English

This American National Standard describes procedures for the measurement of sound pressure levels in the outdoor environment, considering the effects of the ground, the effects of refraction due to wind and temperature gradients, and the effects due to turbulence. This standard is focused on measurement of sound pressure levels produced by specific sources outdoors. The measured sound pressure levels can be used to calculate sound pressure levels at other distances from the source or to extrapolate to other environmental conditions or to assess compliance with regulation.

The propagation of low-amplitude air pressure transients within the drainage and vent systems of underground habitable structures may result in system failure due to trap seal loss and foul odour ingress into the occupied space. This paper develops the simulation of such transient response, and presents comparisons between predicted system air pressures and those monitored during the operation of the drainage and vent system in a large London Underground tube railway station.

Traditionally, ventilation and air conditioning ducts have been manufactured with rectangular cross sections. The rectangular duct can easily be adapted, e.g. to restricted ceiling voids and plant rooms, however, often at the cost of efficient airflow design and possible cost savings. A round duct system normally performs better and offers a more economical solution, which is the reason why it always pays to study and compare the ductwork design before selecting which type is to be used for a specific application.

All internal combustion engines produce exhaust gases containing noxious compounds: carbon monoxide (CO), nitrogen oxides (NOx, carbon oxides (CxHy) and smoke. With the help of a mathematical model the concentrations of some dangerous substances at the end of the tunnel were calculated, and were replaced by a criteria! number. A corresponding computer program was also developed thus enabling quick and simple calculations of some concentrations and the criteria! number.