The Acoustic Camera as a Resource for Localizing and Identifying Sound Emissions

Sound Localization

Sounds do not necessarily have to be high in volume to cause discomfort. In many cases there are quiet sources far subordinate to the main sound that nevertheless seem to be psychoacoustically dominating.

Sound Analysis in the Automotive Industry

Some of the most significant examples of this phenomenon exist in the automotive industry, where the Acoustic Camera has already been in use with great success. Rattling, hissing, or clicking noises are undesired in any vehicle. Even at high speed, the pianissimo parts of classic music should not be drowned out by driving noise.

Shutting the door, however, must produce a full sound despite the lightweight construction. There are similar requirements for the sound of car engines. The roar of a sports car or the sonorous sound of a Sedan are typical distinctive characteristics of car brands. That's why big effort goes into modelling the desired sound and into eliminating disturbances.

Sound issues are playing an increasingly important role in household appliances. Some high-value products can already be identified by their "high-value sound". Noises that are usually associated with faults like clicking, crackling, or whistling can cause annoyance for customers and frequently lead to unnecessary complaints

The time, frequency and modal analyses used so far have a decisive disadvantage: the spatial resolution is limited or non-existent. If you want to record many locations of the machine at the same time, you need a separate microphone for each measuring point, which has to be placed close to the measuring object - a high financial and time expenditure.

Measurement

An entirely new dimension: location-selective measurement of time and frequency

The Acoustic Camera can extend the time and frequency selectivity and add a location-selective component. With this method, not only the progression of the sound signal is shown, but a sequence of acoustic images can be acquired and acoustic films are generated. The analysis clearly shows which sound sources are active when and where. Extreme slow motion is possible, if required, up to a resolution of 192,000 acoustic images per second.

It is possible to monitor ignition, intake, and exhaust sounds of individual cylinders. Noise paths become visible, active sound sources and passive reflections are isolated. It is also possible to analyze sounds from moving objects. Often, entirely new insights and perceptions about the development of sound and noise arise.

Analysis

The Acoustic Camera extends and enhances existing analysis methods.

The Acoustic Camera comprises traditional analysis methods like A-weighting, third octave band analysis and narrow band analysis, filters and many more. Based on these methods, far more detailed research becomes possible. In a spectrogram, for example, sounds can be highlighted in the time and frequency domain. The Acoustic Camera will show the exact origin of these sounds. The approach can also be vice versa: after selection of a spot on the measured object, the sound originating from that spot can be reconstructed, visualized, and broken down into its spectral components. It is also possible to replay the sound via speakers any time after the measurement is completed.