LECTURE 3 
EXPLOSIVE SOURCES 
D.E. Weston 
Admiralty Research Laboratory 
Teddington, Middlesex 
England 
3.1. INTRODUCTION 
This paper deals with transducers, though of a rather special sort. In this 
type of "transducer" there is a rapid and irreversible conversion of chemical 
energy into acoustic energy. I will not be much concerned with explosions as 
such, but will deal with explosions as acoustic sources — particularly underwater 
explosions. Only so-called point sources such as simple blocks of TNT will be 
described, and various special sources such as explosive gas mixtures will not 
be considered. A good deal of the ground covered will be familiar to many. 
This paper falls naturally into three parts. The first (section 3.2) gives some 
historical background. The second or main part (sections 3.3, 3.4, 3.5, and 3.6) 
concerns the characteristics of explosive sources, and draws heavily on two 
recent papers [9, 10] which give more detailed informationthan can be presented 
here. Reference [10] concerns underwater explosions, and [9] presents some 
more general ideas which are applied in particular to underground explosions. 
The approach here differs slightly from that in [9, 10]. The third part (sections 3.7 
and 3.8) describes some of the uses of explosions in underwater acoustics re- 
search and touches upon interpretation of results. 
3.2. BACKGROUND 
Underwater explosions have been used as acoustic or seismic sources in 
many connections, in geophysics, navigation, communications, etc. They were 
first used for underwater acoustics research about the turn of the century and 
received fresh impetus at the time of the First World War. In this early work 
the pressure levels very near the charges were investigated, but charges as 
acoustic sources were used mainly for timing. More work was started during 
the Second World War, and since then much as been done in many countries. It 
was at this time that acoustic levels were first measured and used for the 
quantitative estimation of transmission loss [4]. Why use explosions for this? 
Briefly, it is because they produce a nice loud bang with energy in a wide fre- 
quency range, as discussed further in section 3.8. 
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