Ambient Sound Levels Research Articles

Machine learning-based prediction of outdoor ambient sound levels: Ensemble averaging and feature reduction

Outdoor ambient sound levels can be predicted from machine learning-based models derived from geospatial and acoustic training data. To improve modeling robustness, median predicted sound levels have been calculated using tuned models from different supervised machine learning modeling classes. The ensemble-based model reduces errors at training sites for both overall levels and spectra, and produces more physically reasonable predictions elsewhere. Furthermore, the spread in the ensemble provides an estimate of the modeling accuracy. An initial analysis of feature importance metrics suggests that the number of geospatial inputs can be reduced from 120 to 15 without significant degradation of the model's predictive error, as measured by leave-one-out cross validation. However, the predictions from the reduced-feature modeling may be less physical in certain regions when all differentiating geospatial features are removed. These results suggest the need for more sophisticated data collection and validation methods.

Assessing vessel slowdown for reducing auditory masking for marine mammals and fish of the western Canadian Arctic

Vessel slowdown may be an alternative mitigation option in regions where re-routing shipping corridors to avoid important marine mammal habitat is not possible. We investigated the potential relief in masking in marine mammals and fish from a 10 knot speed reduction of container and cruise ships. The mitigation effect from slower vessels was not equal between ambient sound conditions, species or vessel-type. Under quiet ambient conditions, a speed reduction from 25 to 15 knots resulted in smaller listening space reductions by 16–23%, 10–18%, 1–2%, 5–8% and 8% respectively for belugas, bowheads, bearded seals, ringed seals, and fish, depending on vessel-type. However, under noisy conditions, those savings were between 9 and 19% more, depending on the species. This was due to the differences in species' hearing sensitivities and the low ambient sound levels measured in the study region. Vessel slowdown could be an effective mitigation strategy for reducing masking.

Modeling the effect of electric vehicle adoption on pedestrian traffic safety: An agent-based approach

When operated at low speeds, electric and hybrid vehicles have created pedestrian safety concerns in congested areas of various city centers, because these vehicles have relatively silent engines compared to those of internal combustion engine vehicles, resulting in safety issues for pedestrians and cyclists due to the lack of engine noise to warn them of an oncoming electric or hybrid vehicle. However, the driver behavior characteristics have also been considered in many studies, and the high end-prices of electric vehicles indicate that electric vehicle drivers tend to have a higher prosperity index and are more likely to receive a better education, making them more alert while driving and more likely to obey traffic rules. In this paper, the positive and negative factors associated with electric vehicle adoption and the subsequent effects on pedestrian traffic safety are investigated using an agent-based modeling approach, in which a traffic micro-simulation of a real intersection is simulated in 3D using AnyLogic software. First, the interacting agents and dynamic parameters are defined in the agent-based model. Next, a 3D intersection environment is created to integrate the agent-based model into a visual simulation, where the simulation records the number of near-crashes occurring in certain pedestrian crossings throughout the virtual time duration of a year. A sensitivity analysis is also carried out with 9000 subsequent simulations performed in a supercomputer to account for the variation in dynamic parameters (ambient sound level, vehicle sound level, and ambient illumination). According to the analysis, electric vehicles have a 30% higher pedestrian traffic safety risk than internal combustion engine vehicles under high ambient sound levels. At low ambient sound levels, however, electric vehicles have only a 10% higher safety risk for pedestrians. Low levels of ambient illumination also increase the number of pedestrians involved in near-crashes for both electric vehicles and combustion engine vehicles.

SoundEar noise warning devices cause a sustained reduction in ambient noise in adult critical care.

Elevated sound levels in critical care are associated with sleep deprivation and an increased incidence of delirium. We aimed to determine whether a sound-activated visual noise display meter could cause a sustained reduction in sound levels overnight in an adult critical care unit. Sound levels were recorded overnight for eight days before and after the introduction of a visual noise display meter, with a further eight days recorded four months later after continued use of the visual noise display meter. Median ambient sound levels were significantly reduced from 57.4 dB by 3.9 dB, with a sustained reduction of 3.6 dB from baseline after four months of the device operating. Peak ambient sound levels had a small but significant reduction from 66.0 dB by 0.7 dB, with a sustained reduction of 0.8 dB after four months. Sound-activated visual noise display meters can be effective in providing a sustained reduction in ambient sound overnight in adult critical care units, which would appear to be driven by behavioural change.

Looking for light in the din: An examination of the circadian-disrupting properties of a medical intensive care unit

ObjectiveCritically ill patients exhibit profound disturbances of circadian rhythmicity, most commonly in the form of a phase delay. We investigated the specific zeitgeber properties of a medical intensive care unit to develop a model that explained these abnormalities. Research methodologyProspective, observational study conducted during 2013–2014. Twenty-four-hour ambient light (lux, 672 hours) and sound pressure levels (dBA, 504 hours) were measured in patient rooms. Patients and families were surveyed regarding their perceptions of the environment. SettingUniversity-based adult medical intensive care unit. Main outcome measuresThe timing and intensity of the ambient light-dark cycle and sound environment and the relationship of these measurements to patient/family perceptions. ResultsTwenty-four-hour light-dark cycles were extremely weak and phase delayed relative to the solar cycle. Morning light averaged 12.1 (4.8, 37.2) lux, when only 24.9% ± 10.9% of available light was utilised; yet patients and families did not identify low daytime light levels as problematic. Median noise levels were invariably excessive (nighttime 47.9 [45.0, 51.3] dBA) with minimal variation, consistent with the absence of a defined rest period. ConclusionThe intensive care unit functions as a near-constant routine protocol disconnected from solar time. Behavioural interventions to promote entrainment should be supported by objective measurements of light and sound.

Not so far: attenuation of low-frequency vocalizations in a rainforest environment suggests limited acoustic mediation of social interaction in African forest elephants

Forest elephants Loxodonta cyclotis aggregate in large numbers in forest clearings. Whether they maintain contact as they move through the forest and are able to coordinate these aggregations, similar to the fission-fusion sociality of the well-studied savanna elephants Loxodonta africana, is currently unknown. Since sound attenuates faster in closed as compared to open habitats, the low-frequency rumble vocalizations of forest elephants may exhibit smaller detection ranges than measured for those of savanna elephants, which may restrict the ability of forest elephants to coordinate interactions between separated family units. Here, we modeled the attenuation of forest elephant rumbles using amplitude measurements of rumbles recorded in a rainforest in Gabon and estimated the distances at which elephants might be able to detect them under observed ambient sound conditions. Our results suggest an attenuation rate less than predictions of spherical spreading loss, suggesting that reflection of the sound waves within the forest results in constructive interference. Nevertheless, we found that forest elephant rumbles of average dominant frequency (31.07 Hz) under average ambient sound levels would not be detectable farther than 0.8 km. Moreover, for 50% of analyzed rumbles, the harmonic structure was completely attenuated at only 100 m. However, we estimated detection distances of up to 3.2 km for rumbles of average dominant frequency when ambient sound was at its lowest. Our findings suggest that long-distance communication to coordinate interactions among separated family units may be limited in forest elephants, with potentially important consequences for their social organization. The challenges associated with the extent of, and variation in, detection distances of long-distance vocalizations used by animals to mediate interactions between separated group members has rarely been investigated. While it has been suggested that forest elephants exhibit a fission-fusion sociality similar to savanna elephants, our results indicate shorter detection distances for forest elephant rumbles, suggesting a limited ability to mediate interactions between separated family units. However, under optimal ambient sound conditions, detection distances increased considerably. The long detection distances estimated for savanna elephants may reflect the optimal conditions under which the playback experiments were conducted. On average, savanna elephants may be much more limited in communication distance. Further studies on the constraints and opportunities that the different environments impose on these species’ communication capability may be critical to understanding potential differences in the social complexity they express.

The underwater acoustic environment at SGaan Kinghlas-Bowie Seamount Marine Protected Area: Characterizing vessel traffic and associated noise using satellite AIS and acoustic datasets

Vessel traffic is one of the most wide-spread anthropogenic contributors to ocean noise worldwide and has the potential to alter ecosystems upon which cetaceans and other acoustically sensitive marine organisms rely. Canada's SGaan Kinghlas-Bowie Seamount Marine Protected Area (SK-B MPA) is one such area whose productive ecosystem could benefit from greater monitoring of human induced threats in order to inform management. Despite earning official designation as a Marine Protected Area under the Oceans Act in 2008, little remains known about vessel traffic in the region and the associated potential impacts on vulnerable marine species. Therefore, to increase our understanding of vessel traffic and accompanying noise at SK-B MPA, satellite AIS and acoustic data were investigated. The results of this study suggest that variations in ambient sound levels in the region are driven by near and distant shipping events, thus having implications for future management of the MPA.

Male Greater Prairie-Chickens adjust their vocalizations in the presence of wind turbine noise

ABSTRACT The potential for wind energy facilities to affect species of grouse in the grasslands of the Great Plains of North America is a conservation concern. Communication by male Greater Prairie-Chickens (Tympanuchus cupido pinnatus) is essential for lek mating displays and includes low-frequency vocalizations that could be disrupted by wind turbine noise. We studied the effects of wind turbine noise on the boom, cackle, whine, and whoop vocalizations of male Greater Prairie-Chickens recorded at 14 leks located 703 m to 23 km away from a wind energy facility near Ainsworth, Brown County, Nebraska, USA, in 2013 and 2014. First, we assessed ambient sound levels at our study sites. Wind turbine noise contributed to the soundscape; leks <1,000 m from wind turbines had higher levels of ambient sound than expected on the basis of recordings obtained at remote locations. Our second objective was to determine whether the acoustic characteristics of the 4 vocalizations recorded near the wind energy facility dif...

Out-of-Booth Testing with Noise-canceling Earphones

Out-of-Booth Testing with Noise-canceling Earphones

Underwater sound from vessel traffic reduces the effective communication range in Atlantic cod and haddock

Stellwagen Bank National Marine Sanctuary is located in Massachusetts Bay off the densely populated northeast coast of the United States; subsequently, the marine inhabitants of the area are exposed to elevated levels of anthropogenic underwater sound, particularly due to commercial shipping. The current study investigated the alteration of estimated effective communication spaces at three spawning locations for populations of the commercially and ecologically important fishes, Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus). Both the ambient sound pressure levels and the estimated effective vocalization radii, estimated through spherical spreading models, fluctuated dramatically during the three-month recording periods. Increases in sound pressure level appeared to be largely driven by large vessel activity, and accordingly exhibited a significant positive correlation with the number of Automatic Identification System tracked vessels at the two of the three sites. The near constant high levels of low frequency sound and consequential reduction in the communication space observed at these recording sites during times of high vocalization activity raises significant concerns that communication between conspecifics may be compromised during critical biological periods. This study takes the first steps in evaluating these animals’ communication spaces and alteration of these spaces due to anthropogenic underwater sound.

Acoustic planning of a music festival site

CSTI acoustics worked with a community on the planning of a festival site that will host outdoor concerts. Our work involved measuring sound from an outdoor concert at a nearby venue, documenting ambient sound levels in communities surrounding the proposed festival site, modeling the sound propagation from optional stage locations and orientations, and proposing procedures and sound limits for future performances.

Sound and Light Levels Are Similarly Disruptive in ICU and non-ICU Wards.

To compare ambient sound and light levels, including SLCs, in ICU and non-ICU environments. Observational study. Tertiary-care hospital. Sound measurements of 0.5 Hz were analyzed to provide average hourly sound levels, sound peaks, and SLCs =17.5 decibels (dB). For light data, measurements taken at 2-minute intervals provided average and maximum light levels. The ICU rooms were louder than non-ICU wards; hourly averages ranged from 56.1 ± 1.3 dB to 60.3 ± 1.7 dB in the ICU, 47.3 ± 3.7 dB to 55.1 ± 3.7 dB on the telemetry floor, and 44.6 ± 2.1 dB to 53.7 ± 3.6 dB on the general ward. However, SLCs = 17.5 dB were not statistically different (ICU, 203.9 ± 28.8 times; non-ICU, 270.9 ± 39.5; P = 0.11). In both ICU and non-ICU wards, average daytime light levels were <250 lux, and peak light levels occurred in the afternoon and early evening. Quieter, non-ICU wards have as many SLCs as ICUs do, which has implications for quality improvement measurements. Efforts to further reduce average noise levels might be counterproductive. Light levels in the hospital (ICU and non-ICU) may not be optimal for maintenance of a normal circadian rhythm for most people.

Efficacy of an acoustic hailing device as an avian dispersal tool

ABSTRACTBird strikes are a major safety and financial concern for modern aviation. Audible stimuli are common bird dispersal techniques, but their effectiveness is limited by the saliency and relevance of the stimulus. Furthermore, high ambient sound levels present at airfields might require that effective audible stimuli rely more on total volume (i.e., exceeding physiological tolerances) than ecological relevance. Acoustic hailing devices (AHD) are capable of sound output with a narrow beam width and at volumes high enough to cause physical discomfort at long distances. We tested the effectiveness of an AHD as a dispersal tool on free‐ranging birds recognized as hazardous to aviation safety at the Savannah River Site and Phinizy Swamp Nature Park in South Carolina and Georgia, USA, respectively, between October 2013 and March 2015. Our study design included experimental trials with timed‐interval counts of birds directly before and after AHD treatment. For most species, counts of birds associated with treatment periods (use of AHD) and control periods (no use of AHD) occurred on different days. Sound treatments yielded variable success at dispersing birds. Specifically, AHD treatment was effective for dispersing vultures (Coragyps atratus and Cathartes aura) and gulls (Laridae), but ineffective for dispersing blackbirds (Icteridae), diving ducks (Aythya spp., Bucephala spp., Oxyura spp.), and coots (Fulica americana). Trials were conducted in a relatively quiet environment with birds that were unhabituated to excessive noise; thus, we cannot unequivocally recommend an AHD as a universally effective avian dispersing tool. However, future research should consider AHD testing integrated with other methods, as well as investigation of treatments that might be salient to specific target species. © 2017 The Wildlife Society.

Modeling anthropogenic noise propagation using the Sound Mapping Tools ArcGIS toolbox

We introduce the open-source Sound Mapping Tools (SMT, implemented in ArcGIS with the Spatial Analyst extension) for use in terrestrial outdoor sound propagation modeling. SMT includes three sound propagation models: an updated version of SPreAD-GIS, based on the System for Prediction of Acoustic Detectability model; NMSIMGIS, a GIS implementation of the Noise Model Simulation (NMSim) algorithms; and an implementation of an international outdoor sound propagation standard, ISO 9613–2. SMT produces spatially-explicit predictions of sound pressure levels from one or more sound sources, facilitating the assessment of noise effects from sources such as motorized recreation, energy development, and road traffic. Model results can be weighted to represent variable acoustic sensitivity or compared to ambient sound pressure levels. SMT provides a user-friendly approach to produce sound level predictions across variable landscapes, with applications for environmental, behavioral, population, and community ecology studies and for planning and management of human land use and infrastructure.

In-Ear Audio Wearable: Measurement of Heart and Breathing Rates for Health and Safety Monitoring.

This paper examines the integration of a noninvasive vital sign monitoring feature into the workers' hearing protection devices (HPDs) by using a microphone positioned within the earcanal under the HPD. 25 test-subjects were asked to breathe at various rhythms and intensities and these realistic sound events were recorded in the earcanal. Digital signal processing algorithms were then developed to assess heart and breathing rates. Finally, to test the robustness of theses algorithms in noisy work environments, industrial noise was added to the in-ear recorded signals and an adaptive denoising filter was used. The developed algorithms show an absolute mean error of 4.3 beats per minute (BPM) and 2.7 cycles per minute (CPM). The mean difference estimate is -0.44 BPM with a limit of agreement (LoA) interval of -14.3 to 13.4 BPM and 2.40 CPM with a LoA interval of -2.62 to 7.48 CPM. Excellent denoising is achieved with the adaptive filter, able to cope with ambient sound pressure levels of up to 110 dB SPL, resulting in a small error for heart rate detection, but a much larger error for breathing rate detection. Extraction of the heart and breathing rates from an acoustical measurement in the occluded earcanal under an HPD is possible and can even be conducted in the presence of a high level of ambient noise. This proof of concept enables the development of a wide range of noninvasive health and safety monitoring audio wearables for industrial workplaces and life-critical applications where HPDs are used.

A targeted noise reduction observational study for reducing noise in a neonatal intensive unit.

Excessive noise in neonatal intensive care units (NICUs) can interfere with infants' growth, development and healing.Local problem:Sound levels in our NICUs exceeded the recommended levels by the World Health Organization. We implemented a noise reduction strategy in an urban, tertiary academic medical center NICU that included baseline noise measurements. We conducted a survey involving staff and visitors regarding their opinions and perceptions of noise levels in the NICU. Ongoing feedback to staff after each measurement cycle was provided to improve awareness, engagement and adherence with noise reduction strategies. After widespread discussion with active clinician involvement, consensus building and iterative testing, changes were implemented including: lowering of equipment alarm sounds, designated 'quiet times' and implementing a customized education program for staff. A multiphase noise reduction quality improvement (QI) intervention to reduce ambient sound levels in a patient care room in our NICUs by 3 dB (20%) over 18 months. The noise in the NICU was reduced by 3 dB from baseline. Mean (s.d.) baseline, phase 2, 3 and 4 noise levels in the two NICUs were: LAeq: 57.0 (0.84), 56.8 (1.6), 55.3 (1.9) and 54.5 (2.6) dB, respectively (P<0.01). Adherence with the planned process measure of 'quiet times' was >90%. Implementing a multipronged QI initiative resulted in significant noise level reduction in two multipod NICUs. It is feasible to reduce noise levels if QI interventions are coupled with active engagement of the clinical staff and following continuous process of improvement methods, measurements and protocols.

Does Music Positively Impact Preterm Infant Outcomes?

The hospital environment leaves preterm infants (PTIs) exposed to various stressors that can disrupt their growth and development. Developmental interventions such as music may be an important strategy to mitigate PTI's stress. This brief evaluates current evidence regarding the impact of music therapy on outcomes for PTIs. The question guiding this brief is "Do various types of music therapy positively affect physiologic indicators, feeding behaviors/length of stay (LOS) and pain management outcomes for PTIs?" CINAHL/MEDLINE Complete and PubMed databases were searched using keywords preterm infants, premature infants, preterm baby, premature baby, NICU baby, music, and music therapy. The search was limited to 5 years for English studies evaluating the effects of music therapy on physiological indicators, feeding, pain outcomes, and length of stay. The search yielded 12 studies addressing these concerns. Music therapy was shown to positively affect physiologic indicators, feeding, length of stay, and pain outcomes for PTIs. In addition, music decreased parental stress. Thoughtful consideration should be given regarding the value of diverse types of music and parental involvement when incorporating music into an individualized plan of care. Furthermore, the development of guidelines with a focus on ambient sound reduction is an important strategy when adding music as an intervention. Further research is needed to investigate ambient sound levels in conjunction with musical interventions. In addition, the impact of various types of music, differences in gender, reduction of stress, pain for infants, and parental role in music requires further evaluation.

Community perception of noise impacts—A comprehensive review of background sound data for setting appropriate design goals for source sound (continuous, impulsive, tonal)

Community perception of noise impact is most often influenced by the amount by which a new source of sound exceeds the existing ambient sound level. Various descriptors are used to define existing ambient sound levels. For example, the Massachusetts DEP Noise Policy uses the 90th percentile sound level (LA90), while the New York State DEC Noise Policy uses the equivalent sound level (LAeq). When new transient sounds are introduced into an environment the LA90 or LAeq may not be the best, or only, metrics for defining a design goal or noise ordinance limit. In addition to the lowest existing ambient sound levels, reviewing the first percentile (LA01) sound levels may be a more appropriate way to determine community perception of new transient sounds. Sound surveys from across the country were analyzed to determine maximum-recommended community sound levels (design goals). These design goals are based on marginal increases to the ambient sound level and comparison to existing maximum sound levels (LA01); the specific margin depends on the characteristics of sound experienced at the receptor.

Quiet cars and blind pedestrians

People who are blind use traffic sounds to determine alignment, verify relative position to a street, identify their location, and decide an appropriate time to cross a street. With quieter vehicles, these pedestrians often do not have the amount or kind of acoustic information needed to make good, reliable travel decisions. Blind participants listened to internal combustion vehicles and hybrid vehicles (with and without added artificial sounds) approaching while moving forward, approaching while backing, and turning at an intersection. Participants indicated when they heard a vehicle and the direction of travel. Participants also aligned themselves to passing vehicles or indicated when crossable gaps between vehicles existed. Performance degraded most when ambient sound levels increased. However, even under extremely low ambient conditions, some tasks were not performed well. Some artificial sounds improved performance of particular tasks, but no artificial sound adequately enhanced performance in all tasks. Quieter vehicles have a potentially severe safety impact on pedestrians who are blind. Blind pedestrians may not be aware how their travel is impacted by less acoustic information. Addressing the impact by adding artificial sounds promises only a partial solution and should be augmented by other efforts.

Background noise variability relative to wind direction, temperature, and other factors

Characterization of the ambient acoustic environment is often a critical component in the wind energy permitting process. Collection of ambient data may be required during the pre-construction or post-construction phases to establish a baseline for determining wind turbine sound contribution at different points of reception. The challenge with establishing that baseline is that ambient sound levels continuously fluctuate, affected by multiple factors including existing sound sources, human activity, and meteorological parameters like wind speed and direction. This continuous fluctuation makes both definition and reproducibility of ambient conditions difficult. This paper examines meteorological data collected during surveys at numerous wind energy facilities throughout the United States. Meteorological data were collected at different heights above ground level using a combination of multiparameter weather sensor stations deployed during survey periods as well as other meteorological towers in proximity t...