For many years, it has been recognized by those working in the field of industrial noise that understanding how much noise is needed to cause hearing loss over a lifetime is difficult to communicate to most people, even those who have an understanding of logarithms. The concept of expressing noise exposure in industrial situations without decibels is the focus of this paper. Eldred (“Sound Exposure without Decibels” Internoise-86) discussed this approach for community noise. ANSI Standard S3.44-1996 defines sound exposure with units of Pascals squared seconds, or PASQUES, as noted by Eldred. This paper proposes that a safe value for lifetime occupational exposure to noise be expressed in terms of PASQUES. The authors will discuss the pros and cons of such an approach and offer 11.5 × 106 million PASQUES as the upper limit for a safe lifetime exposure to occupational noise.
Medical researchers often use mice and rats for numerous procedures. In typical rat housing rooms, there can be as many as 200 rats for an investment of $800,000 and in typical mouse rooms, as many as 2570 mice for an investment of $10 million. Do the sound and ultrasound exposures of these animals interfere with the medical research objectives of the scientists? Research has shown that high-noise levels have an effect on the physical and psychological responses of rodents. In order to eliminate this factor from influencing the medical experiments, criteria limiting noise and ultrasound in animal-housing facilities are needed. Mice have a hearing range of 1000–91 000 Hz, rats from 200 to 76 000 Hz, and other rodents can hear well above the human threshold. This makes creating a standard even more important because the majority of the frequencies perceived by rodents, including frequencies in which they communicate, are not perceptible to humans and therefore cannot be easily assessed. This study considers typical environments where these animals are housed, the levels at which mice are effected by noise and ultrasound, and the existing guidelines in non-US countries. Preliminary noise and ultrasound criteria are presented.
When calculating sound levels inside a building due to external sources, should some value be added to the expected sound level? ATSM E966 recommends adding 6 dB to this level. It has been theorized that this is due to pressure doubling. The effect of pressure doubling on the calculated exterior to interior sound transmission in the direct field is, however, often misunderstood. Most texts on the subject simply list a 5- or 6-dB correction factor that is applied to the transmission loss value. The reasoning of this particular number is neither expounded upon nor explained. This paper investigates and explains this correction factor.
There has been a great deal of research in the past ten years pertaining to infrasound. The effect on humans and animals of high levels of infrasound in both water and air has been studied. The effect of infrasound on structures was examined. In some situations, there has been paranoia over the effect of infrasound and, in other cases, infrasound has been overlooked completely when examining an acoustical problem. This study addresses an important element that remains to be studied, the prevalence of infrasound in a variety of locations. Infrasound was measured in a house, at a bus stop, at a typical office environment, and a variety of other situations that a typical person would be exposed to during the course of a week. These levels are then compared to less typical sites such as refineries, dredging areas, manufacturing plants, and community areas where noise complaints have been lodged. These comparisons give a preliminary understanding of peoples’ exposure to infrasound.
In order to characterize the sonic boom response in the interiors of buildings in urban settings, first the loading forces impinging on such buildings must be understood. To do this in an urban setting, many factors must be taken into account including the shape and surface structure of the building of interest, the kind of boom being propagated, and the scale of the propagation space. Nearby buildings and their features also require consideration. In addition, the importance of specular reflection versus diffuse reflections should be addressed. In this study, these factors are discussed and evaluated relative to the impact on the overall sound field. Preliminary results on a simple case are presented. [Work supported by NASA.]
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