| Zugriffsnummer | 16031 |
| Dokumenttyp | Zeitschriftenartikel |
| Sprache | Englisch |
| Titel | The role of static pressure and temperature in building acoustics |
| Autor(in); Institution |
Wittstock, Volker; 1.42, Angewandte Akustik, PTB-Braunschweig
Bethke, Christian; 1.42, Angewandte Akustik, PTB-Braunschweig
|
| Quelle/Jahr | Building acoustics: 10 (2003), 2, 159 - 176 |
| ISSN | 1351-010X |
| Verlag | Brentwood, Essex: Multi-Science Publ. |
| Freie Schlagworte | test suite model |
| Zusammenfassung | The influence of static pressure and temperature on sound reduction indices, impact sound pressure levels, the improvement of impact sound pressure levels and sound reduction indices, and relative installation noise levels is investigated. A theoretical analysis of the sound transmission path revealed that there is a systematic influence on the sound reduction index and the normalized impact sound pressure level. Two effects account for this influence. First, the sound power radiated by a vibrating structure is in direct proportion to the sound impedance in air and thus to the static pressure and to the temperature to the power of -0.5. Secondly, the sound pressure produced in a room by a sound power is equally dependent on the sound impedance, i.e. on static pressure and temperature. Since the excitation of the test specimen is not influenced by static pressure or temperature, the two effects mentioned above are not compensated by any other mechanism, which leaves a temperature and static pressure influence on the sound reduction index as well as on the normalized impact sound pressure level. The theoretical result was verified experimentally by a measurement series in which the sound reduction index was measured in a small test suite model at static pressures between 307 and 970 hPa. Measurement results for single-shell structures showed the expected behaviour, whereas the results for double-shell structures reveal a considerable scatter with a tendency to even larger temperature and static pressure influences. For the comparison of the acoustic properties of building elements, it is therefore advisable to introduce a normalized sound reduction index and a normalized impact sound pressure level, whith both quantities being related to reference conditions as regards static pressure and temperature. The improvement of impact sound pressure levels, the sound reduction index improvement and relative installation noise levels are determined from the differences of sound level differences. As each of the initial differences is influenced in the same manner by meteorological conditions, the resulting difference is independent of static pressure and temperature as long as the two initial differences were determined under the same meteorological conditions. |
