Showing papers in "Canadian Acoustics in 1979"

Method and Interpretation of Surveys on Noise Annoyance

Abstract: Major practical considerations during the design and analysis of sociological noise surveys are briefly discussed, particularly as they relate to choice and interpretation of statistical tests. The discussion concentrates on the appropriate use of data and scale transformations which may not only assist in the interpretation of results but also clarify seeming discrepancies both within a study as well as between apparently conflicting results reported in the literature. Applicable scale transformations are supported by the specification and discussion of theoretically based quantitative functions which may be used to predict human response from noise-level measures of loudness.

Community Response to Aircraft Noise in Relation to Background Levels

Abstract: This paper examines the effect of variations in background noise levels on community reactions to aircraft noise 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 Leq) on individual and aggregate responses to aircraft noise are'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. The direction of the weak effects on individual responses varies by level of aircraft noise exposure and type of response. These findings are compared with those from previous studies.

The Physiological Effects of Noise Exposure on Man

Abstract: No one would argue the point that modem technology has -introduced rapid growth and advancement throughout the world within the last few decades. While achievements are countless, one detrimental adversity which has been, until recently, an unknown consequences is the effect of noise on man. Specifically, noise has introduced irreversible hair cell damage to the cochlea reducing man’s potential for normal hearing sensitivity. Noise induced hearing loss (NIHL) may be caused by either long term exposure above the damage risk criteria, or instantaneous exposure. In any event, hair cell damage to the cochlea is the end result. Depending on man's exposure to noise, either temporary threshold shifts (TTS) or permanent threshold shifts (PTS) will ensue. The intent of this paper is to present current research in the area of noise exposure as it affects physiological changes within the auditory system. In addition, concomitant changes that face man due to a reduction in hearing sensitivity are discussed. Finally, current research by the present author in the area of noise exposure, ototoxicity and the additive effects on high risk infants are presented.

Theoretical Models for Relating Annoyance to Noise Level

Abstract: Theoretical mathematical models are formulated to specify the relationship between human annoyance and levels of noise» based only on well confirmed assumptions The proposed theories are consistent with descriptive models and appear capable of explaining the underlying mechanism as well as previously apparent discrepant findings

Vibration Behaviour of the MTC Experimental Subway Wheel

Abstract: The natural frequencies, mode shapes, and mechanical impedances of a resilient type subway wheel are presented. An impact method which uses Fourier techniques to analyse the vibrations of the wheel is described. Several natural frequencies and mode shapes not previously reported are presented.

Measurements and Prediction of Sound Levels in Quiet Urban Areas -- Urban Hum

Abstract: This paper summarises the results of 40 supervised and 23 unsupervised measure­ ments of Leq in urban and small-town back­ yards. They are used as the basis for a pre­ diction method for minimum equivalent sound levels likely to be found in urban areas. Community noise is made up o f a great many sounds from a large number o f d i f fe r e n t sources: ch i ld ren , dogs, lawn mowers, indu s try , construc t ion , e tc . However, the dominant source o f noise in almost every case is t r a f f i c . While the level o f community noise produced by a m ult itude o f sources would be exceedingly d i f f i c u l t to p re d ic t , tha t due to t r a f f i c is less so. In most areas, th is sound level due to t r a f f i c is close enough to the actual level o f community noise tha t they may be considered id e n t ica l fo r p rac t ica l purposes. While a great deal o f work has been done on p red ic t ion o f sound leve ls close to busy roads, l i t t l e has been done to quan t i fy the acoustical environment in qu ie t areas. The study described below was designed to explore the background \"roar\" or \"hum\" found in re s id en t ia l areas not d i r e c t ly exposed to the noise from t r a f f i c on a sp e c if ic s t re e t . The e f fe c t o f m u lt ip le re f le c t io n s in generating th is \"urban hum\" has been discussed in a review paper

Helicopter Noise Propagation Studies for Air Installation Compatible Land Use Zoning

Abstract: With the helicopter, noise undoubtedly is the environmental pol­ lutant which causes the greatest concern from the point of view of the general public and social acceptability (1), The noise radiated from a helicopter is very complex, composed of sound produced by several different sources, each of which generates acoustic energy by more than one mechanism. These include noise from engines, tail rotor and 'Blade Slap's The former is adequately described in terms of dBA. Certainly the other two are not.