Low Frequency Sound Waves and the Upper Atmosphere

Abstract

THE transmission of low frequency sound waves, such as those from explosions, to very great distances has been an accepted fact for some time, but for careful investigations it was inevitable that mechanical instruments should eventually replace the ear in receiving the waves. These instruments have the advantage of being more certain, more accurate, and of producing a permanent record. Some types show the form of the wave, and all are more sensitive to the longer wavelengths which may be completely missed by the ear, even though they are not quite outside the audible limit. Those beyond this limit are aetually the more useful because they tend to be less strongly absorbed in their passage through the air.