Level discrimination of speech sounds by hearing-impaired individuals with and without hearing amplification

Objectives: The current study was designed to see how hearing-impaired individuals judge level differences between speech sounds with and without hearing amplification. It was hypothesized that hearing aid compression should adversely affect the user's ability to judge level differences. Design: Thirty-eight hearing-impaired participants performed an adaptive tracking procedure to determine their level-discrimination thresholds for different word and sentence tokens, as well as speech-spectrum noise, with and without their hearing aids. Eight normal-hearing participants performed the same task for comparison. Results: Level discrimination for different word and sentence tokens was more difficult than the discrimination of stationary noises. Word level discrimination was significantly more difficult than sentence level discrimination. There were no significant differences, however, between mean performance with and without hearing aids and no correlations between performance and various hearing aid measurements. Conclusions: There is a clear difficulty in judging the level differences between words or sentences relative to differences between broadband noises, but this difficulty was found for both hearing-impaired and normal-hearing individuals and had no relation to hearing aid compression measures. The lack of a clear adverse effect of hearing aid compression on level discrimination is suggested to be due to the low effective compression ratios of currently fit hearing aids

The Sensitivity of Hearing-Impaired Adults to Acoustic Attributes in Simulated Rooms

In previous studies we have shown that older hearing-impaired individuals are relatively insensitive to changes in the apparent width of broadband noises when those width changes were based on differences in interaural coherence [W. Whitmer, B. Seeber and M. Akeroyd, J. Acoust. Soc. Am. 132, 369-379 (2012)]. This insensitivity has been linked to senescent difficulties in resolving binaural fine-structure differences. It is therefore possible that interaural coherence, despite its widespread use, may not be the best acoustic surrogate of spatial perception for the aged and impaired. To test this, we simulated the room impulse responses for various acoustic scenarios with differing coherence and lateral (energy) fraction attributes using room modelling software (ODEON). Bilaterally impaired adult participants were asked to sketch the perceived size of speech tokens and musical excerpts that were convolved with these impulse responses and presented to them in a sound-dampened enclosure through a 24-loudspeaker array. Participants' binaural acuity was also measured using an interaural phase discrimination task. Corroborating our previous findings, the results showed less sensitivity to interaural coherence in the auditory source width judgments of older hearing-impaired individuals, indicating that alternate acoustic measurements in the design of spaces for the elderly may be necessary

Recording and Analysis of Head Movements, Interaural Level and Time Differences in Rooms and Real-World Listening Scenarios

The science of how we use interaural differences to localise sounds has been studied for over a century and in many ways is well understood. But in many of these psychophysical experiments listeners are required to keep their head still, as head movements cause changes in interaural level and time differences (ILD and ITD respectively). But a fixed head is unrealistic. Here we report an analysis of the actual ILDs and ITDs that occur as people naturally move and relate them to gyroscope measurements of the actual motion. We used recordings of binaural signals in a number of rooms and listening scenarios (home, office, busy street etc). The listener's head movements were also recorded in synchrony with the audio, using a micro-electromechanical gyroscope. We calculated the instantaneous ILD and ITDs and analysed them over time and frequency, comparing them with measurements of head movements. The results showed that instantaneous ITDs were widely distributed across time and frequency in some multi-source environments while ILDs were less widely distributed. The type of listening environment affected head motion. These findings suggest a complex interaction between interaural cues, egocentric head movement and the identification of sound sources in real-world listening situations

A comprehensive survey of hearing questionnaires: how many are there, what do they measure, and how have they been validated?

The self-report questionnaire is a popular tool for measuring outcomes in trials of interventions for hearing impairment. Many have been designed over the last fifty years, and there is no single standard questionnaire that is widely accepted and used. We felt it would be a valuable resource to have a comprehensive collection of all adult hearing-loss questionnaires (excluding those wholly devoted to tinnitus, children, or cochlear implants) and to survey their degree of validation. We collated copies of every published hearing difficulty questionnaire that we could find. The search was primarily done by iterative reference searching. Questionnaire topics were obtained by mapping the text of each questionnaire onto a set of categories; reports of validation methods were taken from the primary paper(s) on each questionnaire. In total we found 139 hearing-specific questionnaires (though many others were found that were primarily about something else). Though not formally systematic, we believe that we have included every questionnaire that is important, most of those of some notice, and a fair fraction of those obscure. We classified 111 as “primary” and the remaining 28 as “contractions”, being shortened versions of a primary without any new questions. In total, there were 3618 items across all the primary questionnaires. The median number of items per questionnaire was 20; the maximum was 158. Across all items, about one third were concerned with the person’s own hearing, another third with the repercussions of it, and about a quarter with hearing aids. There was a wide range in validation methods, from only using items chosen statistically from wider pools and with formal validation against independent measures of clinical outcomes, to just reporting a correlation with an audiogram measure of hearing loss. The “state of play” of the field of hearing questionnaires will be discussed

Discrimination of gain increments in speech

During a hearing-aid fitting, the gain applied across frequencies is often adjusted from an initial prescription in order to meet individual needs and preferences. These gain adjustments in one or more frequency bands are commonly verified using speech in quiet (e.g., the clinician’s own voice). Such adjustments may be unreliable and inefficient if they are not discriminable. To examine what adjustments are discriminable when made to speech, the current study measured the just-noticeable differences (JNDs) for gain increments in male, single-talker sentences. Sentences were presented with prescribed gains to the better ears of 41 hearing-impaired listeners. JNDs were measured at d' of 1 for octave-band, dual-octave-band and broadband increments using a fixed-level, same-different task. The JNDs and interquartile ranges (IQRs) for 0.25, 1 and 4 kHz octave-band increments were 6.4 [4.0-7.8], 6.7 [4.6-9.1] and 9.6 [7.3-12.4] dB respectively. The JNDs and IQRs for low, mid and high-frequency dual-octave-band increments were 3.7 [2.5-4.6], 3.8 [2.9-4.7] and 6.8 [4.7-9.1] dB, respectively. The JND for broadband increments was 2.0 [1.5-2.7] dB. High-frequency dual-octave-band JNDs were positively correlated with high-frequency pure-tone thresholds and sensation levels, suggesting an effect of audibility for this condition. All other JNDs were independent of pure-tone threshold and sensation level. JNDs were independent of age and hearing-aid experience. These results suggest using large initial adjustments when using short sentences in a hearing-aid fitting to ensure patient focus, followed by smaller subsequent adjustments, if necessary, to ensure audibility, comfort and stability

The effect of hearing aid microphone mode on performance in an auditory orienting task

OBJECTIVES: Although directional microphones on a hearing aid provide a signal-to-noise ratio benefit in a noisy background, the amount of benefit is dependent on how close the signal of interest is to the front of the user. It is assumed that when the signal of interest is off-axis, users can reorient themselves to the signal to make use of the directional microphones to improve signal-to-noise ratio. The present study tested this assumption by measuring the head-orienting behavior of bilaterally fit hearing-impaired individuals with their microphones set to omnidirectional and directional modes. The authors hypothesized that listeners using directional microphones would have greater difficulty in rapidly and accurately orienting to off-axis signals than they would when using omnidirectional microphones. DESIGN: The authors instructed hearing-impaired individuals to turn and face a female talker in simultaneous surrounding male-talker babble. Participants pressed a button when they felt they were accurately oriented in the direction of the female talker. Participants completed three blocks of trials with their hearing aids in omnidirectional mode and three blocks in directional mode, with mode order randomized. Using a Vicon motion tracking system, the authors measured head position and computed fixation error, fixation latency, trajectory complexity, and proportion of misorientations. RESULTS: Results showed that for larger off-axis target angles, listeners using directional microphones took longer to reach their targets than they did when using omnidirectional microphones, although they were just as accurate. They also used more complex movements and frequently made initial turns in the wrong direction. For smaller off-axis target angles, this pattern was reversed, and listeners using directional microphones oriented more quickly and smoothly to the targets than when using omnidirectional microphones. CONCLUSIONS: The authors argue that an increase in movement complexity indicates a switch from a simple orienting movement to a search behavior. For the most off-axis target angles, listeners using directional microphones appear to not know which direction to turn, so they pick a direction at random and simply rotate their heads until the signal becomes more audible. The changes in fixation latency and head orientation trajectories suggest that the decrease in off-axis audibility is a primary concern in the use of directional microphones, and listeners could experience a loss of initial target speech while turning toward a new signal of interest. If hearing-aid users are to receive maximum directional benefit in noisy environments, both adaptive directionality in hearing aids and clinical advice on using directional microphones should take head movement and orientation behavior into account

The effect of tonsillectomy on the morbidity from recurrent tonsillitis

Background Tonsillitis is a common condition with an incidence in UK general practice of 37 per 1000 population a year.1 Recurrent tonsillitis results in significant morbidity and impacts on individuals’ quality of life. This study assesses the morbidity and quality of life of adults with recurrent tonsillitis, and the impact of surgical intervention on their health state. Objectives To describe disease-specific and global quality of life for adults with recurrent tonsillitis 6 months after tonsillectomy, using two instruments: the health impact of throat problems (HITP) and EuroQol-visual analogue scale questionnaire. To assess the overall health benefit from tonsillectomy as an intervention using the Glasgow Benefit Inventory (GBI). To assess potential predictors of tonsillectomy benefit. Design A prospective, observational cohort audit of patients who have fulfilled Scottish Intercollegiate Guideline Network (SIGN) criteria for tonsillectomy.2 Setting Secondary care, teaching hospital. Participants Seventy patients (57 female), median age 20 years (range 13-41). Results Median preoperative HITP was 47 (range 15-67), compared to 4 (0-72), (P<.001) 6 months following surgery. Median HITP difference was 39.5 (range −20 to 75). There was no significant change in global Quality of Life. Median overall 6 months GBI was 39 (−3 to 100). Patients had an average of 27 episodes of tonsillitis over a period of seven years before “achieving” tonsillectomy, significantly higher than the SIGN guidelines of three or more episodes over three years. Conclusions Recurrent tonsillitis causes a poor disease-specific quality of life. Patients experienced a median of three episodes per year for seven years before tonsillectomy. Following tonsillectomy, patients had a significant improvement in their disease-specific quality of life. Baseline HITP significantly improved after tonsillectomy. The results imply patients with recurrent acute tonsillitis may be experiencing undue dela

Spatial hearing and hearing aids

The questions of whether hearing-impaired listeners are also impaired for the localization of sounds and what benefits hearing aids can provide are important for understanding the wider effects of hearing impairment. We review here 29 studies published since 1983 that have measured acuity for changes in the horizontal-plane direction of sound sources. Where possible, performance is quantified by the root-mean-square error in degrees. Overall, the results demonstrate that (1) hearing-impaired listeners have poorer left–right discrimination than normal-hearing listeners, by 5° when averaged across all experiments, although there is considerable variation across listeners and experiments; (2) hearing aids lead to a deficit of just 1°; (3) directional microphones relative to omnidirectional microphones give a deficit of 3°; (4) custom form factors have no effect relative to the behind-the-ear style; (5) acclimatization gives a benefit of 1°; (6) a unilateral fitting results in a localization deficit of 5° on average, and the deficit can reach nearly 20°; and (7) hearing-impaired listeners are particularly prone to front–back confusions; hearing aids do nothing to reduce these and sometimes increase them. Although statistically significant effects of hearing aids on localization have been reported, few of them are generalizable, as they often occurred for just some source directions, stimuli, hearing aid features, or groups of listeners. Overall, there is no experimental evidence for a benefit from hearing aids for directional acuity

The perceptual limitations of troubleshooting hearing-aids based on patients’ descriptions

ObjectivesHearing-aid frequency-gain responses are routinely adjusted by clinicians to patient preferences and descriptions. This study measured the minimum gain adjustments required to elicit preferences, and the assignment of descriptors to gain adjustments, to perceptually evaluate description-based troubleshooting.DesignParticipants judged whether short sentences with ±0-12 dB gain adjustments in one of three frequency bands were “better”, “worse” or “no different” from the same sentence at their individual real-ear or prescribed gain. If judged “better” or “worse”, participants were then asked to assign one of six common sound-quality descriptors to their preference.Study SampleThirty-two adults (aged 51-75 years) all with hearing-aid experience.ResultsMedian preference thresholds, the minimum gain adjustments to elicit “better” or “worse” judgments, ranged from 4-12 dB, increasing with frequency. There was some between-participant agreement in preferences: participants generally preferred greater low-frequency gain. Within-participant reliability for preferences was moderate. There was, however, little between-participant agreement in descriptor selection for gain adjustments. Furthermore, within-participant reliability for descriptor selection was weak.ConclusionsThe scale of gain adjustments necessary to elicit preferences, along with the low agreement and reliability in descriptors for these adjustments questions the efficiency and efficacy of current description-based troubleshooting, especially with short speech stimuli

Biomimetic direction of arrival estimation for resolving front-back confusions in hearing aids

Sound sources at the same angle in front or behind a two-microphone array (e.g., bilateral hearing aids) produce the same time delay and two estimates for the direction of arrival: A front-back confusion. The auditory system can resolve this issue using head movements. To resolve front-back confusion for hearing-aid algorithms, head movement was measured using an inertial sensor. Successive time-delay estimates between the microphones are shifted clockwise and counterclockwise by the head movement between estimates and aggregated in two histograms. The histogram with the largest peak after multiple estimates predicted the correct hemifield for the source, eliminating the front-back confusions