The InA operates a laboratory for acoustic measurements. The measurement technology available there is used to determine various parameters, including the characterization of structure-borne and airborne sound fields as well as material characterization. In addition, the laboratory offers students the opportunity to carry out experiments independently within the framework of lectures and student work.
The field of airborne sound measurement technology is covered by various devices. In addition to a NOR140 sound level meter (class 1) from Norsonic, there are other class 1 measurement microphones (Norsonic) as well as powerful measurement cards (Goldammer) and analysis software (LabView, in-house). With these devices, sound pressure level measurements, room and building acoustics measurements as well as high-resolution spectrum analyses can be carried out.
Measurement technology in the field of structure-borne sound comprises various sensor types for recording the characteristic quantities of vibration velocity and acceleration. Laser-Doppler-interferometers from Polytec are available for measuring the vibration velocity. The measuring principle is based on the Doppler effect. The laser beam reflected by the structure is subjected to a frequency shift with respect to the incident laser beam. The acceleration of structures is measured using piezoelectric acceleration sensors from PCB Piezotronics. A pulse hammer and a shaker are also available. This enables structure-borne sound levels during operation as well as impedance measurements on smaller components to be carried out.
In addition to the methods for characterizing sound fields, the field of acoustic material characterization plays an important role. The targeted practical use of acoustically effective materials requires precise knowledge of material properties such as flow resistance and absorption coefficient. The flow resistance is the resistance of a sample to interference with the acoustic medium. The InA has an appropriate flow resistance measuring device for determining this value. The degree of absorption of a sample characterizes the ability to dissipate sound energy. This frequency-dependent material property is measured with so-called Kundt's tubes (impedance tubes). The InA has several such tubes based on different measuring principles covering different frequency ranges.
