Ambient Sound Levels Research Articles

A procedure for estimating mitigation effect of air injection on ship underwater radiated noise

Increasing evidence exists that underwater radiated noise (URN) from ships has a negative impact on marine ecosystems. This has led to numerous initiatives aimed at monitoring and mitigating ambient sound levels generated by shipping. Within the European Union, noise abatement is being addressed by a wide range of stakeholders, with activities focused on developing procedures and thresholds for evaluating noise impact as well as knowledge on the effectiveness of a range of mitigation measures. In the SATURN project, MARIN is studying air injection systems for mitigation of both propeller cavitation and machinery noise; the so-called "Prairie" and "Masker" systems. Model-scale tests have been performed in order to quantify performance in terms of sound level reductions for a range of test conditions. In this paper we elaborate a procedure for applying the processed measurement data to ship-scale URN predictions for assessing mitigation potential during the early design stage. Data reduction of the model test results is explained, leading to a model for estimating the mitigation effect and power requirement of the two systems. We subsequently apply the model to a number of test cases, covering both measured and calculated source levels. Limitations of the approach will also be discussed.

Influence of atmospheric state on variability of long-term residual ambient sound level measurements in a subalpine valley.

Two natural influences on the acoustic environments of mountainous parks and communities are flowing water and shifting weather. A central purpose of the acoustic measurement design used by the United States National Park Service is to provide spectral estimates of residual ambient sound level metrics at a seasonal time scale. Acoustic monitoring sampling methodologies are often designed using a sequence of similar measurements. When source and residual ambient spectra overlap, an estimate of variability in the latter is beneficial to successful monitoring design. The observed and modelled effects of atmospheric state on sound level are analyzed to reveal variability due to these effects at a long-term monitoring site in Denali National Park, Alaska. The analysis of variability incorporates a covariate that is otherwise challenging to estimate in remote settings: vertical temperature gradients in the atmospheric boundary layer. Results reveal inversions (positive gradients) in the atmosphere ≥30% between 19:00 and 09:00. Inversion strengths above 0.06 °C/m are associated with 10-15 dB increases in sound level over hourly time scales. Because inversions tend to occur during otherwise quiescent times of day, they ultimately reduce seasonal variability at the site and corresponding uncertainty in noise metrics for transportation noise arriving from varied directions.

Influence of increasing noise at the offshore wind farm area on fish vocalization phenology: A long-term marine acoustical monitoring off the foremost offshore wind farm in Taiwan

The rapid increase of offshore projects at Taiwan Strait in recent decade has been debated for elevated noise levels. However, there are no studies on long-term assessment of noise levels and impact of noise on marine organisms. The passive acoustic monitoring was conducted at the foremost wind farm area in Taiwan to assess the sound levels and the impact of noise on fish vocalization behavior. Predominately, in the soundscape around the Taiwan Strait, two chorusing types (Type 1 and Type 2) from the Sciaenid family of fishes exist. Ambient sound levels significantly increased from 2014 to 2019, while the chorusing Types 1 and 2 were observed in a lower percentage of the recordings. Additionally, chorusing peak intensity and duration significantly reduced over the years for both choruses. This is the first field-based evidence to demonstrate the consequences of increasing anthropogenic noise having the potential to alter the vocalization behavior of the fish.

Quieting the neonatal intensive care unit: A quality improvement initiative.

The neonatal intensive care unit (NICU) is vital for preterm infants but is often plagued by harmful noise levels. Excessive noise, ranging from medical equipment to conversations, poses significant health risks, including hearing impairment and neurodevelopmental issues. The American Academy of Pediatrics recommends strict sound limits to safeguard neonatal well-being. Strategies such as education, environmental modifications, and quiet hours have shown to reduce noise levels. However, up to 60% of the noises remain avoidable. High noise exposure exacerbates physiological disturbances, impacting vital functions and long-term neurological outcomes. Effective noise reduction in the NICU is crucial for promoting optimal neonatal development. To measure the sound levels in a NICU and reduce ambient sound levels by at least 10% from baseline. A quasi-experimental quality improvement project was conducted over 4 mo in a 20-bed level 3 NICU in a tertiary care medical college. Baseline noise levels were recorded continuously using a sound level meter. The interventions included targeted education, environmental modifications, and organizational changes, and were implemented through three rapid Plan-Do-Study-Act (PDSA) cycles. Weekly feedback and monitoring were conducted, and statistical process control charts were used for analysis. The mean noise values were compared using the paired t-test. The baseline mean ambient noise level in the NICU was 67.8 dB, which decreased to 50.5 dB after the first cycle, and further decreased to 47.4 dB and 51.2 dB after subsequent cycles. The reduction in noise levels was 21% during the day and 28% at night, with an overall decrease of 25% from baseline. The most significant reduction occurred after the first PDSA cycle (mean difference of -17.3 dB, P < 0.01). Peak noise levels decreased from 110 dB to 88.24 dB after the intervention. A multifaceted intervention strategy reduced noise in the NICU by 25% over 4 months. The success of this initiative emphasizes the significance of comprehensive interventions for noise reduction.

Times to stabilize sound metrics in rural areas - How long should you monitor?

In areas dominated by the sound from highway traffic, day-to-day sound ambient sound levels can be relatively constant. However, in rural areas, where wind, animals, machinery, airplane overflights, and occasional or distant traffic play larger roles in their contributions to ambient sound. These sources can change day to day, week to week, and season to season. As a result, there is greater variation in sound levels over time in rural areas than in urban areas. This characteristic also affects how long one should collect data with sound level meters to capture a statistically stable sample. In this study, we evaluate the stabilization of sound level metrics LAeq, LA10, LA50, LA90, and LZeq by 1/3 octave band over time for several rural sites. We present recommendations for monitoring times for each metric such that the variation in levels is relatively stable.

Underwater soundscape in Seaview Bay, Antarctica, and triple ascending trill of the leopard seal (Hydrurga leptonyx) underwater vocalizations.

The underwater soundscape was recorded in Seaview Bay off Inexpressible Island, Ross Sea region Marine protected area, for 3 days in December 2021. Leopard seal Hydrurga leptonyx vocalizations were a prominent sound source that led to variations in ambient sound pressure levels in a frequency range of approximately 150-4500 Hz. Among the 14 call types previously identified, except ultrasound vocalizations, six types of broadcast calls were classified, and their acoustic characteristics were analyzed. We focused on the acoustic characteristics of four low-frequency calls, clustered in a relatively narrow bandwidth, which have been relatively less studied. We identified a new call type of a triple ascending trill consisting of three trill parts, expanding upon the findings of previous studies. The audio data extracted from leopard seal vocalization videos, recorded by a monitoring camera on sea ice, enhanced the reliability of identifications of the underwater triple ascending trill. We present the unique results of underwater passive acoustic monitoring conducted at Seaview Bay, designated as Antarctic Specially Protected Area No 178. Our results could contribute to the development of detection and localization algorithms for leopard seal vocalizations and can be used as fundamental data for studies related to the vocalization and behavior of this species.

Cetacean presence and ambient sound level analysis in Bermuda: A comparison to historical records

Marine Protected Areas (MPAs) are established to conserve nature while also preserving ecosystem services and cultural values. Many ongoing MPA discussions are centered on offshore islands, including Bermuda, a British Overseas Territory in the North Atlantic Ocean, which is currently assessing a management plan to protect 20% of its EEZ. Marine mammals are essential targets to monitor as part of effective MPA management because they are keystone species. In addition, as human activities raise ocean noise levels worldwide, monitoring ambient sound levels is essential to evaluating impacts on marine ecosystems. We collected nine months of passive acoustic data (at 250 kHz sampling rate and with 24-bit resolution) between December 2021 and September 2022, approximately 24 nm south of Bermuda, close to a location where previous studies were conducted in 1966 and 2013–2014. The cetacean presence and ambient sound levels derived from our dataset will be compared to these historical datasets. Our comparative analysis focused on humpback whales (Megaptera novaeangliae), fin whales (Balaenoptera physalus), minke whales (Balaenoptera acutorostrata), blue whales (Balaenoptera musculus), sei whales (Balaenoptera borealis), and beaked whales (family Ziphiidae). Results will illustrate how Bermuda’s offshore underwater soundscape has changed over nearly six decades.

Vocal signatures affected by population identity and environmental sound levels.

Passive acoustic monitoring has improved our understanding of vocalizing organisms in remote habitats and during all weather conditions. Many vocally active species are highly mobile, and their populations overlap. However, distinct vocalizations allow the tracking and discrimination of individuals or populations. Using signature whistles, the individually distinct calls of bottlenose dolphins, we calculated a minimum abundance of individuals, characterized and compared signature whistles from five locations, and determined reoccurrences of individuals throughout the Mid-Atlantic Bight and Chesapeake Bay, USA. We identified 1,888 signature whistles in which the duration, number of extrema, start, end, and minimum frequencies of signature whistles varied significantly by site. All characteristics of signature whistles were deemed important for determining from which site the whistle originated and due to the distinct signature whistle characteristics and lack of spatial mixing of the dolphins detected at the Offshore site, we suspect that these dolphins are of a different population than those at the Coastal and Bay sites. Signature whistles were also found to be shorter when sound levels were higher. Using only the passively recorded vocalizations of this marine top predator, we obtained information about its population and how it is affected by ambient sound levels, which will increase as offshore wind energy is developed. In this rapidly developing area, these calls offer critical management insights for this protected species.

ELECTRONICS WOMEN’S SAFETY JACKET

The "Electronics Women's Safety Jacket" is a cutting-edge microcontroller-based project designed to enhance the safety of women in various environments. This innovative jacket integrates advanced electronics to create a proactive safety solution. At its core, the project employs a microcontroller as the central processing unit, serving as the brain of the safety jacket. This microcontroller is equipped with sensors that detect crucial environmental factors, such as ambient light levels, sound levels, and GPS location. These sensors enable the jacket to adapt its functionality based on the wearer's surroundings. One of the key features of the safety jacket is its ability to trigger an alarm in emergency situations. For instance, if the ambient light drops suddenly, signaling potential danger, or if the sound levels indicate distress, the microcontroller activates a loud alarm to attract attention. Additionally, the built-in GPS system allows the jacket to transmit the wearer's location to predefined contacts or emergency services, ensuring swift assistance in critical scenarios. To further empower women's safety, the jacket incorporates a panic button or gesture recognition technology. In times of distress, the wearer can easily activate the alarm system by pressing the panic button or performing a specific gesture, initiating a rapid response mechanism. The project also focuses on user-friendly design, considering the comfort and convenience of the wearer. The electronic components are seamlessly integrated into the fabric of the jacket, maintaining a stylish and inconspicuous appearance. Rechargeable batteries power the system, ensuring long-lasting functionality without compromising mobility. In conclusion, the Electronics Women's Safety Jacket is an intelligent and responsive solution leveraging microcontroller technology to address women's safety concerns. By combining sensor data, GPS capabilities, and user-friendly features, this project aims to provide a reliable and effective tool for enhancing the security and well-being of women in various situations. Key Words: Microcontroller, GPS, GSM, Sensors.

Sound Environment during Dental Treatment in Relation to COVID-19 Pandemic

This study delves into the acoustic environment within dental clinics, particularly focusing on the impact of extraoral suction devices employed for infection control amid the COVID-19 pandemic. The research encompasses a comprehensive investigation, including a questionnaire survey of dental professionals, sound level measurements at suction device openings, acoustic imaging, and a detailed analysis of sound levels and their spectral characteristics during dental procedures. Additionally, ambient sound levels within clinical settings were monitored over two consecutive days. The findings reveal notable observations. Dental professionals expressed concerns regarding increased sound levels and associated distress caused by extraoral suction device operation. Objective measurements identified varying A-weighted sound pressure levels ranging from 86.0 dB to 96.7 dB at suction device openings, highlighting elevated sound pressure levels and a wide frequency range, especially in the vicinity of both the dentist and the patient’s facial area during dental aerosol procedures. On the other hand, for the entire clinical room, the equivalent continuous A-weighted sound pressure level during the consultation hours was not considered problematic. In light of these findings, it becomes evident that there is a pressing necessity to refine the acoustic characteristics of extraoral suction devices to foster a more accommodating acoustic environment for both patients and dental healthcare professionals within dental clinics.

Natural soundscape variation appears to influence the structure of stereotypic calls and repertoires in killer whales

Underwater soundscapes show dynamic variations in natural ambient sound levels at different locations and water depths and levels can vary over a course of a day. This soundscape dynamicity may pose a vocal challenge for highly mobile marine mammals whose habitat overlaps with many dynamic soundscapes. The most prominent communication tool of killer whales is a pulsated often multicomponent call which can be detected at more than 15 kilometers under quiet conditions. Social learning of call structure is a driver for stereotypic long lasting group- or population-specific call repertoires. Here we describe the potential vocal adaptations of killer whales to reduce the influence of sound propagation loss (PL) on their calls. Reliable propagation to identify groups and populations at considerable distances is important. In experimental field trials, the PL of killer whale calls and that of tones and sweeps was examined to determine if call component PL differs among soundscapes. PL is positively correlated with spatial and temporal ambient noise level variation. Furthermore, the use of burst pulses, a common feature of calls increased propagation distances at higher noise levels. We conclude that noise variation is one of the drivers of call structure and may also influence the call repertoire size.

Evaluating machine learning architectures for sound event detection for signals with variable signal-to-noise-ratios in the Beaufort Sea.

This paper explores the challenging polyphonic sound event detection problem using machine learning architectures applied to data recorded in the Beaufort Sea during the Canada Basin Acoustic Propagation Experiment. Four candidate architectures were investigated and evaluated on nine classes of signals broadcast from moored sources that were recorded on a vertical line array of hydrophones over the course of the yearlong experiment. These signals represent a high degree of variability with respect to time-frequency characteristics, changes in signal-to-noise ratio (SNR) associated with varying signal levels as well as fluctuating ambient sound levels, and variable distributions, which resulted in class imbalances. Within this context, binary relevance, which decomposes the multi-label learning task into a number of independent binary learning tasks, was examined as an alternative to the conventional multi-label classification (MLC) approach. Binary relevance has several advantages, including flexible, lightweight model configurations that support faster model inference. In the experiments presented, binary relevance outperformed conventional MLC approach on classes with the most imbalance and lowest SNR. A deeper investigation of model performance as a function of SNR showed that binary relevance significantly improved recall within the low SNR range for all classes studied.

Call rate of oyster toadfish (Opsanus tau) is affected by aggregate sound level but not by specific vessel passagesa).

Anthropogenic sound is a prevalent environmental stressor that can have significant impacts on aquatic species, including fishes. In this study, the effects of anthropogenic sound on the vocalization behavior of oyster toadfish (Opasnus tau) at multiple time scales was investigated using passive acoustic monitoring. The effects of specific vessel passages were investigated by comparing vocalization rates immediately after a vessel passage with that of control periods using a generalized linear model. The effects of increased ambient sound levels as a result of aggregate exposure within hourly periods over a month were also analyzed using generalized additive models. To place the response to vessel sounds within an ecologically appropriate context, the effect of environmental variables on call density was compared to that of increasing ambient sound levels. It was found that the immediate effect of vessel passage was not a significant predictor for toadfish vocalization rate. However, analyzed over a longer time period, increased vessel-generated sound lowered call rate and there was a greater effect size from vessel sound than any environmental variable. This demonstrates the importance of evaluating responses to anthropogenic sound, including chronic sounds, on multiple time scales when assessing potential impacts.

Establishing baselines for predicting change in ambient sound metrics, marine mammal, and vessel occurrence within a US offshore wind energy area

Abstract Evaluating potential impacts on marine animals or increased sound levels resulting from offshore wind energy construction requires the establishment of baseline data records from which to draw inference. This study provides 2 years of baseline data on cetacean species’ presence, vessel activity, and ambient sound levels in the southern New England wind energy area. With eight species/families present in the area for at least 9 months of the year, this area represents an important habitat for cetaceans. Most species showed seasonality, with peak daily presence in winter (harbour porpoise, North Atlantic right, fin, and humpback whales), summer (sperm whales), spring (sei whales), or spring and fall/autumn (minke whales). Delphinids were continuously present and blue whales present only in January. The endangered North Atlantic right whales were present year round with high presence in October through April. Daily vessel presence showed an increase from summer through fall/autumn. On average, ambient sound levels were lowest in summer and increased late 2021 through 2022 with most temporal variability occurring across lower frequencies. The area showed a complex soundscape with several species sharing time–frequency space as well as overlap of vessel noise with the communication range of all baleen whale species.

Marine soundscape and its temporal acoustic characterisation in the Gulf of Oristano, Sardinia (Western Mediterranean Sea)

The soundscape of the marine environment is a combination of geophony, biophony and anthropophony. Here, the soundscape of the Gulf of Oristano, a shallow inlet on the western coast of Sardinia including a special conservation area (Habitat Directive) and a national marine protected area, was investigated. Data collection was performed during July 2019, November 2019 and May 2020 using underwater acoustic equipment. The goal of this study was to characterise the ambient sound levels (Sound Pressure Level dB re 1 μPa) and describe the main soundscape components. The soundscape exhibited significant circadian and seasonal variations: the lowest and highest median SPL values were observed in the Spring (120–140 dB re 1 μPa; post-COVID-19 pandemic lockdown) and the Summer (128–150 dB re 1 μPa) respectively. Biophony was identified and characterised as dolphins’ ‘clicks’ and crustaceans’ ‘snapping’. Shrimp activity was dominant in the summer, while dolphin passages were observed across all sampling periods, accounting for 46.4% of the total recordings. Anthropophony, namely vessel passages, was predominant in the summer during the day-time and represented up to 42% of the acoustic space in the low-frequency band. Geophony increased low-frequency noise, and represented a highly variable component of the local soundscape. The marine soundscape is a valuabletool for defining integrated management plans for marine ecosystems, allowing the assessment of habitat quality, characterisation of sound sources and evaluation of the impact of anthropogenic activities.

Ambient noise levels with depth from an underwater glider survey across shipping lanes in the Gulf of St. Lawrence, Canada.

A two-month-long glider deployment in the Gulf of St. Lawrence, Canada, measured the ambient sound level variability with depth and lateral position across a narrow channel that serves as an active commercial shipping corridor. The Honguedo Strait between the Gaspé Peninsula and Anticosti Island has a characteristic sound channel during the Summer and Fall due to temperature variation with depth. The experiment comprised continuous acoustic measurements in the band 1-1000 Hz and oceanographic (temperature and salinity) measurements from a profiling electric glider down to 210 m water depth. The mean observed ambient sound depth-profile was modeled by placing a uniform distribution of sources near the surface to represent a homogeneous wind-generated ocean wave field and computing the acoustic field using normal modes. The measurements and predictions match within the observed error bars and indicate a minimum in the sound channel at 70 m depth and a relative increase by ∼1 dB down to 180 m depth for frequencies >100 Hz. The impact of detector depth, the distance to a busy shipping corridor, wind noise, flow noise, and self-noise are discussed in the context of passive acoustic monitoring and marine mammal detection.

Sound levels and its effect on physiology of low birth weight newborns in a special care newborn unit — a prospective observational study

BackgroundFrom quiet environment in uterus, neonates in special care newborn units (SCNU) get exposed to a stressful technology-driven environment. Noise level in neonatal intensive care units (NICU) depends on social and psychological realm of people working there. In NICU, an hourly Leq (median equivalent continuous sound level) of sound should be 45 dB, Lmax, 60 dB, and L10 not exceeding 50 dB (AAP, 2007). Noise level in SCNUs of northeast India has not been studied.AimCreate awareness among health workers (HW) regarding noise.ObjectiveTo study (a) noise level in special care newborn unit and (b) its effect on neonatal physiology.MethodologyA prospective observational study was conducted in a teaching hospital in northeast India for 1 month. After IEC approval, ambient sound levels in intensive care unit (ICU) (levels 2 & 3) and kangaroo mother care (KMC) area were measured using inVH by Bosch Engineering Solution (android app) in 3 shifts. Forty hemodynamically stable quiet low birth weight neonates (level 2: 16, level 3: 14, KMC: 10) were evaluated for heart rate and respiratory rate at same time. Acutely sick neonates were excluded. Statistical analysis was done using SPSS.ResultsAverage sound at 10 am, 5 pm, and 11 pm in level 2 was 70.2 (+ 3.78) dB, 71.9 (+ 4.21) dB, and 54.6 (+ 5.38) dB; in level 3: 66.4 (+ 3.71) dB, 64.9 (+ 3.88) dB, and 63.5 (+ 2.52) dB; and KMC: 55.06 (+ 5), 54.66 (+ 5.38), and 47.7 (+ 5.1) dB (p = 0.0052). Of included neonates, mean birthweight in intensive vs KMC area was 1.378 (+ 0.017) vs 1.337 (+ 0.02) kg (p = 0.1) and gestational age 35.45 (+ 0.25) weeks and 34.8 (+ 0.91) weeks (p = 0.2). The mean neonatal heart rate and respiratory rates in level 2 were 154/min and 44 cycles/min, level 3: 148/min and 47 cycles/min; and KMC: 124/min and 40 cycles/min.ConclusionSignificant noise pollution is detected in levels 2 and 3 neonatal intensive care units and minimal in kangaroo mother care area. Raised neonatal heart rates and respiratory rates in intensive care units with respect to KMC area may be related to noise. The social and psychological realm of healthcare workers and caregivers needs urgent improvement so as to reduce ambient noise pollution in special care newborn units.

Underwater sound of three unoccupied aerial vehicles at varying altitudes and horizontal distances.

Unoccupied aerial vehicles (UAVs), or "drones," are increasingly used as a tool for cetacean research, but knowledge about how these tools contribute to underwater sound is lacking. In this study, underwater sound levels of three commonly used UAV models (Mavic Pro Platinum, Phantom 4 Pro v2.0, Inspire 1 Pro) were recorded. For each model, three replicate flights were conducted at 36 positions at standardized horizontal (0-30 m) and vertical (2-40 m) distances from a hydrophone (1 m depth). Median broadband received levels of the Inspire were highest at 96.5 dBrms 141-17 783 Hz re 1 μPa2, followed by the Phantom (92.4 dBrms 141-17 783 Hz re 1 μPa2) and Mavic, which was quietest (85.9 dBrms 141-17 783 Hz re 1 μPa2). Median ambient sound levels in the absence of an UAV were 82.7 dBrms 141-17 783 Hz re 1 μPa2. Significant increases in ambient sound levels associated with UAV flights occurred at higher altitudes than previously reported, and received levels decreased more with increasing horizontal distance of the UAV than with altitude. To minimize potential noise impacts on sensitive marine animal subjects, we recommend increasing horizontal distance to the animal, rather than altitude, and choosing the quietest UAV feasible.

0935 An Investigation of ICU Ambient Noise Levels as a Potential Source for Poor Sleep Outcomes in a Community Hospital Setting

Abstract Introduction Patients in the intensive care unit (ICU) are subject to multiple necessary diagnostic and therapeutic interventions throughout the course of their treatment that contribute to sleep deprivation. These measures increase ambient noise, impacting patient morbidity and mortality by exacerbating confusion, ICU-related delirium, recovery time, and long term sequelae associated with Post-Intensive Care Syndrome. The World Health Organization suggests critically-ill patients not exceed exposure to sound levels higher than 35-40 decibels (dB). In this study, we measured ICU sound levels in a community hospital setting to support intervention with conservative bundle measures or behavior modification with a visual noise monitoring device. Methods This study took place over two months (October-November, 2021) in the critical care unit of St Agnes Medical Center in Fresno, CA. Ambient noise was monitored using a sound decibel meter (Gain Express Holdings, SLM-25) connected to recording software that measured the decibel levels at 1-minute intervals for 24 hours in three areas: two central stations (Station A and B) and one occupied patient room, equidistant to both central stations. The monitor data was exported to Microsoft Excel (2020 version; Microsoft Corp, Redmond, WA, USA) for analysis. Data from each sample was expressed as M±SE (95% confidence interval). Results Both central stations had average levels of 44.1dB± 4.7 and 48.0dB± 4.3, with a frequency range of 40-50 dB greater than 50% of the time. Station A had a frequency range of 50-60 dB approximately 11% of the time and Station B at 30% of the time. The occupied patient room had average levels of 48.0dB± 5.4, with frequency of 40-50 dB greater than 50%, and levels 50-60 dB greater than 30% of the time. Conclusion ICU’s with higher than recommended ambient sound levels may benefit from appropriate intervention such as visual noise monitoring devices or order-sets with protocols on equipment/staff phone volume, earplugs for patients, and limiting staff conversation to distances away from the bedside. Support (if any)

Background Sound Levels in Rural Areas of the U.S.

ANSI S12.9 Part 3 Annex C provides a compilation of the average daytime, nighttime, and day-night sound levels in six land use categories, ranging from Category 1 - "very noisy urban residential" to Category 6 - "very quiet suburban and rural residential." However, the data in table C.1 of the standard, which provides typical day, night, and day-night sound levels by land use category, is based primarily on more urbanized areas, and provides caution in using the data for the less densely developed land use Categories 5 and 6. In this paper we supplement this Annex by providing a collection of ambient sound level data at over 150 rural locations primarily in the northeastern and midwestern U.S. As the ambient sound level is not a single metric, the results include the range of sound levels in various metrics, including the A-weighted L10, L50, L90, and Leq, for the daytime and nighttime, and DNL. Unweighted octave and 1/3 octave band ranges and averages are also presented for each metric. Where possible, we also compare these results at individual locations to the predictions made by national noise mapping programs.