Highway noise criteria study :

Spatial and temporal determinants of A-weighted and frequency specific sound levels—An elastic net approach

In environmental noise control one commonly employs the A-weighted sound level as an approximate measure of the effect of noise on people. A measure that is more closely related to direct human perception of noise is the loudness level. At constant A-weighted sound level, the loudness level of a noise signal varies considerably with the shape of the frequency spectrum of the noise signal. In particular the bandwidth of the spectrum has a large effect on the loudness level, due to the effect of critical bands in the human hearing system. The low-frequency content of the spectrum also has an effect on the loudness level. In this note the relation between loudness level and A-weighted sound level is analyzed for various environmental noise spectra, including spectra of traffic noise, aircraft noise, and industrial noise. From loudness levels calculated for these environmental noise spectra, diagrams are constructed that show the relation between loudness level, A-weighted sound level, and shape of the spectrum. The diagrams show that the upper limits of the loudness level for broadband environmental noise spectra are about 20 to 40 phon higher than the lower limits for narrowband spectra, which correspond to the loudness levels of pure tones. The diagrams are useful for assessing limitations and potential improvements of environmental noise control methods and policy based on A-weighted sound levels.

The airborne and solidborne noise measuring equipment, small in size and light in weight was especialily devised for ship, and various tests have been made for practical use.Using this equipment, noise and vibration measurement were made by several types of ship on their trial navigations. The results of observation about the noise source, spectrum and the calculated loudness will be summarized as follows;1) The relation between the calculated loudness of noise (Loudness Level, Perceived Noise Level, Noise Rating Number) and A, B, C, sound level were established and the results showed that good correlation was obtained between the calculated loudness and the A sound level calculated from the original noise spectra.2) The judgement of ship. noise will be made by using the calculated regression lines or more simply by adding the value of 8 (LL), 15 (PNL), and -3 (NRN) to the indicated A-sound level, so the ship noise shoud be measured by A weighting regardless of noise level.3) In accommodation spaces, the noise, largely solidborne, has a spectrum that slopes off approxim ately 5 dB/oct with increasing frequeny and the A sound level is about 70±20 phon. In engine room, however, noise has more energy at middle and high frequency and the level is nearly 95±10 phon.

Loud launch noise and sonic booms from some military space vehicle launches from Vandenberg Air Force Base impact pinnipeds on the mainland and at San Miguel Island, California, and may cause stampedes, temporary threshold shift or, less likely, permanent hearing damage. Maximum fast A-weighted (MFXA) sound levels approximately 4.8 miles downrange during the launch of three Titan IV rockets were 93.2, 92.7, and 93.0 dB; average sound exposure levels were between 98.9 and 101 dB. Harbor seals fled into the water in response but many returned to land within several hours. A sonic boom was recorded at San Miguel Island during one launch. Its peak flat sound-pressure level was 129.5 dB and maximum fast A-weighted sound level was 86.2 dB; virtually all of the energy was below 500 Hz. Pinniped behavioral responses were mild and brief. Predicted overpressures for focused sonic booms from the Titan IV rocket are substantially greater (≥150 dB). Noninvasive hearing tests using ABR and OAE techniques are being used to determine if pinnipeds suffer temporary threshold shifts or permanent hearing damage from exposure to those sonic booms.

The responses of over 750 national park visitors to sounds of aircraft overflights were measured at six study areas in the Grand Canyon, Hawaii Volcanoes, and Haleakala National Parks. Park visitors were observed as they entered each study area, and were asked to participate in a brief survey as they exited the area. The survey included questions about the visitor’s reasons for visiting the park, and asked visitors to rate their responses to aircraft sounds on five-point scales. Simultaneously, in one to three positions representative of the study area, A-weighted sound levels were recorded at 1-s intervals using extremely low noise instrumentation. In addition, human observers maintained time-synchronized logs of aircraft audibility, types of aircraft audible, types of background sounds, and other factors. Several mitigating variables, such as background sound level and visitor expectations, were tested for their ability to improve the dose-response relationships. Logistic regression was used to generate four separate dose-response relationships, relating two visitor responses (annoyance due to aircraft sounds, and interference of aircraft sounds with natural quiet) to two acoustic doses (percentage of time aircraft are audible, and aircraft A-weighted equivalent sound level). [Work supported by National Park Service.]

MEASUREMENT AND ASSESSMENT OF NOISE WITHIN PASSENGER TRAINS

The National Institute for Occupational Safety and Health (NIOSH) has investigated engineering noise controls to reduce sound levels in cabs on air-rotary drill rigs. A recent investigation revealed that some drillers are exposed to A-weighted sound levels exceeding 85 dB even though a cab is used. NIOSH studied the in-cab sound levels of one such rig. First, preliminary tests were conducted in a controlled environment using accelerometers and microphones with spectral analysis to identify the dominant noise sources for in-cab sound levels. The results indicate that vibration transmitted from multiple hydraulic pumps to the control panel produces a dominant spike in the sound level spectrum in the 400 Hz 1/3-octave band. Next, field tests were performed in a production environment to evaluate noise controls to reduce in-cab sound levels. It was found that utilizing hydraulic noise suppressors reduces the structure-borne noise transmitted to the control panel. Further, using hydraulic noise suppressors and enhancing soundproofing reduced the in-cab A-weighted sound levels by as much as 4 dB.

Intensive care units (ICUs) may disrupt sleep. Quantitative ICU studies of concurrent and continuous sound and light levels and timings remain sparse in part due to the lack of ICU equipment that monitors sound and light. Here, we describe sound and light levels across three adult ICUs in a large urban United States tertiary care hospital using a novel sensor. The novel sound and light sensor is composed of a Gravity Sound Level Meter for sound level measurements and an Adafruit TSL2561 digital luminosity sensor for light levels. Sound and light levels were continuously monitored in the room of 136 patients (mean age = 67.0 (8.7) years, 44.9% female) enrolled in the Investigation of Sleep in the Intensive Care Unit study (ICU-SLEEP; Clinicaltrials.gov: #NCT03355053), at the Massachusetts General Hospital. The hours of available sound and light data ranged from 24.0 to 72.2 hours. Average sound and light levels oscillated throughout the day and night. On average, the loudest hour was 17:00 and the quietest hour was 02:00. Average light levels were brightest at 09:00 and dimmest at 04:00. For all participants, average nightly sound levels exceeded the WHO guideline of < 35 decibels. Similarly, mean nightly light levels varied across participants (minimum: 1.00 lux, maximum: 577.05 lux). Sound and light events were more frequent between 08:00 and 20:00 than between 20:00 and 08:00 and were largely similar on weekdays and weekend days. Peaks in distinct alarm frequencies (Alarm 1) occurred at 01:00, 06:00, and at 20:00. Alarms at other frequencies (Alarm 2) were relatively consistent throughout the day and night, with a small peak at 20:00. In conclusion, we present a sound and light data collection method and results from a cohort of critically ill patients, demonstrating excess sound and light levels across multiple ICUs in a large tertiary care hospital in the United States. ClinicalTrials.gov, #NCT03355053. Registered 28 November 2017, https://clinicaltrials.gov/ct2/show/NCT03355053.

The Relationship Between Vehicle Noise Measures and Perceived Noisiness

The findings from a test campaign aimed at understanding the thrust and acoustic performance of a small-scale, coaxial, corotating rotor in hover are discussed. Measurements of axial thrust are acquired alongside surveys of the near-field acoustics at eight observer positions above and below the tip path plane of the upper rotor. The variables of interest are the index angle and stacking distance between the upper and lower rotors, as well as rotor speed. Standard metrics like thrust coefficient, sound pressure spectrum level, and the sound pressure level of the various blade harmonics and subharmonics are studied. Human ear effects are also considered using the A-weighting standard, which is shown to have a profound influence on the perceived noise levels. The analysis demonstrates how rotor thrust and sound pressure levels are more dependent on rotor index angle than stacking distance. However, the index angle where the peak thrust coefficient resides is more sensitive to stacking distance at low rotation speeds than it is at high rotation speeds. Various rotor speed and index angle combinations of the stacked rotor are also shown to produce the same rotor thrust, all the while resulting in uniquely different sound levels of the various rotor harmonics.

A study of sound levels and spectral distribution as well as people\'s reactions to aircraft noise in three Nigerian international airports have been conducted. The study comprised physical measurements and social survey. Results show that maximum octave band pressure levels (BPLs) for Margaret Ekpo, Port Harcourt and Murtala Mohammed International Airports were 88 dB(A), 94 dB(A) and 99 dB(A), respectively with corresponding the deafening levels recorded as 102.5dB(A), 122.5 dB (A) and 123.5 dB(A). Maximum sound level (L) wasas high as 116 dB(A) in each case. The Day-night level (L), weighted equivalent continuous perceived noise level (WECPNL), noise and number index (NNI), noise exposure forecast (NEF), A-weighted sound level (L), and noise pollution level (L) were also obtained based on acoustical data generated at the airports under study, and were found to exceed the recommended doses of 55, 60, 20, 24, 45 and 60dB (A), respectively. From these results it is clear that octave band pressure levels exceed the recommended 85 dB(A). Octave band pressure levels obtained tend to be Gaussian and the spectra were flat. Percentage responses correlated well with NNI with power law relationships between it and the latter in all the cases considered. Results clearly show that people resident near Nigerian airports are exposed to psychological and physiological damage as a result of excessive aircraft noise with serious activity interference. Keywords: Noise levels, spectra, aircraft noise, damage risk and activity interference.Nigerian Journal of Physics Vol. 19 (2) 2007: pp. 223-227

This study compared sound levels before and after structural reconstruction within an NICU. Using a descriptive design, sound level recordings (in decibels, A-weighted scale) of the Leq, L10, and Lmax were measured continuously for 8 hours (0600-1400) before and after reconstruction in an NICU located in north central Florida. Levels before reconstruction were Leq M = 60.44 dB, L10 M = 59.26 dB, and Lmax M = 78.39 dB. The average overall sound levels after reconstruction were Leq M = 56.4 dB, L10 M = 60.6 dB, and LmaxM = 90.6 dB. Although an approximate 4-decibel decrease in the Leq sound level after reconstruction was noted, a similar decrease in the L10 and Lmax did not occur. Furthermore, sound levels after reconstruction in the NICU still exceeded recommended levels (Leq < 50 dB, L10 < 55 dB, and Lmax < 70 dB). Findings from this study demonstrated the positive impact that reconstruction can have on sound levels (4 dB Leq decrease); however, additional interventions may be needed to meet the current standards for noise reduction in an NICU.

Background & Aims: Noise exposure can impact nurses' performance and may result in disruptions to their tasks.This study aimed to examine the correlation between the average equivalent sound level and the occurrence of medication errors. Materials & Methods:This cross-sectional study involved 150 nurses in Iran in 2020.First, two medical and two surgical wards were randomly selected using a coin toss method.Second, the nurses who worked in those wards were sampled using the convenience method.Nurses' medication errors were assessed using a questionnaire.A sound level meter was used to measure the sound level in decibel.Data were analyzed using analytical tests, including Kruskal-Wallis, Spearman correlation coefficient, and Poisson model. Results:The mean sound equivalent level in the cardio-respiratory internal ward (58.94 ± 1.88) was higher than the same level in the other internal and surgical wards (p < 0.001).An increase in the mean sound equivalent level in the wards was accompanied by an increase in the mean number of medication errors among unmarried individuals (e 0.22 = 1.25), which was 1.25 times more than the errors made by married individuals.Finally, an increase in age and the mean sound equivalent level resulted in the occurrence of medication errors (p < 0.002). Conclusion:The results showed that there was no relationship between the sound pressure level and nurses' medication errors in the research environment.Therefore, it is necessary to conduct more studies to investigate the factors that increase the incidence of medication errors.

Interior noise in trains is a significant contributor to passengers’ comfort and satisfaction. In the design of new rolling stock, the A-weighted average sound level has generally been applied as the standard indicator. However, surveys show that the passengers’ satisfaction varies for different types of rolling stock, even though the sound level is comparable. In order to set consistent design targets, the challenge is to relate emotional and subjective parameters such as comfort and satisfaction to technical and objective parameters such as for example sound level and reverberation time. This is relevant both for prediction and assessment of passenger comfort.

In a laboratory study, the annoyance caused by the passby sounds from a magnetic levitation (maglev) train was investigated. The listeners were presented with various sound fragments. The task of the listeners was to respond after each presentation to the question: “How annoying would you find the sound in the preceding period if you were exposed to it at home on a regular basis?” The independent variables were a) the driving speed of the maglev train (varying from 100 to 400 km/h), b) the outdoor A-weighted sound exposure level (ASEL) of the passbys (varying from 65 to 90 dB), and c) the simulated outdoor-to-indoor reduction in sound level (windows open or windows closed). As references to the passby sounds from the maglev train (type Transrapid 08), sounds from road traffic (passenger cars and trucks) and more conventional railway (intercity trains) were included for rating too. Four important results were obtained. Provided that the outdoor ASELs were the same, 1) the annoyance was independent of the driving speed of the maglev train, 2) the annoyance caused by the maglev train was considerably higher than that caused by the intercity train, 3) the annoyance caused by the maglev train was hardly different from that caused by road traffic, and 4) the results 1) – 3) held true both for open or closed windows. On the basis of the present results, it might be expected that the sounds are equally annoying if the ASELs of the maglev-train passbys are at least 5 dB lower than those of the intercity train passbys. Consequently, the results of the present experiment do not support application of a railway bonus to the maglev-train sounds.