medium input level, and > 70 dB HL at a high input level. Conclusion: There is a risk of damage to hearing for children using nonlinear amplification. Vigilant checking for threshold shift is recommended.

Survey explores how dispensers use and choose their preferred hearing aid brands

Cover Story THE HEARING JOURNAL 23 When consumers shop for any product, they tend to develop a preference for a particular brand. For example, when they go to their local supermarket, some will consistently opt for Clorox rather than the store-brand bleach, they will choose Brawny over Scott paper towels, or pass up the Häagen-Dazs ice cream for a quart of Ben and Jerry’s. Since brand preferences drive consumers’ decisions about everyday purchases, competing companies are constantly attempting to establish themselves as their preferred brand. Are hearing aid companies any different in this regard from manufacturers of bleaches, towels, or ice cream? Probably not. They too want to be preferred over their competitors, though with hearing aids the customers that manufacturers target are more often the hearing healthcare professionals who dispense their products than the consumers who wear them. However, outside of data held in confidence by the marketing departments of hearing aid companies, little is known about dispensers and their individual brand preferences, how their preferences are determined, and the strength of their loyalty to their preferred brands. These topics and related issues are the focus of this month’s cover story. It should be noted that this article does not discuss how dispensers feel about specific brands of hearing aids. Nor does it pass judgment on the use of brand preferences in recommending hearing aids to patients. What it seeks to do is report on the facts about brand preference as they exist, based on data collected earlier this year by the annual Hearing Journal (HJ)/Audiology Online (AO) dispenser survey.

Modern Prescription Theory and Application: Realistic Expectations for Speech Recognition With Hearing Aids

A major decision at the time of hearing aid fitting and dispensing is the amount of amplification to provide listeners (both adult and pediatric populations) for the appropriate compensation of sensorineural hearing impairment across a range of frequencies (e.g., 160–10000 Hz) and input levels (e.g., 50–75 dB sound pressure level). This article describes modern prescription theory for hearing aids within the context of a risk versus return trade-off and efficient frontier analyses. The expected return of amplification recommendations (i.e., generic prescriptions such as National Acoustic Laboratories—Non-Linear 2, NAL-NL2, and Desired Sensation Level Multiple Input/Output, DSL m[i/o]) for the Speech Intelligibility Index (SII) and high-frequency audibility were traded against a potential risk (i.e., loudness). The modeled performance of each prescription was compared one with another and with the efficient frontier of normal hearing sensitivity (i.e., a reference point for the most return with the least risk). For the pediatric population, NAL-NL2 was more efficient for SII, while DSL m[i/o] was more efficient for high-frequency audibility. For the adult population, NAL-NL2 was more efficient for SII, while the two prescriptions were similar with regard to high-frequency audibility. In terms of absolute return (i.e., not considering the risk of loudness), however, DSL m[i/o] prescribed more outright high-frequency audibility than NAL-NL2 for either aged population, particularly, as hearing loss increased. Given the principles and demonstrated accuracy of desensitization (reduced utility of audibility with increasing hearing loss) observed at the group level, additional high-frequency audibility beyond that of NAL-NL2 is not expected to make further contributions to speech intelligibility (recognition) for the average listener.

Despite Having More Advanced Features, Hearing Aids Hold Line on Retail Price

Despite the growing popularity of state-of-the-art opencanal mini-BTEs, which were discussed in last month’s Cover Story, and the increasing prevalence of advanced hearing aid features, the annual Hearing Journal/Audiology Online dispenser survey conducted in January found only small, inflation-appropriate increases in the average retail price of hearing aids over the past 3 years. Specifically, the average price of the hearing aids that participating dispensers reported selling in 2007 was

A Patient-Centered, Provider-Facilitated Approach to the Refinement of Nonlinear Frequency Compression Parameters Based on Subjective Preference Ratings of Amplified Sound Quality.

1986, only marginally higher than the average prices of

An Initial-Fit Comparison of Two Generic Hearing Aid Prescriptive Methods (NAL-NL2 and CAM2) to Individuals Having Mild to Moderately Severe High-Frequency Hearing Loss

1912 and