Brent Edwards

NAL-NL2 (National Acoustic Laboratories Non-Linear 2) is an empirically grounded and clinically validated algorithm for hearing aid fitting. It was developed as the successor to NAL-NL1 to balance ...

To describe the development and evaluation of the NAL-NL3 Comfort in Noise Module; a new algorithm for determining hearing-aid gain that is part of the NAL-NL3 fitting system. Single-site multi-study design with each study and subsequent perceptual modelling informing refinements to module gain targets. Participants completed laboratory studies to investigate gain preferences and to evaluate the effect of the module on speech understanding in noise. Participants also completed real-world evaluations using a smartphone-based Ecological Momentary Assessment app with different brands of hearing aids. 83 adult hearing aid users with mild to severe hearing loss. The new module selectively reduced gain (compared with the NAL-NL3 Prescription) by imposing a limit on the total loudness. Iterative refinements led to progressive increases in user preferences favouring the new module over the NAL-NL3 Prescription in noise with respect to listening comfort. Laboratory-based testing identified no detrimental impact on speech perception in noise. Reducing the level of prescribed gain for hearing aid users in noise compared to in quiet improves comfort without significantly degrading speech understanding. This work supports the broader philosophy of the NAL-NL3 fitting system to provide specialised targets for different populations, situations and device technologies.

To investigate the extent to which Headphone Accommodations in Apple AirPods Pro attend to the hearing needs of individuals with normal audiograms who experience hearing difficulties in noisy envir...

Presbycusis, or age-related hearing loss, is the most common sensory deficit globally, and the biggest modifiable risk factor for a later dementia diagnosis. Despite its ubiquity, however, the primary pathology contributing to presbycusis is reportedly contentious, particularly the relative role of damage to the sensory outer hair cells compared to the stria vascularis, an important inner ear structure that maintains the ionic concentration of inner ear fluids that surround it. To determine what might be the “dogma” of the field regarding the primary pathology in presbycusis, we conducted an online Google survey ( https://forms.gle/GPreoePmRxBBkchc7 ) asking relevant respondents in the field their opinions on the matter. In Question (Q1), respondents were asked to rate ‘ in your opinion ’ from ‘least likely’ to ‘most likely’ (on a scale 1 to 4 [being ‘most likely’]) ‘ what is the primary pathology contributing to presbycusis? ’ in terms of ‘ damage to ’: i) the inner hair cells, ii) outer hair cells (OHCs), iii) spiral ganglion, iv) stria vascularis. The term ‘dogma’ suggests that the proportion of people in the field who believe that the main cause of presbycusis is damage to the stria vascularis is at least 50%. The results of our survey estimated this proportion to be 19/101 = 0.188 (95% CI [0.124 0.275]) and a two-sided test of the null hypothesis that this proportion is at least 0.5 was rejected ( p < 10 ⁻¹⁰ ). When it came to opining what ‘ other professionals in the field consider to be the primary pathology contributing to presbycusis ’ (Q2), the tendency to rank ‘damage to OHCs’ as being the primary pathology was 45%. S tria vascularis was least likely to be ranked 4 (11%) by professionals in the field opining about the beliefs of others. Even when ‘noise damage was excluded’ as a factor (Q3), the ‘most likely’ contributing factor to presbycusis was stated to be damage to the OHCs (42%). Our data suggest the dogma of the field is that damage to outer hair cells is the primary pathology in presbycusis.

Objectives: Current hearing aids have a limited bandwidth, which limits the intelligibility and quality of their output, and inhibits their uptake. Recent advances in signal processing, as well as novel methods of transduction, allow for a greater useable frequency range. Previous studies have shown a benefit for this extended bandwidth in consonant recognition, talker-sex identification, and separating sound sources. To explore whether there would be any direct spatial benefits to extending bandwidth, we used a dynamic localization method in a realistic situation. Design: Twenty-eight adult participants with minimal hearing loss reoriented themselves as quickly and accurately as comfortable to a new, off-axis near-field talker continuing a story in a background of far-field talkers of the same overall level in a simulated large room with common building materials. All stimuli were low-pass filtered at either 5 or 10 kHz on each trial. To further simulate current hearing aids, participants wore microphones above the pinnae and insert earphones adjusted to provide a linear, zero-gain response. Results: Each individual trajectory was recorded with infra-red motion-tracking and analyzed for accuracy, duration, start time, peak velocity, peak velocity time, complexity, reversals, and misorientations. Results across listeners showed a significant increase in peak velocity and significant decrease in start and peak velocity time with greater (10 kHz) bandwidth. Conclusions: These earlier, swifter orientations demonstrate spatial benefits beyond static localization accuracy in plausible conditions; extended bandwidth without pinna cues provided more salient cues in a realistic mixture of talkers.

There exist perceptible differences between sound emanating from a talker who faces and a talker who does not face a listener: Sound from a non-facing talker is attenuated and acquires a spectral tilt. The present study assessed the role that these facing-orientation cues play for speech perception. Digit identification for a frontal target talker in the presence of two spatially separated interfering talkers was measured for 10 normal-hearing (NH) and 11 hearing-impaired (HI) listeners. Overall-level differences and spectral tilts were reproduced by means of digital filtering and playback via loudspeakers. Both NH and HI listeners performed significantly better when the interfering talkers were simulated not to be facing them. Spectral tilts and level differences across talkers reduced target-interferer confusions. They enabled the NH listeners to sequentially stream the digits. This was not the case for the HI listeners, who showed smaller benefits, irrespective of whether they were aided by their own hearing aids or not. While hearing-aid amplification increased audibility, it may not have aided target-interferer segregation or target selection. The present results suggest that facing orientation cannot be neglected in the exploration of speech perception in multitalker situations.

The encoding mechanisms for amplitude modulation (AM) and frequency modulation (FM) were investigated using AM-FM discrimination tasks. In the first experiment, AM and FM were set at equally detectable levels within a trial, and discrimination thresholds were obtained adaptively in a 3IFC task. Here, AM-FM discrimination thresholds were considerably larger than both AM and FM detection thresholds. This is consistent with an encoding system whereby AM and FM are partially encoded by the same mechanism. In the second experiment, performance on AM-FM discrimination is measured with a fixed-level procedure. Psychometric functions obtained for a constant modulation depth of AM were nonmonotonic with FMs modulation index beta and each displayed a single minimum. The nonmonotonic nature of the functions is consistent with a model in which FM is encoded primarily with the same mechanism that encodes AM but also with a second mechanism, probably related to changes in instantaneous frequency, that is independent of the mechanism that extracts AM. The fact that minima in the discrimination psychometric functions increase from d' = 0 as beta increases indicates that the information encoded by the second mechanism becomes more detectable with increasing beta.