Auditory Science Research Articles

The upper frequency limit of hearing is negatively correlated with head size in mammals

My favorite graph in auditory science shows that the upper frequency limit of hearing is negatively correlated with the head size in mammals (defined as the functional interaural distance). It shows that sound localization is such an important requirement for survival that it was probably the driving factor that led to all the mammalian ear specializations required for the sensitivity and discrimination of high-frequency sounds. This was shown across 60 terrestrial mammals in several publications by Heffner and Heffner (e.g., 2016 Acoust Today). The wavelength of sound is inversely proportional to frequency. As frequency increases and the wavelength becomes shorter than a given head size, there is a level difference between the two ears. As head size decreases for smaller animals like mice, higher frequency hearing was required to exploit interaural spectral intensity differences needed to localize sounds. In order support such high frequency capabilities, the pinna, the middle ear, cochlea, and central mechanisms evolved together. Heffner and Heffner (1992) proposed that another important function of sound localization is to direct the eyes to the sound source and show a beautiful relationship between auditory and visual acuity. Hearing aids are limited to 3–4 kHz and, thus, do not make use of these high frequency capabilities. I have successfully argued to investors the importance of making wideband hearing aids and this culminated in the Earlens light driven wideband hearing aid (Levy et al. 2015 and Puria et al. 2016).

Changing Knowledge, Principles, and Technology in Contemporary Clinical Audiological Practice: A Narrative Review.

The field of audiology as a collection of auditory science knowledge, research, and clinical methods, technologies, and practices has seen great changes. A deeper understanding of psychological, cognitive, and behavioural interactions has led to a growing range of variables of interest to measure and track in diagnostic and rehabilitative processes. Technology-led changes to clinical practices, including teleaudiology, have heralded a call to action in order to recognise the role and impact of autonomy and agency on clinical practice, engagement, and outcomes. Advances in and new information on loudness models, tinnitus, psychoacoustics, deep neural networks, machine learning, predictive and adaptive algorithms, and PREMs/PROMs have enabled innovations in technology to revolutionise clinical principles and practices for the following: (i) assessment, (ii) fitting and programming of hearing devices, and (iii) rehabilitation. This narrative review will consider how the rise of teleaudiology as a growing and increasingly fundamental element of contemporary adult audiological practice has affected the principles and practices of audiology based on a new era of knowledge and capability. What areas of knowledge have grown? How has new knowledge shifted the priorities in clinical audiology? What technological innovations have been combined with these to change clinical practices? Above all, where is hearing loss now consequently positioned in its journey as a field of health and medicine?

Exploring the Performance of ChatGPT-4 in the Taiwan Audiologist Qualification Examination: Preliminary Observational Study Highlighting the Potential of AI Chatbots in Hearing Care.

Artificial intelligence (AI) chatbots, such as ChatGPT-4, have shown immense potential for application across various aspects of medicine, including medical education, clinical practice, and research. This study aimed to evaluate the performance of ChatGPT-4 in the 2023 Taiwan Audiologist Qualification Examination, thereby preliminarily exploring the potential utility of AI chatbots in the fields of audiology and hearing care services. ChatGPT-4 was tasked to provide answers and reasoning for the 2023 Taiwan Audiologist Qualification Examination. The examination encompassed six subjects: (1) basic auditory science, (2) behavioral audiology, (3) electrophysiological audiology, (4) principles and practice of hearing devices, (5) health and rehabilitation of the auditory and balance systems, and (6) auditory and speech communication disorders (including professional ethics). Each subject included 50 multiple-choice questions, with the exception of behavioral audiology, which had 49 questions, amounting to a total of 299 questions. The correct answer rates across the 6 subjects were as follows: 88% for basic auditory science, 63% for behavioral audiology, 58% for electrophysiological audiology, 72% for principles and practice of hearing devices, 80% for health and rehabilitation of the auditory and balance systems, and 86% for auditory and speech communication disorders (including professional ethics). The overall accuracy rate for the 299 questions was 75%, which surpasses the examination's passing criteria of an average 60% accuracy rate across all subjects. A comprehensive review of ChatGPT-4's responses indicated that incorrect answers were predominantly due to information errors. ChatGPT-4 demonstrated a robust performance in the Taiwan Audiologist Qualification Examination, showcasing effective logical reasoning skills. Our results suggest that with enhanced information accuracy, ChatGPT-4's performance could be further improved. This study indicates significant potential for the application of AI chatbots in audiology and hearing care services.

Predicting speech-in-speech recognition: Short-term audibility and spatial separation.

Quantifying the factors that predict variability in speech-in-speech recognition represents a fundamental challenge in auditory science. Stimulus factors associated with energetic and informational masking (IM) modulate variability in speech-in-speech recognition, but energetic effects can be difficult to estimate in spectro-temporally dynamic speech maskers. The current experiment characterized the effects of short-term audibility and differences in target and masker location (or perceived location) on the horizontal plane for sentence recognition in two-talker speech. Thirty young adults with normal hearing (NH) participated. Speech reception thresholds and keyword recognition at a fixed signal-to-noise ratio (SNR) were measured in each spatial condition. Short-term audibility for each keyword was quantified using a glimpsing model. Results revealed that speech-in-speech recognition depended on the proportion of audible glimpses available in the target + masker keyword stimulus in each spatial condition, even across stimuli presented at a fixed global SNR. Short-term audibility requirements were greater for colocated than spatially separated speech-in-speech recognition, and keyword recognition improved more rapidly as a function of increases in target audibility with spatial separation. Results indicate that spatial cues enhance glimpsing efficiency in competing speech for young adults with NH and provide a quantitative framework for estimating IM for speech-in-speech recognition in different spatial configurations.

Streamlining experiment design in cognitive hearing science using OpenSesame

Auditory science increasingly builds on concepts and testing paradigms originated in behavioral psychology and cognitive neuroscience – an evolution of which the resulting discipline is now known as cognitive hearing science. Experimental cognitive hearing science paradigms call for hybrid cognitive and psychobehavioral tests such as those relating the attentional system, working memory, and executive functioning to low-level auditory acuity or speech intelligibility. Building complex multi-stimuli experiments can rapidly become time-consuming and error-prone. Platform-based experiment design can help streamline the implementation of cognitive hearing science experimental paradigms, promote the standardization of experiment design practices, and ensure reliability and control. Here, we introduce a set of features for the open-source python-based OpenSesame platform that allows the rapid implementation of custom behavioral and cognitive hearing science tests, including complex multichannel audio stimuli while interfacing with various synchronous inputs/outputs. Our integration includes advanced audio playback capabilities with multiple loudspeakers, an adaptive procedure, compatibility with standard I/Os and their synchronization through implementation of the Lab Streaming Layer protocol. We exemplify the capabilities of this extended OpenSesame platform with an implementation of the three-alternative forced choice amplitude modulation detection test and discuss reliability and performance. The new features are available free of charge from GitHub: https://github.com/elus-om/BRM_OMEXP.

Virginia Woolf, Anechoic Architecture, and the Acoustic Hermeneutic

Abstract This article describes Virginia Woolf's preoccupation with acoustics and its relationship both to her writing process and to the development of sensibility that she narrativizes in The Waves. It situates Woolf's theoretical and fictional models of listening with respect to the rising science of architectural acoustics and to the social imperative to control sound in urban spaces. It argues that Woolf responds to the psychological and social exigencies of modern sound by integrating textual and architectural listening modes in an acoustic hermeneutic: a listening practice common to the objects of architecture and text, one that accommodates both scientific and aesthetic ends. The acoustic hermeneutic marks the convergence of oft-estranged listening practices—one that apprehends the silent materiality of the text as if it were an audible room and, conversely, one that apprehends architecture with the auditory imagination traditionally exerted toward literature. While the article explores Woolf's particular invocations of auditory science in her formal innovation, it also aims toward a widely applicable critical approach to the inaudibilities of the novel.

Η Θετική Έκβαση των Ελέγχων υπό το Φως του Management

The implementation of the key management functions (planning, organization, management, control, decision making) modernizes and improves the Auditory Science, helping to achieve audit objectives, minimizing resources wastage and overcoming potential obstacles. The audit methodology must continually evolve and assess its unstable political, socio-economic, technical, legal, cultural and administrative environment, as well as the particularities of the audited entities. In the framework of the School of Behavioral Approach, in which the appropriate person has to be employed in the work for which he/she has the necessary qualifications, the auditors, the main human factor in conducting the audits, should be distinguished, among other things, for their integrity, objectivity, confidentiality and fairness. The auditing coordinator assumes the role of manager and ensures the unity of the audit process and the achievement of audit objectives.

Life experience and the asymmetry of the human auditory system: clinical and auditory science laboratory implications

It is now almost 60 years since Doreen Kimura first described the asymmetries of the human auditory system (HAS). It is 30 years since Kenneth Hugdahl, and almost 15 years since David Poeppel, did the same. Our knowledge of these asymmetries is now considerable and detailed. Here we review some of the literature concerning what is known about the asymmetry of the HAS, and use it to construct a simple model of how the central and peripheral components work together. The model details some of the asymmetry, the life-experience-dependant maturation of this asymmetry throughout the first two decades, possible reasons for the population variance in speech-in-noise perception, the central role of the corpus callosum, the involvement of the efferent auditory pathways, and the corticofugal control of the peripheral auditory system. Although our knowledge of HAS asymmetry remains incomplete, this should not prevent the introduction of required changes to the current practices of audiologists and auditory science researchers, practices which fail to recognize the existence of any asymmetry in the HAS. The model described here suggests a clear need for: “asymmetry sensitive” hearing test tools that provide normative data for the lifespan, closer childhood and aging-adult hearing monitoring, and the development of a range of auditory training modules. Notably, the model suggests that without such tools our HAS asymmetry knowledge will remain incomplete. The status quo is a preoccupation with understanding hearing through knowledge of the peripheral hearing system, no answers for those with a “normal audiogram” but with an obvious difficulty hearing speech-in-noise, limited success cochlear implant rehabilitation, and missed opportunities to successfully intervene with childhood hearing/speech/language development problems.

Supra-Threshold Hearing and Fluctuation Profiles: Implications for Sensorineural and Hidden Hearing Loss.

An important topic in contemporary auditory science is supra-threshold hearing. Difficulty hearing at conversational speech levels in background noise has long been recognized as a problem of sensorineural hearing loss, including that associated with aging (presbyacusis). Such difficulty in listeners with normal thresholds has received more attention recently, especially associated with descriptions of synaptopathy, the loss of auditory nerve (AN) fibers as a result of noise exposure or aging. Synaptopathy has been reported to cause a disproportionate loss of low- and medium-spontaneous rate (L/MSR) AN fibers. Several studies of synaptopathy have assumed that the wide dynamic ranges of L/MSR AN fiber rates are critical for coding supra-threshold sounds. First, this review will present data from the literature that argues against a direct role for average discharge rates of L/MSR AN fibers in coding sounds at moderate to high sound levels. Second, the encoding of sounds at supra-threshold levels is examined. A key assumption in many studies is that saturation of AN fiber discharge rates limits neural encoding, even though the majority of AN fibers, high-spontaneous rate (HSR) fibers, have saturated average rates at conversational sound levels. It is argued here that the cross-frequency profile of low-frequency neural fluctuation amplitudes, not average rates, encodes complex sounds. As described below, this fluctuation-profile coding mechanism benefits from both saturation of inner hair cell (IHC) transduction and average rate saturation associated with the IHC-AN synapse. Third, the role of the auditory efferent system, which receives inputs from L/MSR fibers, is revisited in the context of fluctuation-profile coding. The auditory efferent system is hypothesized to maintain and enhance neural fluctuation profiles. Lastly, central mechanisms sensitive to neural fluctuations are reviewed. Low-frequency fluctuations in AN responses are accentuated by cochlear nucleus neurons which, either directly or via other brainstem nuclei, relay fluctuation profiles to the inferior colliculus (IC). IC neurons are sensitive to the frequency and amplitude of low-frequency fluctuations and convert fluctuation profiles from the periphery into a phase-locked rate profile that is robust across a wide range of sound levels and in background noise. The descending projection from the midbrain (IC) to the efferent system completes a functional loop that, combined with inputs from the L/MSR pathway, is hypothesized to maintain "sharp" supra-threshold hearing, reminiscent of visual mechanisms that regulate optical accommodation. Examples from speech coding and detection in noise are reviewed. Implications for the effects of synaptopathy on control mechanisms hypothesized to influence supra-threshold hearing are discussed. This framework for understanding neural coding and control mechanisms for supra-threshold hearing suggests strategies for the design of novel hearing aid signal-processing and electrical stimulation patterns for cochlear implants.

A European Perspective on Auditory Processing Disorder-Current Knowledge and Future Research Focus.

Current notions of “hearing impairment,” as reflected in clinical audiological practice, do not acknowledge the needs of individuals who have normal hearing pure tone sensitivity but who experience auditory processing difficulties in everyday life that are indexed by reduced performance in other more sophisticated audiometric tests such as speech audiometry in noise or complex non-speech sound perception. This disorder, defined as “Auditory Processing Disorder” (APD) or “Central Auditory Processing Disorder” is classified in the current tenth version of the International Classification of diseases as H93.25 and in the forthcoming beta eleventh version. APDs may have detrimental effects on the affected individual, with low esteem, anxiety, and depression, and symptoms may remain into adulthood. These disorders may interfere with learning per se and with communication, social, emotional, and academic-work aspects of life. The objective of the present paper is to define a baseline European APD consensus formulated by experienced clinicians and researchers in this specific field of human auditory science. A secondary aim is to identify issues that future research needs to address in order to further clarify the nature of APD and thus assist in optimum diagnosis and evidence-based management. This European consensus presents the main symptoms, conditions, and specific medical history elements that should lead to auditory processing evaluation. Consensus on definition of the disorder, optimum diagnostic pathway, and appropriate management are highlighted alongside a perspective on future research focus.

Multi-fiber coding on the auditory nerve and the origin of critical-band masking

Understanding the physiological mechanisms that underlie the exquisite frequency discrimination abilities of listeners remains a central problem in auditory science. We describe a computational model of the cochlea and auditory nerve that was developed to evaluate the frequency analysis capabilities of a system in which the output of a basilar membrane filter, transduced into a probability-of-firing function by an inner hair cell, is encoded on the auditory nerve as the instantaneous sum of firings on a critical band of fibers surrounding that filter channel and transmitted to the central nervous system for narrow-band frequency analysis. Performance of the model on vowels over a wide range of input levels was found to be robust and accurate, comparable to the Average Localized Synchronized Rate results of Young and Sachs [J. Acoust. Soc. Am. 1979, 66, 1381-1403]. Model performance in perceptual threshold simulations was also evaluated. The model succeeded in replicating psychophysical results reported in classic studies of critical band masking.

The Modern Cochlear Implant: A Triumph of Biomedical Engineering and the First Substantial Restoration of Human Sense Using a Medical Intervention.

Even as recently as the mid-1980s, many experts in otology and auditory science thought that restoration of useful hearing with crude and pervasive electrical stimulation of the cochlea was a fool's dream. The esteemed Prof. Rainer Klinke from Frankfurt (Figure 1) was among the chorus of critics, asserting in 1978 that "from a physiological point of view, cochlear implants will not work." Many others made similar categorical statements.

Auditory Sketches: Very Sparse Representations of Sounds Are Still Recognizable.

Sounds in our environment like voices, animal calls or musical instruments are easily recognized by human listeners. Understanding the key features underlying this robust sound recognition is an important question in auditory science. Here, we studied the recognition by human listeners of new classes of sounds: acoustic and auditory sketches, sounds that are severely impoverished but still recognizable. Starting from a time-frequency representation, a sketch is obtained by keeping only sparse elements of the original signal, here, by means of a simple peak-picking algorithm. Two time-frequency representations were compared: a biologically grounded one, the auditory spectrogram, which simulates peripheral auditory filtering, and a simple acoustic spectrogram, based on a Fourier transform. Three degrees of sparsity were also investigated. Listeners were asked to recognize the category to which a sketch sound belongs: singing voices, bird calls, musical instruments, and vehicle engine noises. Results showed that, with the exception of voice sounds, very sparse representations of sounds (10 features, or energy peaks, per second) could be recognized above chance. No clear differences could be observed between the acoustic and the auditory sketches. For the voice sounds, however, a completely different pattern of results emerged, with at-chance or even below-chance recognition performances, suggesting that the important features of the voice, whatever they are, were removed by the sketch process. Overall, these perceptual results were well correlated with a model of auditory distances, based on spectro-temporal excitation patterns (STEPs). This study confirms the potential of these new classes of sounds, acoustic and auditory sketches, to study sound recognition.

Equivalence of plane wave and spherical harmonics rendering of binaural room impulse response

Binaural technology has various applications in virtual acoustics, architectural acoustics, tele-communications, and auditory science. One key element in binaural technology is the binaural room impulse response (BRIR), which represents a continuum of plane waves spatially filtered by head related transfer functions (HRTFs). Such BRIRs can be rendered from spherical microphone array recordings and free-field HRTFs, either in the space domain using plane-wave composition or in the spherical-harmonics domain using order-limited spherical harmonics representation of the sound field. While these approaches have been individually employed in a number of recent studies, it appears that the literature does not offer a comprehensive analysis or a theoretical framework relating the two representations with respect to binaural reproduction and perception. In this paper, we provide a mathematical analysis showing that when certain sampling conditions are maintained, the plane-wave and spherical-harmonics representations are equivalent. Further, we show that under these conditions, resulting binaural signals are independent of the employed spatial sampling schemes. The analysis is complemented by a listening experiment, in which both plane-wave and spherical-harmonics representations are perceptually evaluated for different spatial sampling schemes and spherical harmonic orders.

Hypotheses for Hair Cell Ribbon Synapses Probed by a Biomimetic System

The conversion of sound waves to electrical impulse in the auditory nerve of the inner ear takes place in the organ of Corti through the process of synaptic transmission in and around the ribbon synapse. Finding the relation between the functional and physiological characteristics of the ribbon synapse is one of the central issues in auditory science nowadays. There has been a hypothesis on inner hair cells (IHC) that complex broad band sounds can be encoded by multiple ribbon synapses in an IHC. We provide a hypothesis on the spectral analysis by multiple ribbon synapses, where heterogenous glutamate release rates in a IHC is the key to the spectral analysis. To demonstrate our hypothesis, we fabricate a neuromorphic device that models the hair cell bundle and its afferent neuron, and investigate its response to pure-tone and human voice sounds. Our biomimetic experimental results go beyond theoretical simulation While mechanical oscillators’ velocity dependence of relaxation and noise can not but be assumed theoretically, our biomimetic approach goes beyond this limitation of such assumption and is self-consistent by its own. We observe that for the neuronal spike rates to mimic the voice sound signal of a word, a distribution of the spontaneous neurotransmitter relaxation rates is necessary. We also discuss a physical microscopic model for the ribbon synapse which is based on charge transport theory.

Sound effects with AUditory syntaX—A high-level scripting language for sound processing

AUditory syntaX (AUX) is a high-level scripting programming language specifically crafted for the generation and processing of auditory signals (Kwon, 2012; Behav Rev 44, 361–373). AUX does not require knowledge or prior experience in computer programming. Rather, AUX provides an intuitive and descriptive environment where users focus on perceptual components of the sound, without tedious tasks unrelated to the perception such as memory management or array handling often required in other computer languages such as C + + or MATLAB that are popularly used in auditory science. This presentation provides a demonstration of AUX for the generation and processing of various sound effects, particularly “fun” or “spooky” sounds. Processing methods for sound effects widely used in arts, films and other media, such as reverberation, echoes, modulation, pitch shift, and flanger/phaser, will be reviewed and coding in AUX to generate those effects and the generated sounds will be demonstrated.

Spectral resolution and its effects on temporal analysis in cochlear-implant perception

Sid Bacon's contributions to auditory science span a wide range of topics but two areas were constant themes throughout his career: temporal modulation perception, and peripheral processing and frequency selectivity. In this study, speech understanding in noise was measured, with a focus on the role of inherent temporal fluctuations in noise maskers. Tonal maskers, presented to cochlear-implant users, were placed at the center frequencies of each frequency channel of the implant, thereby producing the same masker energy as a noise masker in each frequency channel, but without the inherent fluctuations. In contrast to the results from normal-hearing subjects listening through a tone-excited envelope vocoder, cochlear-implant users gained no benefit from eliminating the inherent fluctuations from the maskers. Further experiments suggested that the poor spectral resolution of cochlear implants resulted in a smoothing of the temporal envelope of the noise maskers. The results indicate an important, and potentially overlooked, effect of spectral resolution on the temporal representations of speech and noise in cochlear implants. The results also suggest a new interpretation for why cochlear-implant users, and perhaps hearing-impaired listeners, generally show reduced masking release when additional temporal modulations are imposed on noise maskers. [Work supported by NIH grant R01DC012262.]

Attention and effort during speech processing

The concepts of attention and effort are not new in auditory science, yet it is only recently that we have started systematically studying their involvement in speech processing. The task of deciphering speech can vary in its cognitive demands, depending on a number of factors, such as sound quality, the state of the auditory and cognitive systems, room acoustics, and the semantic complexity of the signal itself. Understanding these interactions does not only shed light on the functions supporting speech processing, but is also critical when it comes to evaluating new hearing aids and cochlear implant strategies. This presentation will describe work that is either based on Erv Hafter’s ideas while I was at UC Berkeley or inspired by discussions with him in subsequent years. Its central theme is the measuring of listening effort and its implications to digital signal processing, cochlear implants, aging, or understanding non-native languages.

Pathways

Pathways

The Auditory Hair Cell Ribbon Synapse: From Assembly to Function

Cochlear inner hair cells (IHCs), the mammalian auditory sensory cells, encode acoustic signals with high fidelity by Graded variations of their membrane potential trigger rapid and sustained vesicle exocytosis at their ribbon synapses. The kinetics of glutamate release allows proper transfer of sound information to the primary afferent auditory neurons. Understanding the physiological properties and underlying molecular mechanisms of the IHC synaptic machinery, and especially its high temporal acuity, which is pivotal to speech perception, is a central issue of auditory science. During the past decade, substantial progress in high-resolution imaging and electrophysiological recordings, as well as the development of genetic approaches both in humans and in mice, has produced major insights regarding the morphological, physiological, and molecular characteristics of this synapse. Here we review this recent knowledge and discuss how it enlightens the way the IHC ribbon synapse develops and functions.