Knowledge

Acoustic Cameras: A Beginner's Guide

21.10.2021

Every company aims to deliver customers the best products. At the same time, they must keep an eye on employee health and comply with legal requirements. Disturbing noises on products or the company premises often pose an obstacle in trying to achieve so.
The question: How can I prevent this?

Noise protection and noise reduction respectively are becoming more and more important in today's world. Legal requirements for noise emissions are becoming stricter and both companies and end customers are becoming increasingly sensitive to disturbing noise from products and processes. Faced with this fact, many companies are discovering a new, exciting technology for themselves - acoustic cameras.

 

Grafik zeigt laute Maschine und Lärmausbreitung in einem Büroraum

 

What is an acoustic camera?

An acoustic camera is a measurement instrument comprising many microphones for locating sound sources and determining their corresponding frequency content and sound pressure level. In contrast to well-known acoustic measurement instruments such as sound pressure level meters, the acoustic camera provides a visual identification and quantification of sound, similar to a thermal imaging camera.

 

Frontalbilder der akustischen Kamera von Seven Bel

 

When do you need an acoustic camera?

Noise and other acoustic disturbances are audible - but locating them accurately often presents a challenge for those affected. Localizing by listening is rarely successful – especially at low frequencies, and simple measurement of sound pressure levels does not necessarily provide enough information to identify the cause of an acoustic problem. In such cases, the use of an acoustic camera quickly yields useful results. The visual identification of sound sources speeds up the search for the cause, giving the user enough time and information to work on targeted solutions. In addition to operators in maintenance and repair, engineers in product development benefit most from these advantages.

 

Areas of Application

The potential range of applications for acoustic cameras includes a wide variety of industries:

 

The technical functionality

The functionality of an acoustic camera can best be explained by taking a closer look at our human sensory system. With our two ears, we are able to estimate the direction of a sound source. A sound event, such as a vehicle approaching from the right, generates a sound wave that is perceived by the two ears at slightly different points in time. Even the smallest temporal differences of far less than a thousandth of a second are sufficient for our brain to successfully identify the direction of a single sound event.

Acoustic cameras make use of this measurement principle and, through enormous technical effort, enable a localization accuracy far superior to that of humans, even for complex sound events with multiple sources of different volume and frequency components. The two ears are replaced by a so-called microphone array - hundreds of microphones distributed over an area of up to several square meters. In this way, up to 200 megabytes of audio data are processed per second, color-coded, and overlaid with an optical image of the measurement scene.

Essential quality criteria for acoustic cameras are on the one hand the area of the microphone array and on the other hand, the number of microphones distributed on it. Since industrial sound events typically have low-frequency content far below two kilohertz, the diameter of the microphone array area should in any case be larger than one meter in order to obtain an acceptable spatial resolution. Also, the array should include several hundred distributed microphones to achieve a high dynamic range and thus evaluate loud and quiet sources in one acoustic image.

 

Grafik zum Preis/-Leistungsverhältnis bei akustischen Kameras

 

The Innovation - Sound Scanners

Seven Bel has taken on the challenge of breaking up the tense interrelations between mobility, image quality at low frequencies, and price by introducing a radically new technology for sound imaging: the Sound Scanner. This technology is based on a patented method called Coherence Scanning Holography (CSH), which enables Seven Bel to design compact and cost-effective acoustic cameras with more than 400 virtual microphones scanning an area of up to five square meters. This allows low-frequency sound events – as typically seen in industrial environments - to be measured with unprecedented spatial resolution and dynamic range. Operating the Sound Scanner has been made as simple as possible, thus enabling users from diverse applications to get successfully started with sound imaging.