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The secret behind listening devices

Leak detection has come a long way since the days of dye kits and bucket tests when it comes to the technology that can pinpoint leaks that were once elusive. Among the main weapons in a leak detectors arsenal is a quality listening device. Choosing the right listening device for your company is an important decision. And like listening for a leak, when researching listening devices, there can be a lot of “noise” to sift through. So, what makes the best listening device?

There are many factors to think about such as cost, dependability, and customer service after the sale. There are also some more technical criteria to consider when looking at purchasing a swimming pool leak listening device. Since listening devices range from your standard geophones to highly sophisticated technology, here are some tips for what criteria to consider: Sensitivity: how well the device amplifies sounds from the transmitter.

Frequency Range: how broadly the device can hear all the sounds created by a leak.

Filtering: how effectively the device can filter out background noise enabling you to focus on a leak sound.


The standard ground microphones that come with listening devices use piezoelectric microphones because these are known to be the best type of microphone to use in situations where sounds are being picked up from liquids or solids. Virtually every company that makes serious equipment for locating underground plumbing leaks for municipal work incorporates piezoelectric technology.

Unlike normal air microphones, piezoelect r ic microphones are almost completely insensitive to air vibrations but transduce only structure-borne sound.

But sensitivity alone is not the only important performance criteria. Most any device will be able to amplify a sound to the point that it can hurt the ears. What’s more important is hearing the right sound and distinguishing it from background noise. That’s where the other two important criteria come into play.

Frequency Range

Both pressurized underground plumbing leaks and static-shell leaks in the pool make noises in a wide range of frequencies depending on a variety of conditions.

Similar to instruments in an orchestra, different conditions produce different kinds of leaks and make characteristic sounds that a veteran leak detector can learn to identify. Although every leak is different, as general rule, underground plumbing leaks make sounds in the lower frequency ranges while static leaks in the shell of the pool are in the higher range. If your listening device doesn’t pick up sounds at the top or bottom of this range, you will be missing the fullness of the sound a leak makes or you may miss it altogether.

Filtering Capability

The final performance criteria, and what is considered to be the most important for swimming pool applications, is in filtering capability.

A listening device’s filter allows the user to specifically highlight (or eliminate) a specific range of sounds. Filtering is important because the devices are so sensitive that the user will likely hear other sounds around the pool (it always seems as though the nextdoor neighbor wants to mow their grass when you’re trying to find a leak!). The filter helps the user zero in on the leak sound without being distracted by the background noise.

Additionally, different ranges of sound behave differently underground or underwater. Low-frequency sounds travel much further than high-frequency sounds. By selecting high-frequency sounds once a leak sound has been identified, the frequency filter can help in pinpointing leaks to a small area.

Remember you can always call manufacturers and talk through the buying process or for technical help regarding a leak or leak-detection equipment.

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