dB Sound Pressure Level Research Articles

Contribution of ambient noise and hyperbaric atmosphere to olfactory and gustatory function.

IntroductionTaste and smell are important for occupational performance and quality of life. Previous studies suggested that the function of these senses might be influenced by ambient pressure and noise. This knowledge would be helpful for divers, submarine crews, or mine workers. The present study aimed to investigate the effects of noise and hyperbaric pressure on olfactory and gustatory functions.MethodsThis prospective controlled study included 16 healthy male divers. Inside a hyperbaric chamber, participants performed olfactory and gustatory function tests at sea level pressure and at 2 bar pressure. The olfaction threshold, and the discrimination and identification of odorants were measured with validated ´Sniffin sticks´. Taste identification and the gustation threshold scores were examined with validated filter paper strips. Tests were performed under two conditions: noise reduction (silence) and white noise stimulation presented at 70 dB sound pressure level.ResultsThe results showed that normobaric and hyperbaric ambient pressures did not significantly affect olfactory or gustatory function. Moreover, noise had no relevant impact on taste or odor sensation. The odor identification score was not influenced in hyperbaric conditions, and the odor threshold score was not influenced by ambient noise or both barometric conditions. The only taste modality affected by hyperbaric conditions was the sensitivity to salty taste, but it was not significant.ConclusionWe concluded that hyperbaric and noisy environments have no influence on gustatory and olfactory function. From a practical point of view, the influence of pressure in moderate hyperbaric occupations should be negligible.

Management of transmodiolar and transmacular cochleovestibular schwannomas with and without cochlear implantation.

IntroductionHearing rehabilitation with cochlear implants has attracted increasing interest also for patients with cochleovestibular schwannoma. The authors report their experience with the surgical management of tumors with rare transmodiolar or transmacular extension and outcomes after cochlear implantation (CI).MethodsThis retrospective case series included nine patients with either primary intralabyrinthine tumors or secondary invasion of the inner ear from the internal auditory canal. The primary endpoint with CI, performed in six patients, was word recognition score at 65 dB SPL (sound pressure level). Secondary endpoints were intra- and postoperative electrophysiological parameters, impedance measures, the presence of a wave V in the electrically evoked (via the CI) auditory brainstem responses, the specifics of postoperative CI programming, and adverse events.ResultsHearing rehabilitation with CI in cases of transmodiolar tumor growth could be achieved only with incomplete tumor removal, whereas tumors with transmacular growth could be completely removed. All six patients with CI had good word recognition scores for numbers in quiet conditions (80–100% at 65 dB SPL, not later than 6 to 12 months post CI activation). Four of these six patients achieved good to very good results for monosyllabic words within 1–36 months (65–85% at 65 dB SPL). The two other patients, however, had low scores for monosyllables at 6 months (25 and 15% at 65 dB SPL, respectively) with worsening of results thereafter.ConclusionsCochleovestibular schwannomas with transmodiolar and transmacular extension represent a rare entity with specific management requirements. Hearing rehabilitation with CI is a principal option in these patients.Video onlineThe online version of this article (10.1007/s00106-020-00919-9) includes a video (2D and 3D versions) of the described surgical technique. Article and supplementary material are available at www.springermedizin.de. Please enter the title of the article in the search field, the supplementary material can be found under “Ergänzende Inhalte”.

Characterization of interstimulus interaction in the multiple auditory steady-state responses at high sound levels.

Multiple auditory steady-state response (MASSR) is recommended to estimate hearing thresholds in difficult-to-test individuals. The multiple stimuli that evoke MASSR may present an interstimulus interaction (ISI) that is able to distort the generation of responses. No consensus exists on the effects of the ISI in MASSR when dealing with high sound level stimuli or cases of sensorineural hearing loss. This study investigated the effects of ISI on the amplitude and detectability of auditory steady-state responses, with a focus at and above 65 dB sound pressure level (SPL). Normal hearing (NH) and sensorineural hearing impaired (SNHI) adults were tested with different stimulus types [amplitude modulation (AM) One octave chirp (OC), and a weighted OC (WOC)], stimulus levels, and modalities (single or multiple stimuli). ISI typically attenuated response amplitude of a control stimulus caused by an interference stimulus one octave above the control stimulus. At and above 80 dB SPL, attenuations of around 50% decreased the number of detectable responses near SNHI thresholds, especially for OC and WOC. AM stimuli obtained a higher detection rate than OC and WOC when presented 10 dB above the behavioral hearing threshold of SNHI participants. Using OC in MASSR when assessing elevated thresholds might diminish accuracy on threshold estimation, and extend test duration.

Steam and/or Semi-occluded Vocal Tract Exercise as Morning Vocal Warm-up Strategy

This study was designed to evaluate the effectiveness of either steam, semi-occluded vocal tract (SOVT) exercises, or a combination of both as a speaking voice warm-up strategy to be used at the start of the day. This prospective study assessed the impact of three different vocal warm-up conditions on phonatory threshold pressure (PTP). The three conditions were: (1) Steam - breathing steam for 3 minutes; (2) SOVT exercise - blowing bubbles through a straw into a cup of water while phonating /u/ for 3 minutes; and (3) Steam+SOVT - both conditions 1 and 2. Participants were 12 females with a mean age of 24. They were assessed on three different mornings, with one condition being tested each morning. Condition order and combination order were counterbalanced. Each morning prior to arriving, participants were asked to be up for about an hour, with no shower, no hot drinks or food, minimal voice-use, and no exercise. PTP was measured prior to each condition and immediately after. Participants also qualitatively described the experience of each condition and provided their subjective impression of how their voice felt after each condition. There were 36 data points, reflecting change in PTP from before to after each condition. Results reflected high variability within each individual and condition. Due to this variability, means and standard deviations for each separate condition are meaningless, requiring deeper investigation into trends in the data. The investigators eliminated all data points where the sound pressure level (SPL) in the pre-experimental measure exceeded 67 dB; this was interpreted as the participant not performing the PTP task as softly as possible. First, data were examined within each participant, excluding all data from any participant who exceeded 67 dB SPL in any of the three pre-experimental measures. Of the seven participants remaining, steam was the best condition for one, SOVT was the best for three, and Steam+SOVT was the best for three. Of these, only two people experienced an improvement in PTP of greater than or equal to 0.5 cm H 2 O, both under the SOVT condition. Of the same seven participants, steam was the worst condition for three, SOVT was the worst for one, and Steam+SOVT was the worst for two. The three participants for whom steam was the worst reported strongly disliking the condition. Only three people experienced a worsening of PTP greater than or equal to 0.5 cm H 2 O: one in the SOVT condition; and two in the Steam+SOVT. It is typically expected that increases or decreases in PTP and SPL will be systematically related. Since the goal of a warm-up is to increase phonatory efficiency, and improve the viscosity of the vocal folds, a reduction in PTP after any condition was interpreted favorably. For the 9 data points across all conditions where PTP and SPL both decreased, there was a mean decrease in PTP of 0.34 cm H2O (SD=0.28 cm H2O ). Mean decrease in SPL was 2.00 dB (SD=0.88 dB). This indicates that individuals were able to decrease PTP and SPL as expected after a warm-up strategy. Finally, a trend appeared in six data points, where despite an increase in SPL, PTP decreased, potentially indicating improvement in vocal efficiency. Of these data points the mean decrease in PTP was 0.36 cm H2O ( SD=0.17 cm H2O ), with a mean increase in SPL of 1.70 dB (SD=1.21 dB). Of these six data points, indicating increased efficiency, three were with steam, two with Steam+SOVT, and one with SOVT. This study revealed that these strategies are not universally successful, and clinicians should recommend them only after assessing their effectiveness for their client. Clinicians need to be custom tailoring these exercises to their client's goals and proclivities. Another consideration is the importance of teaching proper SOVT technique, so it is done correctly without added tension. Even blowing bubbles into a cup of water with phonation can be done poorly, in some cases yielding counterproductive results. Another interesting trend suggests that the inclusion of steam in vocal warm-up may increase vocal efficiency. Future studies should explore how time of day and vocal condition impact each strategy's effectiveness, and which strategy may be most appropriate for different desired outcomes, such as vocal warmup versus vocal rescue.

Frequency Modulation System and Bone Conduction Hearing Aid: Electroacoustic Verification.

Introduction A protocol has not yet been developed to perform electroacoustic measurements and behavioral tests to fit the frequency modulation (FM) system in bone conduction hearing aid (BCHA) users. Electroacoustic verification, with “FM transparency” achieved, ensures user audibility of FM transmitter and hearing aid signals. Objective To propose and validate a protocol for electroacoustic verification of the FM system coupled to the BCHA. Method Twenty-four sets of FM system and BCHA were submitted to electroacoustic verification, using a receiver and a plastic adapter to connect the BCHA to a 2cc coupler in the hearing instrument analyzer. The measurements were performed in the acoustic box, at 65 dB sound pressure level (SPL), with International Speech Test Signal (ISTS), first to the BCHA microphone and then to the FM system microphone, to determine the transparency, in which equivalent inputs for both microphones result in equivalent outputs. The FM gain or volume has been adjusted to try to gain transparency for the outputs of the two input devices. Results Transparency was achieved for all sets evaluated, but in some combinations, adjustments to the FM receiver gain over the manufacturer's default setting were required. Conclusion The proposed protocol proved to be effective for the electroacoustic verification of the FM system coupled to the BCHA.

Management of transmodiolar and transmacular cochleovestibular schwannomas with and without cochlear implantation. German version

Hearing rehabilitation with cochlear implants has attracted increasing interest also for patients with cochleovestibular schwannoma. The authors report their experience with the surgical management of tumors with rare transmodiolar or transmacular extension and outcomes after cochlear implantation (CI). This retrospective case series included nine patients with either primary intralabyrinthine tumors or secondary invasion of the inner ear from the internal auditory canal. The primary endpoint with CI, performed in six patients, was word recognition score at 65 dB SPL (sound pressure level). Secondary endpoints were intra- and postoperative electrophysiological parameters, impedance measures, the presence of awaveV in the electrically evoked (via the CI) auditory brainstem responses, the specifics of postoperative CI programming, and adverse events. Hearing rehabilitation with CI in cases of transmodiolar tumor growth could be achieved only with incomplete tumor removal, whereas tumors with transmacular growth could be completely removed. All six patients with CI had good word recognition scores for numbers in quiet conditions (80-100% at 65 dB SPL, not later than 6 to 12months post CI activation). Four of these six patients achieved good to very good results for monosyllabic words within 1-36months (65-85% at 65 dB SPL). The two other patients, however, had low scores for monosyllables at 6months (25 and 15% at 65 dB SPL, respectively) with worsening of results thereafter. Cochleovestibular schwannomas with transmodiolar and transmacular extension represent arare entity with specific management requirements. Hearing rehabilitation with CI is aprincipal option in these patients.

Prediction of Individual Cochlear Implant Recipient Speech Perception With the Output Signal to Noise Ratio Metric.

A cochlear implant (CI) implements a variety of sound processing algorithms that seek to improve speech intelligibility. Typically, only a small number of parameter combinations are evaluated with recipients but the optimal configuration may differ for individuals. The present study evaluates a novel methodology which uses the output signal to noise ratio (OSNR) to predict complete psychometric functions that relate speech recognition to signal to noise ratio for individual CI recipients. Speech scores from sentence-in-noise tests in a "reference" condition were mapped to OSNR and a psychometric function was fitted. The reference variability was defined as the root mean square error between the reference scores and the fitted curve. To predict individual scores in a different condition, OSNRs in that condition were calculated and the corresponding scores were read from the reference psychometric function. In a retrospective experiment, scores were predicted for each condition and subject in three existing data sets of sentence scores. The prediction error was defined as the root mean square error between observed and predicted scores. In data set 1, sentences were mixed with 20 talker babble or speech weighted noise and presented at 65 dB sound pressure level (SPL). An adaptive test procedure was used. Sound processing was advanced combinatorial encoding (ACE, Cochlear Limited) and ACE with ideal binary mask processing, with five different threshold settings. In data set 2, sentences were mixed with speech weighted noise, street-side city noise or cocktail party noise and presented at 65 dB SPL. An adaptive test procedure was used. Sound processing was ACE and ACE with two different noise reduction schemes. In data set 3, sentences were mixed with four-talker babble at two input SNRs and presented at levels of 55-89 dB SPL. Sound processing utilised three different automatic gain control configurations. For data set 1, the median of individual prediction errors across all subjects, noise types and conditions, was 12% points, slightly better than the reference variability. The OSNR prediction method was inaccurate for the specific condition with a gain threshold of +10 dB. For data set 2, the median of individual prediction errors was 17% points and the reference variability was 11% points. For data set 3, the median prediction error was 9% points and the reference variability was 7% points. A Monte Carlo simulation found that the OSNR prediction method, which used reference scores and OSNR to predict individual scores in other conditions, was significantly more accurate (p < 0.01) than simply using reference scores as predictors. The results supported the hypothesis that the OSNR prediction method could accurately predict individual recipient scores for a range of algorithms and noise types, for all but one condition. The medians of the individual prediction errors for each data set were accurate within 6% points of the reference variability and compared favourably with prediction methodologies in other recent studies. Overall, the novel OSNR-based prediction method shows promise as a tool to assist researchers and clinicians in the development or fitting of CI sound processors.

Effect of presentation level and age on release from masking: Behavioral measures.

The effect of presentation level and age on release from masking (RFM) was examined. Two speech-in-noise paradigms [i.e., fixed speech with varying signal-to-noise ratios (SNRs) and fixed noise with varying speech levels] were employed with competing continuous and interrupted noises. Young and older normal-hearing adults participated (N = 36). Word recognition was assessed at three presentation levels (i.e., 20, 30, and 40 dB sensation level) in SNRs of -10, 0, and 10 dB. Reception thresholds for sentences (RTSs) were determined at three presentation levels (i.e., 55, 65, and 75 dB sound pressure level). RTS SNRs were determined in both noises. RFM was computed by subtracting word recognition scores in continuous noise from interrupted noise and RTS SNRs in interrupted noise from continuous noise. Significant effects of presentation level, group, and SNR were seen with word recognition performance. RFM increased with increasing sensation level, was greater in younger adults, and was superior at -10 dB SNR. With RTS SNRs, significant effects of presentation level and group were found. The findings support the notion that RFM is a level dependent auditory temporal resolution phenomenon and older listeners display a deficit relative to younger listeners.

Individualized estimation of the Speech Intelligibility Index for short sentences: Test-retest reliability

The speech intelligibility index (SII) model was modified to allow individualized parameters. These parameters included the relative weights of speech cues in five octave-frequency bands ranging from 0.25 to 4 kHz, i.e., the band importance function, and the transfer function that allows the SII to generate predictions on speech-recognition scores. A Bayesian adaptive procedure, the quick-band-importance-function (qBIF) procedure, was utilized to enable efficient estimation of the SII parameters from individual listeners. In two experiments, the SII parameters were estimated for 30 normal-hearing adults using Institute of Electrical and Electronics Engineers (IEEE) sentences at speech levels of 55, 65, and 75 dB sound pressure level (in Experiment I) and for 15 hearing-impaired (HI) adult listeners using amplified IEEE or AzBio sentences (in Experiment II). In both experiments, even without prior training, the estimated model parameters showed satisfactory reliability between two runs of the qBIF procedure at least one week apart. For the HI listeners, inter-listener variability in most estimated SII parameters was larger than intra-listener variability of the qBIF procedure.

Dextromethorphan Attenuates Sensorineural Hearing Loss in an Animal Model and Population-Based Cohort Study.

The effect of dextromethorphan (DXM) use in sensorineural hearing loss (SNHL) has not been fully examined. We conducted an animal model and nationwide retrospective matched-cohort study to explore the association between DXM use and SNHL. Eight-week-old CBA/CaJ hearing loss was induced by a white noise 118 dB sound pressure level for 3 h. DXM (30 mg/kg) was administered intraperitoneally for 5 days and boost once round window DXM socking. In population-based study, we examined the medical records over 40 years old in Taiwan’s National Health Insurance Research Database between 2000 and 2015 to establish retrospective matched-cohort to explore the correlation between DXM use and SNHL. Using click auditory brainstem response (ABR), hearing threshold was measured as 48.6 ± 2.9 dB in control mice compared with 42.6 ± 7.0 dB in DXM mice, which differed significantly (p = 0.002) on day 60 after noise exposure with a larger ABR wave I amplitude in DXM mice. In human study, we used a Cox regression hazard model to indicate that a significantly lower percentage individuals developed SNHL compared with and without DXM use (0.44%, 175/39,895 vs. 1.05%, 1675/159,580, p < 0.001). After adjustment for age and other variables [adjusted hazard ratio: 0.725 (95% confidence interval: 0.624–0.803, p < 0.001)], this study also demonstrated that DXM use appeared to reduce the risk of developing SNHL. This animal study demonstrated that DXM significantly attenuated noise-induced hearing loss. In human study, DXM use may have a protective effect against SNHL.

Numerical Investigation of Unsteady Flow and Aerodynamic Noise Characteristics of an Automotive Axial Cooling Fan

Low-speed axial cooling fans are frequently used to manage engine temperature by ensuring that adequate quantities of air pass through heat exchangers, even at low vehicle speeds or in the idle condition. This study aims to provide a better understanding of the unsteady flow behavior around an automotive axial cooling fan with seven blades and its impact on the aerodynamic noise generation. Large Eddy Simulation (LES) near the near-field region and the Ffowcs-Williams and Hawkinbygs (FW-H) method were performed to analyze the flow characteristics around the fan and predict the aerodynamic noise emitted from the fan under a constant rotational speed of 2100 rpm. The simulation results for the velocity distributions and aerodynamic noise were compared with the experimental data measured by single hot-wire probe and in a dead-sound room. The results showed a comparatively good agreement upstream and downstream from the fan and at two different receivers of 0.5 m and 1.0 m. When the fan was rotating, a strong tonal noise numerically existed near the leading edge of the blades at the tip and amounted to 110 dB sound pressure level (SPL) caused by the increasing angles of attack with the increasing radial velocity near the ring, which caused the entire air foil to emit a low-frequency noise. Furthermore, the different SPL decay characteristics of approximately 5 dB in the near-field region and 6 dB in the far-field region were observed each time the distance from the fan doubles. The findings of this research can provide important insights into the design of axial fans with low noise and high performance.

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

Comparison of real-ear insertion gains in Japanese-speaking individuals wearing hearing aids with DSLv5 and NAL-NL2

ObjectiveWe used real-ear insertion gain (REIG), with the international speech test signal (ISTS), to evaluate the amplifying characteristics of hearing aids, set for patients who have been wearing such aids for a long time in a stable manner. We further compared this to the target values of the DSLv5 and NAL-NL2 methods. MethodsThe subjects were adults with moderate sensorineural hearing loss. We examined 40 ears in 25 individuals (15 people wearing hearing aids in both ears and ten people wearing aid in only one ear). Fit assessments were performed based on the speech performance-intensity functions and tolerance of environmental noise, and the ears studied were categorized as either ears with sufficient benefit or ears with insufficient benefit. Additionally, we evaluated the REIG for international speech test signals at 65-dB and 80-dB sound pressure level (SPL). We compared the REIG and target values for voice input at 65-dB and 80-dB SPL, calculated from the DSLv5 and NAL-NL2 methods. ResultsAmong the 40 ears, 34 received sufficient benefit and six received an insufficient benefit from hearing aids. The REIG for ISTS at 65-dB in the sufficient benefit ears, at frequencies of 1,000 Hz and 2,000 Hz, were similar to the target values of NAL-NL2 and DSLv5 but were significantly lower at 250 Hz, 500 Hz, and 4,000 Hz frequencies. The compression ratio of REIG for sufficient benefit ears was similar to that of DSLv5. The REIG for ISTS at 65-dB in the insufficient benefit ears was smaller than that in the sufficient benefit ears at frequencies of 2,000 Hz and 4,000 Hz. ConclusionThis study suggested that the target values of NAL-NL2 and DSLv5 are appropriate, even for Japanese-speaking individuals, at mid-pitch sounds. Although it is necessary to investigate the necessity for low-pitch and high-pitch gains further in the future, this study provides meaningful data regarding the amplifying characteristics in Japanese-speaking individuals who have been wearing hearing aids in a stable manner.

Effect of level on spectral-ripple detection threshold for listeners with normal hearing and hearing loss.

This study investigated the effect of presentation level on spectral-ripple detection for listeners with and without sensorineural hearing loss (SNHL). Participants were 25 listeners with normal hearing and 25 listeners with SNHL. Spectral-ripple detection thresholds (SRDTs) were estimated at three spectral densities (0.5, 2, and 4 ripples per octave, RPO) and three to four sensation levels (SLs) (10, 20, 40, and, when possible, 60 dB SL). Each participant was also tested at 90 dB sound pressure level (SPL). Results indicate that level affected SRDTs. However, the effect of level depended on ripple density and hearing status. For all listeners and all RPO conditions, SRDTs improved from 10 to 40 dB SL. In the 2- and 4-RPO conditions, SRDTs became poorer from the 40 dB SL to the 90 dB SPL condition. The results suggest that audibility likely controls spectral-ripple detection at low SLs for all ripple densities, whereas spectral resolution likely controls spectral-ripple detection at high SLs and ripple densities. For optimal ripple detection across all listeners, clinicians and researchers should use a SL of 40 dB SL. To avoid absolute-level confounds, a presentation level of 80 dB SPL can also be used.

A Digital Capacitive MEMS Microphone for Speech Recognition With Fast Wake-Up Feature Using a Sound Activity Detector

This brief presents a digital capacitive MEMS microphone for speech recognition with fast wake-up feature using a sound activity detector. The proposed microphone wakes up only when an acoustic event within the voice-band occurs using the sound activity detector, which can significantly reduce the average current consumption. All wake-up processes are performed on-chip, which enables the fast wake-up feature to prevent missing keywords. In addition, the proposed deglitching technique is applied to prevent the sound activity detector from responding to non-acoustic signals such as glitch signals. An auxiliary low-dropout regulator is used to further reduce the wake-up time. Our microphone consumes only 16 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{A}$ </tex-math></inline-formula> in deep-sleep mode. In active mode, a high-performance readout circuit converts the voice signal into a digital signal. The proposed microphone achieves an A-weighted signal-to-noise ratio (SNR) of 62.8 dBA and an acoustic overload point of 119.4 dB sound pressure level. The readout circuit itself of our microphone, fabricated in a 0.18 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> CMOS process, has an A-weighted SNR of 65.8 dBA.

Echolocation at high intensity imposes metabolic costs on flying bats

Vocalizations are of pivotal importance for many animals, yet sound propagation in air is severely limited. To expand their vocalization range, animals can produce high-intensity sounds, which can come at high energetic costs. High-intensity echolocation is thought to have evolved in bats because the costs of calling are reported to be negligible during flight. By comparing the metabolic rates of flying bats calling at varying intensities, we show that this is true only for low call intensities. Our results demonstrate that above 130 dB sound pressure level (SPL, at a reference distance of 10 cm), the costs of sound production become exorbitantly expensive for small bats, placing a limitation on the intensity at which they can call.

Auditory Evoked Potentials P50: Pure-tones vs Clicks. There is a Similar Supression?

Objective: Clinical application of middle-latency auditory evoked potential (MLAEPs) has been increasing, highlighting the importance of understanding the nature of P50, a component of middle-latency auditory evoked potential. We manipulated stimulus frequency bands in auditory stimuli in order to investigate the nature of P50 in human auditory evoked potentials.&#x0D; Methods: Two paradigms have been used to obtain P50: one is a conditioning /testing paradigm in which paired of pure tone (1000Hz) are delivered, and the other was presented paired of clicks, both with an intensity of 60 dB sound pressure level above the auditory threshold. A total of 30 healthy volunteers were recruited for this study among Center of genetic engineering (fifteen man and fifteen women, mean age of 36, 5). All without consumption of caffeine, cigarettes and drugs.&#x0D; Results: No statistically significant differences occurred between the P50 amplitudes and latencies for the pure tone and those for the clicks.&#x0D; Conclusions: Our present results indicate that P50 in humans may reflect a feed-forward mechanism of the brain where a preceding stimulus drives sensory gating mechanisms in preparation for a second stimulus, but the contained frequency doesn't influence on the P50. Both types (tones or clicks) can be used in the exploration of patient with this evoked potential.

Caffeine as a Tool to Explore Active Cognitive Processing Stages in Two-Choice Tasks.

Background: We used caffeine as a tool to explore the active cognitive-processing stages in a simple Go/NoGo task, in terms of the event-related potential (ERP) components elicited by the Go and NoGo stimuli.Methods: Two hundred and fifty milligrams of caffeine was administered to adult participants (N = 24) in a randomized double-blind placebo-controlled repeated-measures crossover study. Two blocks of an equiprobable auditory Go/NoGo task were completed, each with a random mix of 75 tones at 1000 Hz and 75 at 1500 Hz, all 60 dB sound pressure level (SPL).Results: Major ERP effects of caffeine were apparent in enhancements of the Go N1-1, P3b, and Slow Wave (SW), and the NoGo Processing Negativity, SW, and NoGo Late Positivity.Conclusions: Novel differential findings indicate the potential of our caffeine as a tool approach to elucidate the functional nature of ERP markers of active cognitive processing in a range of developmental and clinical populations.

Enhancement of the low-frequency acoustic energy harvesting with auxetic resonators

A new concept to enhance efficiency of the acoustic energy harvesting is presented and experimentally tested in this paper. An auxetic latticed resonator backed by an acoustic rectangular tube is proposed for this purpose. The concept is tested and proved by comparing the extracted power against performance of a conventional cantilever resonator at resonant-resonant condition. The problem is modeled by the Finite Element Method. The models are validated using experimental tests. The energy harvesting performance is numerically evaluated in different sound powers, geometrical aspects and electrical properties. In a parametric study, performance of the proposed auxetic resonator is compared with a plain one. It is shown that employing the concept can remarkably enhance performance of the acoustic energy harvesting system. At low frequencies, 138 Hz in this study, at an optimum situation we could arrive at a large magnification factor around 10.5 for 100 dB sound pressure level.

A Study on the Korean Conversation Speech Level and Spectrum in Sound-Treated Environment

Purpose: Several studies have reported the differences between Korean and other countries’ speech in long-term average speech spectrum (LTASS) and band importance function. Authors tried to identify the conversational speech level, the resulting spectrum, and the LTASS for Korean. The purpose of this study was to support the production of a Korean-type hearing aid fitting formula to effectively improve the sound quality of hearing aids and the communication abilities with hearing aids, and to standardize the sound stimuli required to measure the performance of hearing aids. Methods: A total of 73 participants with normal hearing and with no specific voice and language deficits was voluntarily recruited from capital, Gyeongsang and Jeolla areas. The conversational speech level was measured by vocalizing ‘soft,’ ‘moderate,’ ‘raised,’ and ‘loud’ at a distance of 1.0 m from the speaker. And LTASS was measured by vocalizing it at a distance of 0.2 m from the speaker. Results: There was a difference in the mean of males and females in the conversation level, but no significant regional differences were shown. The conversational speech level corresponding to 30th, 65th, and 99th percentiles was 59.67, 64.74, and 79.07 dB sound pressure level, respectively. And the speech spectrum of 30th, 65th, and 99th percentile and LTASS showed in different forms from the international speech test signal. Conclusion: The results of this study should help to calculate the Korean type hearing aid fitting formula and should be used as the basic data to determine the characteristics of the sound stimuli when measuring the performance of the hearing aid.