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Background: An important goal of providing amplification to children with hearing loss is to ensure that hearing aids are adjusted to match targets of prescriptive procedures as closely as possible. The Desired Sensation Level (DSL) v5 and the National Acoustic Laboratories’ prescription for nonlinear hearing aids, version 1 (NAL-NL1) procedures are widely used in fitting hearing aids to children. Little is known about hearing aid fitting outcomes for children with severe or profound hearing loss. Purpose: The purpose of this study was to investigate the prescribed and measured gain of hearing aids fit according to the NAL-NL1 and the DSL v5 procedure for children with moderately severe to profound hearing loss; and to examine the impact of choice of prescription on predicted speech intelligibility and loudness. Research Design: Participants were fit with Phonak Naida V SP hearing aids according to the NAL-NL1 and DSL v5 procedures. The Speech Intelligibility Index (SII) and estimated loudness were calculated using published models. Study Sample: The sample consisted of 16 children (30 ears) aged between 7 and 17 yr old. Data Collection and Analysis: The measured hearing aid gains were compared with the prescribed gains at 50 (low), 65 (medium), and 80 dB SPL (high) input levels. The goodness of fit-to-targets was quantified by calculating the average root-mean-square (RMS) error of the measured gain compared with prescriptive gain targets for 0.5, 1, 2, and 4 kHz. The significance of difference between prescriptions for hearing aid gains, SII, and loudness was examined by performing analyses of variance. Correlation analyses were used to examine the relationship between measures. Results: The DSL v5 prescribed significantly higher overall gain than the NAL-NL1 procedure for the same audiograms. For low and medium input levels, the hearing aids of all children fit with NAL-NL1 were within 5 dB RMS of prescribed targets, but 33% (10 ears) deviated from the DSL v5 targets by more than 5 dB RMS on average. For high input level, the hearing aid fittings of 60% and 43% of ears deviated by more than 5 dB RMS from targets of NAL-NL1 and DSL v5, respectively. Greater deviations from targets were associated with more severe hearing loss. On average, the SII was higher for DSL v5 than for NAL-NL1 at low input level. No significant difference in SII was found between prescriptions at medium or high input level, despite greater loudness for DSL v5 than for NAL-NL1. Conclusions: Although targets between 0.25 and 2 kHz were well matched for both prescriptions in commercial hearing aids, gain targets at 4 kHz were matched for NAL-NL1 only. Although the two prescriptions differ markedly in estimated loudness, they resulted in comparable predicted speech intelligibility for medium and high input levels.

Background: Hearing aid prescriptive recommendations for hearing losses having a conductive component have received less clinical and research interest than for losses of a sensorineural nature; as a result, much variation remains among current prescriptive methods in their recommendations for conductive and mixed hearing losses (Johnson and Dillon, 2011). Purpose: The primary intent of this brief clinical note is to demonstrate differences between two algebraically equivalent expressions of hearing loss, which have been approaches used historically to generate a prescription for hearing losses with a conductive component. When air and bone conduction thresholds are entered into hearing aid prescriptions designed for nonlinear hearing aids, it was hypothesized that that two expressions would not yield equivalent amounts of prescribed insertion gain and output. These differences are examined for their impact on the maximum power output (MPO) requirements of the hearing aid. Subsequently, the MPO capabilities of two common behind-the-ear (BTE) receiver placement alternatives, receiver-in-aid (RIA) and receiver-in-canal (RIC), are examined. Study Samples: The two expressions of hearing losses examined were the 25% ABG + AC approach and the 75% ABG + BC approach, where ABG refers to air-bone gap, AC refers to air-conduction threshold, and BC refers to bone-conduction threshold. Example hearing loss cases with a conductive component are sampled for calculations. The MPO capabilities of the BTE receiver placements in commercially-available products were obtained from hearing aids on the U.S. federal purchasing contract. Results: Prescribed gain and the required MPO differs markedly between the two approaches. The 75% ABG + BC approach prescribes a compression ratio that is reflective of the amount of sensorineural hearing loss. Not all hearing aids will have the MPO capabilities to support the output requirements for fitting hearing losses with a large conductive component particularly when combined with significant sensorineural hearing loss. Generally, current RIA BTE products have greater output capabilities than RIC BTE products. Conclusions: The 75% ABG + BC approach is more appropriate than the 25% ABG + AC approach because the latter approach inappropriately uses AC thresholds as the basis for determining the compression ratio. That is, for hearing losses with a conductive component, the AC thresholds are not a measure of sensorineural hearing loss and cannot serve as the basis for determining the amount of desired compression. The Australian National Acoustic Laboratories has been using the 75% ABG + BC approach in lieu of the 25% ABG + AC approach since its release of the National Acoustic Laboratories—Non-linear 1 (NAL-NL1) prescriptive method in 1999. Future research may examine whether individuals with conductive hearing loss benefit or prefer more than 75% restoration of the conductive component provided adequate MPO capabilities to support such restoration.

Background: Prescriptive methods have been at the core of modern hearing aid fittings for the past several decades. Every decade or so, there have been revisions to existing methods and/or the emergence of new methods that become widely used. In 2001 Byrne et al provided a comparison of insertion gain for generic prescriptive methods available at that time. Purpose: The purpose of this article was to compare National Acoustic Laboratories—Non-linear 1 (NAL-NL1), National Acoustic Laboratories—Non-linear 2 (NAL-NL2), Desired Sensation Level Multistage Input/Output (DSL m[i/o]), and Cambridge Method for Loudness Equalization 2—High-Frequency (CAMEQ2-HF) prescriptive methods for adults on the amplification characteristics of prescribed insertion gain and compression ratio. Following the differences observed in prescribed insertion gain among the four prescriptive methods, analyses of predicted specific loudness, overall loudness, and bandwidth of cochlear excitation and effective audibility as well as speech intelligibility of the international long-term average speech spectrum (ILTASS) at an average conversational input level were completed. These analyses allow for the discussion of similarities and differences among the present-day prescriptive methods. Research Design: The impact of insertion gain differences among the methods is examined for seven hypothetical hearing loss configurations using models of loudness perception and speech intelligibility. Study Sample: Hearing loss configurations for adults of various types and degrees were selected, five of which represent sensorineural impairment and were used by Byrne et al; the other two hearing losses provide an example of mixed and conductive impairment. Data Collection and Analysis: Prescribed insertion gain data were calculated in 1/3-octave frequency bands for each of the seven hearing losses from the software application of each prescriptive method over multiple input levels. The insertion gain data along with a diffuse field-to-eardrum transfer function were used to calculate output levels at the eardrums of the hypothetical listeners. Levels of hearing loss and output were then used in the Moore and Glasberg loudness model and the ANSI S3.5-1997 Speech Intelligibility Index model. Results: NAL-NL2 and DSL m[i/o] provided comparable overall loudness of approximately 8 sones for the five sensorineural hearing losses for a 65 dB SPL ILTASS input. This loudness was notably less than that perceived by a normal-hearing person for the same input signal, 18.6 sones. NAL-NL2 and DSL m[i/o] also provided comparable predicted speech intelligibility in quiet and noise. CAMEQ2-HF provided a greater average loudness, similar to NAL-NL1, with more high-frequency bandwidth but no significant improvement to predicted speech intelligibility. Conclusions: Definite variation in prescribed insertion gain was present among the prescriptive methods. These differences when averaged across the hearing losses were, by and large, negligible with regard to predicted speech intelligibility at normal conversational speech levels. With regard to loudness, DSL m[i/o] and NAL-NL2 provided the least overall loudness, followed by CAMEQ2-HF and NAL-NL1 providing the most loudness. CAMEQ2-HF provided the most audibility at high frequencies; even so, the audibility became less effective for improving speech intelligibility as hearing loss severity increased.

Purpose: To determine the amount of importance audiologists place on various items related to their selection of a preferred hearing aid brand manufacturer. Research Design: Three hundred forty-three hearing aid–dispensing audiologists rated a total of 32 randomized items by survey methodology. Results: Principle component analysis identified seven orthogonal statistical factors of importance. In rank order, these factors were Aptitude of the Brand, Image, Cost, Sales and Speed of Delivery, Exposure, Colleague Recommendations, and Contracts and Incentives. While it was hypothesized that differences among audiologists in the importance ratings of these factors would dictate their preference for a given brand, that was not our finding. Specifically, mean ratings for the six most important factors did not differ among audiologists preferring different brands. A statistically significant difference among audiologists preferring different brands was present, however, for one factor: Contracts and Incentives. Its assigned importance, though, was always lower than that for the other six factors. Conclusions: Although most audiologists have a preferred hearing aid brand, differences in the perceived importance of common factors attributed to brands do not largely determine preference for a particular brand.

Background: New and improved methods of feedback suppression are routinely introduced in hearing aids; however, comparisons of additional gain before feedback (AGBF) values across instruments are complicated by potential variability across subjects and measurement methods. Purpose: To examine the variability in AGBF values across individual listeners and an acoustic manikin. Research Design: A descriptive study of the reliability and variability of the AGBF measured within six commercially available feedback suppression (FS) algorithms using probe microphone techniques. Study Sample: Sixteen participants and an acoustic manikin. Results: The range of AGBF across the six FS algorithms was 0 to 15 dB, consistent with other recent studies. However, measures made in the participants ears and on the acoustic manikin within the same instrument suggest that across instrument comparisons of AGBF measured using acoustic manikin techniques may be misleading, especially when differences between hearing aids are small (i.e., less than 6 dB). Individual subject results also revealed considerable variability within the same FS algorithms. The range of AGBF values was as small as 7 dB and as large as 16 dB depending on the specific FS algorithm, suggesting that some models are much more robust than others. Conclusions: These results suggest caution when selecting FS algorithms clinically since different models can demonstrate similar AGBF when averaging across ears, but result in quite different AGBF values in a single individual ear.

Purpose: To evaluate sound quality preferences of participants wearing hearing aids with different strengths of nonlinear frequency compression (NFC) processing versus no NFC processing. Two analysis methods, one without and one with a qualifier as to the magnitude of preferences, were compared for their percent agreement to differentiate a small difference in perceived sound quality as a result of applied NFC processing. Research Design: A single-blind design was used with participants unaware of the presence or strength of NFC processing (independent variable). The National Acoustic Laboratories-Nonlinear 2 (NAL-NL2) prescription of amplification was chosen because audibility is intentionally not prescribed in the presence of larger sensorineural hearing loss thresholds. A lack of prescribed audibility, when present, was deemed an objective qualifier for NFC. NFC is known to improve the input bandwidth available to listeners when high-frequency audibility is not otherwise available and increasing strengths of NFC were examined. Experimental condition 3 (EC3) was stronger than the manufacturer default (EC2). More aggressive strengths (e.g., EC4 and EC5), however, were expected to include excessive distortion and even reduce the output bandwidth that had been prescribed as audible by NAL-NL2 (EC1). Study Sample: A total of 14 male Veterans with severe high-frequency sensorineural hearing loss. Data Collection and Analysis: Participant sound quality preference ratings (dependent variable) without a qualifier as to the magnitude of preference were analyzed based on binomial probability theory, as is traditional with paired comparison data. The ratings with a qualifier as to the magnitude of preference were analyzed based on the nonparametric statistic of the Wilcoxon signed rank test. Results: The binomial probability analysis method identified a sound quality preference as well as the nonparametric probability test method. As the strength of NFC increased, more participants preferred the EC with less NFC. Fourteen of 14 participants showed equal preference between EC1 and EC2 perhaps, in part, because EC2 showed no objective improvement in audibility for six of the 14 participants (42%). Thirteen of the 14 participants showed no preference between NAL-NL2 and EC3, but all participants had an objective improvement in audibility. With more NFC than EC3, more and more participants preferred the other EC with less NFC in the paired comparison. Conclusions: By referencing the recommended sensation levels of amplitude compression (e.g., NAL-NL2) in the ear canal of hearing aid wearers, the targeting of NFC parameters can likely be optimized with respect to improvements in effective audibility that may contribute to speech recognition without adversely impacting sound quality. After targeting of NFC parameters, providers can facilitate decisions about the use of NFC parameters (strengths of processing) via sound quality preference judgments using paired comparisons.

Background: Johnson and Dillon (2011) provided a model-based comparison of current generic hearing aid prescriptive methods for adults with hearing loss based on the attributes of speech intelligibility, loudness, and bandwidth. Purpose: This study compared the National Acoustic Laboratories—Non-linear 2 (NAL-NL2) and Cambridge Method for Loudness Equalization 2—High-Frequency (CAM2) prescriptive methods using adult participants with less high-frequency hearing loss than Johnson and Dillon (2011). Of study interest was quantification of prescribed audibility, speech intelligibility, and loudness. The preferences of participants for either NAL-NL2 or CAM2 and preferred deviations from prescribed settings are also reported. Research Design: Using a single-blind, counter-balanced, randomized design, preference judgments for the prescriptive methods with regard to sound quality of speech and music stimuli were obtained. Preferred gain adjustments from the prescription within the 4–10 kHz frequency range were also obtained from each participant. Speech intelligibility and loudness model calculations were completed on the prescribed and adjusted amplification. Study Sample: Fourteen male Veterans, whose average age was 65 yr and whose hearing sensitivity averaged normal to borderline normal through 1000 Hz sloping to a moderately severe sensorineural loss, served as participants. Data Collection and Analysis: Following a brief listening time (˜10 min), typical of an initial fitting visit, the participants made paired comparison of sound quality between the NAL-NL2 and CAM2 prescriptive settings. Participants were also asked to modify each prescription in the range of 4–10 kHz using an overall gain control and make subsequent comparisons of sound quality preference between prescriptive and adjusted settings. Participant preferences were examined with respect to quantitative analysis of loudness modeling, speech intelligibility modeling, and measured high-frequency bandwidth audibility. Results: Consistent with the lack of difference in predicted speech intelligibility between the two prescriptions, sound quality preferences on the basis of clarity were split across participants while some participants did not have a discernable preference. Considering sound quality judgments of pleasantness, the majority of participants preferred the sound quality of the NAL-NL2 (8 of 14) prescription instead of the CAM2 prescription (2 of 14). Four of the 14 participants showed no preference on the basis of pleasantness for either prescription. Individual subject preferences were supported by loudness modeling that indicated NAL-NL2 was the softer of the two prescriptions and CAM2 was the louder. CAM2 did provide more audibility to the higher frequencies (5–8 kHz) than NAL-NL2. Participants turned the 4–10 kHz gain recommendation of CAM2 lower, on average, by a significant amount of 4 dB when making adjustments while no significant adjustment was made to the initial NAL-NL2 recommendation. Conclusions: NAL-NL2 prescribed gains were more often preferred at the initial fitting by the majority of participating veterans. For those patients with preference for a louder fitting than NAL-NL2, CAM2 is a good alternative. When the participant adjustment from the prescription between 4 and 10 kHz exceeded 4 dB from either NAL-NL2 (2 of 14) or CAM2 (11 of 14), the participants demonstrated a later preference for that adjustment 69% of the time. These findings are viewed as limited evidence that some individuals may have a preference for high-frequency gain that differs from the starting prescription.

The effect of feedback reduction (FBR) systems on sound quality recorded from two commercially available hearing aids was evaluated using paired comparison judgments by 16 participants with mild to severe sloping hearing loss. These comparisons were made with the FBR systems on and off without audible feedback and while attempting to control for differences in gain and clinical fitting factors. Wilcoxon signed rank test analyses showed that the participants were unable to differentiate between signals that had been recorded with the FBR systems on and off within the same hearing aid. However, significant between-instrument differences in sound quality were identified. The results support the activation of the FFT-phase cancellation FBR systems evaluated herein without concern for a noticeable degradation of sound quality. Se evaluó el efecto de los sistemas de reducción de la retroalimentaciñn (FBR) sobre la calidad del sonido registrado por medio de dos auxiliaries auditivos disponibles comercialmente, utilizando juicios de comparación en pares, de 16 participantes con una hipocusia leve a moderada de pendiente pronunciada. Estas comparaciones se realizaron con los sistemas FBR apagados y encendidos, sin retroalimentación audible y tratando de controlar las diferencias en cuanto a ganancia y a factores clínicos de adaptación. Los análisis de pruebas de rango certificados por Wilcoxon mostraron que los participantes no podian diferenciar entre señales que habian sido registradas con los sistemas de FBR encendidos o apagados dentro del mismo auxiliar auditivo. Los resultados apoyan la activación de los sistemas de FBR de cancelación de fase FFT, aqui evaluados, sin preocupaciones por una degradación identificable en la calidad del sonido.

Speech understanding in noise is affected by both the energetic and informational masking components of the background noise. In addition, when the background noise is everyday speech, the relative contributions of the energetic and informational masking components to the overall difficulties in understanding speech are unclear. This study estimated informational masking effects, in conversational speech settings, on the speech understanding of persons with and without hearing loss. The benefits and limitations of amplification in settings containing both informational and energetic masking components were also explored. Speech recognition was assessed in the presence of two types of maskers (speech and noise) that varied in the amount of informational masking they were expected to produce. Persons with hearing loss were tested both unaided and aided. Study results suggest that background noise, consisting of individual talkers, results in both informational and energetic masking. In addition, the benefits of amplification are limited when the background noise contains both informational and energetic masking components.