A camera that listens with its eyes

Unfortunately, it’s not always easy to determine where noise actually comes from. However, Hauni from Körber’s Business Area Tobacco has found a solution for this problem. Known as the “acoustic camera,” this system enables the sources of irritating noises to be made visible in photos or videos so that they can be precisely localized. Like a normal film camera, the acoustic camera is set up in front of the machine in question. However, the camera doesn’t film the machine. Instead, it uses sensors to measure the soundwaves that it emits. “Wherever we detect unusual sources of noise, it either means that the machine isn’t running properly or the sound insulation is insufficient,” explains Adam Budde, who is responsible for the acoustic camera at Hauni’s development department.

Real-time measurement using thirty microphones

Digital technology enables the camera to pinpoint the noise source with surprising accuracy — much more accurately, in fact, than the human ear could. To make this possible, thirty directional microphones are arranged in an array. “We take advantage of the fact that the sound takes different amounts of time to travel from its source to each of these thirty microphones,” says Budde. “These delays enable us to calculate the angle from which the soundwave comes, and thus to determine the location of the source of the noise.” Using this information, the camera’s software then makes the location of the loudest noise visible in a video. In short, the camera combines sound and images. It’s a simple principle that is complicated to implement but produces excellent results.

The method’s biggest advantage is that conventionally pinpointing noise sources by means of sound field mapping requires individual measurements to be made at different times. The acoustic camera, by contrast, makes it possible to localize the noise source more quickly and to visualize it in real time. The resulting videos also enable processes that change over time, such as a machine’s run-up phases or blow-out processes, to be examined easily and quickly

The new method saves time and money

The new method with the “listening camera” is also used to examine newly developed and enhanced machines, such as those at Hauni. As a result, formerly expensive and time-consuming process examinations can now be conducted comparatively easily and cost-efficiently. This makes it possible to test new casing concepts for machines at an early stage, for example, in order to determine and evaluate irritating noise sources. 

Another advantage of the acoustic camera is that it can be easily transported in a suitcase and quickly set up for use. This makes the camera very versatile so that it can be employed at Hauni, in other Körber Business Areas, or directly at customers’ facilities. 

Background information: How is sound generated?

We refer to irritating sounds as “noise.” Sounds are created by vibrations that spread through the air as soundwaves. It’s possible to measure the strength of the sound, which influences the intensity of the noise. The parameter measured is the sound pressure. The measured value is the sound pressure level, which is given in decibels (dB). The perception of volume is fundamentally determined by this sound pressure as well as by the sound’s frequency. The frequency (number of vibrations per second) defines the sound’s pitch. The higher the frequency, the higher the pitch of the sound.

www.hauni.com