In-cavity Acoustic Camera

Cavity noise measurements are often time-constrained, whether for taxiing, wind tunnel or flight tests. Additionally, in reverberant environments, acoustic reflections off the cavity walls interfere with acoustic measurements. MicrodB developed and patented its 3DCam rigid spherical array to be able to respond to these problems. The 3DCam provides a three-dimensional “snapshot” of the positioning of acoustic sources on the walls of a passenger compartment or any other cavity.

The 3DCam is initially dedicated to medium- and high-frequency noise, to keep its size to a minimum. It is available in 30 cm sizes, with 36 to 54 microphones for a frequency range of 100 Hz to 5,000 Hz and 100 Hz to 10,000 Hz respectively. To study structure-related low-frequency sources, this array can be extended with a larger open sphere.

For cavity source representations, MicrodB developed its own digitizing tool. Positioned at the same measurement point as the array, it consists of a robotic arm equipped with distance measurement and image capture (photography or Kinect-type sensor). It generates a textured acoustic mesh on which the identified noise sources are superimposed without any realignment. This 3D representation facilitates the display of results, improves location accuracy, and replaces sources in the real environment. It is also possible to import a mesh.

Measurements and processing are carried out in the Siemens SimCenter TestLab environment. Spherical-wave beamforming processing rapidly locates noise sources in space. Advanced deconvolution and inverse processing enhance dynamics and resolution. The software also offers a unique contribution method for each source zone at the measurement point. From this data, it is possible to determine the pressure gain at the point of measurement by processing one of the source zones, which is useful for optimizing enclosures, for example.