Vibration enhanced cell growth induced by surface acoustic waves as in vitro wound-healing model.

We report on in vitro wound-healing and cell-growth studies under the influence of radio-frequency (rf) cell stimuli. These stimuli are supplied either by piezoactive surface acoustic waves (SAWs) or by microelectrode-generated electric fields, both at frequencies around 100 MHz. Employing live-cell imaging, we studied the time- and power-dependent healing of artificial wounds on a piezoelectric chip for different cell lines. If the cell stimulation is mediated by piezomechanical SAWs, we observe a pronounced, significant maximum of the cell-growth rate at a specific SAW amplitude, resulting in an increase of the wound-healing speed of up to 135 ± 85% as compared to an internal reference. In contrast, cells being stimulated only by electrical fields of the same magnitude as the ones exposed to SAWs exhibit no significant effect. In this study, we investigate this effect for different wavelengths, amplitude modulation of the applied electrical rf signal, and different wave modes. Furthermore, to obtain insight into the biological response to the stimulus, we also determined both the cell-proliferation rate and the cellular stress levels. While the proliferation rate is significantly increased for a wide power range, cell stress remains low and within the normal range. Our findings demonstrate that SAW-based vibrational cell stimulation bears the potential for an alternative method to conventional ultrasound treatment, overcoming some of its limitations.

Efficacy of Binaural Beat Meditation Technology for Treating Anxiety Symptoms: A Pilot Study.

The objective of this study was to examine the efficacy of a novel binaural beat meditation technology for the treatment of anxiety symptoms in both psychiatric outpatients and nonpatients. Twenty psychiatric outpatients with anxiety disorder and eight individuals (nonpatients) in the healing professions were given the opportunity to use this meditation technology over the course of 2 weeks to 2 months. The State-Trait Anxiety Inventory scores were measured in all participants over the course of the study. Of the 20 outpatients who took part in the study, nine used the meditations as planned, whereas 11 did not for various reasons (could not download, forgot, did not have time, etc.), resulting in the formation of three treatment groups: psychiatry + meditation (n = 8), psychiatry only (n = 10), and meditation only (n = 8). The psychiatry + meditation group showed a 13.5-point (26.5%) decrease in State-Anxiety (t = 5.28, p = 0.001), a 14.1-point (24.7%) decrease in Trait-Anxiety (t = -5.12, p = 0.001), and a 27.6-point (25.6%) decrease in Total Anxiety (t = 7.63, p ≤ 0.001). The psychiatry-only group showed a 4.2-point (8.4%) decrease in State-Anxiety (t = -2.20, p = 0.05) and a 7.0-point (6.9%) decrease in Total Anxiety (t = -2.61, p = 0.02). The meditation only showed a 3.5-point (9.8%) decrease in Trait-Anxiety (t = -2.47, p = 0.04). In a multiple regression analysis controlling for sociodemographic factors, medications, and treatment-related variables, the only statistically significant improvement in anxiety was seen in the psychiatry + meditation group for the Total Anxiety score (p < 0.01). These findings suggest that use of this meditation technology may exhibit a positive effect on self-reported measures of anxiety in the context of a psychiatry/psychotherapy practice. However, larger-scale randomized, placebo-controlled trials are needed to confirm our findings.

Analysis of probe fitting stimulus properties on transient evoked otoacoustic emissions.

Objective: The objectives of the current study are first, to evaluate the subjective evaluation of probe fitting stimulus properties, and second, to analyse the effects of different probe fittings on transient evoked otoacoustic emission (TEOAE) response and noise amplitudes in subjects.Design: The Q methodology was used to sort 48 probe fittings differing in stimulus properties in seven categories from totally unacceptable to certainly acceptable. Further, TEOAE response and noise amplitudes were measured in one baseline condition with optimal probe fitting and eight experimental conditions with less than optimal probe fittings.Study sample: The probe fittings were ranked by 18 participants, while the repeated measures design was performed in 34 ear.Results: First, it was found that only 19.61% of all distributions of the probe fittings by the participants had a mutual correlation of at least 70.00%. Almost 60% of the variance of distributions was explained by 83.33% of the participants, although most probe fittings significantly differed from other fittings based on spectral broadness. Second, significant differences in TEOAE response and especially noise amplitudes between conditions were found. Further, TEOAE response and noise amplitudes between the baseline and experimental conditions were significantly different depending on ringing and spectral flatness of the stimulus.Conclusion: A substantial amount of subjectivity during TEOAE measurements is involved with regard to the evaluation of probe fitting stimulus properties. TEOAE response but especially noise amplitudes are influenced by varying stimulus parameters which stresses the importance of inspecting these parameters prior to or during EOAE measurements. Although more research is needed, some guidelines regarding these parameters are given which could improve the accuracy of TEOAEs in practice.

Equivalent hearing threshold levels for the RadioEar IP30 insert earphone and short-term stimuli: comparison of peak-equivalent and RMS-based measures.

Objective: To determine equivalent threshold sound pressure levels (ETSPL) for the RadioEar IP30 insert earphone for standardised short-term stimuli: IEC 60645-3 reference clicks and tonebursts in the frequency range from 250 Hz to 6 kHz, using the standardised peak-equivalent ETSPL procedure (peETSPL) and a new proposal based on the unweighted equivalent continuous sound pressure level LZeq. of the periodically repeated short-term stimuli (LZeqETSPL).Design: Determination of peETSPL and LZeqETSPL hearing threshold levels with otologically normal test subjects under the conditions given in ISO 389-9 using the standardised occluded-ear simulator according to IEC 60318-4.Study sample: The study was based on tests with 25 subjects.Results: The peETSPLs for the RadioEar IP30 insert earphone were compared with the respective reference threshold levels of the insert earphone ER-3A as standardised in the ISO 389 standards series. The LZeqETSPL approach was tested by estimating the LZeqETSPLs from the peRETSPLs and comparing the estimate with the direct results.Conclusions: Equivalent hearing threshold levels for standardised short-term stimuli for the RadioEar IP30 insert earphone were determined according to ISO 389-9 and given as both peETPSL and LZeqETSPL. The RMS-based LZeqETSPL approach turned out to be well applicable for the RadioEar IP30 insert earphone.

A comparison of ear-canal-reflectance measurement methods in an ear simulator.

Ear-canal reflectance has been researched extensively for diagnosing conductive hearing disorders and compensating for the ear-canal acoustics in non-invasive measurements of the auditory system. Little emphasis, however, has been placed on assessing measurement accuracy and variability. In this paper, a number of ear-canal-reflectance measurement methods reported in the literature are utilized and compared. Measurement variation seems to arise chiefly from three factors: the residual ear-canal length, the ear-probe insertion angle, and the measurement frequency bandwidth. Calculation of the ear-canal reflectance from the measured ear-canal impedance requires estimating the ear-canal characteristic impedance in situ. The variability in ear-canal estimated characteristic impedance and reflectance due to these principal factors is assessed in an idealized controlled setup using a uniform occluded-ear simulator. In addition, the influence of this measurement variability on reflectance-based methods for calibrating stimulus levels is evaluated and, by operating the condenser microphone of the occluded-ear simulator as an electro-static speaker, the variability in estimating the emitted pressure from the ear is determined. The various measurement methods differ widely in their robustness to variations in the three principal factors influencing the accuracy and variability of ear-canal reflectance.

Sensorimotor influences on speech perception in infancy.

The influence of speech production on speech perception is well established in adults. However, because adults have a long history of both perceiving and producing speech, the extent to which the perception-production linkage is due to experience is unknown. We addressed this issue by asking whether articulatory configurations can influence infants' speech perception performance. To eliminate influences from specific linguistic experience, we studied preverbal, 6-mo-old infants and tested the discrimination of a nonnative, and hence never-before-experienced, speech sound distinction. In three experimental studies, we used teething toys to control the position and movement of the tongue tip while the infants listened to the speech sounds. Using ultrasound imaging technology, we verified that the teething toys consistently and effectively constrained the movement and positioning of infants' tongues. With a looking-time procedure, we found that temporarily restraining infants' articulators impeded their discrimination of a nonnative consonant contrast but only when the relevant articulator was selectively restrained to prevent the movements associated with producing those sounds. Our results provide striking evidence that even before infants speak their first words and without specific listening experience, sensorimotor information from the articulators influences speech perception. These results transform theories of speech perception by suggesting that even at the initial stages of development, oral-motor movements influence speech sound discrimination. Moreover, an experimentally induced "impairment" in articulator movement can compromise speech perception performance, raising the question of whether long-term oral-motor impairments may impact perceptual development.

Evanescent waves in simulated ear canals: Experimental demonstration and method for compensation.

Evanescent waves emerge from a small sound source that radiates into a waveguide with a larger cross-sectional area, but unlike planar waves, do not propagate far from the source. Evanescent waves thus contaminate in-ear calibration of acoustic stimuli. Measurements with an otoacoustic-emission (OAE) probe inserted at the entrance of long tubes of various diameters show a decline in the evanescent wave with distance from the source when advancing a probe tube through the OAE probe and into the long tube. The amplitude of the evanescent pressure increases with frequency and depends strongly on the diameter of the long tube. Modifying the shape of the aperture of the probe's sound source, thus effectively enlarging its diameter and redirecting acoustic flow, greatly reduced evanescent waves. The reduction in evanescent-wave pressure was observed in calibration cavities used to determine the Thévenin-equivalent source pressure and impedance of the probe. Errors in source calibrations were considerably larger in the unmodified configuration. An alternative method is proposed for calculation of acoustic source parameters that models the evanescent-wave pressure and reduces its influence on the calculation. This reduction greatly improves the quality of source calibrations, which should improve the accuracy of ear-canal impedance measurements and related quantities.

Effects of ear canal occlusion on hearing sensitivity: A loudness experiment.

Over the last century, hearing research has repeatedly reported differences in loudness perception when different types of transducers are being used. One of the effects of using different transducers is that listening may be performed via an open ear (loudspeaker), a cushioned ear (headphones), or an occluded ear (hearing aid receivers, insert earphones). The question of whether varying the acoustic load applied to the ear canal might impact hearing sensitivity has therefore become essential given the need to establish realistic noise damage risk criteria in an attempt to prevent noise-induced hearing loss for any given listening condition. Although such loudness discrepancies in the cushioned ear have been recently proven to be caused by loudness measurement artifacts, currently available data do not exclude a possible impact of ear canal occlusion on loudness perception. This paper presents the results of a loudness balance test carried out on 18 normal-hearing listeners. Using an earplug to occlude the canal, in-ear sound pressure levels were compared between the occluded ear and the cushioned ear at equal loudness. The results show agreement within 1 dB between the two listening conditions, and support the conclusion that loudness does not depend on the type of acoustic load applied to the ear canal.

Acoustic features of auditory medical alarms-An experimental study of alarm volume.

Audible alarms are a ubiquitous feature of all high-paced, high-risk domains such as aviation and nuclear power where operators control complex systems. In such settings, a missed alarm can have disastrous consequences. It is conventional wisdom that for alarms to be heard, "louder is better," so that alarm levels in operational environments routinely exceed ambient noise levels. Through a robust experimental paradigm in an anechoic environment to study human response to audible alerting stimuli in a cognitively demanding setting, akin to high-tempo and high-risk domains, clinician participants responded to patient crises while concurrently completing an auditory speech intelligibility and visual vigilance distracting task as the level of alarms were varied as a signal-to-noise ratio above and below hospital background noise. There was little difference in performance on the primary task when the alarm sound was -11 dB below background noise as compared with +4 dB above background noise-a typical real-world situation. Concurrent presentation of the secondary auditory speech intelligibility task significantly degraded performance. Operator performance can be maintained with alarms that are softer than background noise. These findings have widespread implications for the design and implementation of alarms across all high-consequence settings.

Externalization of remote microphone signals using a structural binaural model of the head and pinna.

In a remote microphone (RM) system, a talker speaks into a microphone and the signal is transmitted to the hearing aids worn by the hearing-impaired listener. A difficulty with remote microphones, however, is that the signal received at the hearing aid bypasses the head and pinna, so the acoustic cues needed to externalize the sound source are missing. The objective of this paper is to process the RM signal to improve externalization when listening through earphones. The processing is based on a structural binaural model, which uses a cascade of processing modules to simulate the interaural level difference, interaural time difference, pinna reflections, ear-canal resonance, and early room reflections. The externalization results for the structural binaural model are compared to a left-right signal blend, the listener's own anechoic head-related impulse response (HRIR), and the listener's own HRIR with room reverberation. The azimuth is varied from straight ahead to 90° to one side. The results show that the structural binaural model is as effective as the listener's own HRIR plus reverberation in producing an externalized acoustic image, and that there is no significant difference in externalization between hearing-impaired and normal-hearing listeners.

Neonate auditory brainstem response repeatability with controlled force gauge bone-conducted stimulus delivery.

OBJECTIVE: The feasibility and repeatability of neonate auditory brainstem responses (ABRs) with a controlled hand-held applied force gauge for bone-conducted stimulus delivery was examined. DESIGN: A repeated measures test-retest design was employed. STUDY SAMPLE: Participants were 27 healthy neonates. A 4000 Hz bone-conducted CE-Chirp octave band stimulus evoked the ABRs. Intra- and intertester conditions were employed with a prototype hand-held applied force gauge (Etymotic Research) attached to the superior aspect of the bone vibrator. The bone vibrator was placed in a superoposterior auricular position and held manually. The force gauge displayed a desired coupling force via an LED light indicator. RESULTS: Three sets of replicated ABRs were recorded from all neonates: initial test and retest with one tester (i.e. intratester 1 and 2) and final test with a second tester (i.e. intertester). No significant differences in intra- or intertester ABR wave V latencies or amplitudes were found (p > 0.05). Coefficients of reliability (Cronbach's α) were .95 and .43 for wave V latencies and amplitudes, respectively. CONCLUSIONS: A hand-held applied force gauge may be a reliable means of delivering controlled bone-conducted stimuli in ABR assessments in neonates and infants.

A feasibility study of predictable and unpredictable surf-like sounds for tinnitus therapy using personal music players.

OBJECTIVE: To evaluate the feasibility of predictable or unpredictable amplitude-modulated sounds for tinnitus therapy. DESIGN: The study consisted of two parts. (1) An adaptation experiment. Loudness level matches and rating scales (10-point) for loudness and distress were obtained at a silent baseline and at the end of three counterbalanced 30-min exposures (silence, predictable and unpredictable). (2) A qualitative 2-week sound therapy feasibility trial. Participants took home a personal music player (PMP). STUDY SAMPLE: Part 1: 23 individuals with chronic tinnitus and part 2: seven individuals randomly selected from Part 1. RESULTS: Self-reported tinnitus loudness and annoyance were significantly lower than baseline ratings after acute unpredictable sound exposure. Tinnitus annoyance ratings were also significantly lower than the baseline but the effect was small. The feasibility trial identified that participant preferences for sounds varied. Three participants did not obtain any benefit from either sound. Three participants preferred unpredictable compared to predictable sounds. Some participants had difficulty using the PMP, the average self-report hours of use were low (less <1 h/day). CONCLUSIONS: Unpredictable surf-like sounds played using a PMP is a feasible tinnitus treatment. Further work is required to improve the acceptance of the sound and ease of PMP use.

Proof of Concept for an Intracochlear Acoustic Receiver for Use in Acute Large Animal Experiments.

(1) Background: The measurement of intracochlear sound pressure (ICSP) is relevant to obtain better understanding of the biomechanics of hearing. The goal of this work was a proof of concept of a partially implantable intracochlear acoustic receiver (ICAR) fulfilling all requirements for acute ICSP measurements in a large animal. The ICAR was designed not only to be used in chronic animal experiments but also as a microphone for totally implantable cochlear implants (TICI). (2) Methods: The ICAR concept was based on a commercial MEMS condenser microphone customized with a protective diaphragm that provided a seal and optimized geometry for accessing the cochlea. The ICAR was validated under laboratory conditions and using in-vivo experiments in sheep. (3) Results: For the first time acute ICSP measurements were successfully performed in a live specimen that is representative of the anatomy and physiology of the human. Data obtained are in agreement with published data from cadavers. The surgeons reported high levels of ease of use and satisfaction with the system design. (4) Conclusions: Our results confirm that the developed ICAR can be used to measure ICSP in acute experiments. The next generation of the ICAR will be used in chronic sheep experiments and in TICI.

OBAT: An open-source and low-cost operant box for auditory discriminative tasks.

Operant-conditioning boxes are widely used in animal training, allowing researchers to shape specific behaviors through reinforcements and/or punishments. Commercially available devices are expensive and run with proprietary software and hardware, hampering adaptations for the specific needs of an experiment. Therefore, many low-cost and open-source devices have recently been developed, but there are still few options for studying auditory behaviors. To overcome this problem, we developed a device based on a computer and an Arduino Mega 2560 board, named OBAT (Operant Box for Auditory Tasks), designed to present two different auditory stimuli to small primates. It has three modules: sound delivery, response bars, and reward system. We estimate that OBAT is at least 4-10 times cheaper than commercially available operant-conditioning boxes. Data from a behavioral pilot test ensured that the device can be used to train a marmoset in an auditory discrimination task. In addition, despite its low cost, accuracy tests showed that the OBAT operates with a high temporal precision. All schematics and software source code are available so that other groups can easily replicate the experiment or adapt the device to their own needs.

Frequency selectivity without resonance in a fluid waveguide.

This study analyzes a waveguide consisting of two parallel fluid-filled chambers connected by a narrow slit that is spanned by two coupled elastic beams. A stiffness gradient exists in the longitudinal direction. This simple linear system, which contains no lumped mass, is shown to act as a spectral analyzer. Fluid waves traveling in the waveguide exhibit a distinct amplitude peak at a longitudinal location that varies systematically with frequency. The peaking is not based on resonance, but entirely on wave dispersion. When entering its peak region, the wave undergoes a sharp deceleration associated with a transition in which two propagation modes exchange roles. It is proposed that this mode shape swapping underlies the frequency analysis of the mammalian cochlea.

The localization of non-individualized virtual sounds by hearing impaired listeners.

Although many studies have evaluated the performance of virtual audio displays with normal hearing listeners, very little information is available on the effect that hearing loss has on the localization of virtual sounds. In this study, normal hearing (NH) and hearing impaired (HI) listeners were asked to localize noise stimuli with short (250 ms), medium (1000 ms), and long (4000 ms) durations both in the free field and with a non-individualized head-tracked virtual audio display. The results show that the HI listeners localized sounds less accurately than the NH listeners, and that both groups consistently localized virtual sounds less accurately than free-field sounds. These results indicate that HI listeners are sensitive to individual differences in head related transfer functions (HRTFs), which means that they might have difficulty using auditory display systems that rely on generic HRTFs to control the apparent locations of virtual sounds. However, the results also reveal a high correlation between free-field and virtual localization performance in the HI listeners. This suggests that it may be feasible to use non-individualized virtual audio display systems to predict the auditory localization performance of HI listeners in clinical environments where free-field speaker arrays are not available.

Going wireless and booth-less for hearing testing in industry.

OBJECTIVE: To assess the test-retest variability of hearing thresholds obtained with an innovative, mobile wireless automated hearing-test system (WAHTS) with enhanced sound attenuation to test industrial workers at a worksite as compared to standardised automated hearing thresholds obtained in a mobile trailer sound booth. DESIGN: A within-subject repeated-measures design was used to compare air-conducted threshold tests (500-8000 Hz) measured with the WAHTS in six workplace locations, and a third test using computer-controlled audiometry obtained in a mobile trailer sound booth. Ambient noise levels were measured in all test environments. STUDY SAMPLE: Twenty workers served as listeners and 20 workers served as operators. RESULTS: On average, the WAHTS resulted in equivalent thresholds as the mobile trailer audiometry at 1000, 2000, 3000 and 8000 Hz and thresholds were within ±5 dB at 500, 4000 and 6000 Hz. CONCLUSIONS: Comparable performance may be obtained with the WAHTS in occupational audiometry and valid thresholds may be obtained in diverse test locations without the use of sound-attenuating enclosures.

Pre-market version of a commercially available hearing instrument with a tinnitus sound generator: feasibility of evaluation in a clinical trial.

OBJECTIVE: This report considers feasibility of conducting a UK trial of combination devices for tinnitus, using data from the study which evaluated different listener programmes available within the pre-market version of Oticon Alta with Tinnitus Sound Generator. DESIGN: Open and closed questions addressed the following feasibility issues: (1) Participant recruitment; (2) Device acceptability; (3) Programme preferences in different self-nominated listening situations; (4) Usability; (5) Compliance; (6) Adverse events. STUDY SAMPLE: Eight current combination hearing aid users (all males) aged between 62-72 years (mean age 67.25 years, SD = 3.8). RESULTS: All eight participants reported the physical aspects and noise options on the experimental device to be acceptable. Programmes with amplification and masking features were equally preferred over the basic amplification-only programme. Individual preferences for the different programme options varied widely, both across participants and across listening situations. CONCLUSIONS: A set of recommendations for future trials were formulated which calls for more "real world" trial design rather than tightly controlling the fitting procedure.

[Technical advancements in cochlear implants : State of the art]. / Technische Entwicklungen bei Cochleaimplantaten : Stand der Technik.

Twenty years ago, cochlear implants (CI) were indicated only in cases of profound hearing loss or complete deafness. While from today's perspective the technology was clumsy and provided patients with only limited speech comprehension in quiet scenarios, successive advances in CI technology and the consequent substantial hearing improvements over time have since then resulted in continuous relaxation of indication criteria toward residual hearing. While achievements in implant and processor electronics have been one key factor for the ever-improving hearing performance, development of electro-acoustic CI systems-together with atraumatic implantation concepts-has led to enormous improvements in patients with low-frequency residual hearing. Manufactures have designed special processors with integrated hearing aid components for this patient group, which are capable of conveying acoustic and electric stimulation. A further milestone in improvement of hearing in challenging listening environments was the adoption of signal enhancement algorithms and assistive listening devices from the hearing aid industry. This article gives an overview of the current state of the art in the abovementioned areas of CI technology.

[Pediatric hearing rehabilitation with the Baha® Attract implant system]. / Fiatalkori hallásrehabilitáció Baha® Attract implantátumrendszerrel.

INTRODUCTION: Baha® Attract is a new transcutaneous bone-conduction hearing aid, which is more preferable in childhood than the conventional percutaneous systems. AIM: Our aim was to demonstrate the possibilities of application in childhood. METHOD: Eight children have undergone surgeries (mean age of 13.2 ± 3.2 years; "posterosuperior" incision technique, 5 mm implants). The thickness of the skull bone was determined in 72 children (1-8 years old) at the recommended implant site, based on CT scans. RESULTS: The average duration of surgeries was 30 minutes. There were no intra- and postoperative complications observed. Sound processors were fitted at the postoperative 4th week. Hearing measurements proved 51.58±11.22SD dBHL gain in warble tone thresholds, and 43.3 ± 16.02 SD dB in speech discrimination thresholds. The skull bone thickness was measured as 3.39 ± 1.05 SD mm. CONCLUSION: The Baha Attract system is a new tool for hearing rehabilitation in pediatric population. Preoperative CT provides valuable knowledge about skull bone thickness. Orv. Hetil., 2017, 158(8), 304-310.