Progress update on ANSI/ASA S12.2, criteria for evaluating room noise

This research investigated differences in task performance and perception under six non-time-varying ventilation-type background noise spectra with differing tonality. The results were related to five indoor noise criteria systems: noise criteria, balanced noise criteria, room criteria, room criteria mark II, and the A-weighted equivalent sound pressure level (L(Aeq)). These criteria systems are commonly used in the U.S. building industry, but concerns exist over whether they are appropriate for all noise situations. Thirty test subjects completed three types of performance tasks (typing, reasoning, and math) and answered questions about their perception of the indoor environment under each noise condition. Results showed that performance scores did not change significantly across the six noise conditions, but there were differences in subjective perception. For example, perception trends for tonality, annoyance, and distraction changed based on the frequency and prominence of discrete tones in noise. However, these perceptual changes were not fully reflected in the criteria level or spectral quality ratings. Additionally, task performance was related to subjective perception but not to criteria level predictions. As a result, the authors suggest that the current criteria should be modified to account for the frequency and prominence of tones in background noise.

MEASUREMENT AND ASSESSMENT OF NOISE WITHIN PASSENGER TRAINS

In many occupations there are high levels of noise in the environment. Habitual, unprotected exposure to high levels of noise can result in injury to hearing. This type of injury to hearing is additional to the decline in hearing acuity which accompanies ageing. Injury to hearing due to habitual noise exposure develops rapidly in the early years of exposure and later more slowly. With the accumulation of injury to hearing and age-effect there comes a point where the individual is handicapped (See Note). This point, in terms of measured hearing level, varies from person to person. The Committee believes that a reasonable objective would be to restrict occupational exposure to noise so that handicap should not occur in more than 1 per cent of persons exposed for a working lifetime. According to present knowledge, this objective will be achieved if the noise-induced impairment of hearing acuity (See Note) at the end of a working lifetime does not exceed a level of 40 dB (calculated as the average value for the 6 standard audiometric frequencies in the range 0·5–6·0 kHz) in more than 1 per cent of the population. The degree of exposure to noise may be defined in terms of “noise immission”. This is calculated from two parameters; A-weighted sound level and total duration of exposure. It is recommended that in order to achieve the objectives indicated in paras. 3 and 4, the amount of noise received by those exposed should not exceed an immission of 105 dB. Any combination of sound level, pattern and duration of exposure which causes this immission to be exceeded is considered to be unacceptable. This immission represents an equivalentcontinuous noise level experienced over a working lifetime of 30 yr (each year representing 48 working weeks of 40 hr exposure) of 90 dB(A). The Standard includes values of equivalent-continuous noise level for use where the working lifetime is anticipated to be in excess of 30 yr. When it is necessary for persons to work in areas where the recommended limit for immission would be exceeded, steps should be taken to safeguard the hearing of those exposed. The data in this Standard relate specifically to wide-band noise. They should not be applied to situations where significant pure tones are present, i.e. those in which the noise level in any octave band exceeds the levels in both adjacent octave bands by 5 dB or more. This Standard is subject to review in the light of new evidence. In any case, it will be reviewed 3 yr from its date of first publication.

A series of calculations was performed to ascertain how well one frequency-weighted rating, such as weighted sound level, loudness level, or perceived noise level, may be predicted from another such rating. A total of 103 average sound level spectra, measured at several distances from different types of highways, were used in these calculations. It was found that knowing a single noise rating, such as the A-weighted sound level, enables one to predict other outdoor ratings in this set of 103 spectra with a standard deviation of the order of 1 to 2 dB. If, in addition, traffic speed and mix and the distance to the highway are taken into account, these standard deviations can be reduced to 0.5 to 1 dB, depending upon the particular noise rating of interest. Equations are given for predicting one rating from another; the associated standard deviations are presented as a measure of how well any given rating can be predicted from a single measured, or otherwise known, noise rating. It is concluded that it is not very critical which frequency-weighting procedure is used in conjunction with highway noise criteria since one descriptor can be predicted from another with a rather small statistical uncertainty. Thus, if human response criteria, or stimulus-response relationships, have been developed in terms of one frequency-weighting procedure, these may be translated into equivalent criteria expressed in terms of a metric that is easier to measure or predict.

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

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.

In June 2013, the Commonwealth of Massachusetts launched a Community Wind Energy Initiative to provide support and guidance to municipalities, developers and stakeholders for land-based wind projects. The initiative convened a technical advisory group of experts to solicit input on wind turbine sound policy. This Wind and Noise Technical Advisory Group (WNTAG) is led by the Massachusetts Department of Environmental Protection (MassDEP) and includes other state agency representatives, wind energy experts, industry representatives, affected community representatives, health experts, and acoustical consultants. The WNTAG has met several times since July 2013 and has addressed many aspects of wind turbine noise that may influence and/or become a part of a new statewide noise policy for land-based wind turbines. In this presentation, the authors provide perspective on the process, progress toward a revised policy, and the policy and technical aspects that were discussed, which included absolute vs. relative noise criteria, noise level metrics, measurement protocols for compliance evaluation, amplitude modulation, and modeling approaches for pre-construction permitting.

A large fraction of emissions of carbon dioxide (CO 2 )-the greenhouse gas produced by human activities in the greatest quantities-is long lived in the atmosphere, so decisions made today to continue adding CO 2 into the atmosphere may lock future generations into a range of human health and environmental impacts, some of which could become very severe, according to a committee of the National Research Council (NRC). In a report that looks at the short-and long-term effects of the stabilization of Earth's temperature, the NRC committee quantifies, as much as possible, the outcomes of different stabilization targets for the planet, with a focus on the United States. 1

Amplitude modulation in wind turbine noise refers to the distinct periodic variation in amplitude which can be perceived more than a constant level. A method for rating amplitude modulation in wind turbine noise, intended for noise in 1/3 octave bands between 50 and 800 Hz, is described in Final Report A Method for Rating Amplitude Modulation in Wind Turbine Noise 9 Aug 2016 Version 1, Institute of Acoustics IOA Noise Working Group (Wind Turbine Noise) Amplitude Modulation Working Group. This paper examines the measurement and rating of amplitude modulation in wind turbine noise below 50 Hz, below the intended range of the method described in the Institute of Acoustics report. A tonal analysis as per ETSU-R-97 is also made, and the results compared.

Transfusion-related acute lung injury: three decades of progress but miles to go before we sleep.

An algorithm for multichannel adaptive IIR (infinite impulse response) filtering is presented and applied to the active control of broadband random noise in a small reverberant room. Assuming complete knowledge of the primary noise, the theoretically optimal reductions of acoustic energy are initially calculated by means of a frequency-domain model. These results are contrasted with results of a causality constrained theoretical time-domain optimization which are then compared with experimental results, the latter two results showing good agreement. The experimental performances of adaptive multichannel FIR (finite impulse response) and IIR filters are then compared for a four-secondary-source, eight-error microphone active control system, and it is found that for the present application FIR filters are sufficient when the primary noise source is a loudspeaker. Some experiments are then presented with the primary noise field generated by a panel excited by a loudspeaker in an adjoining room. These results show that far better performances are provided by IIR and FIR filters when the primary source has a lightly damped dynamic behavior which the active controller must model.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Electron beam-based instruments are sensitive to the environment in which they operate. Adverse environments may limit their achievable resolution. Many equipment manufacturers provide specifications for the acceptable level of various environmental conditions, such as vibration, EMI, and acoustic noise. However, the quality of the specifications vary significantly, from well-defined to conjectural. Additionally, during the design of a facility, the specific instruments that will be used may not yet be known. Thus, it is useful to have "generic" criteria, intended to represent entire classes of instruments, to use in the design of facilities. Generic vibration criteria exist to aid in the design of laboratories, though there have been no such instrument-based generic criteria available for acoustic noise. The generic noise criteria that are currently used in lab design (NC, NR, dBA, etc.) were established to address the effect of noise on human beings. Using noise specifications for a significant number of instruments with varying resolving powers, correlation of resolution with environmental noise is demonstrated. Based on the data reviewed, generic noise criterion curves have been developed and presented for use in the design of facilities that contain noise-sensitive equipment. These are applicable when other well-defined and specific criteria are not available.

The development of bone mineral densitimometry methodologies, especially central dual energy X-ray absorptiometry (DXA) methods have allowed this quantitative tool to be used to diagnose osteoporosis before the first fragility fracture has occurred. The World Health Organization osteoporosis working group set the stage for the BMD cut-off criteria development. The wide application of DXA has brought the treatment of osteoporosis to the primary care level, a very necessary step if this increasingly prevalent disease is to have a decline in its incidence. The most difficult osteoporosis cases, for which there are many and their associated difficult DXA results and interpretation will always require specialists' involvement. In particular, the embracement of the WHO absolute fracture risk validated project will take DXA to a much greater level of value in making management decisions. In particular, the WHO absolute risk data will allow physicians, health-economic policy makers, and payors of medical services to come closer together to decide which patients are at a level of unacceptable fracture risk that justifies treatment intervention. The implementation of this validated project will also remove the unacceptable subjective computer printouts on DXA reports that often lead to the over-treatment of low risk patients and at times the under-treatment of high risk patients. The evolution of the clinical interpretation of bone densitometry has been a work in progress. Challenges in the clinical measurement of bone strength remain and will also evolve. The field of osteoporosis has grown with the use of DXA and will continue to embrace this technology as other technologies to measure fracture risk become applied in clinical practice.

Koubek Auditorium is used for architecture classes and guest lectures in the School of Architecture and Planning at the Catholic University of America in Washington, DC. Inadequate acoustics in this space result in ineffective use of the space as well as a poor teaching environment. The main problem areas are excessive background levels and reverberation times. Using a 1/3-octave band, background levels range from 47.6 dB–56.5 dB, reverberation times range from 0.9–1.6 s, and the noise criteria (NC) is anywhere from NC40 to as high as NC60, depending on where one is seated. The intent of this paper is to discuss the analysis and implementation of the acoustical corrections, as well as the end result of the changes and how those results improve the learning environment in the space.

A behavioral preference procedure, the ’’acoustic menu,’’ was used to assess human aversion to the sounds from two samples of transmission line audible noise and from samples of other environmental noises. The audible (corona) noise produced by extra-high voltage (EHV), overhead transmission lines was tape-recorded during moist weather. Reproduced samples of corona noise, other common environmental noises, and artificial reference stimuli were compared in two experiments. The two corona noise samples were found to be equally preferred to: (1) a 1000 Hz octave band of noise about 11 dB SPL higher than the corona noises and (2) a collection of other environmental noises about 8 dB SPL higher than the corona noises. The corona noise samples were more aversive than the ambient sounds (including rainfall) occurring near rural transmission lines and were roughly equivalent in aversiveness to the noise from a room air conditioner (indoor recording). Knowledge of the source of the corona noise (from photographs and a brief description) did not affect its aversiveness. Of the simple frequency-weighting scales, the A-weighted sound level reduced the difference between the two corona noise samples and the set of other environmental sounds from about 8 dB SPL to about 3 dB. The D-weighted sound level further reduced this discrepancy to about 2 dB. These results were obtained with only two samples of corona noise; other samples may give different results.