Heath Consultants Aqua-Scop - Manual (Page 29)

If you are inspecting an intersection with several valves, these results
may be predicted:
1. Using the Direct Contact Microphone at point 3, a leaking valve
packing will give a very high pitched sound. Using the same amplifier
intensity at points 1, 2, and 4, will result in much lower sound
readings on the meter.
(Figure 15)
2. A total break of the line at point 3 will give nearly similar values on
the meter at all four test points. However, a slight increase at point
3 will indicate the direction for further search.
E. Graphical and Numerical Determination of the Point of Leakage
The reading of the exact measurement of sound intensity with the
instrument allows the graphical or the numerical determination of the
location of the leak. The procedure, therefore, is controlled measurement
with the Direct Contact Microphone at two points on the same line at two
valves, two hydrants, two curb valves, or at two direct contacts if the line
is exposed. For these measurements it is recommended to use the optional
Magnet Attachment, which will provide uniform contact and will give
very constant values. It is necessary to observe the sound over a period
of time to determine an average value it the reading is changing. For this
method we assume that the product of sound intensity and distance is
a constant. Therefore, for two points A and B and distance XA and XB
from a leak:
IA XA = IB XB
Where: IA and IB are the values for intensity at points A and B
respectively, and the total distance between test points is:
XA + XB = X
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