Sound Noise Research Articles

Owl-inspired leading-edge serrations play a crucial role in aerodynamic force production and sound suppression

Owls are widely known for silent flight, achieving remarkably low noise gliding and flapping flights owing to their unique wing morphologies, which are normally characterized by leading-edge serrations, trailing-edge fringes and velvet-like surfaces. How these morphological features affect aerodynamic force production and sound suppression or noise reduction, however, is still not well known. Here we address an integrated study of owl-inspired single feather wing models with and without leading-edge serrations by combining large-eddy simulations (LES) with particle-image velocimetry (PIV) and force measurements in a low-speed wind tunnel. With velocity and pressure spectra analysis, we demonstrate that leading-edge serrations can passively control the laminar-turbulent transition over the upper wing surface, i.e. the suction surface at all angles of attack (0° < AoA < 20°), and hence play a crucial role in aerodynamic force and sound production. We find that there exists a tradeoff between force production and sound suppression: serrated leading-edges reduce aerodynamic performance at lower AoAs < 15° compared to clean leading-edges but are capable of achieving both noise reduction and aerodynamic performance at higher AoAs > 15° where owl wings often reach in flight. Our results indicate that the owl-inspired leading-edge serrations may be a useful device for aero-acoustic control in biomimetic rotor designs for wind turbines, aircrafts, multi-rotor drones as well as other fluid machinery.

Developing a multivariate model for predicting the noise annoyance responses due to combined water sound and road traffic noise exposure

People in an urban environment are exposed to different types of natural and man-made sounds. Human sound perceptions due to exposure to a single noise source, in particular road traffic and aircraft noises, have been investigated for a long time. However, only very few studies have been focused on exposure to a combination of sound sources. Also, there is a lack of multivariate models that can help to predict the preferences or annoyance responses as a result of adding a wanted sound to an unwanted sound. Accordingly, this study aimed at developing a multivariate model to predict the probability of invoking a high noise annoyance response due to combined water sound and road traffic noise exposure. A series of laboratory experiments were performed. Participants were presented with a series of acoustical stimuli before being asked to assign their annoyance ratings. Results suggested that other than acoustical properties like sound pressure levels, personality traits were found to exert considerable influences on the maximum likelihoods of the model prediction and thus should not be excluded from the model specification form. Also, the quality of the acoustical environment could be improved by adding water sounds to road traffic noises at high levels. The capability of stream sound to moderate noise annoyance was found to be slightly stronger than that of fountain sound. In addition, the formulated multivariate model enables to reveal the tradeoff decisions performed by people. An increase in the SPL of road traffic noise by 1dB was considered to be equivalent to a reduction in the SPL of water source by 1.7dB for a given probability value. Results arising from this study should provide valuable insights on understanding how humans respond to the combined water sound and road traffic noise exposure.

Statistical–Empirical Modeling of Airfoil Noise Subjected to Leading-Edge Serrations

With the objective of reducing the broadband noise from the interaction of highly turbulent flow and airfoil leading edge, sinusoidal leading-edge serrations were investigated as an effective passive treatment. An extensive aeroacoustic study was performed to determine the main influences and interdependencies of factors, such as the Reynolds number, turbulence intensity, serration amplitude, and wavelength as well as the angle of attack on the noise-reduction capability. A statistical–empirical model was developed to predict the overall sound pressure level and noise reduction of a NACA 65(12)-10 airfoil with and without leading-edge serrations in the range of chord-based Reynolds numbers of . The observed main influencing factors on the noise radiation were quantified in a systematic order for the first time. Moreover, significant interdependencies of the turbulence intensity and the serration wavelength, as well as the serration wavelength and the angle of attack, were observed, validated, and quantified. The statistical–empirical model was validated against an external set of experimental data, which is shown to be accurate and reliable.

Background noise exerts diverse effects on the cortical encoding of foreground sounds.

In natural listening conditions, many sounds must be detected and identified in the context of competing sound sources, which function as background noise. Traditionally, noise is thought to degrade the cortical representation of sounds by suppressing responses and increasing response variability. However, recent studies of neural network models and brain slices have shown that background synaptic noise can improve the detection of signals. Because acoustic noise affects the synaptic background activity of cortical networks, it may improve the cortical responses to signals. We used spike train decoding techniques to determine the functional effects of a continuous white noise background on the responses of clusters of neurons in auditory cortex to foreground signals, specifically frequency-modulated sweeps (FMs) of different velocities, directions, and amplitudes. Whereas the addition of noise progressively suppressed the FM responses of some cortical sites in the core fields with decreasing signal-to-noise ratios (SNRs), the stimulus representation remained robust or was even significantly enhanced at specific SNRs in many others. Even though the background noise level was typically not explicitly encoded in cortical responses, significant information about noise context could be decoded from cortical responses on the basis of how the neural representation of the foreground sweeps was affected. These findings demonstrate significant diversity in signal in noise processing even within the core auditory fields that could support noise-robust hearing across a wide range of listening conditions.NEW & NOTEWORTHY The ability to detect and discriminate sounds in background noise is critical for our ability to communicate. The neural basis of robust perceptual performance in noise is not well understood. We identified neuronal populations in core auditory cortex of squirrel monkeys that differ in how they process foreground signals in background noise and that may contribute to robust signal representation and discrimination in acoustic environments with prominent background noise.

An Office of Naval Research perspective on Ira Dyer's Legacy

The talk will highlight a few of the many important contributions Professor Dyer made to underwater acoustics through his interactions with ONR as a researcher, advisor, and educator. His wide ranging expertise included sound and vibration in complex structures that led the way for the U.S. Navy to develop ultra-quiet submarines, as well as the statistics of sound propagation in the ocean, submarine sonar design, and advances in sonar signal processing. Beginning in 1978, he led and participated in six Arctic field programs, including the Canadian Basin Arctic Reverberation Experiment that imaged the entire Arctic basin with acoustics. Over the course of these efforts, that he really enjoyed talking about, he and his students developed a systematic understanding of sound propagation and noise in the Arctic.

Pool equipment mechanical noise impact

The paper discusses noise impact from mechanical systems in residential buildings. The project presented discusses noise impact related to pool equipment mechanical systems. Sound readings were taken and recorded with different settings. Sound analysis and noise mitigation solutions will be discussed. Project located in Paradise Island, Nassau, Bahamas.

The Impact of Noise Pollution on Workers’ Health in Selected Industries of Mirzapur Industrial Area, Tangail, Bangladesh

The unwanted and intolerable sound causes noise. The study was conducted through interviewing of workers and measuring of noise levels on six types of industries. The data were collected on April, May and June, 2013. The data of noise levels were measured at main gate, administration office and working place of the selected industries. The noise level at the working places during day time of the selected industries were 81.50 dB (textile mill), 104.20 dB (cotton mill), 90.50 dB (jute mill), 95.90 dB (spinning mill), 89.25 dB (knit and garments factory) and 83.50 dB (knitting factory), respectively. All the recorded noise level data in working places of the industries exceeded the DoE standard (75 dB at day time and 70 dB at night time) that caused noise pollution. The important contributors of noise pollution were machineries and overcrowding of the workers in the industry. Most of the common impacts of noise pollution were headache, heart diseases and hearing problem. To resolve the noise problem in industry it was suggested to eliminate the noise sources substituting noisy machineries and so on.J. Environ. Sci. &amp; Natural Resources, 9(2): 155-160 2016

Study of the traffic noise source intensity emission model and the frequency characteristics for a wet asphalt road

The traffic noise source intensity emission model is the basis of traffic noise prediction. In addition, the presence of water on the road is an important factor of road traffic noise. However, to date, none of the traffic noise source intensity emission models account for a situation in which the road surface is wet. Therefore, the main objective of this paper is to build a traffic noise source intensity emission model on a wet asphalt road based on traffic noise measurements, in which speed, sound pressure level and frequency spectrum were recorded as a single vehicle passed by. By using statistical analysis on the measurement data, a traffic noise source intensity emission model on a wet asphalt road was acquired, which conforms to correlation test, F-test and t-test. The result shows that the sound pressure level increases considerably with the presence of water on asphalt road for all types of vehicles; the mean difference in the sound pressure level between the wet and dry asphalt roads for light, middle-size, and heavy vehicles are 10.09dB(A), 5.56dB(A), and 4.26dB(A), respectively. In addition, the noise difference between a wet and dry asphalt road decreases as the speed and vehicle size grow. Furthermore, the frequency characteristics of the road traffic noise were analysed through the sound pressure level and noise energy percentage in the 1/3 octave band spectrum. The result shows that for the wet asphalt road, the sound pressure level is high at high frequency and low at low frequency, which is completely different from the response on a dry asphalt road. In addition, for a dry asphalt road, the vehicle’s noise energy percentage at low frequency decreases as the speed increases, whereas at high frequency, the percentage increases as the speed grow. However, for a wet asphalt road, the noise energy percentage changes little with speed. The findings can be applied to the accurate traffic noise prediction and noise control, especially in the rainy regions.

가스터빈 차폐막의 소음 저감효과에 관한 연구

A gas turbine is the main equipment used in a combined heat and power plant. It generates a high sound pressure noise level. To reduce the noise level, an enclosure is installed around the turbine. The sound insulation performance of the enclosure affects the amount of external noise reduction. In this study, a sound transmission loss analysis is performed using the boundary element method to predict sound insulation performance according to the numbers and shapes of the supporter. Radiated noise analysis is also performed for the main external points of the enclosure using ray-acoustics. The results of these analyses are presented and a design plan is proposed that reduces the sound pressure noise level of the enclosure.

수직축 풍력터빈 성능예측을 위한 2.5-D CFD 적용

Recently, vertical axis wind turbines have been widely used to produce electricity even in urban. This system has several merits, such as low sound noise, easy installation of the generator, and simple structure without a yaw-control mechanism and so on. However, its blades are operated under the influence of the trailing vortices generated by the preceding blades. This phenomenon deteriorates its output power, and also makes difficulty in predicting correctly its performance. Even though there are many prediction methods, the CFD could be a very accurate prediction method. For this, this method needs the transient analysis and three-dimensional (3-D) computation. However, this full 3-D CFD could be hard to be a practical tool because it requires huge computation time. Therefore, the reduced computational domain was applied as a practical method. In this study, the computations were conducted in the reduced computational domain and compared with the experimental results reported in the literature. It was examined the mechanism of the difference between the experimental results and the computational results. In addition, it showed this computational method could be an effective method in the design methodology using the optimization algorithm.

Hybrid Nelder-Mead search based optimal Least Mean Square algorithms for heart and lung sound separation

Algorithms for separation of heart sounds from background lung sound noises are vital for accurate diagnosis of heart diseases. In this paper, an improved adaptive noise cancellation technique based on the Least Mean Square (LMS) algorithm is used to separate heart sounds from lung sounds. The step size parameter in the LMS algorithm is optimally chosen using a hybrid Nelder-Mead (H-NM) optimization algorithm. The NM algorithm is initialized with a good initial solution by using computationally cheap random search to compute a rough estimate of the global minimum. Initialization of the NM algorithm with a good initial guess avoided convergence to shallow local minima and improved the quality of the final solution. The effects of using two state-of-the-arts biologically inspired heuristic optimization algorithms instead of the H-NM algorithm and three variants of the standard LMS algorithm are investigated. The correlation coefficient between the ideal and filtered heart sound signal and running time-complexity of different algorithms are taken as the metric for comparison of different heart sound separation approaches. Simulation results indicate that the approach presented in this paper performs significantly better than a variety of alternate approaches on heart sound separation problems.

Cochlear implant effectiveness in postlingual single-sided deaf individuals: what’s the point?

Objectives: By extending the indication criteria for cochlear implants (CI), the population of CI candidates increased in age, as well as range and type of hearing loss. This qualitative study identified factors that contributed to seek CI treatment in single-sided deaf individuals and gained insights how single-sided deafness (SSD) and hearing with a CI affect their lives. Design: An open-ended questionnaire and a standardised inventory (IOI-HA) were used. Qualitative data reflecting the reasons to seek CI treatment and the individual experiences after CI switch-on were collected. Study sample: A total of 19 postlingually deafened single-sided deaf CI users. Results: Participants use their CI daily and stated that their life satisfaction increased since CI activation. The analysis of the qualitative data revealed four core categories: sound localisation, tinnitus and noise sensitivity, fear to lose the second ear and quality of life. Conclusions: Our results show how strongly and diversely quality of hearing and quality of life is affected by acquired SSD and improved after CI activation. Our data suggest that the fear of hearing loss (HL) on the normal hearing (NH) ear is an important but so far neglected reason to seek treatment with a CI in individuals with postlingual SSD.

Robust interactions between the effects of auditory and cutaneous electrical stimulations on cell activities in the thalamic reticular nucleus

The thalamic reticular nucleus (TRN), a cluster of GABAergic cells, is thought to regulate bottom-up and top-down streams of sensory processing in the loop circuitry between the thalamus and cortex. Provided that sensory inputs of different modalities interact in the TRN, the TRN could contribute to fast and flexible cross-modal modulation of attention and perception that incessantly takes place in our everyday life. Indeed, diverse subthreshold interactions of auditory and visual inputs have been revealed in TRN cells (Kimura, 2014). To determine whether such sensory interaction could extend across modalities as a universal neural mechanism, the present study examined TRN cell activities elicited by auditory and cutaneous electrical stimulations in anesthetized rats. Juxta-cellular recording and labeling techniques were used. Recordings were obtained from 129 cells. Auditory or somatosensory responses were modulated by subthreshold electrical stimulation or sound (noise burst) in the majority of recordings (77 of 85 auditory and 13 of 15 somatosensory cells). Additionally, 22 bimodal cells and seven cells that responded only to combined stimulation were recognized. Suppression was predominant in modulation that was observed in both early and repeatedly evoked late responses. Combined stimulation also induced de novo cell activities. Further, response latency and burst spiking were modulated. Axonal projections of cells showing modulation terminated in first- or higher-order thalamic nuclei. Nine auditory cells projected to somatosensory thalamic nuclei. These results suggest that the TRN could regulate sensory processing in the loop circuitry between the thalamus and cortex through the sensory interaction pervasive across modalities.

Performance estimation of an oil-free linear compressor unit for a new compact 2K Gifford-McMahon cryocooler

Since 2012, a new, compact Gifford-McMahon (GM) cryocooler for cooling superconducting single photon detectors (SSPD) has been developed and reported by Sumitomo Heavy Industries, Ltd. (SHI). Also, it was reported that National Institute of Information and Communications Technology (NICT) developed a multi-channel, conduction-cooled SSPD system. However, the size and power consumption reduction becomes indispensable to apply such a system to the optical communication of AdHoc for a mobile system installed in a vehicle. The objective is to reduce the total height of the expander by 33% relative to the existing RDK-101 GM expander and to reduce the total volume of the compressor unit by 50% relative to the existing CNA-11 compressor. In addition, considering the targeted cooling application, we set the design cooling capacity targets of the first and the second stages 1 W at 60 K and 20 mW at 2.3 K respectively. In 2016, Hiratsuka et al. reported that an oil-free compressor was developed for a 2K GM cryocooler. The cooling performance of a 2K GM expander driven by an experimental unit of the linear compressor was measured. No-load temperature less than 2.1 K and the cooling capacity of 20 mW at 2.3 K were successfully achieved with an electric input power of only 1.1 kW. After that, the compressor capsule and the heat exchanger, etc. were assembled into one enclosure as a compressor unit. The total volume of the compressor unit and electrical box was significantly reduced to about 38 L, which was close to the target of 35 L. Also, the sound noise, vibration characteristics, the effect of the compressor unit inclination and the ambient temperature on the cooling performance, were evaluated. The detailed experimental results are discussed in this paper.

Evaluation of noise effects on standard threshold shift employees of technical and professional organization according to the audiogram and sound overall level measurement in Ilam: A cross-sectional study

Background: Noise is one of the most prevalent physically harmful factors in working environment which can cause many problems that one of them is hearing loss. Therefore, the aim of this study was to assess occupational exposure with sound (noise) in training workshops of Technical and Vocational Organization of Ilam and to determine the rate of change in hearing threshold of people working in these workshops. Materials and Methods: A cross-sectional study was carried out on 60 people which working in 8 workshops of Technical and Vocational Organization of Ilam which are selected by census report. Demographic data of studied people are collected using a researcher-made checklist and measuring the overall balance of sound level meter set model 450 is used. Changes in hearing threshold of people are assessed using audiometer. Finally, data are analyzed using SPSS 20 by conduct Spearman correlation and Pearson's correlation statistical tests in asignificant level of 0.05. Results: The results show that there have been 8.62 dB change in hearing threshold of the left ear, 8.73 dB in right ear, and 6.74 dB in both ears of studied people averagely. The highest level of sound pressure balance is related to cutting-wood workshop, and the Equivalent exposure level (Leq) is more than national standard level (85 dB) in mosaic, lapidary, and welding workshops. Spearman correlation test shows a significant relationship between the highest level of sound balance in welding workshop (112 dB) and the average total loss (8.15 dB) for both ears (P

Influence of Density on Sound Absorption Coefficient of Fibre Board

For acoustic applications such as theaters, cinema halls, auditoriums the data on acoustic properties i.e. sound absorption coefficient and sound transmission loss are required to evaluate the acoustic behavior of panel products and to facilitate the necessary design computations. Fibre boards are widely used in private and commercial buildings, but not much data are available on acoustic efficiency of fibre boards. The study was carried using acoustic pulse tester based on standing wave method for evaluating sound absorption coefficient. Wood fibre boards of different densities ranging from 200 to 800 kg/m3 were taken and their sound absorption coefficients at frequencies ranging from 125 Hz to 4000 Hz were evaluated in third octave band. Noise reduction coefficient of the samples was also computed. From the study, it is observed that low density fibre board possess high sound absorption coefficient and noise reduction coefficient when compared with high density fibre boards. It was seen that sound absorption coefficient increases with decrease in density and vice versa.

Potential for spatial displacement of Cook Inlet beluga whales by anthropogenic noise in critical habitat

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 32:43-57 (2017) - DOI: https://doi.org/10.3354/esr00786 Theme Section: 21st century paradigms for measuring and managing the effects of anthropogenic ocean noise Potential for spatial displacement of Cook Inlet beluga whales by anthropogenic noise in critical habitat Robert J. Small1,*, Brian Brost2, Mevin Hooten3,2,4, Manuel Castellote5,6, Jeffrey Mondragon1 1Alaska Department of Fish and Game, 1255 West 8th Street, Juneau, AK 99801, USA 2Department of Fish, Wildlife, and Conservation Biology, Colorado State University, 1484 Campus Delivery, Fort Collins, CO 80523, USA 3U.S. Geological Survey, Colorado Cooperative Fish and Wildlife Research Unit, 1484 Campus Delivery, Fort Collins, CO 80523, USA 4Department of Statistics, Colorado State University, 1484 Campus Delivery, Fort Collins, CO 80523, USA 5Joint Institute for the Study of the Atmosphere and Ocean (JISAO), University of Washington, 3737 Brooklyn Avenue NE, Seattle, WA 98105, USA 6Alaska Fisheries Science Center, Marine Mammal Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115, USA *Corresponding author: bob.small@alaska.gov ABSTRACT: The population of beluga whales in Cook Inlet, Alaska, USA, declined by nearly half in the mid-1990s, primarily from an unsustainable harvest, and was listed as endangered in 2008. In 2014, abundance was ~340 whales, and the population trend during 1999-2014 was -1.3% yr-1. Cook Inlet beluga whales are particularly vulnerable to anthropogenic impacts, and noise that has the potential to reduce communication and echolocation range considerably has been documented in critical habitat; thus, noise was ranked as a high potential threat in the Cook Inlet beluga Recovery Plan. The current recovery strategy includes research on effects of threats potentially limiting recovery, and thus we examined the potential impact of anthropogenic noise in critical habitat, specifically, spatial displacement. Using a subset of data on anthropogenic noise and beluga detections from a 5 yr acoustic study, we evaluated the influence of noise events on beluga occupancy probability. We used occupancy models, which account for factors that affect detection probability when estimating occupancy, the first application of these models to examine the potential impacts of anthropogenic noise on marine mammal behavior. Results were inconclusive, primarily because beluga detections were relatively infrequent. Even though noise metrics (sound pressure level and noise duration) appeared in high-ranking models as covariates for occupancy probability, the data were insufficient to indicate better predictive ability beyond those models that only included environmental covariates. Future studies that implement protocols designed specifically for beluga occupancy will be most effective for accurately estimating the effect of noise on beluga displacement. KEY WORDS: Beluga whales · Anthropogenic noise · Spatial displacement · Occupancy models Full text in pdf format Supplementary material PreviousNextCite this article as: Small RJ, Brost B, Hooten M, Castellote M, Mondragon J (2017) Potential for spatial displacement of Cook Inlet beluga whales by anthropogenic noise in critical habitat. Endang Species Res 32:43-57. https://doi.org/10.3354/esr00786 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 32. Online publication date: February 07, 2017 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2017 Inter-Research.

Facet Analysis and Designing of Fault Sound and Background Noise of Large Central Air Conditioner

Facet Analysis and Designing of Fault Sound and Background Noise of Large Central Air Conditioner

Basic study on active noise control for considering characteristics of vibration of plate by giant magnetostrictive actuator

In recent years, micro-compact electric vehicles have been developed and actively marketed, and has become popular as a new short-distance transfer mobility tool. While micro-compact electric vehicles do not have generate an engine sound, road and wind noises cause interior noise, and have a large impact on user comfort in the interior space. Recently the use of interior noise reduction by ANC has been used in the automobile industry. In this study, we propose a system whereby a giant magnetostrictive actuator is installed on the front window of a micro-compact electric vehicle to actively cut interface vibration noise, i.e., road noise, transmitted to the interior of the vehicle. In the experiment, we used an enclosure to simulate the interior of a vehicle and investigated the installation position of the giant magnetostrictive actuator to study the vibration characteristics of a window plate.

Placing of aroma compounds by food sales promotion in chosen services business

There are several ways to get higher sale involving human senses too. One of the options is a security of stimulating atmosphere of sale/ business environment. In addition to equipment, design and staff, the lighting, sound (noise), and last ones but not least smell, respectively air quality significantly take part on that. Aroma is the element that inherently belongs to the visual merchandising tools. It can influence not only emotions, memory, but total customers´ satisfaction and preferences as well as spending time in that place. In this context, it is important to find right compromise when choosing the aromatic compounds for various products, in the process of their application (intensity, process of aromatization) and security of sufficient air quality, because everybody perceives the odours with different sensitivity. Properly chosen smell and factors of air quality bring for business operators (services trades) many advantages; from staff, who more relax and friendly behave to the guests until making of various associations and stimulations of customers, who spend time inside of service. Fragrance or air quality looks like based on of present researches as the most important factor directly on point-of-sale, while aroma acquires the importance in case of memory too. On the one side, the thinks, which are seen or heard by customers, could be memorized by them few days or weeks, so on the second side, the thinks which are smelled, could be memorized by guests many decades. Except this, the Scientifics studies show, that over 75 % of all emotions are generated based on scent´ perception. The main aim of this paper is a research, how aroma influences customer purchasing decision (preferences) in chosen service provider through the tracking of daily sales of baked baguettes (Paninis) with using of aroma equipment; Aroma Dispenser.