Sound Transmission in Helium and Various Gases at Low Pressures

摘要

This investigation was concerned with (a) the attenuation of sound in atmospheres of room air, 100% nitrogen, oxygen, or helium, and a 50-50 helium-oxygen mixture at reduced barometric pressures, and (b) a pilot study in evaluating oral communications in a 50-50 helium-oxygen atmosphere at a reduced barometric pressure. Reference tables have been prepared to assist in estimating the degree of sound reduction that will take place in each gas or gas mixture at different reduced barometric pressures. The pilot sound study has shown that tonal modification in the helium-oxygen atmosphere does not result in unintelligible oral communications at 395 mm. hg atmospheric pressure. In comparing the value of helium and nitrogen, it is suggested that, because of several yet unknown effects of helium on living systems, nitrogen may serve as a more suitable inert gas if such a gas is employed in the atmosphere of aerospace vehicles. (Author)