Sound Level Data Research Articles

Effect of background levels on community responses to aircraft noise

The effect of variations in background noise levels on community reactions to aircraft noise has been investigated by using questionnaire and sound level data collected at a stratified random sample of residential sites in the vicinity of Toronto International Airport. The effects of variations in background noise (24 hour L eq ) on both individual and aggregate responses to aircraft noise have been examined. The response variables considered include annoyance, activity interference and complaints. The results of various statistical analyses show that the effect of background level is generally not significant. These findings are consistent with relevant findings from previous laboratory studies, but not with those from previous field studies.

Method to convolve sound-level distributions for prediction of community sound levels

Predicting community noise levels requires the addition of background ambient sound levels and the source’s contribution to ambient sound levels. Baseline data are obtained, from community sound surveys, in the form of histograms and cumulative distributions. Source (for example, a construction site) sound level data are also obtained as histograms and cumulative distributions. The problem of combining the two distributions is made somewhat difficult by the logarithmic nature of the physical variable. The prediction is accomplished by the mathematical convolution of the variables representing baseline and the source. Since the data are provided as histograms rather than as continuous probability density functions, it is convenient to decompose the density functions into a sequence of Dirac delta functions. The result can be programmed for a rapid and efficient computation. Results are provided for the combination of various construction site sound level distributions (e.g., normal and bimodal) with community background ambient sound. Data are shown of the effect on community noise of a source contribution which is attenuated by distance. Subject Classification: [43]50.75.

Sediment mass balance of a large estuary, Long Island Sound

Acoustic reflection profiles and bottom sampling are used to measure the volume of sediments accumulated in Long Island Sound. There is present 1.0 × 10 10m 3 of sediment of which 5.3 × 10 9m 3 is marine mud and 4.9 × 10 8m 3 is probably of pre-marine, lacustrine origin. The balance consists of reworked sand derived from glacial drift. The acoustically determined sub-bottom structure of the Sound and available sea level data indicate that the Sound basin was occupied by a large lake for at least 6000 years and has been an arm of the sea since 8000 years b.p. The volume of lacustrine sediment is accounted for by direct riverine input over 6000 years but the volume of marine mud present substantially exceeds the riverine supply over 8000 years. The Sound is shown to act as a trap for sediments originating on the continental shelf.

Predicting ambient sound levels

Predicting community noise levels requires the addition of background ambient sound levels and the source's contribution to ambient sound levels. Baseline data are obtained, from community sound surveys, in the form of histograms and cumulative distributions. Source (for example, a construction site) sound level data are also obtained as histograms and cumulative distributions. The problem of combining the two distributions is made somewhat difficult by the logarithmic nature of the physical variable. The prediction is accomplished by the mathematical convolution of the variables representing baseline and the source. Since the data are provided as histograms rather than continuous probability density functions, it is convenient to decompose the density functions into a sequence of dirac delta functions. The result, h(z) = Σαβδ{z − 10log[antilog(i/10) + antilog(j/10)]}, can be programmed for a rapid and efficient computation. Results are provided for the combination of various construction site sound level distributions (e.g., single valued, normal, biomodal) with community background ambient sound. Data are shown of the effect on community noise of a source contribution which is attenuated by distance.

Motor vehicle noise emission while accelerating up a hill

A noise survey was performed in 1975 to determine motor vehicle noise emissions while accelerating up a grade. A-weighted sound levels were measured at locations 50 ft from urban streets with grades carrying between 4.3% and 9.6%. The recorded sound level data are presented as a function of grade for five classes of vechicles: passenger cars, light trucks (GVW: under 8000 lb), light-medium trucks (GVW: 8–14 000 lb), medium trucks (GVW: 14–24 000 lb), and heavy trucks (GVW: over 24 000 lb). Statistical distributions of the recorded sound level data are presented for each class of vehicle and compared to level street acceleration data measured in 1974 [Michael F. Nechvatal and Robert D. Hellweg Jr., J. Acoust. Soc. Am. 56, S34(A) (1974)].

Field Measurement of Noise Reduction between Spaces

The present ASTM procedure for field measurement of the noise reduction between spaces is time consuming and costly because it requires numerous measurements in order to compute the noise isolation class (NIC), particularly when separate measurements must be made at multiple microphone positions to obtain adequate spatial averaging. The purpose of the present investigation is to explore the relationships between NIC values based on 13-oct band data and more easily obtained ratings of isolation based on either octave band data or on A-weighted or C-weighted sound level data. A large number of curves of 13-oct band noise reduction versns frequency were calculated from data on transmission loss of partitions, assumed room geometry, assumed values for the source sound power spectrum, and assumed values for the sound absorption in the source and receive rooms. For each of these 13-oct band noise reduction curves, the following quantities were calculated and compared: NIC rating, Ia rating (13-oct band data), Ia rating (octave band data), the A-weighted sound level difference, and the difference between the C-weighted level in the source room and the A-weighted level in the receive room.

Assessment of Noise Pollution in the Ashuganj Fertilizer Industrial Area, Ashuganj

Noise pollution in industries is now a serious environmental concern in Bangladesh. In this study sound levels are observed inside the Ashuganj Fertilizer Company Ltd (AFCL) Ashuganj. Continuous running of high speed turbo machinery, vibration of pipelines and structures, transmission of high pressure gas, sudden release of high pressure gas generate noise hazard inside the factory during the time of production. The sound level data was collected at seventeen different locations in the ammonia production plant, ten different locations in the urea production plant and ten different locations in the residential area of AFCL. In the ammonia plant, significantly high level of sound was observed (>90dB) from the process gas cooler, let-down station, boiler-feed water pump, synthesis-gas compressor, process air compressor, alternator and ammonia compressor areas. In the Urea plant, Prill tower (top), Prill tower (absorber vent) are the most noise vulnerable areas with sound level >90 dB. Residential area found less affected by noise pollution (43-53 dB) but in some areas like playground, main gate of the residential area sound level sometimes cross the standard sound level of residential area (50 dB). In the ammonia and urea plant, the sound levels are much higher than the standard sound level (75 dB) for the industrial area, which is considered a hazard of noise may induce hearing loss, annoyance and other adverse effects on the health of the workers of AFCL. Therefore, some remedial measures should be taken to reduce the sound level inside the factory. Key words: Noise pollution; Ashuganj Fertilizer Company Ltd (AFCL); Ammonia production plant; Urea production plant; Sound level; Health hazard. DOI: http://dx.doi.org/10.3329/bjsir.v46i2.8184 Bangladesh J. Sci. Ind. Res. 46(2), 183-190, 2011

Room Noise Spectra at Subscribers' Telephone Locations

Information on the sound levels of room noise at subscribers' telephone locations has been presented before this Society by Mr. D. F. Seacord and was published in the July, 1940, issue of the Journal. The present paper contains information which permits the interpretation of the sound level data in terms of the distribution of sound as a function of frequency by presenting the results of physical measurements of sound spectra at telephone locations in and around Philadelphia. An average spectrum, giving the absolute sound pressure as a function of frequency is presented for a given sound level of room noise. In addition data are given for the results of similar measurements made in two Bell System office buildings in New York and the results are compared with the Philadelphia data.