Hearing aid saturation and aided loudness discomfort.

Clinical measurements of the loudness discomfort level (LDL) are generally performed while the subject listens to a particular stimulus presented from an audiometer through headphones (AUD-HP). The assumption in clinical practice has been that the sound pressure level (SPL) corresponding to the sensation of loudness discomfort under AUD-HP conditions will be the same as the corresponding to LDL with the hearing aid. This assumption ignores the fact that the distortion produced by a saturating hearing aid could have an influence on the sensation of loudness. To examine these issues, 5 hearing-impaired subjects were each fit with four linear hearing aids, each having a different saturation sound pressure level (SSPL90). Probe-tube microphone measurements of ear canal SPL at LDL were made while the subjects listened to continuous discourse in quiet under aided and AUD-HP conditions. Also using continuous discourse, real-ear coherence measures were made at various output sound pressure levels near LDL. All four hearing aid types produced mean LDLs that were lower than those obtained under AUD-HP conditions. Those hearing aids with higher SSPL90 produced significantly higher LDLs than hearing aids with lower SSPL90. A significant negative correlation was found between real-ear SPL and real-ear coherence. Quality judgments made at LDL indicated that sound quality of hearing aids with higher SSPL90 was preferred to that of hearing aids with lower SSPL90. Possible fitting implications regarding the setting of SSPL90 from AUD-HP LDL measures are discussed.     

Duration, compression, and the aided loudness discomfort level

OBJECTIVE: The purpose of this investigation is to determine how the unaided and aided loudness discomfort level (LDL) varies with the duration of the input signal and whether the electroacoustic characteristics of compression circuits affect this relationship in a manner that may alter the listener's dynamic range for short duration sounds. DESIGN: Ten hearing-impaired and 20 normal-hearing listeners participated. LDLs were determined for noise bursts of durations ranging in six steps from 32 to 1024 msec, using a two-alternative, forced-choice adaptive tracking procedure in which input level varied until LDL was achieved. LDLs were also obtained for continuous discourse, using a clinical procedure. Subjects were also given the opportunity to self adjust maximum output SPL to their LDL using either output limiting or volume controls in response to fixed 90 dB SPL noise bursts. Testing was conducted unaided and with hearing aids representing two analog (output compression limiting, wide dynamic range compression) and four digital compression circuits. Primary circuit contrasts included compression threshold, compression ratio, attack time and the presence or absence of unity gain at high levels. RESULTS: For the unaided condition, both normal-hearing and hearing-impaired subjects showed increasing LDLs with decreasing signal duration. Under aided conditions, circuits with compression thresholds of 45 to 50 dB SPL and compression ratios of 2:1 produced LDL functions that were similar in slope to the impaired listener's unaided functions. Slopes were steeper when the attack time was slow (128 msec) than when it was fast (2 msec). Circuits with compression ratios of 8:1 produced flat LDL duration functions (i.e., a loss of duration-dependent effects). Similar duration-dependent LDL effects were also observed when subjects adjusted their own hearing aid output characteristics in response to 90 dB noise bursts. CONCLUSION: For the unaided condition, results suggest that normal-hearing and hearing-impaired listeners can tolerate short duration sounds at higher levels than long duration sounds, a finding that has implications for hearing aid design. Circuits that preserve the relationship between duration and LDL should allow brief phonemes to be presented at higher levels without discomfort than circuits that do not, possibly resulting in greater audibility or speech recognition. Current results suggest that circuits with low compression thresholds, low compression ratios, and slow attack times might accomplish this objective better than circuits with high compression thresholds, high compression ratios and fast attack times.     

Binaural loudness summation in the hearing impaired

Binaural loudness summation was measured using three different paradigms with 10 normally hearing and 20 bilaterally symmetrical high-frequency sensorineural hearing loss subjects. An adaptive paradigm and a loudness matching procedure measured summation at the lower and upper level of comfortable loudness and the loudness discomfort level (LDL). Monaural and binaural LDLs also were obtained with a clinical procedure designed to select maximum output of hearing aids. Stimuli for all three tasks consisted of 500- and 4000-Hz pure tones and a speech spectrum noise. Binaural summation increased with presentation level using the loudness matching procedure, with values in the 6-10 dB range. Summation decreased with level using the adaptive paradigm, and no summation was present with the clinical LDL task. The hearing-impaired subjects demonstrated binaural summation that was not significantly different from the normally hearing subjects. The results suggest that a bilaterally symmetrical sensorineural hearing loss does not affect binaural loudness summation. The monaural and binaural dynamic range widths were similar, and the LDL results suggest that binaural loudness summation may not be an important factor in selecting maximum output of hearing aids.     

Magnitude estimation of loudness. III: Performance of selected hearing aid users

Aided and unaided loudness functions for narrow-band noise stimuli were obtained from hearing-impaired listeners with a magnitude estimation procedure. A comparison of aided loudness functions with those obtained from normal-hearing subjects suggests that the hearing aids did not restore normal loudness relations among the spectral components of speech stimuli. Instead, aided loudness functions tend to reflect an interaction between the abnormal loudness growth that frequently characterizes sensorineural hearing loss and the saturation characteristics of the hearing aid.     

The objective estimation of loudness discomfort level using auditory brainstem evoked responses

The loudness discomfort level (LDL) is of importance in the fitting of hearing aids, but very young children are unable to provide a subjective judgement of LDL. Therefore the relationship between Jewett wave V latency and subjective loudness was investigated to ascertain if objective estimation of LDL is possible. ABR recordings were taken from 8 normally hearing subjects at the stimulus intensity corresponding to their LDL and at stimulus levels from 10 to 30 dB below this. The wave V latency/intensity function did not correlate well with the LDL. However, the slope of this function did correlate to a high degree and a predictive model of LDL was derived. Identical measurements were then taken from a sample of 12 cochlear-impaired subjects with a range of audiometric profiles. Their subjective LDLs could be predicted from the wave V latency function to an accuracy of +/- 5 dB, using the model derived from the normally-hearing subjects. This model appeared to be equally valid for all the degrees and profiles of hearing loss included in the sample and showed a closer relationship to LDL than did absolute wave V latency or estimates derived from the acoustic reflex.     

Various uncomfortable loudness thresholds, their correlation and use in general practice]

In the present study we examined the relationship of the loudness discomfort level LDL of different signals. We carried out measurements in 97 patients, all of whom suffered from a sensorineural hearing loss. The results showed almost no difference between the LDL of pure tones and narrow band noise. The LDL of broad band noise showed a good correlation to the LDL of 250 Hz. Only the LDL of monosyllables ranged at a higher SPL. For an up-to-date hearing aid fitting, all forms of LDL should be taken into consideration. This is especially necessary when using digital hearing aids.     

Fitting hearing aids using clinical prefitting speech measures: an evidence-based review

A systematic review of the literature addressed the question "Is there evidence of a good correlation between unaided prefitting speech measures and aided satisfaction on self-report measures?" This restricted question is only one of several possible questions related to speech measures and hearing aid fittings. The levels of evidence that were accepted included meta-analyses, randomized controlled trials, and nonrandomized intervention studies. Nearly 300 articles and book chapters were identified during the initial search; 220 were eliminated on the basis of their abstracts; and 80 papers and book chapters were reviewed in depth. Five studies met the criteria set forth in this review. No significant correlation between traditional unaided prefitting speech measures and aided satisfaction was found in any of the five studies. One of the studies showed a correlation between the results of a prefitting speech-in-noise test and self-reported aided satisfaction.     

The value of speech audiometry in hearing-aid rehabilitation.

The purpose of the present study was to evaluate the aided speech recognition score (SRS) as predictor of HA-use by relating aided SRS measurements to an extensive questionnaire describing the self-assessed use and benefit of an in-the-canal hearing aid (Danavox 131). A sample of 124 subjects with moderate, predominantly sensorineural hearing loss, 61 males and 63 females at a median age of 68 years, range 21-89, were included in the present investigation. The hearing-aid fitting was checked by insertion gain measurements based on the POGO amplification strategy, and the improvement in word recognition offered by the aid was expressed as the difference between the aided and unaided SRS measured in background noise (SRSN) (S/N = + 10 dB). Correlations between the aided SRSN and questions concerning the use and benefit of this type of hearing aid were performed after subdividing the sample into two age groups, below and above 70 years of age, in order to avoid differences in hearing aid gain which could be ascribed to an age effect. The results demonstrated that a prediction of the aided SRSN from the unaided SRSN can be performed. However, no significant correlation between the self-assessed time-related use, situational use or satisfaction and the aided SRSN could be found. It is concluded that aided SRSN with this clinical setup cannot predict the use or benefit of a modern hearing aid, though the measurements may, in combination with insertion gain measurements, prove useful for the comparison between different hearing aids, also in the individual person.     

Effect of hearing aids on hearing

We examined 114 patients aged 10 to 91 years with different kinds of hearing aids fitted in one ear only, the unaided ear acting as a control. They were re-examined several times during a period of follow-up from 1 to 9 years comparing the relative change in hearing due to hearing aid usage with various degrees of amplification of the aid. We compared the degree of hearing loss in the aided and unaided ear looking for evidence of a possible change in hearing related to the frequency of hearing aid usage in hours per day and in years, the maximum power output (MPO) and the gain of the aid. According to our findings there is no change in hearing between the aided and the unaided ear at the alpha = 0.05 probability level at least for 8 years. There is no effect of the long-term amplification of the hearing aid on deterioration of hearing comparing the aided ear and the unaided ear, but with high MPO of the aid, the patient should be followed up more frequently than with low MPO amplification.     

Aided loudness growth and satisfaction with everyday loudness perception in compression hearing aid users

The primary goal of this study was to examine the relationship between listeners' loudness growth and their satisfaction with loudness when wearing wide-dynamic-range compression (WDRC) hearing aids. An absolute-magnitude-estimate procedure was used to obtain listeners' unaided and aided loudness growth functions in response to a 500 and 2000 Hz warble tone. In general, listeners' unaided loudness growth functions were steeper than the average normal-hearing listeners' functions for both frequencies, and their aided loudness growth functions were shallower than their unaided functions. Loudness growth functions tended to be undercompressed for 500 Hz but overcompressed for 2000 Hz. The Profile of Aided Loudness (PAL) questionnaire was administered to determine listeners' loudness satisfaction in everyday listening situations. Most listeners were satisfied with their perception of soft, average, and loud environmental sounds, regardless of how well or not well their WDRC aids normalized their aided loudness growth.     

Unaided and aided performance with a directional open-fit hearing aid

Differences in performance between unaided and aided performance (omnidirectional and directional) were measured using an open-fit behind-the-ear (BTE) hearing aid. Twenty-six subjects without prior experience with amplification were fitted bilaterally using the manufacturer's recommended procedure. After wearing the hearing aids for one week, the fitting parameters were fine-tuned, based on subjective comments. Four weeks later, differences in performance between unaided and aided (omnidirectional and directional) were assessed by measuring reception thresholds for sentences (RTS in dB), using HINT sentences presented at 0 degrees with R-Space restaurant noise held constant at 65dBA and presented via eight loudspeakers set 45 degrees apart. In addition, the APHAB was administered to assess subjective impressions of the experimental aid. Results revealed that significant differences in RTS (in dB) were present between directional and omnidirectional performance, as well as directional and unaided performance. Aided omnidirectional performance, however, was not significantly different from unaided performance. These findings suggest for the hearing aids and experimental condition used in this study, a patient would require directional microphones in order to perform significantly better than unaided or aided with omnidirectional microphones, and that performance with an omnidirectional microphone would not be significantly better than unaided. Finally, the APHAB-aided scores were significantly better than unaided scores for the EC, BN, RV, and AV subscales indicating the subjects, on average, perceived the experimental aid to provide significantly better performance than unaided, and that aided performance was more aversive than unaided.     

Unaided and aided performance with a directional open-fit hearing aid

Differences in performance between unaided and aided performance (omnidirectional and directional) were measured using an open-fit behind-the-ear (BTE) hearing aid. Twenty-six subjects without prior experience with amplification were fitted bilaterally using the manufacturer's recommended procedure. After wearing the hearing aids for one week, the fitting parameters were fine-tuned, based on subjective comments. Four weeks later, differences in performance between unaided and aided (omnidirectional and directional) were assessed by measuring reception thresholds for sentences (RTS in dB), using HINT sentences presented at 0° with R-Space^TM restaurant noise held constant at 65dBA and presented via eight loudspeakers set 45° apart. In addition, the APHAB was administered to assess subjective impressions of the experimental aid.

Results revealed that significant differences in RTS (in dB) were present between directional and omnidirectional performance, as well as directional and unaided performance. Aided omnidirectional performance, however, was not significantly different from unaided performance. These findings suggest for the hearing aids and experimental condition used in this study, a patient would require directional microphones in order to perform significantly better than unaided or aided with omnidirectional microphones, and that performance with an omnidirectional microphone would not be significantly better than unaided. Finally, the APHAB-aided scores were significantly better than unaided scores for the EC, BN, RV, and AV subscales indicating the subjects, on average, perceived the experimental aid to provide significantly better performance than unaided, and that aided performance was more aversive than unaided.     

Acclimatization in first-time hearing aid users using three different fitting protocols

OBJECTIVE: To study auditory acclimatization and outcome in first time hearing aid users fitted with state of the art hearing aids as a function of different hearing aid fitting protocols. METHODS: Twenty-eight adult subjects participated in the study. Each subject was assigned to one of three study groups (named audiologist driven, AD; patient driven, PD; set-to-target, STT according to the fitting protocol used) and fitted with digital hearing aids (Bernafon Symbio). Speech recognition scores were measured in aided and unaided conditions over a 6-month period. RESULTS: Five subjects (three from the PD-group, two from the STT group) decided to withdraw from the study during the 6-month-study period, leaving a total of 23 complete data sets for analysis. Aided speech understanding increased significantly over this time period in all three groups. However, average hearing aid insertion gain changes were small over the same period. There were no statistically significant differences in aided or unaided speech recognition scores between the three groups after 2 weeks or after 6 months. On average, twice as many fine tunings of the hearing aids were requested by the patients in the AD and the STT group than in the PD group and subjects in the AD and STT group used their hearing aids approximately twice as much as subjects in the PD group. CONCLUSIONS: The substantial increase in speech intelligibility without significant changes of the insertion gain of the hearing aids over a 6-month period in all three groups suggests a significant acclimatization effect. Although the speech recognition with hearing aids did not differ significantly among the three study groups after 6 months, the lower average wearing time and the higher number of withdrawals from the study in the PD group suggest that the patients' needs are not adequately met. In terms of aided speech recognition scores and hearing aid wearing time the STT group and the AD group were very similar. However, comments of the patients and the higher rate of withdrawals in the STT group suggest an over-all advantage for the AD fitting protocol.     

Benefits of amplification for unaided speech discrimination in age-related hearing loss with flat type audiogram

ObjectiveThe present study aimed to investigate whether hearing aid use can induce improvement as acclimatization effect in unaided speech perception in patients with age-related hearing loss.MethodsFifty ears in 41 patients (age range: 65-91 years) diagnosed as age-related hearing loss were enrolled in this study. They used hearing aids for more than 8 hours per day. Unaided speech audiometry using 67-S Japanese monosyllabic word list was performed one or two years after the commencement of hearing aid use. The changes in the unaided speech discrimination score before and after the commencement of hearing aid use were analyzed. To investigate factors for improvement, the patients’ backgrounds in terms of age, sex, pure tone average, unaided maximum speech discrimination score, fitting period (one year/two years), fitting ear (bilateral/unilateral), audiogram type (flat-type/other-type), and the level of amplification were also analyzed.ResultsSignificant improvement in the unaided speech discrimination score after hearing aid use was seen only in the flat-type audiogram group. More than half of older patients in the flat-type audiogram group improved their unaided maximum speech discrimination score 10 % or more. The analysis of aided hearing thresholds revealed that the flat-type audiogram group had significantly lower thresholds of 3kHz and 4kHz than the other-type audiogram group. The age, sex, pure tone average, fitting period, fitting ear, functional gain were not influential factors for improvement. On the other hand, unaided maximum speech discrimination score before using hearing aid and aided hearing threshold at 4kHz had a negative correlation with improvement.ConclusionThe findings suggested that older patients with age-related hearing loss whose audiogram is a flat type can benefit from amplification as means of improving their unaided speech perception since flat-type audiogram can be more easily adjusted to sufficiently amplify speech sound at high frequencies. It should be considered that the potential for experience-dependent plasticity is retained even in older adults.     

Loudness discomfort levels in patients with conductive and mixed hearing loss

OBJECTIVE: The purpose of this study is to investigate the effects of conductive component on the loudness discomfort level (LDL) judgments. The relation between LDL value and the magnitude of air-bone gap in such subjects was also assessed. METHODS: LDLs were obtained from 100 ears of 50 hearing-impaired subjects. Twenty five subjects (50 ears) had either conductive or mixed hearing loss for both ears. Another 25 subjects (50 ears) with bilateral sensorineural hearing loss served as control. LDL measurements were performed using the method reported by Hawkins et al. in 1987. LDL data were plotted and analyzed as a function of hearing loss for three stimulus frequencies (0.5, 1.0 and 2 kHz). Also, LDL values were plotted as a function of air-bone gap in the conductive group. RESULTS: LDLs were significantly higher in subjects with conductive or mixed hearing loss for all three tested frequencies. There is a significant positive correlation between LDL value and the magnitude of air-bone gap for all three test frequencies. Considerable intersubject variability was found in LDLs obtained from subjects with conductive component which prevented the accurate prediction of LDLs from threshold data for such patients. CONCLUSION: The large intersubject variation in LDL data strongly suggests the need for individualized LDL measurements in patients with conductive or mixed hearing loss. Higher LDLs indicates that higher maximal power output can be prescribed for such patients without worrying about loudness intolerance.     

A multi-center,double blind clinical trial comparing benefit from three commonly used hearing aid circuits

OBJECTIVE: Although numerous studies have demonstrated that hearing aids provide significant benefit, carefully controlled, multi-center clinical trials have not been conducted. A multi-center clinical trial was conducted to compare the efficacy of three commonly used hearing aid circuits: peak clipping, compression limiting, and wide dynamic range compression. DESIGN: Patients (N = 360) with bilateral, sensorineural hearing loss were studied using a double blind, three-period, three-treatment crossover design. The patients were fit with each of three programmable hearing aid circuits. Outcome tests were administered in the unaided condition at baseline and then after 3 mo usage of each circuit, the tests were administered in both aided and unaided conditions. The outcome test battery included tests of speech recognition, sound quality and subjective scales of hearing aid benefit, including patients' overall rank-order rating of the three circuits. RESULTS: Each hearing aid circuit improved speech recognition markedly, with greater improvement observed for soft and conversationally loud speech in both quiet and noisy listening conditions. In addition, a significant reduction in the problems encountered in communication was observed. Some tests suggested that the two compression hearing aids provided a better listening experience than the peak clipping hearing aid. In the rank-order ratings, patients preferred the compression limiting hearing aid more frequently than the other two hearing aids. CONCLUSIONS: The three hearing aid circuits studied provide significant benefit both in quiet and in noisy listening situations. The two compression hearing aids appear to provide superior benefits compared to the linear circuit, although the differences between the hearing aids were smaller than the differences between unaided and aided conditions.