Some considerations in choosing an explosive source and processing filter for the measurement of transmission loss

Abstract

Explosives are often used as a source of acoustic energy in transmission measurements in the ocean because of the broad-band spectra of underwater explosions and the wide range of levels that can be generated. At the same time, this broad-band spectrum can complicate a transmission loss measurement because the spectral character of the shock wave and subsequent bubble pulses of the shot can be very similar to the spectral character of the loss which is due to the multipath structure of the propagation. This complication can be avoided by the proper choice of the detonation depth and the charge weight. When these choices have been made, the properties of the analyzing filter of the data processing system must then be selected; this must be done with regard for the nature of that portion of the multipath structure to be resolved as well as the nature of the charge spectrum. This paper discusses the principles involved in making these choices and gives illustrations of both short- and long-range measurements.