Upon completing this chapter, you should be able to do the following:
1. Describe the purpose of acoustic minesweeping.
2. Recall the different types of sound frequencies a ship will produce.
3. Recall the purpose and function of acoustic devices and their associated equipment.
Ships under way produce varying amounts of sound
The Acoustic Device A Mk 2(g) (commonly known
(acoustics). Over the years, mines that detonate in
as rattle bars) Acoustic-Device-Tb-26-A-Mk-6-B-178.html">(figure 9-1) is a mechanical device that
response to some of these sounds have been developed.
produces a chattering sound for countering acoustic
Some of the mines detonate as soon as they detect a
certain sound. Others register a count each time they
detect the sound and detonate when they reach a specific
The A Mk 2(g) consists of a frame made of three 34-
count. Acoustic minesweeping is used to either
inch parallel bars and two end plates and two 30-inch,
detonate these mines or to cause their detecting devices
movable parallel bars. The two 30-inch bars are
to register a ship count. Acoustic-Minesweeping-177.html">Table 9-1 lists the types of
mounted at each end to swing arms that allow them to
sounds that may be used to trigger acoustic mines.
oscillate in the center of the frame. As the A Mk 2(g) is
towed through the water, the flow of water between its
Acoustic minesweeping equipment is designed to
parallel pipes and bars causes them to hit each other
simulate the acoustic signature of a ship and to detonate
with great force, producing sound. The sound output
the mines a safe distance from the minesweeper.
depends on ship's speed. Higher speed increases the
output; lower speed decreases it. During turns, the
device has a tendency to stop chattering unless its speed
through the water can be maintained.
Acoustic minesweeping equipment consists of
The A Mk 2(g) is made of corrosion-resistant steel
power-driven devices, which are normally towed
and weighs approximately 135 pounds. It has a
astern, and waterflow-operated devices that are
relatively short life because of the mechanical stress
operated by the flow of water as they are towed.
placed on its parts. This stress increases in proportion to
the speed of tow. The device also is subject to fouling by
Acoustic-Minesweeping-177.html">Table 9-1.--Frequency Ranges and Sources
weeds and debris.
Main propulsion machinery, hull
The auxiliary depressor Acoustic-Device-Tb-26-A-Mk-6-B-178.html">(figure 9-1) is used to
prevent excessive hogging (or arching) of the sweep
wire at high-speed sweeping operations. It is a roof-
Auxiliary and main machinery
shaped device, 23-1/2 inches long, 11 inches wide, and
4 inches high, made of stainless steel, and weighs 15