Development of measuring methods of the sound absorption coefficient of materials and acoustic baffles insulation in the frequency range above 5 kHz.

The project developed a method of determining the directional factor of sound absorbing of materials in the frequency range up to 40 kHz. It is an impulse method in which sound absorption factor is specified in an incidence function of the acoustic wave. During the measurements performance by this method following requirements must be met: eliminated are any unwanted reflections, the sound source emits a plane wave and dimensions of tested material are several times bigger than the wavelength of the acoustic. Research room was designed and manufactured, as well as software controlling tests was developed, including impulses generation, plus registration and measurement the level of acoustic sound pressure. For the purposes of determining the baffle sound insulation in the frequency range above 5 kHz two methods were developed. The first allows in laboratory conditions to measure appropriate insulation from air sounds in the frequency of 8 kHz. The second allows appointment of baffle acoustic insulation pressure in one-third octave centre frequencies of 5-25 kHz. Obtained results of the baffle sound acoustic insulation pressure were prepared in a catalog cards form containing a concise description of the baffle and photographs.