 |
Acoustics - gypsum regulates sound
| | For several centuries the flexibility and mouldable properties of gypsum have provided the inspiration for beautiful decorative work. Today production of the material has been industrialised. But the flexibility and mouldability of gypsum are nevertheless exploited, one means being to punch perforation holes and patterns, which as well as adding aesthetic qualities also makes for good acoustic properties. The acoustic properties are achieved partly by vibrations in the panelling material and partly by generating resonance vibrations by means of air gaps in the perforation. The result is a loss of acoustic power: sound absorption. Plain tiles exploit vibrations in the panelling material to achieve good absorption in the low bass frequencies (see section on perforation types). Plain tiles can therefore be used for smaller rooms, where absorption of high-frequency sounds is effected by furniture, carpets, curtains and shelving. Plain tiles can also be used in conjunction with perforated tiles, e.g. in lecture halls where the fine reflective properties of the board ensure good dispersion of speech sound. Perforated tiles, Globe and Quadril, provide good sound absorption in the intermediate frequency range. This is where the consonants containing the most important signals in our comprehension and perception of the spoken language are located. Globe and Quadril perforations provide good sound reflection and hence good dispersion of speech sound. It is recommended using these types of perforations in medium sized rooms with hard materials or in larger rooms with a good spread of furniture, carpeting and suchlike. |
Final regulation is usually done in the choice of ceiling or wall absorbents. It is important to choose a sound-absorbing product based on its absorption profile. The quality and balance of acoustic conditions can be compared with tuning a musical instrument: acoustic ceiling panels "tune" the room and give it the "right" sound. The surfaces of Danoline acoustic gypsum products have the advantage of being able to be maintained without any deterioration to the acoustic properties (see section on operation and maintenance). Sound absorption measurement is performed in a revebaration chamber in accordance with ISO 354. Classification and transcription to the practical absorption value are done in accordance with ISO 11654. The absorption coefficients shown below are those most widely in use. When making a rough estimate, they can be used without taking account of the chosen product. Where special acoustic tasks call for fine tuning, information can be obtained on products' specific sound absorption.
The Danoline microperforation is used where it is wished to have both good sound absorption throughout the frequency range and extra attenuation in the high frequencies. Microperforated boards can be used where acoustic conditions are more critical, which is typically the case in large, high-ceilinged rooms, schools and institutions. Early in the planning of a room, it is possible to compute its acoustic qualities by extrapolation. All materials used in buildings have sound absorption. The important thing is simply to weight the sum of materials over the whole frequency range linearly.
|
|
