In recent years, acoustic imaging has been growing in prominence as a predictive maintenance tool. Acoustic imagers are used to visualize the sounds of air, gas, or vacuum leaks in valves, pipes, and compressed air systems, as well as other types of ultrasonic noise. Advancements in sensing technology have made acoustic imaging more accurate and easier to use in industrial settings, but there are other factors driving the interest in this technology.

To meet environmental, social, and governance (ESG) goals, many companies are actively looking to reduce their energy consumption. Detecting leaks is necessary to literally plug the gaps and improve energy efficiency. But leaks are also costly. A quarter inch air leak can cost between $2,500 to $8,000 a year; with an estimated 30 percent average leak rate, that’s a loss of nearly $3.2 billion a year in North America alone.

Given these pressures, modern acoustic imagers like the Fluke SV600 are disruptive, offering manufacturers huge benefits compared to traditional methods of detecting leaks. So let’s take a closer look at how these systems work.

The Physics of Sound

To start understanding acoustic imaging, it’s important to understand the basics of acoustics and the science of sound.

Sound is a pressure wave, moving through air or another medium. The volume of sound, measured in decibels (dB), indicates the amplitude of the sound wave—louder sounds create more pressure and a higher amplitude in the wave. A normal conversation is around 55 to 60 dB, while the sound of a helicopter might be 100dB. 

The next consideration is the frequency of the sound wave, measured in hertz (Hz), which impacts the pitch of the sound. The average person can hear sounds from 20Hz to 20kHz. Industrial equipment typically produces sounds in the range of 1 to 28 kHz—meaning that a maintenance engineer can generally hear if something sounds off. However some issues, like partial discharge of electrical equipment (32kHz or higher) or small air leaks (around 37 to 42kHz) are well outside of the audible range.

The goal of acoustic imaging is to make these inaudible sounds visible instead.

Understanding Acoustic Imaging

The Fluke SV600 acoustic imager is made up of 64 microphones and a camera. Combining these two elements, the sensor listens to your assets and produces a visual representation of the output. The microphones are arranged in a sunflower pattern. Each microphone is equidistant to its neighbor and the camera is placed in the center of the array. Using onboard intelligence, the sensor processes incoming sound to improve the signal-to-noise ratio and precisely identify noise anomalies like air leaks.

When a pressure wave comes in, the sensor aligns it to every microphone on the array, and overlays the audio signal with the image captured by the camera. This data can then be displayed for an operator to review, overlaid on the RGB camera image with the pressure (dB), frequency (Hz), and location of the anomalous sound.

Automating Ultrasonic Inspections with Spot

Acoustic imagers can be hand-held for manual inspections, fixed as part of an IoT installation, or integrated with Spot to perform autonomous acoustic inspections. Automating ultrasonic inspections helps free up time and resources, while reducing lost efficiency from leaks.

Deploying Spot equipped with an acoustic imager makes it easy to detect and fix leaks early.

  • Plan an inspection route, determining where you want the robot to go and what assets you want to inspect
  • Record the route on Spot and configure thresholds for the specific noise anomalies you want to identify
  • Schedule when and how often these autonomous inspections should occur

Spot does the rest and you start receiving the real time insights.

Our asset reliability solution makes it simple to identify issues like air leaks, consolidate disparate inspection data, and improve operational efficiency. With our integration with the SV600 sensor, Spot is ready for you to deploy today and quickly realize ROI with autonomous acoustic imaging. To learn more, check out our webinar: Improving Energy Efficiency with Robotic Acoustic Inspection.

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