Heath Consultants Aqua-Scop - Manual (Page 28)

D. Exercises with the Direct Contact/Ground Microphone
Initially it is necessary to become acquainted with the background noise
of the instrument under different positions of intensity.
Beyond positions 6 and 7, the Amplifier noise is easily heard. To have
some idea about the efficiency of amplification, the Direct Contact
Microphone should be tried with different positions of intensity while
in contact with a mechanical type watch. Due to the high amplification,
the sound of the watch, which is normally not heard, is as audible as
the noise of a small leak.
The third exercise is the amplification of a typical noise of water usage.
This is especially true on metallic lines. For this purpose a Direct
Contact Microphone will be (with the position of Volume set from 4
to 6) placed in contact with a curb valve and one of the faucets in the
house and also some faucets of houses in the neighborhood opened.
Open and close each of these outlets in the sequence of several seconds.
Exercises on different types of pipe material will give some idea on
transmission of sound.
Exercises with the Ground Microphone: Listening to background sounds
using various sensitivities is necessary. For example, check to hear the
sound of a walking pedestrian. Become acquainted with the change of
background noise when you are placing the Ground Microphone over
different surfaces, such as pavement, sod, or other types of surfaces.
With the Ground Microphone directly at the curb wall over a service
line valve, water flowing through the service might be heard. Opening
and closing the outlet also is recommended as an exercise.
Type of Leak and Different Types of Leak Noises: The experienced listener
will know from the type of noise which type of leak is present, the distance
of the leakage location, and also the type and amount of leakage. Small holes,
especially in steel lines under high pressure, will give very high frequency
sounds. A total breakdown of the line with a large amount of water leaving
the line will produce a typically deep roaring sound.
25