How an Acoustic Imaging Camera Works, and How to Choose One
An acoustic imaging camera does one remarkable thing: it makes sound visible. A dense array of microphones works out where every noise is coming from, and the camera paints it as colour over a live image, so a leak, an arcing connection or a failing bearing stops being invisible. This guide explains the physics in plain terms, walks through the three detection modes, shows how a crew uses the camera, and helps you pick the right Hertzinno model. SepcoTech supplies and supports the range as an Authorised Hertzinno Distributor.
Making sound into a picture
Sound reaches a microphone array at slightly different moments depending on the direction it travels from. An acoustic camera packs many small MEMS microphones behind a single optical lens and measures those tiny differences in arrival time. A technique called beamforming then works backwards from them: by combining the channels with the right delays, the processor can ask “how much sound is coming from this direction?” for every point in the field of view. The answer is drawn as a colour overlay, a “sound map”, on the live camera image, so the loudest point sits exactly over whatever is making the noise.
The key is ultrasound: sound above the range of human hearing. Pressurised gas escaping through a tiny gap, and electrical discharge inside high-voltage equipment, both radiate strongly in that ultrasonic band, while most background machinery noise stays lower, in the audible range. By listening above the din, the camera isolates the leak or the discharge cleanly, often long before it is large enough to hear, smell or see. Because the sensor only listens, the inspection is entirely non-contact: nothing is opened, touched or taken offline, and one operator gets a decisive picture from metres away.
One camera, three jobs
The same array reads three different invisible faults, with the on-device software tuned to each. Each links through to the matching camera family.
Find arcing before it becomes a flashover
In high-voltage switchgear, cables and terminations, insulation that is starting to fail produces tiny electrical discharges, long before anything trips. Each discharge emits a faint ultrasonic crackle the camera can locate from a safe distance. On-device PRPD (phase-resolved partial discharge) analysis then plots the pulses against the AC cycle and the AI classifies the mechanism:
- Corona: discharge into air around a sharp point or conductor
- Surface: tracking across the face of an insulator
- Floating: from a metal part that has lost its bond to earth
- Particle noise: a loose conductive particle moving in the field
See the escape, then put a number on it
Gas under pressure forcing its way through a flange, valve gland or seal generates ultrasound. The camera maps that sound onto the live image, so even a leak you cannot hear stands out across a deck. Once it is located, the software estimates the leak rate and can express it as an annual cost and carbon mass, turning a vague hiss into a figure to act on.
The HA3LX goes a step further: a built-in TDLAS laser methane sensor measures methane concentration directly, in ppm·m, at a stand-off distance, so for natural gas and LNG/LPG vapour the leak is not just located but quantified.
Methane & gas-leak cameras →
Hear the one bearing that has changed
In a room full of running machinery, the camera isolates the source whose sound signature is abnormal, a worn bearing, a misaligned shaft, poor lubrication or cavitation on a pump. It locates the offending component on the image and reports condition parameters drawn from the signal, such as kurtosis, crest factor and spectrum variance, which respond to impact and roughness in the vibration before failure.
- Pinpoints the faulty part among many running machines
- Condition indicators support trend-based maintenance
- Catches wear while it is still cheap to fix
Five steps, every inspection
The workflow is the same whether you are chasing a leak, a discharge or a bearing, and it ends with the report already written.
1 · Scan
Stand back at a safe distance and sweep the camera across the equipment. The array listens; nothing is touched, opened or taken offline.
2 · Localise
The sound map highlights the source on the live image, so you see the exact flange, terminal or bearing, not a rough area.
3 · Quantify / Classify
Read the leak rate, methane concentration, the PRPD discharge type or the mechanical condition parameters: a number, not a hunch.
4 · Analyse on device
One-click on-device analysis interprets the capture immediately, with PC and cloud analysis available afterwards for deeper review.
5 · Report
Generate the inspection report on the spot, with photos and annotations, and export it before you leave the deck.
Match the model to the job
Every Hertzinno camera runs all three modes, carries a 13 MP optical camera and supports on-device, PC and cloud analysis with on-site report generation. They differ in array size, frequency band, whether they add thermal imaging or laser methane, battery life and ATEX certification. Click a model to open its category page.
| Model | Microphones | Frequency | Thermal | Methane laser | Battery | ATEX | Best for |
|---|---|---|---|---|---|---|---|
| HA3 | 144 MEMS | 2–130 kHz | – | – | Li-Ion ~4 h (removable) | ATEX (Ex ib IIC T4 Gb) | All-round PD / leak / mechanical |
| HA3T | 144 MEMS | 2–130 kHz | 640×512 IR | – | ~4 h (removable) | Confirm at quote | PD + hot-spot, electrical & mechanical |
| HA3TX | 144 MEMS | 2–150 kHz | 640×512 IR | – | ~4 h (removable) | ATEX (Ex ib IIC T4 Gb / IIIC T130 °C) | ATEX PD + hot-spot in Zone 1 & 2 |
| HA3LX | 144 MEMS | 2–130 kHz | – | Laser (TDLAS) 5–50,000 ppm·m, 30 m | ~4 h (removable) | ATEX (Ex ib IIC T4 Gb / IIIC T130 °C) | Methane / gas-carrier leak quantification |
| HZ-HA-270P | 138 MEMS | 2–100 kHz | 640×512 IR | – | Internal 4 h | ATEX (Ex ib IIC T4 Gb / IIIC T80 °C) | ATEX leak + thermal, rugged |
| HZ-HA-170P | 138 MEMS | 2–100 kHz | – | – | Internal 4 h | ATEX (Ex ib IIC T4 Gb / IIIC T80 °C) | ATEX acoustic all-rounder |
| HZ-HA-271P | 128 MEMS | 2–100 kHz | 640×512 IR | – | Replaceable, 7 h | On request | Long-route PD + thermal |
| HZ-HA-171P | 128 MEMS | 2–100 kHz | – | – | Replaceable, 7 h | On request | Long-route acoustic |
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Series differences: the HA3 series (HA3 / HA3T / HA3LX) add Bluetooth, a 1080P screen, 128 GB storage, a laser rangefinder and an electronic compass; the P-series (HZ-HA-170P / 270P / 171P / 271P) use a 720P screen, 64 GB storage and Wi-Fi transfer. All models run the partial-discharge, gas-leak and mechanical modes.
Why this is the hardest place to inspect
An LNG or LPG carrier brings all three faults together in one of the most demanding environments afloat. Cargo containment and manifolds must be checked for methane or vapour escaping under pressure, in classified zones where only an ATEX-certified instrument may be used. The engine room is full of rotating machinery whose bearings and compressors need watching. And the high-voltage switchboard carries partial-discharge risk that a visual check will never catch.
A single acoustic camera covers all three from a safe distance and produces the evidence on the spot. The dedicated carrier page sets out where each mode earns its place aboard, and how the on-site report fits an inspection regime.
See the LNG & LPG carrier solution → EU Methane Regulation & LDAR →
The terms, plainly
- Acoustic camera / acoustic imaging
- An instrument that locates sound with a microphone array and overlays it as a colour map on a live optical image, so you can see where a noise comes from.
- Beamforming
- The processing that combines the microphone channels with precise time delays to work out how much sound arrives from each direction: the maths that turns raw audio into a sound map.
- MEMS microphone
- A micro-electro-mechanical microphone: a tiny, stable, low-noise sensor on a chip. Packing many of them into one array is what gives an acoustic camera its resolution.
- Ultrasound
- Sound at frequencies above human hearing (roughly above 20 kHz). Gas leaks and electrical discharge emit it strongly, while most background noise does not, so it is the band the camera listens in.
- SPL (dB)
- Sound pressure level, measured in decibels: how loud a sound is. The camera reports it to grade how strong a leak or discharge signal is.
- Partial discharge (PD)
- A small, localised electrical discharge that partially bridges insulation in high-voltage equipment without fully breaking it down: an early warning of insulation failure.
- PRPD
- Phase-resolved partial discharge: plotting discharge pulses against the phase of the AC cycle. The pattern reveals the discharge type, which the camera's AI classifies.
- Corona / surface / floating discharge
- The main partial-discharge mechanisms: corona around sharp conductors in air, surface tracking across an insulator, and discharge from an ungrounded ("floating") metal part, each with its own urgency.
- TDLAS
- Tunable diode laser absorption spectroscopy: a laser technique that measures gas concentration by how much of a specific wavelength the gas absorbs. The HA3LX uses it to quantify methane.
- ppm·m
- Parts-per-million times metres: the unit a path-integrated laser gas sensor reports; concentration multiplied by the depth of gas the beam passes through.
- Leak rate
- How fast gas is escaping, typically expressed in litres per minute. The camera estimates it from the acoustic signal and can convert it to annual cost and carbon mass.
- ATEX (Ex ib, intrinsic safety)
- European certification for equipment used in explosive atmospheres. "Ex ib" intrinsic safety limits energy so the device cannot ignite gas, allowing use in classified zones such as a gas-carrier deck.
- NETD
- Noise-equivalent temperature difference: a thermal-camera figure of merit meaning the smallest temperature difference the infrared sensor can resolve. Lower is better for spotting faint hot spots.
- Kurtosis / crest factor
- Statistical measures of a vibration or sound signal that rise when sharp impacts appear, used in mechanical mode as early indicators of bearing wear and similar faults.
Common questions about acoustic cameras
What is an acoustic imaging camera?
Why does it listen to ultrasound for leak detection?
Does more microphones mean a better camera?
What is PRPD?
Can it quantify a gas leak?
Is it safe to use in explosive zones?
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