Sound Amplification Research Articles

The impact of sound field amplification systems on speech perception of pupils with and without language disorders in natural conditions

The purpose of the study was to investigate in natural conditions the impact of sound field amplification systems (SFAS) on the perception of monosyllabic nonsense words in first to fourth-grade students with and without language disorders in classrooms with different acoustics.One hundred forty-five monolingual primary school pupils were included in the study. Two study groups were formed: pupils with typical language development (TD) (n = 145) and pupils with developmental language disorders (LD) (n = 72). Acoustic measurements were made in twelve classrooms with different reverberation time. Monosyllabic nonsense words perception tests, presented by an examiner, were carried out in classrooms with and without SFAS.The number of errors in the test carried out with SFAS in different acoustic conditions reduced in pupils of Grade 1 with TD (Z = –2.273, p = .023; Z = –1.965, p = .049) and with LD (Z = –2.410, p = .016; Z = –2.156, p = .031). The SFAS installed in large classrooms with long reverberation time significantly increased the number of errors in nonsense monosyllables perception (rS = 0.361, p < .01, rS = 0.229, p < .01). The mean number of errors in children with LD was higher than in children with TD in monosyllabic nonsense words tests carried out with and without SFAS (U = 3194, p < .001; U = 3518.5, p < .001).First-grade students benefit from sound field amplification in perception of monosyllabic nonsense words regardless of classrooms acoustics, and irrespective of the level of language development. The positive effect of SFAS on nonsense word perception was not observed in pupils of Grade 2, 3, and 4 of primary school. Classroom acoustics affects the expected positive impact of SFAS for children older than first graders. Amplification increases speech perception and decreases the number of errors in the reproduction of monosyllabic nonsense words in classrooms with short reverberation time.

High-Gain Ka-Band Analog Photonic Link Using High-Power Photodiode at 1064 nm

We report high-gain, low-noise-figure, and high linearity analog photonic links at 1064 nm using InP/InGaAs modified uni-traveling-carrier (MUTC) photodiodes. Balanced photodiodes reach output powers of 17.7 dBm, 19.8 dBm, 20.7 dBm, and 22 dBm at 38 GHz, 29 GHz, 27 GHz, and 24.5 GHz, respectively. High common-mode rejection ratio (CMRR) of 25 dB and good linearity with a third-order intercept point (OIP3) of up to 34 dBm were measured at 38 GHz for 10-μm-diameter balanced photodiodes. We demonstrate two analog photonic links with different noise reduction techniques without electronic amplification. In the first link, we use balanced detection with a quadrature-biased Mach–Zehnder modulator (MZM) for noise cancellation. Link gain of 6.8 dB, noise figure (NF) of 25.8 dB and spurious free dynamic range (SFDR3) of 114 dB·Hz2/3 at 38 GHz were achieved. The second link works at low bias modulation for improved signal-to-noise ratio with a single photodetector. Record-high gain (19.3 dB at 26 GHz and 17 dB at 38 GHz) and low noise figure (14.5 dB at 26 GHz and 17 dB at 38 GHz) were demonstrated.

100th Anniversary of Macromolecular Science Viewpoint: Soft Materials for Microbial Bioelectronics.

Bioelectronics brings together the fields of biology and microelectronics to create multifunctional devices with the potential to address longstanding technological challenges and change our way of life. Microbial electrochemical devices are a growing subset of bioelectronic devices that incorporate naturally occurring or synthetically engineered microbes into electronic devices and have broad applications including energy harvesting, chemical production, water remediation, and environmental and health monitoring. The goal of this Viewpoint is to highlight recent advances and ongoing challenges in the rapidly developing field of microbial bioelectronic devices, with an emphasis on materials challenges. We provide an overview of microbial bioelectronic devices, discuss the biotic-abiotic interface in these devices, and then present recent advances and ongoing challenges in materials related to electron transfer across the abiotic-biotic interface, microbial adhesion, redox signaling, electronic amplification, and device miniaturization. We conclude with a summary and perspective of the field of microbial bioelectronics.

Argumentum ad Ignorantiam: Smartphone-Connected Listening Devices.

In this article, we review the current literature assessing the application and benefits of connected hearing technologies, as well as their potential to improve accessibility to and affordability of hearing healthcare. Over the past decade, there has been a proliferation of hearing devices that connect wirelessly to smartphone technologies via Bluetooth. These devices include (1) smartphone-connected hearing aids that must be obtained from a licensed audiologist or hearing aid dispenser; (2) direct-to-consumer devices, such as personal sound amplification products; and (3) smartphone-based hearing aid applications (or apps). Common to all these connected devices is that they permit the user to self-adjust and customize their device programs via an accompanying smartphone app. There has been a growing body of literature assessing connected hearing devices in adults living with hearing loss. Overall, the evidence to date supports the notion that all connected hearing devices can improve accessibility to and affordability of amplification. It is unclear, however, whether connected technologies are a clinically effective alternative to traditional hearing aids. Even so, the impact of connectivity is especially pertinent given the sudden disruption caused by the recent global COVID-19 pandemic, whereby connected technologies enable patients to receive treatment through mobile-based, tele-audiology platforms.

Auditory Measures for the Next Billion Users.

A range of new technologies have the potential to help people, whether traditionally considered hearing impaired or not. These technologies include more sophisticated personal sound amplification products, as well as real-time speech enhancement and speech recognition. They can improve user's communication abilities, but these new approaches require new ways to describe their success and allow engineers to optimize their properties. Speech recognition systems are often optimized using the word-error rate, but when the results are presented in real time, user interface issues become a lot more important than conventional measures of auditory performance. For example, there is a tradeoff between minimizing recognition time (latency) by quickly displaying results versus disturbing the user's cognitive flow by rewriting the results on the screen when the recognizer later needs to change its decisions. This article describes current, new, and future directions for helping billions of people with their hearing. These new technologies bring auditory assistance to new users, especially to those in areas of the world without access to professional medical expertise. In the short term, audio enhancement technologies in inexpensive mobile forms, devices that are quickly becoming necessary to navigate all aspects of our lives, can bring better audio signals to many people. Alternatively, current speech recognition technology may obviate the need for audio amplification or enhancement at all and could be useful for listeners with normal hearing or with hearing loss. With new and dramatically better technology based on deep neural networks, speech enhancement improves the signal to noise ratio, and audio classifiers can recognize sounds in the user's environment. Both use deep neural networks to improve a user's experiences. Longer term, auditory attention decoding is expected to allow our devices to understand where a user is directing their attention and thus allow our devices to respond better to their needs. In all these cases, the technologies turn the hearing assistance problem on its head, and thus require new ways to measure their performance.

Cochlear implant in Kearns-Sayre syndrome: A case study of twin sisters

&lt;p&gt;Hearing loss may be related to several factors, including hearing loss resulting from certain genetic syndromes. Kearns-Sayre syndrome is characterized by mutations in mitochondrial DNA (deoxyribonucleic acid), responsible for the production of energy (adenosine triphosphate-ATP), which is extremely important for the development of structures that require it, such as the cochlea. The case was followed up at the hospital since 2000, due to the progressive characteristic of hearing loss found in audiological tests and findings in cases related to the syndrome. The intervention with individual sound amplification devices proved to be of little benefit for good oral communication of one of the patients, who was diagnosed with bilateral profound hearing loss. Thus, after discussions in clinical meetings, the team opted for the indication of the cochlear implant for the patient, according to the current criteria for indication of this surgery, and with which it obtained good results. His twin sister, who presented good results with hearing aids, will continue in audiological follow-up, to verify the evolution of the case and discuss a new approach, if necessary. Patients with suspected or diagnosed Kearns-Sayre syndrome should seek audiological diagnosis, because it is a possible progressive hearing loss, requiring rehabilitation with the use of hearing devices. Maintaining oral communication is extremely important because, in these cases, other functions will be impaired, such as muscle tone and vision.&lt;/p&gt;

Flicker-noise. Features, diversity and management

The article refers to the field of research of noise fluctuations or flicker-noises in electronic amplifiers. The variety of flicker-noise in the energy and frequency dimension is shown, that the manifestation of flicker-noise is not limited to ultra-low frequency range, but under certain conditions can extend to medium and high frequencies. Some areas of radio electronics exposed or using flicker-noise properties are illuminated. It is shown that flicker-noises have a limit level of build-up in accordance with the energy and frequency band forming its thermal and fractional noises. It is shown that for electronic amplifiers flicker-noise is impractical to approximate the simplified ratio of 1/f. Methods of elimination or leveling of flicker-noise are given.

Broadband acoustic lens design using the principle of reciprocity and gradient-based optimization

In this work, we will present a gradient-based optimization method for the design of an acoustic lens. This design is based on an optimization process using the semi-analytical optimization approach and applying the principle of reciprocity. Here, we will illustrate the use of acoustic reciprocity to define the pressure at the focal point due to a source located in a far-field. The reciprocity enables us to relate the response by configuration of scatterers for an incident plane wave in terms of the far-field Green's function. The idea differs from earlier inverse designs that use topology optimization tools and generic algorithms. The gradient-based optimization algorithm maximizes the sound amplification at the focal point by evaluating pressure derivative with respect to the cylinder positions and then perturbatively optimizing the position of each cylinder in the lens while taking into account acoustic the multiple scattering between the cylinders. Computations are performed on MATLAB using “fmincon” function with a MultiStart optimization solver, and supplying the gradient of pressure at the focus. The reciprocal formulation of inverse design of acoustic lens leads to the closed-form solution that takes lesser time to compute the absolute pressure and it gradients at the focal point. The numerical results for the optimization of the broadband acoustic lens will be illustrated for configurations of uniform rigid cylinders.

Acoustic Characteristics of Vocal Sounds Used by Professional Actors Performing Classical Material Without Microphones in Outdoor Theatre

Theatre actors use voice in virtually any physical position, moving or still, and perform in a wide range of venues. The present study investigated acoustic qualities required to perform classical material without electronic amplification in outdoor spaces. Eight professional actors, four female, four male, from NY Classical Theatre performed one-minute monologues, first stationary, then moving, for audio recording in Central Park. Four subjects recorded two monologues each, from productions in which they played both male and female characters. Data were analyzed for fundamental frequency (F0), sound pressure level (SPL), and long-term average spectrum (LTAS). Overall, F0 ranged between 75.38 and 530.33 Hz. Average F0 was 326 Hz stationary and 335.78 Hz moving for females, 248.54 Hz stationary, 252.82 Hz moving for males. SPL ranged from 28.54 to 110.51 dB for females, and 56.69 to 124.44 dB for males. Average SPL was 82 dB for females, 96.98 dB for males. On LTAS, females had a peak between 3 and 4 kHz ranging from 1.5 to 4.5 dB and another between 4 and 5 kHz ranging from 2 to 4.5 dB, while males had a peak between 3 and 4 kHz ranging from 1 to 8.5 dB. Actors appear to use a similar F0 range across gender and performing conditions. Average F0 increased from stationary to moving. Males had greater SPL values than females, and the amplitude of peaks in the region of the Actor's Formant of LTAS curves was higher in male than female voices.

Innovative Technologies in Vocal Training: Technological Culture Formation of Future Musical Art Teachers

Under the conditions of present-day modernization of education, the urgency of dealing with educational issues and challenges in terms of the coronavirus pandemic, the teacher’s technological culture enhancement who is capable to effectively apply innovative technologies in the educational process has acquired particular significance. Therefore, special attention is paid today to the formation of future music teachers’ technological culture by means of applying innovative technologies in vocal training at the institution of higher artistic and artistic-pedagogical education. The technological culture of the teacher is considered as a professional and personal phenomenon based on value-and-technology worldview and way of thinking, skills in the application of technological knowledge, those formed and implemented in creative artistic and pedagogical activities as well as the ability to creatively use pedagogical tools. Students have to master a wide range of technologies for teaching singing and then use them in their practical activities as music teachers, namely: technologies aimed at mastering performing and methodological foundations of singing for future teachers; information and computer technologies, including remote ones, aimed at teaching the art of singing in remote access and mastering the basics of sound amplification equipment by both future performers and music teachers; technologies that have a music therapy and healthcare effect. The methodological basis for technological culture formation of future music teachers in the process of vocal training features such scientific approaches as: culturological, technological, competence approach along with creative one. In order to effectively form the technological culture of future musical art teachers, the following elements have been determined: the structure of this phenomenon, which includes axiological-culturological, epistemological-emotional, technological and activity approaches as well as creative-professional one; their level of formation is determined by the identified criteria, in particular: value-axiological, cognitive-emotional, vocal-operational and creative-professional.

Impact of Hearing Loss and Universal Face Masking in the COVID-19 Era

Impact of Hearing Loss and Universal Face Masking in the COVID-19 Era

Age-related changes in the biophysical and morphological characteristics of mouse cochlear outer hair cells.

Age-related hearing loss (ARHL) is a very heterogeneous disease, resulting from cellular senescence, genetic predisposition and environmental factors (e.g. noise exposure). Currently, we know very little about age-related changes occurring in the auditory sensory cells, including those associated with the outer hair cells (OHCs). Using different mouse strains, we show that OHCs undergo several morphological and biophysical changes in the ageing cochlea. Ageing OHCs also exhibited the progressive loss of afferent and efferent synapses. We also provide evidence that the size of the mechanoelectrical transducer current is reduced in ageing OHCs, highlighting its possible contribution in cochlear ageing. Outer hair cells (OHCs) are electromotile sensory receptors that provide sound amplification within the mammalian cochlea. Although OHCs appear susceptible to ageing, the progression of the pathophysiological changes in these cells is still poorly understood. By using mouse strains with a different progression of hearing loss (C57BL/6J, C57BL/6NTac, C57BL/6NTacCdh23+ , C3H/HeJ), we have identified morphological, physiological and molecular changes in ageing OHCs (9-12kHz cochlear region). We show that by 6months of age, OHCs from all strains underwent a reduction in surface area, which was not a sign of degeneration. Although the ageing OHCs retained a normal basolateral membrane protein profile, they showed a reduction in the size of the K+ current and non-linear capacitance, a readout of prestin-dependent electromotility. Despite these changes, OHCs have a normal Vm and retain the ability to amplify sound, as distortion product otoacoustic emission thresholds were not affected in aged, good-hearing mice (C3H/HeJ, C57BL/6NTacCdh23+ ). The loss of afferent synapses was present in all strains at 15months. The number of efferent synapses per OHCs, defined as postsynaptic SK2 puncta, was reduced in aged OHCs of all strains apart from C3H mice. Several of the identified changes occurred in aged OHCs from all mouse strains, thus representing a general trait in the pathophysiological progression of age-related hearing loss, possibly aimed at preserving functionality. We have also shown that the mechanoelectrical transduction (MET) current from OHCs of mice harbouring the Cdh23ahl allele is reduced with age, highlighting the possibility that changes in the MET apparatus could play a role in cochlear ageing.

Acoustic inerter: Ultra-low frequency sound attenuation in a duct.

This letter investigates an acoustic metamaterial exhibiting a unique sound pressure amplification mechanism for ultra-low frequency sound attenuation. The system is constructed by integrating a flexible panel into the side-branch duct of a Herschel-Quincke (HQ) tube. A new peak emerges in the Sound Transmission Loss (STL) at a frequency far lower than the frequencies of the HQ tube-induced STL peaks. It cannot, after careful comparisons, be attributed to any local resonances, including structural resonances of the flexible panel or air resonances inside the side-branch cavities. To explain the underlying physics, several numerical simulations are performed. The results reveal that analog to a mechanical inerter, a "push-pull" force is created by the sound pressure difference between the sub-cavities in which a pressure amplification mechanism is generated at the interface of the embedded panel. This force is large enough to activate an out-of-plane motion of the flexible panel, trapping the incident sound power in a circular flow around the duct-branch loop. The unique phenomenon is successfully reproduced in experiment, where the flexible panel is made of carbon fiber. The proposed acoustic metamaterial can be used as silencing components for ultra-low frequency noise control in duct.

Gradient-index phononic crystals for omnidirectional acoustic wave focusing and energy harvesting

The design, fabrication, and analysis of omnidirectional gradient-index (GRIN) phononic crystals (PnCs) for acoustic wave focusing and energy harvesting have been demonstrated both numerically and experimentally. Despite that omnidirectional functionality is a key factor to alleviate the directivity dependence issues, the concept has not yet been incorporated into acoustic energy harvesting. In this work, a symmetrical GRIN PnC structure consisting of cylinders with variation in filling fractions has been presented to tailor the spatial acoustic refractive index, thus enforcing the acoustic waves in any direction toward the targeted center area for focusing purposes. Both a numerical simulation and experimental validation confirm substantial sound energy amplification of the designed GRIN PnC over a broad frequency range from 250 Hz to 1 kHz. Notably, the maximum sound amplification occurs at the hybrid resonant frequency of the GRIN PnC structure and the acoustic duct system used to generate incident plane waves. Numerical simulation reveals that the cavity resonance and the refraction of the GRIN PnC mainly contribute to enhanced sound amplification in addition to the reflection from the acoustic duct. The GRIN PnC structure coupled with the acoustic duct system leads to enhanced harvesting output performance when integrated with a piezoelectric energy harvesting device.

Functional Postnatal Maturation of the Medial Olivocochlear Efferent-Outer Hair Cell Synapse.

The organ of Corti, the auditory mammalian sensory epithelium, contains two types of mechanotransducer cells, inner hair cells (IHCs) and outer hair cells (OHCs). IHCs are involved in conveying acoustic stimuli to the CNS, while OHCs are implicated in the fine tuning and amplification of sounds. OHCs are innervated by medial olivocochlear (MOC) cholinergic efferent fibers. The functional characteristics of the MOC-OHC synapse during maturation were assessed by electrophysiological and pharmacological methods in mouse organs of Corti at postnatal day 11 (P11)-P13, hearing onset in altricial rodents, and at P20-P22 when the OHCs are morphologically and functionally mature. Synaptic currents were recorded in whole-cell voltage-clamped OHCs while electrically stimulating the MOC fibers. A progressive increase in the number of functional MOC-OHC synapses, as well as in their strength and efficacy, was observed between P11-13 and P20-22. At hearing onset, the MOC-OHC synapse presented facilitation during MOC fibers high-frequency stimulation that disappeared at mature stages. In addition, important changes were found in the VGCC that are coupled to transmitter release. Ca2+ flowing in through L-type VGCCs contribute to trigger ACh release together with P/Q- and R-type VGCCs at P11-P13, but not at P20-P22. Interestingly, N-type VGCCs were found to be involved in this process at P20-P22, but not at hearing onset. Moreover, the degree of compartmentalization of calcium channels with respect to BK channels and presynaptic release components significantly increased from P11-P13 to P20-P22. These results suggest that the MOC-OHC synapse is immature at the onset of hearing.SIGNIFICANCE STATEMENT The functional expression of both VGCCs and BK channels, as well as their localization with respect to the presynaptic components involved in transmitter release, are key elements in determining synaptic efficacy. In this work, we show dynamic changes in the expression of VGCCs and Ca2+-dependent BK K+ channels coupled to ACh release at the MOC-OHC synapse and their shift in compartmentalization during postnatal maturation. These processes most likely set the short-term plasticity pattern and reliability of the MOC-OHC synapse on high-frequency activity.

(Invited) Organic Semiconductor, Receptor Material and Circuit Design for Organic Electronic Vapor Sensors and Biosensors

We will present our recent results on the design of semiconducting material, dielectric receptor matrices, and stabilizing and amplifying circuit structures for detection of volatile analytes in the atmosphere and proteins in aqueous solution. Besides our natural interest in designing materials that respond more strongly to analytes of interest than to likely interferents, we also emphasize the use of chemical and electronic amplification methods to increase the ratio of the desired responses to the drift (signal/noise ratio). Printable materials, especially polymers, are emphasized for the responsive layers. The use of multiple sensing elements, typically field-effect transistors (FETs), to create patterns of responses increases the selectivity of the information, either by narrowing the classes of compounds providing the responses, distinguishing time-dependent from dose-dependent responses, and/or increasing the ratio of analyte responses to environmental drifts. As a specific example, using pairs of FETs, in series or in parallel, allows device drifts to be substantially canceled while analyte responses are maintained and even reinforced. This strategy has led to significant improvements in the use of polymer-based FETs to detect pollutant gases such as nitrogen dioxide and ammonia. To increase the stability of systems used to detect analytes in solution, we sometimes separate the sensing surface from the output device in an arrangement known as a remote gate. We show that the output device may be an organic-based or a silicon-based transistor, and can respond to electrochemical potential changes at the sensing surface arising from a variety of chemical interactions. This type of configuration was applied to the understanding of vapor sensors and the effect of receptor polarity on the detection of brain injury biomarker proteins. New details about the mechanisms for sensor responses to analytes can be obtained from remote gate configurations, including connection of interfacial voltages and charge densities in responsive polymer semiconductors.

Efficacy of a Smartphone Hearing Aid Simulator

Almost all smartphone-based personal sound amplification applications (PSAPs) do not provide amplification specifications as well as medical hearing aid (HA) products. Therefore, the main purpose of this study is to develop an HA-simulator and investigate the possible fitting range of this smartphone-based PSAP app equipped with a commercial headset, and to evaluate whether the aided outcome provides reasonable benefits for individuals with hearing loss by analyzing the Speechmap and speech intelligibility index (SII). An HA-simulator with a four-channel compression structure was developed and evaluated using a smartphone equipped with Apple EarPods. Measurement methods specified by the ANSI S3.22 were used to evaluate the electroacoustic performance of the proposed system. The Speechmap method and SII were used to check if the amplified speech for five different hearing loss configurations. These ANSI S3.22 and Speechmap measurement results were then compared with a digital HA under the same test conditions. The results demonstrated that the proposed HA-simulator system provided an adequate output sound level for patients with mild-to-moderate hearing loss and a tolerable group delay for the user while providing an electroacoustic performance comparable to that of a digital HA based on ANSI S3.22 test criteria. The amplified speech signals presented by Speechmap and the corresponding SII values indicated that the proposed HA-simulator provided benefits comparable to those of medical HA. These results indicate that a smartphone-based HA simulator could provide suitable performance to that of a medical HA, and it potentially aid individuals with hearing loss.

Cooperativity of Kv7.4 channels confers ultrafast electromechanical sensitivity and emergent properties in cochlear outer hair cells.

The mammalian cochlea relies on active electromotility of outer hair cells (OHCs) to resolve sound frequencies. OHCs use ionic channels and somatic electromotility to achieve the process. It is unclear, though, how the kinetics of voltage-gated ionic channels operate to overcome extrinsic viscous drag on OHCs at high frequency. Here, we report ultrafast electromechanical gating of clustered Kv7.4 in OHCs. Increases in kinetics and sensitivity resulting from cooperativity among clustered-Kv7.4 were revealed, using optogenetics strategies. Upon clustering, the half-activation voltage shifted negative, and the speed of activation increased relative to solitary channels. Clustering also rendered Kv7.4 channels mechanically sensitive, confirmed in consolidated Kv7.4 channels at the base of OHCs. Kv7.4 clusters provide OHCs with ultrafast electromechanical channel gating, varying in magnitude and speed along the cochlea axis. Ultrafast Kv7.4 gating provides OHCs with a feedback mechanism that enables the cochlea to overcome viscous drag and resolve sounds at auditory frequencies.

Ionic amplifying circuits inspired by electronics and biology

Integrated circuits are present in all electronic devices, and enable signal amplification, modulation, and relay. Nature uses another type of circuits composed of channels in a cell membrane, which regulate and amplify transport of ions, not electrons and holes as is done in electronic systems. Here we show an abiotic ionic circuit that is inspired by concepts from electronics and biology. The circuit amplifies small ionic signals into ionic outputs, and its operation mimics the electronic Darlington amplifier composed of transistors. The individual transistors are pores equipped with three terminals including a gate that is able to enrich or deplete ions in the pore. The circuits we report function at gate voltages < 1 V, respond to sub-nA gate currents, and offer ion current amplification with a gain up to ~300. Ionic amplifiers are a logical step toward improving chemical and biochemical sensing, separations and amplification, among others.

DESIGN OF AN ELECTRO HYDRAULIC SERVO DRIVE ON THE BASIS OF THE PRINCIPLE OF MINIMIZING ENERGY COSTS

The questions of the possibility of choosing the optimal parameters of an electro-hydraulic servo drive from the point of view of energy excellence at the design stage are considered in two cases: under the action of only inertial load and when combined with inertial and static loads. The resulting engineering methodology for calculating the drive allows one to minimize power consumption by choosing the minimal required cylinder size and the optimal pressure setting for the pressure valve. Analytical dependences are obtained for calculating the power, the steady-state speed of the executive element and the flow rate, which allow choosing the rational form of the transient process in the drive and are the basis for the next stage of the dynamic synthesis of the electro-hydraulic servo drive, namely, choosing the optimal value of the gain of the electronic amplifier, as well as the structure and parameters of the correction link.