Phonoscopy laboratory

Vibration levels (1/3 octave of 800 Hz) in the wavenumber domain for a half partition composed of plasterboard mounted on metallic frame. The obtained ellipse represents the orthotropy of the tested partition

Or acoustic imaging to gain insight into acoustic phenomena...

Based on a near-field holography technique, it is possible to visualize the vibro-acoustic behavior of heterogeneous walls (such as juxtaposed panels for example) having a real size (4x3 m²) by means of vibrational level, pressure level and intensity level mappings, and to identify waves  and anisotropy of complex wall systems (such as composite panels for example).

The investigated component can be excited by an airborne excitation (diffuse acoustic field type by mean of loud speaker in reverberant room), or by a structural excitation (force type by mean of electrodynamic shaker). The reception room is mounted with an anechoic (absorbing) wall facing the tested component or the vertical partition in which the element is located. The transmitted acoustic pressure is measured in a plane parallel to the vertical partition (at a 2 to 5 cm distance). A wave by wave decomposition of the measured acoustic field by a Fourier transform is performed, then a backward propagation on the vertical partition allows recomposing of the different acoustic fields (velocity, pressure and intensity).

For a combination of components, it is then possible to identify the weak parts with respect to acoustics at different frequencies.

Operational principle of phonoscopy laboratory

Operational principle of phonoscopy laboratory
Transmitted acoustic intensity map for a window with a roller shutter in the 1250 third octave band. It can be observed that the roller shutter does not transmit any noise; in this third octave band the acoustic transmission through the window frame is important, furthermore the blocking of the air inlet on the window right hand side has not been properly performed for the test.

Place :

GRENOBLE

Contact

Michel Villot

Tel.: +33 (0)4 76 76 25 25
e-mail: michel.villot@remove-this.cstb.fr