Lorienne M. Jenstad

Comparison of linear gain and wide dynamic range compression hearing aid circuits: aided speech perception measures.

OBJECTIVES The goal of this study was to test the theoretical advantages of a single-channel wide dynamic range compression (WDRC) circuit for speech intelligibility and loudness comfort for five speech spectra. DESIGN Twelve adolescents and young adults with moderate to severe hearing loss were fitted with the Siemens Viva 2 Pro behind-the-ear instrument set to DSL 4.0 targets for both linear gain and WDRC processing. Speech intelligibility was measured in the unaided, linear gain and WDRC conditions using two tasks in quiet: nonsense words and sentences. The items were digitally filtered to represent five speech spectra: average speech at 4 m, average speech at 1 m, own voice at ear level, classroom at 1 m, and shouted speech at 1 m. The subjects also rated the loudness of each hearing aid/speech spectrum combination using a categorical rating scale. RESULTS Both the linear gain and WDRC settings provided improved speech recognition relative to the unaided condition, and the two circuits resulted in equivalent performance for average speech input levels. On average, the WDRC aid resulted in high and uniform speech recognition scores across the five spectra. In contrast, the linear gain aid resulted in a lower recognition score for soft speech and shouted speech relative to that obtained with an average speech level. Analysis of individual speech recognition benefit scores revealed that 11 out of 12 subjects had equal or greater performance with the WDRC processing than the linear processing. Subjective loudness ratings in the linear gain condition were compatible with decreased sensation level for soft speech and loudness discomfort for shouted speech. CONCLUSIONS WDRC processing has potential applications in hearing aid fittings for listeners with moderate to severe hearing loss because it provides a consistently audible and comfortable signal across a wide range of listening conditions in quiet without the need for volume control adjustments.

Measuring the acoustic effects of compression amplification on speech in noise

This letter contains a description of an inversion technique that allows for separation of speech and noise and its application to quantifying the acoustic effects of wide-dynamic-range compression (WDRC) on speech in background noise. Three main findings are reported: that fast-acting WDRC further degrades signal-to-noise ratio; that the effective compression ratio is lower for speech in noise than speech in quiet; and that in contrast to speech in quiet, the amplitude envelope of speech is mostly unaffected when compressed in background noise.

Comparison of linear gain and wide dynamic range compression hearing aid circuits II : Aided loudness measures

Objectives: The goal of this study was to test the theoretical advantages of a single‐channel wide dynamic range compression (WDRC) circuit fitted using the DSL method for increased dynamic range and normalized loudness growth. Design: Ten adolescents and young adults with moderate to severe sensorineural hearing loss were fitted monaurally with the Siemens Viva 2 Pro behind‐the‐ear instrument set to DSL 4.0 targets for both linear gain and WDRC processing. Threshold, upper limit of comfort and loudness growth were measured in the unaided, linear gain and WDRC conditions for warble tones, environmental sounds and speech. Twelve adult listeners with normal hearing also were tested monaurally in the unaided condition to provide normative data for comparison purposes. Results: The WDRC hearing aid provided a greater input dynamic range than the linear circuit for all stimuli. The dynamic range was normalized for more subjects with the WDRC than the linear hearing aid. In addition, exponential loudness growth functions fitted to the loudness growth data showed that, on average, loudness growth was more normalized with the WDRC hearing aid fitted to DSL[i/o] targets than the linear hearing aid fitted to DSL[i/o] targets. Conclusions: WDRC processing, fitted using the DSL[i/o] method, has potential applications in hearing aid fittings for listeners with moderate to severe hearing loss because it provides an audible, comfortable and tolerable amplified signal across a wider range of inputs than linear gain processing, without the need for volume control adjustments.

Validity and Repeatability of Level-independent Hl to Spl Transforms

Objective: The purpose of this study was to evaluate the reliability and validity of the real ear to coupler difference (RECD) and the real ear to dial difference (REDD) in predicting real ear SPL (RESPL). Design: The RESPL, RECD, and REDD were measured in the right ear of 24 normal‐hearing subjects using probe microphone equipment and both insert and supra‐aural earphones. The phones and probe tube were removed and replaced, and the RECD and REDD were remeasured. Results: RESPL was predicted using the RECD for insert earphone data and the REDD for supra‐aural earphone data. Reliability estimates were calculated as the difference between test and retest values for the RECD and REDD. Validity estimates were calculated as the difference between measured and predicted RESPL. Results indicate that the RECD and REDD have equal and high reliability and validity in predicting RESPL. Conclusions: It is concluded that the RECD and REDD may be used as level‐independent HL to SPL transforms as a substitute for in situ audiometric procedures.

Effects Of Test Procedure On Individual Loudness Functions

Objective: To determine if measurement procedure effects occur for loudness perception data measured using a categorical rating scale. Design: Loudness data were obtained from 40 normal‐hearing adult volunteers, using 30 levels of pure tones at four frequencies (500, 1000, 2000, and 4000 Hz), with judgments made on a 9‐point categorical scale. Two presentation orders, random and sequential, were compared within subjects. Subjects were divided into two groups: one group heard only a single tone on every trial, whereas the other group was presented with a maximum level reference tone at the start of each trial. Results: A significant difference was found between loudness function exponents measured with the random and sequential presentation order of stimulus level. A significant difference was found between loudness function exponents measured when a high‐level referent was presented at the start of each trial. The sequential presentation order was further subdivided into ascending and descending runs, and the loudness function exponents for each run were examined separately. The results showed a significant interaction between sequence (ascending versus descending) and group. Conclusions: For normal‐hearing listeners, the procedure used to measure loudness has an effect on the loudness function exponent obtained. These results appear to be related to stimulus context effects. Loudness function exponents are smaller when the stimulus is preceded by a stimulus level greater than the level of the test tone. This occurred when a high‐level referent was presented at the start of each trial or when the stimulus level from the previous trial was greater than the test level, as in a descending run. It seems likely that the difference between loudness function exponents obtained with a random and sequential presentation of level can be explained by the same phenomenon. The significance of these results for hearing aid fittings in which loudness normalization is the goal is discussed.

Using multichannel wide-dynamic range compression in severely hearing-impaired listeners: Effects on speech recognition and quality

Objective: The objective of this study was to compare speech recognition across a sampling of amplification choices available for listeners with severe loss. This includes conventional options (linear with peak clipping and linear with compression limiting) and newer strategies (multichannel wide-dynamic range compression [WDRC]) theorized to better accommodate reduced dynamic range. A second objective was to compare speech quality across the same conditions using a paired-comparison test. Design: Participants were 13 adults with severe sensorineural hearing loss and a control group of seven adults with normal hearing. Test materials included consonant-vowel syllables (speech recognition) and sentences (speech quality). Four amplification conditions were included: peak clipping; compression limiting; two-channel WDRC; and three-channel WDRC, with overall audibility similar across conditions. In the WDRC conditions, the compression ratio was fixed at 3:1 in each channel. Consonant recognition was measured using a closed-set task, and speech quality was measured using a paired-comparison test. Results: For the listeners with severe loss, recognition and preference were lower for a three-channel WDRC system than for a compression limiting system. Specific errors were consistent with poorer transmission of amplitude envelope information by the multichannel WDRC systems. Conclusions: Under some conditions, the benefit of fast-acting, multichannel WDRC systems relative to more linear amplification strategies may be reduced in listeners with severe loss. Performance decrements with these systems are consistent with consequences of broader auditory filters.

Systematic review of barriers and facilitators to hearing aid uptake in older adults

A key element to success in the implementation of any screening for a health condition is that an effective treatment is available, accessible, and complied with. As the main treatment for adult-onset hearing loss is hearing aids, but only about 25% of those who could benefit from hearing aids actually use them (e.g., Kochkin, 2000; Meister, et al., 2008), it is necessary to identify the factors that affect compliance with this treatment recommendation. Several investigators have explored the barriers that may prevent those with hearing loss from choosing to purchase and use hearing aids to assist with their communication needs (e.g., Meister, et al., 2008). Among some of the barriers to hearing aid use are stigmatization, underestimation of hearing loss by the individual, coping strategies, personality factors, low trust in hearing aid benefit, cognitive and functional restrictions, cost, false expectations (Meister, et al., 2008), and communication styles (Helvik, et al., 2008). The goal of this study was to conduct a systematic review of the literature to identify the main barriers and facilitators to hearing aid (HA) uptake in healthy elderly (age 65+) non-users of hearing aids who have hearing loss (i.e., have been diagnosed as having hearing loss and had hearing aids recommended, but did not purchase aids).

Evaluation of the desired sensation level [input/output] algorithm for adults with hearing loss : The acceptable range for amplified conversational speech

Objectives: This study had two related purposes: first, to define the range of optimal ear canal levels of aided speech in both high frequency and low frequency regions for adults, using both subjective and objective definitions of optimal; and second, to determine whether a prescribed frequency response, such as that given by Desired Sensation Level [Input/Output], falls within the adult listeners optimal range. Design: Twenty-three adult listeners with mild to moderately severe sensorineural hearing loss were selected from a pool of research volunteers. They were fitted in the laboratory with the Siemens Signia hearing instrument and tested with 20 nominally different frequency responses. All advanced processing options of the hearing instrument were disabled. Subjective ratings of loudness and quality and objective measures of consonant identification were obtained for every frequency response. Results: These adult listeners had, on average, a 10 dB range of measured responses in both the low and the high frequencies that resulted in optimal performance on all the measurements. The range did not vary with degree or configuration of hearing loss, or previous hearing aid experience. Desired-Sensation-Level Input/Output targets were within the optimal range for the low frequencies, and 3 dB above the optimal range for the high frequencies. Conclusions: A range of aided ear canal frequency responses was determined within which adults with mild to moderately severe hearing loss performed optimally on both objective and subjective outcomes. Clinical implications of this finding include the following: prescriptive methods providing different targets may all result in optimal fittings; and a range of targets may be more appropriate than a single target when setting the frequency-gain characteristics of the hearing instrument.

Slow Cortical Potentials and Amplification—Part I: N1-P2 Measures

Slow cortical potentials (SCPs) are currently of great interest in the hearing aid fitting process for infants; however, there is conflicting evidence in the literature concerning the use of SCPs for this purpose. The current study investigated SCP amplitudes and latencies in young normal-hearing listeners in response to a 60 ms duration tonal stimulus (1000 Hz) presented at three intensities (30, 50, and 70 dB SPL) in aided and unaided conditions using three hearing aids (Analog, DigitalA, and DigitalB) with two gain settings (20 and 40 dB). Results showed that SCP amplitudes were smaller for the digital hearing aids compared with the analog hearing aid, and none of the hearing aids resulted in a reliable increase in response amplitude relative to the unaided across conditions. SCP latencies in analog conditions were not significantly different from latencies in the unaided conditions; however, both digital hearing aids resulted in significantly delayed SCP latencies. The results of the current study (as well as several previous studies) indicate that the SCP may not accurately reflect the amplified stimulus expected from the prescribed hearing aids. Thus, “aided-SCP” results must be interpreted with caution, and more research is required concerning possible clinical use of this technique.

Slow Cortical Potentials and Amplification—Part II: Acoustic Measures

In a previous study, we investigated slow cortical potential (SCP) N1-P2 amplitudes and N1 latencies in aided and unaided conditions, with the finding that despite being set to provide 20 or 40 dB of gain, none of the hearing aids resulted in a reliable increase in SCP response amplitude relative to the unaided (Marynewich et al., in press). The current study investigates the effects of hearing-aid processing on acoustic measures for two 1000-Hz tonal stimuli: short (60 ms) and long (757 ms), presented at three intensities (30, 50, 70 dB SPL) in aided and unaided conditions using three hearing aids (Analog, DigitalA, DigitalB) with two gain settings (20, 40 dB). Acoustic results indicate that gain achieved by the hearing aids, measured at 30 ms after stimulus onset, for both the short and long stimuli, was less than real-ear insertion gain measured with standard hearing aid test signals. Additionally, the digital hearing aids altered the rise time of the stimuli such that maximum gain was reached well past 30 ms after stimulus onset; rise times differed between the digital aids. These results indicate that aided SCP results must be cautiously interpreted and that further research is required for clinical application.