Exploration of Head Related Transfer Function and Environmental Sounds as a Means to Improve Auditory Scanning for Children Requiring Augmentative and Alternative Communication.

Many individuals who require augmentative and alternative communication (AAC) cannot directly select items on computer-based displays. Individuals who also have visual impairments may need to rely on sequential announcement of array choices in auditory scanning. The method is challenging and there is a lack of research to improve this access method. Two potential solutions were tested: using environmental sounds to represent items (e.g., the sound of a clock ticking for a clock) and providing spatial cues regarding the organization of items (e.g., presenting auditory information and altering temporal and spectral features so that sounds are heard as left, right, up, or down relative to each other). The individual and combined effects of these cues were tested with typically developing 3-year-old children. After collecting and validating a set of stimulus sounds, 24 children participated in a within-subjects design with four conditions (spoken word label only, associated environmental sound only, spoken word label with spatial information, associated environmental sound plus spatial information). Dependent measures included reaction time (RT) and accuracy. Results indicated that the use of sounds without any spatial cues revealed slower RTs than any other conditions. Also, sounds regardless of spatial cues led to less accurate scores than words.

Pspan: A New Tool for Assessing Pitch Temporal Processing and Patterning Capacity.

Purpose The purpose of this study was to evaluate whether merging the clinical pitch pattern test procedure with psychoacoustic adaptive methods would create a new tool feasible to capture individual differences in pitch temporal processing and patterning capacity of children and adults. Method Sixty-six individuals, young children (ages 10-12 years, n = 22), older children (ages 13-15 years, n = 23), and adults (ages 18-33 years, n = 21), were recruited and assigned to subgroups based on reported duration (years) of instrumental music instruction. Additional background information was collected in order to assess if the pitch temporal processing and patterning span developed, the Pspan, was sensitive to individual differences across participants. Results The evaluation of the Pspan task as a scale indicated good parallel reliability across runs assessed by Cronbach's alpha, and scores were normally distributed. Between-subjects analysis of variance indicated main effects for both age groups and music groups recruited for the study. A multiple regression analysis with the Pspan scores as the dependent variable found that 3 measures of music instruction, age in years, and paternal education were predictive of enhanced temporal processing and patterning capacity for pitch input. Conclusions The outcomes suggest that the Pspan task is a time-efficient data collection tool that is sensitive to the duration of instrumental music instruction, maturation, and paternal education. In addition, results indicate that the task is sensitive to age-related auditory temporal processing and patterning performance changes during adolescence when children are 10-15 years old.

Dominance of persistence over adaptation in forward masking.

Persistence of excitation and neural adaptation are competing theories proposed to explain the mechanisms underlying psychophysical forward masking. Previous research has been directed towards finding models that accurately describe the phenomenon but cannot account for the underlying explanation. The current study was designed to determine which theory best accounts for results obtained from behavioral gap duration adjustment tasks. Thirteen adults adjusted the gap within asymmetrical noise markers to be subjectively equal to the gap within equal-intensity-noise markers. The duration of the perceived gap between the asymmetrical markers is expected to vary depending on which theory dominates perception. The persistence of excitation mechanism would lead to longer duration gaps when the second noise marker is lower in intensity than the preceding. Neural adaptation would result in matched gaps that are shorter in duration when the second noise marker was lower in level. The outcome of our data analysis is consistent with the persistence of excitation as a dominant mechanism in forward masking.

High- and Low-Frequency Decrement Contribution to Spectral Enhancement.

PURPOSE: The relative benefit of a single, flanking, high- or low-frequency decrement was assessed to better understand properties of spectral enhancement that may aid in algorithm design. METHOD: Detection thresholds were measured for intensity increments applied to a narrow target band of frequencies embedded in a broadband signal while 400-Hz-wide, 9- or 12-dB-deep intensity decrements were placed above, below, or on both sides of the target band. A mono condition with no decrements was used as a control. Eight participants with normal hearing and 8 participants with hearing impairment took part in this experiment. RESULTS: Performance improved in the presence of decrements for both groups and was equivalent for both high- or low-frequency decrements. Comparison with individually measured auditory filters revealed that participants with normal hearing made use of energy cues available within these filters, whereas some participants with hearing impairment, despite improved increment detection, underutilized this information. CONCLUSION: Inclusion of a single, adjacent, high- or low-frequency decrement improved increment detection but not to the same extent as when decrements flanked both sides.

Effects of transient noise reduction algorithms on speech intelligibility and ratings of hearing aid users.

PURPOSE: The goal of this study was to assess the functional utility of transient noise reduction (TNR) algorithms available in hearing aids via speech intelligibility and user preferences. METHOD: Two pairs of hearing aids, 1 pair each from Siemens and Unitron, were programmed for 17 hearing impaired individuals after a hearing evaluation. Intelligibility was measured for each participant for sentences presented in quiet, with 2 types of transient noise, multitalker babble, and in a combination of each type of transient noise and multitalker babble. Each condition was tested with TNR activated and TNR deactivated in a counterbalanced, single-blinded format. Subjective ratings of overall speech understanding, comfort, and sound quality were obtained for each condition. RESULTS: A significant improvement in speech intelligibility was measured with the TNR activated when speech was presented in multitalker babble, in the presence of chair clang transient noises, and when combining these noises. Activation of the TNR algorithm did not result in significant improvements for any of the subjective ratings. CONCLUSIONS: While improvements were limited to certain conditions, specifically those with the chair clang transient and/or multitalker babble, TNR appears to offer an incremental step in improving the listening experience for hearing aid users.

Verification of in situ thresholds and integrated real-ear measurements.

BACKGROUND: Accurate prescriptive gain results in a more accurate fit, lower return rate in hearing aids, and increased patient satisfaction. In situ threshold measurements can be used to determine required gain. The Widex Corporation uses an in situ threshold measurement strategy, called the Sensogram. Real-ear measurements determine if prescriptive gain targets have been achieved. Starkey Laboratories introduced an integrated real-ear measurement system in their hearing aids. PURPOSE: To determine whether the responses obtained using the Widex Sensogram were equivalent to those obtained using current clinical threshold measurement methods. To determine the accuracy of the Starkey IREMS™ (Integrated Real Ear Measurement System) in measuring RECD (real-ear to coupler difference) values compared to a dedicated real-ear measurement system. RESEARCH DESIGN: A verification design was employed by comparing participant data measured from standard, benchmark equipment and procedures against new techniques offered by hearing-aid manufacturers. STUDY SAMPLE: A total of 20 participants participated in this study. Ten participants with sensorineural hearing loss were recruited from the Ohio University Hearing, Speech, and Language Clinic participated in the first experiment. Ten participants with normal hearing were recruited from the student population at Ohio University participated in both experiments. The normal-hearing group had thresholds of 15 dB HL or better at the octave frequencies of 250-8000 Hz. The hearing-impaired group had thresholds of varying degrees and configurations with thresholds equal to or poorer than 25 dB HL three-frequency pure-tone average. DATA COLLECTION AND ANALYSIS: The order of measurement method for both experiments was counterbalanced. In Experiment 1, thresholds obtained via the Widex Sensogram were compared to thresholds obtained for each participant using a clinical audiometer and ER-3A insert ear phones. In Experiment 2, RECD values obtained via the Starkey IREMS were compared to RECD values obtained via the Audioscan Verifit™. A repeated-measures analysis of variance (ANOVA) was used for statistical analysis, and a Fisher's LSD (least significant difference) was used as a post hoc analysis tool. RESULTS: A significant difference between Sensogram thresholds and conventional audiometric thresholds was found with the Sensogram method resulting in better threshold values at 0.5, 1.0, and 2.0 kHz for both groups. In Experiment 2, a significant difference between RECD values obtained by the Starkey IREMS and the Audioscan Verifit system was found with significant differences in RECD values found at 0.25, 0.5, 0.75, 1.5, 2.0, and 6.0 kHz. CONCLUSIONS: The Sensogram data differ significantly from traditional audiometry at several frequencies important for speech intelligibility. Real-ear measures are still required for verification of prescribed gain, however, calling into question any claims of shortened fitting time. The Starkey IREMS does perform real-ear measurements that vary significantly from benchmark equipment. These technologies represent a positive direction in prescribing accurate gain during hearing-aid fittings, but a stand-alone system is still the preferred method for real-ear measurements in hearing-aid fittings.

Effects of recurrent tonal information on auditory working memory for pitch.

This study ascertained the influence of repeating pitch information within an intervening tonal sequence upon the extent of interference for a pitch standard held within auditory working memory as measured by the difference limen for frequency (DLF). Standard and comparison tones were presented to subjects and same/different responses were obtained using a touch screen monitor and the DLF was measured using single interval adjustment matrix (SIAM) procedure [Kaernbach, C., 1990. A single-interval adjustment-matrix (SIAM) procedure for unbiased adaptive testing. J. Acoust. Soc. Am. 88, 2645-2655]. Estimates of the DLF were obtained in a control condition with a silent inter-comparison interval and three conditions containing intervening tones within the temporal gap between the standard and comparison stimuli. The presence of intervening stimuli produced a significant increase in the DLF when the intervening tonal sequence contained tones with pitches that differed from that of the standard (Int condition) as well as when the sequence contained a tone with a pitch identical to that of the comparison (RptCmp condition). Further, the DLFs obtained for RptCmp condition were significantly higher than those measured in the Int condition. The DLFs measured in the condition where the pitch of an intervening tone was identical to the standard were significantly lower than those for the Int and RptCmp condition, but did not differ from the DLFs for the control condition. These results indicate that either a release from or an increase in interference in auditory working memory for pitch can occur dependent upon the frequency relationships between of the standard, comparison, and intervening tones.

The role of temporal-masking patterns in the determination of subjective duration and loudness for ramped and damped sounds.

The association between temporal-masking patterns, duration, and loudness for broadband noises with ramped and damped envelopes was examined. Duration and loudness matches between the ramped and damped sounds differed significantly. Listeners perceived the ramped stimuli to be longer and louder than the damped stimuli, but the outcome was biased by the stimulus context. Next, temporal-masking patterns were measured for ramped- and damped-broadband noises using three (0.5, 1.5, and 4.0 kHz) 10 ms probe tones presented individually at various temporal delays. Predictions of subjective duration derived from masking results underpredicted the matching results. Loudness estimates derived from models that assume persistence of neural activity after stimulus offset [Glasberg B. R., and Moore, B. C. J. (2002). "A model of loudness applicable to time-varying sounds," J. Audio. Eng. Soc. 50, 331-341; Chalupper, J., and Fastl, H. (2002) "Dynamic loudness model (DLM) for normal and hearing-impaired listeners," Acust. Acta Acust. 88, 378-386] were greater for ramped sounds than for damped sounds and were close to the average results obtained via the matching task. Differences in simultaneous-masked thresholds for these stimuli could not account for the loudness-matching results. Decay suppression of the later occurring portion of the damped stimulus may account for the differences in perception due to the stimulus context; however, a parsimonious implementation of this process that accounts for both subjective duration and loudness judgments remains unclear.

Response method in audiometry.

PURPOSE: This study compared the speed, false-alarm rate, and participant preference of different response methods (raising a hand, pushing a response button, and giving an oral response) for measuring pure-tone thresholds. METHOD: Thirty female university students with normal hearing participated. Response method order was randomly assigned to 6 different groups. Air-conduction thresholds were measured twice for each response method for each participant in octave intervals between 250 Hz and 8000 Hz. The 2nd threshold measurements were performed on a different day but within 2 weeks of the initial measurement. RESULTS: A significant difference was found when comparing the amount of time necessary to complete the test for each response method. On average, it took about 1 min less when using the push-button response than when using hand-raise or verbal response methods. There was also a significant participant preference for using the response button. No significant difference between response method for threshold level and number of false positives was found. CONCLUSION: This study supports the use of the response button when measuring auditory thresholds for young adults with normal hearing.

Response growth using a low-frequency suppressor.

Numerous psychophysical studies on two-tone suppression have been carried out. More recently, researchers have attempted to relate the magnitude of suppression to the level of suppressee. [Wojtczak, M., Viemeister, N.F., 2005. Psychophysical response growth under suppression. In: Pressnitzer, D., de Cheveigne, A., McAdams, S., Collet, L. (Eds.), Auditory Signal Processing: Physiology, Psychoaccoustics, and Models. Springer, New York, pp. 67-74] demonstrated that the magnitude of suppression for a higher-frequency, fixed-level suppressor decreases with increasing level of the suppressee. This suggests a linearization of the basilar membrane response in presence of a high-frequency suppressor. The present study expands these results to a low-frequency suppressor of varying intensity levels. Detection of a 10-ms, 4.0-kHz probe was measured under different forward-masking conditions: one with a 200-ms, 4.0-kHz masker (suppressee) presented with no suppressor and another with the same masker paired with a 2.2-kHz, 200-ms suppressor. The 4.0-kHz masker level was varied adaptively and a range of probe levels was used to measure the growth of suppression. Results indicate that (1) the magnitude of suppression increases with increasing suppressor level and (2) generally, the probe level was not related to the magnitude of suppression.

Stapedial reflex and ears with high static acoustic admittance.

PURPOSE: To evaluate modified acoustic reflex diagnostic protocols for a group of individuals (n = 9) with high peak compensated static acoustic admittance (Y(tm)) tympanograms. METHOD: A modified procedure designed to improve acoustic stapedius reflex threshold (ASRT) measurements in individuals with high-admittance tympanograms was employed in both an experimental and a control group. ASRTs were measured at 0.5, 1.0, and 2.0 kHz, ipsilateral and contralateral. Measurements were obtained within each condition for 7 ear canal pressures that were set to 0, +/-50, +/-100, and +/-150 daPa (relative to tympanometric peak pressure [TPP]). RESULTS: Though measuring ASRTs at -50 daPa (relative to TPP) in the high-admittance and normal groups did not result in significantly better thresholds than at TPP, the absent reflex rate was reduced when the ear canal pressure was changed by -50 daPa during ASRT measurements. CONCLUSIONS: Based on this sample, it is suggested that a patient presenting with high peak compensated static acoustic admittance (peak Y(tm) > or = 2.1 mmho) undergo ASRT evaluation with the ear canal pressure set to -50 daPa (relative to TPP).

Auditory filters and the benefit measured from spectral enhancement.

Algorithms designed to improve speech intelligibility for those with sensorineural hearing loss (SNHL) by enhancing peaks in a spectrum have had limited success. Since testing of such algorithms cannot separate the theory of the design from the implementation itself, the contribution of each of these potentially limiting factors is not clear. Therefore, psychophysical paradigms were used to test subjects with either normal hearing or SNHL in detection tasks using well controlled stimuli to predict and assess the limits in performance gain from a spectrally enhancing algorithm. A group of normal-hearing (NH) and hearing-impaired (HI) subjects listened in two experiments: auditory filter measurements and detection of incremented harmonics in a harmonic spectrum. The results show that NH and HI subjects have an improved ability to detect incremented harmonics when there are spectral decrements surrounding the increment. Various decrement widths and depths were compared against subjects' equivalent rectangular bandwidths (ERBs). NH subjects effectively used the available energy cue in their auditory filters. Some HI subjects, while showing significant improvements, underutilized the energy reduction in their auditory filters.

Spontaneous recovery of sudden sensorineural hearing loss: possible association with autoimmune disorders.

A 46-year-old white male diagnosed with systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS) was seen for audiological testing 15 minutes following a sudden onset hearing loss in the right ear. The test battery included pure-tone audiometry, word-recognition testing, speech-recognition threshold (SRT) testing, immittance testing, and distortion-product otoacoustic emissions (DPOAE) testing. Testing revealed a sensorineural hearing loss in the right ear. Shortly after testing, the patient indicated that his condition had improved. Testing was repeated, and the second round of tests revealed normal hearing in both ears. Four days later, a follow-up test again indicated normal hearing in both ears. Possible connections of this brief occurrence of idiopathic hearing loss with the patient's medical conditions are discussed. Specifically, symptoms were consistent with a transient ischemic attack (TIA) affecting his right cochlea in the stria vascularis region, resulting in a temporary, sensorineural hearing loss. No residual effects were observed clinically.

A psychophysical evaluation of spectral enhancement.

Listeners with sensorineural hearing loss have well-documented elevated hearing thresholds; reduced auditory dynamic ranges; and reduced spectral (or frequency) resolution that may reduce speech intelligibility, especially in the presence of competing sounds. Amplification and amplitude compression partially compensate for elevated thresholds and reduced dynamic ranges but do not remediate the loss in spectral resolution. Spectral-enhancement processing algorithms have been developed that putatively compensate for decreased spectral resolution by increasing the spectral contrast, or the peak-to-trough ratio, of the speech spectrum. Several implementations have been proposed, with mixed success. It is unclear whether the lack of strong success was due to specific implementation parameters or whether the concept of spectral enhancement is fundamentally flawed. The goal of this study was to resolve this ambiguity by testing the effects of spectral enhancement on detection and discrimination of simple, well-defined signals. To that end, groups of normal-hearing (NH) and hearing-impaired (HI) participants listened in 2 psychophysical experiments, including detection and frequency discrimination of narrowband noise signals in the presence of broadband noise. The NH and HI listeners showed an improved ability to detect and discriminate narrowband increments when there were spectral decrements (notches) surrounding the narrowband signals. Spectral enhancements restored increment detection thresholds to within the normal range when both energy and spectral-profile cues were available to listeners. When only spectral-profile cues were available for frequency discrimination tasks, performance improved for HI listeners, but not all HI listeners reached normal levels of discrimination. These results suggest that listeners are able to take advantage of the local improvement in signal-to-noise ratio provided by the spectral decrements.