Acoustic Camera Working Distance Explained: How Far Can You Detect?
Manufacturers quote detection ranges such as "up to 120 m" or "up to 200 m", but real-world working distance depends on the source, the background and what you are trying to find. Here is what the number means and how to plan an inspection.
What a Quoted Detection Range Means
A detection range on a datasheet is measured with a known reference source under controlled conditions. It tells you the maximum distance at which the camera can separate a source from the background — not the distance at which you will always find a small defect in a noisy plant.
Think of it like the "maximum range" of a thermal camera lens: technically possible, but the useful range for a specific small target is shorter.
The Physics: Sound Pressure, Frequency and Microphone Array
Acoustic cameras detect ultrasonic energy emitted by a source. Three things govern range:
- Source strength — a large compressed-air leak emits more ultrasonic energy than a tiny one. A corona discharge on a high-voltage line can be very strong.
- Frequency band — most industrial acoustic cameras listen in the 2 kHz-100 kHz range, which avoids most audible plant noise but still carries directional information.
- Array geometry — more microphones and a larger aperture improve angular resolution, letting the camera pinpoint a source at greater distance.
The camera software converts the time delays between microphones into a bearing, then overlays the source location on the optical image. The farther the source, the smaller the sound pressure at the array, and the more important the array quality becomes.
PD vs Gas Leaks vs Compressed Air: Different Distances
| Application | Typical useful range | Why |
|---|---|---|
| Corona / PD on HV lines | Longest (often tens of metres) | Strong, continuous ultrasonic emission |
| Compressed air leaks | Medium (typically 5-50 m depending on leak size) | Smaller sources, background-dependent |
| SF6 / gas leaks from pressurised equipment | Medium (similar to air leaks) | Pressure and orifice size dominate |
| Partial discharge inside enclosed switchgear | Short (direct path needed) | Ultrasound is blocked by metal enclosures |
Detection Range by Acoustic Camera Class
Unitech Tools supplies acoustic imaging cameras across a range of capabilities. Actual detection range should be confirmed against your application and the specific model, because the useful distance depends on the source as described above.
| Series | Microphone count | Typical positioning |
|---|---|---|
| ESW64 / entry-level | 64 | Close-range leak screening |
| SW136 | 136 | General electrical and leak inspection |
| SW234 | 234 | Longer-range PD and substation work |
| GSW Series | Combined IR + acoustic | Multi-purpose inspection |
Confirm the model's specified detection range with your supplier for your exact use case before purchase.
Field Factors That Reduce Working Distance
- Background noise — transformers, cooling fans and traffic create ultrasound that competes with the target.
- Obstructions — the camera needs a direct acoustic path; a fence, wall or another asset blocks detection.
- Small leaks — a 0.5 mm leak is much harder to find at 30 m than a 3 mm leak.
- Wind — strong wind adds broadband noise and can deflect or mask the signal.
How to Plan an Inspection Distance
- Identify the smallest likely source (smallest leak, early-stage PD).
- Estimate the access distance you can safely achieve.
- Choose a camera class with a comfortable margin — if your target is at 30 m, do not buy the entry-level 64-microphone model for that job.
- Verify with the supplier using a demonstration or reference test at your site if possible.
Unsure which acoustic camera range you need?
Tell us the application, the distance to the asset and the type of source (PD, compressed air, gas). We will recommend the microphone count and model with the right margin.