Leak noise correlation
| Leak noise correlation | |
| Type | Detection method |
|---|---|
| Also known as | Leak correlation |
| Detects | Position of a leak on a pipe run |
| Requires | Two access points on the same pipe, and pressure |
| Output | A distance along the pipe |
Leak noise correlation locates a leak on a buried pipe by measuring the same leak sound at two points on the pipe and calculating the position from the difference in the time the sound takes to reach each sensor. Unlike acoustic listening, which compares loudness, correlation produces a distance along the pipe, so it can locate a leak that is not audible from the surface at all. No statute or published standard defines the method, so the description below is of established industry practice and carries no citation; the leak detection code of practice that would be the natural reference is not available as a verifiable source.
Principle[edit]
Two sensors are attached to the pipe at accessible points either side of the suspected leak, typically at stop taps, hydrants or exposed fittings. The leak noise reaches the nearer sensor first. Cross-correlating the two signals gives the time difference, and from that, the pipe length between the sensors, and the speed at which sound travels in that pipe, the position of the leak follows arithmetically.
Three inputs therefore have to be right: the distance between the sensors, the material and diameter of every section between them, and the assumption that there is only one dominant leak. An error in the measured distance moves the calculated result by a proportional amount, which is why the pipe route is usually traced and measured before correlating rather than estimated from a plan.
Propagation velocity[edit]
Sound travels at different speeds in different pipe materials and diameters, and the correlator's result depends directly on the figure used. Cast iron and steel carry sound faster than polyethylene. A run containing more than one material must be entered as separate sections rather than averaged, or the result will be displaced towards the section whose velocity was overstated.
Limitations[edit]
Correlation needs two points of contact on the same pipe, so it is limited where access is scarce. It assumes a single dominant noise source; two leaks of similar size on one run produce a result that corresponds to neither. Very small leaks on plastic pipe may not generate enough signal to correlate at all, and pumps, partly closed valves and flow noise can produce a strong correlation that is not a leak.
As with acoustic listening, the output is a position to be confirmed rather than a conclusion. Standard practice is to verify the indicated point by a second method before excavating.
Use by ADI Leak Detection[edit]
Leak correlation is one of the six detection technologies ADI Leak Detection publishes, under the heading leak noise correlator.[1] The company also states that its engineers complete in-house training in acoustic correlation as part of joining.[2]
It is listed on fewer engineer profiles than acoustic listening: four of the 22 published engineers name leak correlation among their methods, which is consistent with it being applied to buried mains work rather than to every job.[3]
See also
- ADI Leak Detection
- Acoustic leak detection
- Water leak detection
- Supply pipe
- MDPE pipe
- Ground penetrating radar
References
- ^Leak Noise Correlator. ADI Leak Detection (primary source). Retrieved 2026-09-05
- ^About ADI Leak Detection. ADI Leak Detection (primary source). Retrieved 2026-09-05
- ^Meet Our Leak Detection Engineers. ADI Leak Detection (primary source). Retrieved 2026-09-05