Showing papers in "Acoustics Australia in 2017"

A Review of the Factors that Influence Sound Absorption and the Available Empirical Models for Fibrous Materials

Abstract: There is a drastic need in industries, such as the automotive and construction industry, for easy-to-use empirical models that can effectively and efficiently predict the sound absorption coefficient of fibrous absorbers. Hence, this paper presents a review of the factors that influence sound absorption, such as bulk density, composite thickness, porosity, fibre diameter, airflow resistivity, tortuosity and surface impedance. Also, the available empirical models for the prediction of the sound absorptions coefficient of porous fibrous materials and their working range are presented. These models have been tested using experimental data, based on natural fibres such as coir, kenaf, hemp and sheep’s wool, in order to test their accuracy. An analysis of the data is presented. It is seen that the present empirical models available are not adequate for the prediction of the sound absorption coefficient for the natural fibres presented, and hence, new models that can accurately predict the sound absorption coefficient need to be developed. The current models available are also seen to be extremely sensitive to composite thickness and bulk density changes. However, they are able to give the designer a good starting point. Therefore, this review is intended to be a comprehensive and valuable reference source for designers of sound absorbing materials in order to save time and costs during the design phase. Therefore, this contribution will enable the designers to make quick informed decisions on the type of absorber to use for a particular application as well as allow for quick selection of an appropriate empirical model for accurate prediction of the sound absorption coefficient of the selected fibrous porous material.

Review of Underwater and In-Air Sounds Emitted by Australian and Antarctic Marine Mammals

Abstract: The study of marine soundscapes is a growing field of research. Recording hardware is becoming more accessible; there are a number of off-the-shelf autonomous recorders that can be deployed for months at a time; software analysis tools exist as shareware; raw or preprocessed recordings are freely and publicly available. However, what is missing are catalogues of commonly recorded sounds. Sounds related to geophysical events (e.g. earthquakes) and weather (e.g. wind and precipitation), to human activities (e.g. ships) and to marine animals (e.g. crustaceans, fish and marine mammals) commonly occur. Marine mammals are distributed throughout Australia’s oceans and significantly contribute to the underwater soundscape. However, due to a lack of concurrent visual and passive acoustic observations, it is often not known which species produces which sounds. To aid in the analysis of Australian and Antarctic marine soundscape recordings, a literature review of the sounds made by marine mammals was undertaken. Frequency, duration and source level measurements are summarised and tabulated. In addition to the literature review, new marine mammal data are presented and include recordings from Australia of Omura’s whales (Balaenoptera omurai), dwarf sperm whales (Kogia sima), common dolphins (Delphinus delphis), short-finned pilot whales (Globicephala macrorhynchus), long-finned pilot whales (G. melas), Fraser’s dolphins (Lagenodelphis hosei), false killer whales (Pseudorca crassidens), striped dolphins (Stenella coeruleoalba) and spinner dolphins (S. longirostris), as well as the whistles and burst-pulse sounds of Australian pygmy killer whales (Feresa attenuata). To date, this is the most comprehensive acoustic summary for marine mammal species in Australian waters.

Developing an Underwater Sound Recorder: The Long and Short (Time) of It...

Abstract: Passive acoustic recording of marine noise has advanced considerably over recent years. For a long time, a lack of widely available technology limited the acquisition of long-term acoustic data sets to a small number of large, cabled installations mostly restricted to military use. For other users, recordings were limited by the available technology to short snapshots of minutes to possibly days of data at a time. As technology has improved, passive acoustic monitoring has shown marine soundscapes are filled with biotic and abiotic sounds that occur on a range of often unpredictable timescales. Thus, snapshot recordings can lead to biased data. In 1999, the Centre for Marine Science and Technology, together with Australia’s Defence Science and Technology Organisation, began developing remote underwater sound recorders to increase the duration and quality of recordings. As time passed, the sound recorders were developed significantly, have been deployed over 600 times at a variety of Australian and international locations and have identified a plethora of biological, geophysical and anthropogenic sound sources. This paper presents a brief history of the recorders’ development and characteristics, some examples of the information they have provided and future direction for their next generation.

Aerial and underwater sound of unmanned aerial vehicles (UAV)

Abstract: Unmanned aerial vehicles/systems (UAV/UAS, drones) are increasingly being used for terrestrial and marine ecological surveying and research Studies on the potential disturbance of fauna by UAVs ha

A Case Study of the Influence of Urban Morphology on Aircraft Noise

Abstract: Aircraft noise is a very important environmental problem that has been addressed in many ways over the years. Many strategies have been developed to mitigate aircraft noise exposure. To help identify the problem, computer simulations with mathematical models for aircraft noise have been developed. However, those models do not consider urban morphology effects on aircraft noise propagation. Urban morphology contains a set of features that modify noise, and it is necessary to be aware of its effects as it can be a factor that can potentially increase sound pressure levels to which the general population is exposed. This paper evaluates different aspects of urban morphology and determines the impact of street topologies, line of sight angles of buildings, facade positions, facade heights, and the combination of street topologies and LOS angles on aircraft noise. Measurements in front of the facade and in free field conditions were performed around buildings that make up educational facilities near Madrid Adolfo Suarez Barajas and Pisa Galileo Galilei airports. With the experimental work, it was demonstrated that front facades, U topologies, and greater LOS angles result in higher levels on facade as all these factors contribute to the transmission of noise in an urban environment. Correction factors for measurements made in facades with and without direct transmission with similar surroundings to the ones measured in this study and within a 95% confidence level were proposed for extrapolating the levels of aircraft noise events in free field conditions.

Shape Dependence of Acoustic Performances of Buildings with a Hyperbolic Paraboloid Cable Net Membrane Roof

Abstract: The paper investigates the shape dependence of the acoustic performances of space with different plans covered by a hyperbolic paraboloid cables net and membrane roof In addition, the paper study the differences of acoustic performances between four different configurations: sport arena and empty, partially occupied and full concert hall The aim is to compare the shape dependence of the acoustic response for each configuration The study is focused on different geometries: four different plan shapes (ie, square, circular, rectangular and elliptical) and two different curvatures The differences of acoustic efficiency are compared using some representative parameters like the reverberation time, ( $$T_{30}$$ ), the clarity ( $$C_{80}$$ ), the definition ( $$D_{50}$$ ) and the initial time delay gap In addition, the paper compares the acoustic response for all concert hall configurations and all geometries with permanent and temporary improvements

Study of a New Highly Absorptive Acoustic Element

Abstract: The highly absorptive acoustic element studied in this paper is constituted by two mating plates provided with slots and a number of micro-channels engraved on the contact surface This fibre-less element has been first presented in a previous work, with the name of micro-grooved element (MGE), as a potential substitute of the well-known micro-perforated element (MPE) (Auriemma et al in SAE Int J Mater Manuf 6(3), 2013) Compared to MPE, it offered advantages in terms of cost-effectiveness of the production process, but similar acoustic behaviour In this paper, MGEs with improved design are presented The new geometry of the outer layers results in inner micro-channels with smaller overall dimensions, while still keeping adequate porosity As a result, the acoustic behaviour is enhanced and the sound absorption of traditional MPEs is finally overcome The transfer impedances of several MGE and MPE samples are measured, modelled and compared The impedance end corrections are extrapolated with a completely experimental procedure and the behaviour in nonlinear regime is studied and described by means of a semi-empirical formulation

A Tale of Two Soundscapes: Comparing the Acoustic Characteristics of Urban Versus Pristine Coastal Dolphin Habitats in Western Australia

Abstract: Underwater noise environments are increasingly being considered in marine spatial planning and habitat quality assessments. Although the overall aim of regulation is to quieten anthropogenically noise-rich habitats whilst maintaining pristine habitats free of man-made noise, effective management plans require knowledge upon which to base decisions. This is particularly true for managers of acoustically specialised species. This study aimed to compare the acoustic environment of coastal dolphins in two locations within Western Australia by comparing a ‘pristine’ habitat (Roebuck Bay) with an ‘urban’ habitat (Fremantle Inner Harbour). Autonomous underwater acoustic recorders collected approximately 940 and 1080 h of data from these two sites, respectively. Additionally, in Roebuck Bay opportunistic in situ recordings with concurrent visual observations were collected in the presence of two dolphin species. Acoustic data were assessed via weekly spectrograms, power spectrum density percentile plots and probability densities, octave band levels, broadband noise levels, and generalised estimating equations. Results indicated that the two sites had highly contrasting acoustic environments. In Roebuck Bay, the local soundscape was dominated by biotic sounds, with only sporadic vessel noise. However, in Fremantle Inner Harbour, anthropogenic noise was prevalent. On average, Roebuck Bay was 20 dB quieter than the Fremantle Inner Harbour over the frequency band 10 Hz–11 kHz. Dolphin communications had a greater potential to be masked in Fremantle Inner Harbour than in Roebuck Bay based on elevated anthropogenic noise levels. If noise levels were to increase in Roebuck Bay, coastal dolphins may show behavioural and/or acoustical responses as observed at other locations.

Health Effects and Work Disability Caused by Exposure to Hand-Transmitted Vibration Among Stone Cutting Workers

Abstract: There are limited epidemiologic data to allow reliable conclusions about industrial workers’ exposure to hand-transmitted vibration and its disorders in developing countries. This study aimed to investigate the clinical features of hand–arm vibration syndrome (HAVS) and work disability caused by exposure to hand-transmitted vibration in stone cutting workers. The study population consisted of 40 stone cutting workers and 30 metal workers as a control group employed in the workshops located in Hamadan (western province of Iran). Measuring exposure to hand-transmitted vibration (HTV) was performed using a vibration meter (model 2260, B and K) and its analyzer (model 1700). By means of a clinically administered questionnaire, information on HAVS symptoms was obtained. The cold water provocation and touch sensory tests were performed for determining sensorineural and vascular functions. The grip strength and manual dexterity tests were also conducted for diagnosis of work disability. The daily vibration exposures of stone cutting workers were significantly higher than the national exposure limit. The prevalence of fingers’ blanching and fingers’ sensation disorders in stone cutting workers was 37.5 and 35%, respectively, but none of the controls had these symptoms. It is revealed that the work abilities of the stone cutting workers have been decreased from 18 to 35% compared with the control group. The findings confirmed that the vascular and sensorineural disorders have significantly reduced the work ability of the stone cutting workers during long-term exposure to HTV. This study covered the lack of information regarding the HAVS symptoms experienced by stone cutting workers and provided a local database for further research about dose–effect relationships.

Stage Acoustics in Eight Australian Concert Halls: Acoustic Conditions in Relation to Subjective Assessments by a Touring Chamber Orchestra

Abstract: Although auditorium acoustics has been extensively studied from an audience perspective, studies of musicians’ preferences on stage are far more limited. The present work tests and extends the hypothesis, suggested in recent studies by others, that the directional distribution of early reflected energy on stage is subjectively important to musicians. The paper presents results of subjective surveys completed by musicians of the Australian Chamber Orchestra immediately after performing in eight Australian purpose-built concert halls and compares these with complementary on-stage acoustic measurements undertaken in the same eight auditoria using a 32-channel spherical microphone array (Eigenmike). Spatial acoustic parameters are investigated together with the traditional omnidirectional parameters defined in the international standard for auditorium acoustics measurements, and a parameter is proposed that compares early energy arriving on stage from above relative to the sides. The parameter is shown to correlate well with musicians’ subjective ratings, with generally lower values preferred. By contrast, standard omnidirectional parameters provided only limited insights into musician preferences for the eight auditorium stages surveyed.

Adaptive Matched Field Processing for Source Localization Using Improved Diagonal Loading Algorithm

Abstract: Matched field processing (MFP) has been a method widely applied for shallow underwater target localization, which is a critical issue in underwater acoustic. To enhance the efficiency of conventional MFP methods, different adaptive MFP algorithms have been developed; the white noise constraints (WNC) MFP or diagonal loading (DL) algorithm is such a typical one. The WNC or DL one has been considered to be the most desirable method because it is more robust to environment mismatch in practical in comparison with the minimum-variance distortionless response MFP algorithm, a popular high-resolution method. Although having exceptional ability to localize underwater sources in mismatch scenarios, the DL method has still been not reach high resolution in certain cases. In the paper, we proposed an adaptive method known as improved diagonal loading algorithm to make an increase in the resolution and the peak background rate in the ambiguity surface of source localization results in comparison with DL one. The proposed algorithm works by adding one more parameter that is adjusted in the steering vector of the DL algorithm. The simulation results show that the new algorithm attains better beamforming performance in terms of high resolution than the existing adaptive MFP algorithms in the case of environmental mismatch caused by noise effects and the limitation of the snapshots.

Automated Insect Detection Using Acoustic Features Based on Sound Generated from Insect Activities

Abstract: This paper presents an automated insect detection technique using acoustic features and machine learning techniques based on sound signals generated from insect activities. The input sound signal was first pre-processed and segmented into windows frames from which the low-level set of signal properties and Mel-Frequency Cepstrum Coefficients were extracted. The detection accuracy of the features was tested on 11 insects of 6 species using a number of classifiers. The results have shown that a suitable acoustic feature set can be used to detect insects with high accuracy. Furthermore, the ensemble classifiers such as Bagged Tree provided the best accuracy in detecting both species classification (over 97.1%) and insect classification (over 92.3%). On the other hand, fine k-nearest neighbour classifier offered a balance between the quick training time (around 1 s) and the detection accuracy (over 88.5%).

An Unsupervised Acoustic Description of Fish Schools and the Seabed in Three Fishing Regions Within the Northern Demersal Scalefish Fishery (NDSF, Western Australia)

Abstract: Fisheries acoustics is now a standard tool for monitoring marine organisms. Another use of active-acoustics techniques is the potential to qualitatively describe fish school and seafloor characteristics or the distribution of fish density hotspots. Here, we use a geostatistical approach to describe the distribution of acoustic density hotspots within three fishing regions of the Northern Demersal Scalefish Fishery in Western Australia. This revealed a patchy distribution of hotspots within the three regions, covering almost half of the total areas. Energetic, geometric and bathymetric descriptors of acoustically identified fish schools were clustered using robust sparse k-means clustering with a Clest algorithm to determine the ideal number of clusters. Identified clusters were mainly defined by the energetic component of the school. Seabed descriptors considered were depth, roughness, first bottom length, maximum Sv, kurtosis, skewness and bottom rise time. The ideal number of bottom clusters (maximisation rule with D-Index, Hubert Score and Weighted Sum of Squares), following the majority rule, was three. Cluster 1 (mainly driven by depth) was the sole type present in Region 1, Cluster 2 (mainly driven by roughness and maximum Sv) dominated Region 3, while Region 2 was split up almost equally between Cluster 2 and 3. Detection of indicator species for the three seabed clusters revealed that the selected clusters could be related to biological information. Goldband snapper and miscellaneous fish were indicators for Cluster 1; Cods, Lethrinids, Red Emperor and other Lutjanids were linked with Cluster 2, while Rankin Cod and Triggerfish were indicators for Cluster 3.

Imaging Marine Fauna with a Tritech Gemini 720i Sonar

Abstract: Multibeam sonar systems are increasingly used to detect, quantify and monitor behaviour of marine fauna. Over ranges of tens to hundreds of metres, animals can be detected as targets. However, at shorter ranges (typically \({ }1 \, \hbox {kHz}\)) sonar systems can provide high-quality images earning the term ‘acoustic cameras’ and have become particularly advantageous for discriminating and counting fish. However, limitations of power and the significant increase in attenuation with frequency limit the achievable range of such acoustic cameras. Systems that operate at frequencies between those of mapping and fisheries sonar (typically \({<}400\, \hbox {kHz}\)) and acoustic cameras (\({\approx }1 \, \hbox {MHz}\)) are often used for short-range navigation and to evaluate underwater structures. While these systems produce images at reduced resolution compared to acoustic cameras, they may also be capable of distinguishing features of marine fauna and do so at greater ranges. This study utilised a Tritech Gemini 720i imaging sonar to produce images from 14 species of fauna at close range. It assessed some simple morphological parameters, such as length and breadth, and highlighted the possibilities of using these to categorise targets. It also provided a coarse description of issues associated with using such a system for monitoring marine animals.

Potential Use of Broadband Acoustic Methods for Micronekton Classification

Abstract: Broadband acoustic methods are an emerging technology with potential use in identification and classification of marine organisms. The application of broadband methods to scientific surveys of mesopelagic micronektons (animals of 2–20 cm length found at depths of 200–1000 m) is described. The principles of the broadband system are briefly outlined with particular emphasis on its use for micronekton detection and identification employing the TS-frequency curve of single targets. The use of acoustic scattering models to determine characteristics of the marine organism such as size and material properties is also discussed. As an example of the application of this technique, broadband echosounders mounted on a depth-profiling platform were used to collect high-frequency (55–160 kHz) acoustic data from mesopelagic depths (up to 600–1000 m) of the Great Australian Bight region. Some example results from narrowband and broadband echosounders are compared. The resulting frequency-dependent target strength curves of selected targets enabled classification into different acoustic groups, demonstrating the significant advantage provided by the broadband system. There is still a large gap between the achievable acoustic classification and the ultimate aim of species level classification, and to this end some limitations of broadband echosounder systems in identifying targets are discussed along with the use of video and still cameras to assist in the interpretation of acoustic data.

The Tympanal Recess of the Cetacean Cochlea: Function and Evolution

Abstract: Cetaceans (whales and dolphins) primarily use sound to communicate and hunt for prey. Their auditory anatomy is highly specialised, but much about its function remains unknown. In particular, a feature of the cochlea known as the tympanal recess present in some mysticetes (baleen whales) and odontocetes (toothed whales) has defied functional explanation. Here, we present and discuss several hypotheses that may clarify the function and evolution of the tympanal recess. One potential function in particular, the vibroacoustic duct mechanism, seems most plausible although further work is needed to test the hypothesis, which hints at the possibility of sperm whales and beaked whales being able to detect both high and low frequencies.

Differences in Vocalisation Patterns of Dugongs Between Fine-Scale Habitats Around Talibong Island, Thailand

Abstract: Examining characteristics of a species’ fine-scale habitat use contributes to effective and practical spatially explicit conservation. Dugongs (Dugong dugon) are endangered herbivorous mammals that use vocalisation for communication. In a small, specific area of Thai waters, classified here as a “vocal hotspot,” vocalisation rates are elevated, implying that in this area acoustic communication plays an important role. We recorded dugong calls in the vocal hotspot and a nearby feeding area. We then compared temporal patterns of vocalisation between the two sites to investigate the degree of variability in vocalisation between fine-scale habitats, which is important for understanding dugong habitat use by passive acoustic monitoring. From the 489 total hours of recording, 6607 and 2032 calls were observed in the vocal hotspot and feeding area, with mean vocalisation rates (calls per hour) 13.5 and 4.2, respectively. Vocalisation rate had distinctive 24-h periodicity in only the vocal hotspot. Environmental factors that correlated with changes in detected vocalisation rate also differed between the two locations. Water level correlated with vocalisation rate in the feeding area; in contrast, current direction correlated with vocalisation rate in the vocal hotspot. In conclusion, the vocalisation pattern for dugongs differed between the two sites, and we suggest that their habitat use varies at fine spatial scales.

Sequential Inversion for Geoacoustic Parameters in the South China Sea Using Modal Dispersion Curves

Abstract: This paper presents an inversion scheme that uses two wideband explosive sources based on modal dispersion characteristics to synchronously obtain sound speed profile and bottom parameters. The signal received on a single hydrophone in a vertical line array is decomposed into a series of propagation modes within the framework of normal mode theory, and the dispersive characteristics of the modes are analyzed using time–frequency analysis. Time-warping transform is applied to resolve the propagation modes of explosive sources from the South China Sea in 2007. The relative travel time differences of the propagation modes are used to invert the environmental parameters, including empirical orthogonal function coefficients, sediment thickness, sound speed, density, basement sound speed and density. Sediment density and basement density are constrained by Hamilton’s empirical relationship, and relative mode energy ratio is used to estimate the bottom attenuation coefficient. An adaptive simplex simulated annealing algorithm is used for the inversion. The reliability of the inversion results is verified via uncertainty analysis. The transmission loss calculated using the deduced parameters matches the experimental data well.

Design and Validation of a Simulator Tool Useful for Designers and Policy Makers in Urban Sound Planning

Abstract: Currently, the design of the urban soundscapes has been approached from distinct perspectives, which include, in all cases, the evaluation of how people perceive sound. An effective way to know how people experience an acoustic environment is through the use of simulators, where the inhabitants can design and establish their preferred sound levels. Making these tools available to different urban specialists, so they can be applied in individual common working environments, will allow them to be incorporated into the distinct stages of urban design, considerably improving solutions that promote more pleasant and restorative soundscapes for users. This paper describes the design and testing of a software based on a portable simulation tool whose function is to evaluate the acceptability of a variety of environmental noise sources categorized in four groups—water, birds, music and people. The experiment also evaluates the acceptability of these sounds sources with and without traffic noise mixed into the replayed sound. In order to validate it, two experiments with separate groups of people have been applied in two different places. With the exception of the “people” group of sounds, the results showed no correlation between sound level and acceptability, vibrancy, calmness both with and without the traffic and also the same preferred sounds were chosen in both places. These results suggest that it is possible to make prior participatory listening tests out of the laboratory. Finally, the participants commented that this experience improves their understanding of the acoustic environment and makes them aware of it.

Underwater particle motion (acceleration, velocity and displacement) from recreational swimmers, divers, surfers and kayakers

Abstract: When humans take to the water, they generate sound. This is helpful for the detection, classification, localisation and tracking of certain activities for purposes of border security, health and safety of offshore industrial development, environmental management, etc. The most commonly measured acoustic quantity is pressure. Vector quantities related to particle motion, such as particle velocity and acceleration, can equally identify the activity and they carry directional information. Acoustic pressure and particle motion were measured from 10 water sports activities within an Olympic-sized pool: swimming backstroke, breaststroke, butterfly and freestyle; snorkelling with fins; kicking a boogie board with fins; paddling with alternating or simultaneous arms while lying on a surfboard; scuba-diving; kayaking and jumping into the pool. Activities that occurred at the surface and that involved repeatedly piercing the surface were the strongest sound generators. Surface activities that produced fewer bubbles and scuba-diving at depth generated less broadband power. The vector fields around water sports activities can be expected somewhat different in the open ocean from within a pool, and more research is needed to understand how marine fauna might perceive these vector quantities.

Flow Noise Calculation and Experimental Study for Hydrophones in Fluid-Filled Towed Arrays

Abstract: Understanding the physical features of the flow noise for hydrophones in a fluid-filled towed array is important for designing a towed line array sonar. The flow noise of hydrophones in fluid-filled towed arrays generated by the turbulent pressure is derived by the frequency–wave number decomposition method. The results show that the flow noise increases rapidly with the towed speed and decreases with the length of the hydrophone. Meanwhile, the flow noise is closely related to the material parameters of the elastomer tube. It decreases with the attenuation factor, outside radius, and thickness of the elastomer tube. Furthermore, a spatial filter designed by the constant sector inverse-beamforming method is used for suppressing the tow-ship-radiated noise and the ambient noise from the sensor data. The analysis results of the experimental data are consistent well with the theoretical values, which indicate that the tow-ship-radiated noise and the ambient noise are suppressed effectively by the spatial filter. In addition, the correlation features of the flow noise received by the acoustic array are analyzed, which is important for the sonar system design.

Vertical Correlation of the Acoustic Field in Deep Water Measured with Explosive Sources

Abstract: In this paper we report the measurement and analysis on vertical correlations of acoustic signals received by a vertical line array deployed near the sea bottom in deep water. The source data were from one calibration experiment of sound exposure level of explosive charges. The source–receiver range is about 17 km. The sound transmission duct is the well-known reliable acoustic path (RAP). The vertical correlation coefficients are estimated at center frequencies of 300, 600, 1000 and 1500 Hz with 1/3 octave bands. Two types of explosive charges are used with nominal source depths of 50 and 300 m, respectively. The variation of vertical correlation coefficients strongly relies on source depth and center frequency. For each scene, ten groups of experiment data exhibit uniform variation of vertical correlation coefficients with fractional differences due to the fluctuation of ocean waveguide. Besides, the noise-free numerical modeling results reach good agreements with the measured ones, which reflect the stability of RAP as a sound transmission duct in the space/frequency domain. Due to the obvious arrival structures of rays, the theoretical solution of vertical correlation coefficient is derived based on the ray theory. At last, the effects of source–receiver geometry on the variability of vertical correlation are discussed.

Sound Quality Experiments in a Student Hostel with Newly Designed Sonic Crystal Window

Abstract: A new design of sonic crystal window was designed to replace the existing glass louver window in a student hostel in NUS in order to achieve good balancing of natural ventilation, daylighting and noise mitigation. Numerical studies were performed on the SC window to confirm the window design. The noise level inside the room was measured using sound quality head and torso simulator for simulated white noise, pink noise and construction noise on the ground floor as well as the actual environmental noise. Ten human subjects were asked to evaluate the construction noise and environmental noise inside the room. Psychoacoustics analyses were also performed on these two types of noises. The SC window was designed such that it can attenuate the noise at frequency range of traffic noise. The SC window was able to attenuate extra 4.59 and 9.40 dBA of white noise at full frequency range and frequencies ranging from 700 to 1400 Hz, respectively. The overall amount of pink noise attenuated by the SC window was similar to that of white noise. It can be concluded that gender affected the human subjective perception toward construction noise. All human subjects felt that the degree of annoyance for environmental noise passing through the glass louver window was higher than the SC window. The SC window would successfully reduce the loudness of the construction and environmental noises compared to the glass louver window.

Sound Production by Mulloway ( Argyrosomus japonicus ) and Variation Within Individual Calls

Abstract: Several soniferous (sound-producing) fish species can generate a number of different call types, providing significant information for intended recipients and observers. Understanding the level of variation they are capable of and whether it is voluntary or not gives an indication of how individually specific their calls might be. Similar to other Sciaenidae, mulloway (Argyrosomus japonicus) produce calls associated with spawning behaviour by vibrating their swimbladder. Dissection revealed mature mulloway have bi-lateral, highly vascularised ‘sonic’ muscles, with dorsoventrally orientated muscle fibres along the posterior two-thirds of the swimbladder, similar to French meagre (A. regius). Repetitive contraction of these muscles likely impinges on the sides of a loosely supported swimbladder, to generate motion. In the Swan River, Western Australia, mulloway produce a category of ‘long’ calls comprising 11–32 contractions at pulse repetition intervals and resulting carrier frequencies of approximately 16.6 ms and 60 Hz, respectively. However, throughout the $$\approx $$ 0.3 s calls this repetition rate may stay constant, rise, fall or a combination. In 13% of analysed calls, a pre-call pulse of lower amplitude than subsequent pulses was observed. A category of short calls (1–5 pulses) employed carrier frequencies of up to 114 Hz initially, but this decreased with each pulse, suggesting that these calls are at the limit of contraction rates of the sonic muscles. The study shows that even within previously defined call categories mulloway have the ability to produce several variations. Whether these variations are generated voluntarily or not and whether they can be perceived by the intended recipient are unknown and suggested as a topic of further work.

Reducing the Ambulance Siren Noise for Distant Auscultation of the Lung Sound

Abstract: Ambulance sirens sound very loud for transportation safety. However, loud sounds interfere with the auscultation of lung sounds. This study proposed an auscultation system that includes (1) an ACER Aspire 17 notebook as a server; (2) a smart mobile as a wireless hotspot (HwaWei Amazing A6); and (3) an ACER Aspire 5 notebook as a client. National Instruments data socket software gives read and write privileges to the IP addresses of the server and client. This real-world distant auscultation system works. The real-time adaptive filter reduced siren noise of 60 dB in power intensity. Surprisingly, a previous simulation of the adaptive filter had performed a noise reduction of 60 dB. Therefore, this real-time remote auscultation system is a reliable device for the ambulance service.

Characterization and Clinical Trials of the Prototype Ear Simulator Designed for Neonates Hearing Assessment

Abstract: This article aims to describe the characterization of the new prototype ear simulator for neonates and demonstrate its utility in clinical measurements Experimental evaluations have been performed in order to demonstrate consistency with the theoretical model in acoustic transfer impedance Temperature and atmospheric pressure dependency measurements have been applied for verification of the stability of the ear simulator in variable environmental conditions Thus, the main objective of this study is to outline the benefits of the new ear simulator in audiometric measurements for neonates Acoustic transfer impedance of the ear simulator has been determined and compared with the theoretical model, and its environmental dependence has been studied between 100 Hz and 10,000 Hz A modified method usually applied for reciprocity calibration of microphones has been used in measurements Comparison of the new ear simulator with the IEC 60318-4 ear simulator and a $$2\,\hbox {cm}^{3}$$ coupler has been presented The ear simulator has been used to calibrate acoustics stimuli from an audiometer (Interacoustics AD226 with Otometrics insert earphone) and two otoacoustic emission devices (Otodynamics Otoport and Interacoustics Titan) The consistency of experimental evaluations in acoustic transfer impedance with the theoretical model has been confirmed In clinical trials, an audiometer and two otoacoustic emission devices were investigated and a smaller standard deviation of 10 dB, 08 dB and 07 dB at 1 kHz, 2 kHz and 4 kHz, respectively, has been achieved compared to the old $$2\,\hbox {cm}^{3}$$ coupler which has a 15 dB, 18 dB and 19 dB standard deviations at same frequencies Average differences and standard deviations between the two couplers (IEC 60318-4 and the universal ear simulator) are $$114 \pm 03\,\hbox {dB}$$ at 1 kHz, $$110 \pm 01\,\hbox {dB}$$ at 2 kHz and $$133 \pm 02\,\hbox {dB}$$ at 4 kHz These differences represent the error incurred by using an adult ear simulator for neonates applications The new universal ear simulator designed especially for hearing assessments of neonates has been characterized and used in clinical trials The consistency between theoretical model and experimental measurements has been approved Clinical trials showed that a more accurate calibration of OAE and audiometers for neonates would be possible However, further applications for different age groups and broader clinical trials should be planned Intercomparisons between different laboratories and clinics can maintain the comparability of hearing measurements and higher impact

Low-Frequency Acoustic Propagation Modelling for Australian Range-Independent Environments

Abstract: Large portions of the Australian continental shelf have a seabed composed of layered cemented or semi-cemented calcarenite. This work investigates the ability of a wavenumber integration sound propagation model, two normal mode sound propagation models, and a parabolic equation sound propagation model to consistently predict the acoustic field over four types of calcarenite style seabeds. The four geoacoustic models that are presented here represent seabed types that are likely to be found in the Australian marine environment. Transmission loss results for each geoacoustic model are computed using each sound propagation model, which are compared over a broad band of low frequencies in order to assess their relative performance. The performance of the wavenumber integration model, SCOOTER, and the two normal mode models over a broad band of low frequencies was found to be accurate and robust for all the tested scenarios. However, for one of the normal mode models, KRAKENC, long computational runtimes were incurred to produce accurate results. The parabolic equation model RAMSGeo produced accurate transmission loss results at some of the frequencies, but it also produced some unrealistic transmission loss predictions when thin layers were present in the seabed. The normal mode model ORCA was found to have the best balance between accuracy and efficiency because it had the shortest runtimes for most of the calculation frequencies and the shortest overall runtime.

Passive Localization Based on Multipath Time-Delay Difference with Two Hydrophones in Deep Ocean

Abstract: In this study, we propose a localization method based on multipath time-delay difference (MTD). We extract the time-delay difference of the direct and sea surface-reflected sound rays by the signal from hydrophones in deep sea to establish the MTD matching vector. The predicted matching vectors are obtained using Bellhop to build an ocean acoustic field model. The spatial distribution of MTD are simulated and analyzed. The matching ambiguity plane is obtained by the objective function. The maximum point of ambiguity plane is the position of the sound source. We show that the sound field propagation error can be replaced by the geometric error. We then analyze the influence of the received position error on the localization accuracy. The effects of errors caused by skewing of hydrophone and horizontal variation in SSP are studied. Simulation and experimental results at sea show that the proposed method is robust and can locate the sound source with a small aperture array of two hydrophones.

High-Frequency Modulated Signals Recorded Off the Antarctic Peninsula Area: Are Killer Whales Emitting Them?

Abstract: High-frequency modulated signals with a stereotyped down-swept contour were recorded in the northwestern Antarctic Peninsula using an autonomous recorder and a towed hydrophone array. Signals have a mean start frequency at 21.6 kHz, end frequency at 15.7 kHz, −10 dB bandwidth of 5.9 kHz, and duration of 65.2 ms. Bouts of signals were generally recorded with a median inter-signal interval of 2.1 s. HFM signals partially modulated in the non-ultrasonic range similar to the ones described in this paper have already been reported for killer whales in the North Pacific, Western South Atlantic and Western Australian coast. The HFM signals were recorded in the presence of other odontocete sounds such as whistles, echolocation clicks and burst-pulsed sounds. The similarities of these sounds with vocalizations described for killer whales in the Western Australian coast lead us to strongly believe that the described HFM signals were produced by Antarctic killer whales. This paper described for the first time HFM signals in Antarctica and discussed evidence suggesting that Antarctic type A killer whales are the most probable candidates to produce such signals. However, a visual confirmation is still needed and the function of the HFM signals remains unknown.

Is Community Noise Associated with Metabolic Control in Patients with Cardiovascular Disease

Abstract: This study aimed to explore the association between community noise exposure and indicators of metabolic control (blood lipids and glucose) among Bulgarian patients with CVD. A representative cross-sectional sample ( $$n = 217$$ ) was taken from three tertiary hospitals in the city of Plovdiv, Bulgaria. We collected blood samples, anthropometric measurements, and data on sociodemographics, lifestyle, medical conditions, and housing characteristics. A global noise annoyance (GNA) scale was constructed based on different residential noise annoyances. Day-evening-night ( $$L_{\mathrm{den}})$$ and nighttime ( $$L_\mathrm{night})$$ road traffic noise levels were determined in a subsample of 132 participants at their living room and bedroom facades, respectively, and further corrected to indoor levels, based on the window-opening frequency, orientation of rooms, and soundproofing insulation. Multilevel linear models were employed to study the effect of these noise indicators on participants’ lipid profile and blood glucose. The most consistent finding was for triglycerides, which increased significantly per one interquartile range increase in GNA (0.26 mmol/l, 95% CI 0.04, 0.47) and per 5 dB increase in outdoor $$L_\mathrm{den}$$ (0.24 mmol/l, 95% CI 0.12, 0.35), indoor $$L_\mathrm{den}$$ (0.18 mmol/l, 95% CI 0.08, 0.28), and indoor $$L_\mathrm{night}$$ (0.08 mmol/l, 95% CI 0.001, 0.16). Outdoor (0.16 mmol/l, 95% CI 0.02, 0.29) and indoor (0.13 mmol/l, 95% CI 0.01, 0.25) $$L_\mathrm{den}$$ were associated with an increase in LDL-cholesterol. In sensitivity analyses, we identified several effect modifiers of the relationship between noise and total cholesterol. To conclude, community noise exposure could be an important risk factor for unsatisfactory blood lipid control.