The use of straw bales in construction is not as old as one may suppose. The first straw bale houses date back to the invention of the baling machine at the end of the 19th century and were built in Nebraska. After a long period of abandonment, this construction technique was rediscovered in the 1970s and since then it has significantly evolved, gaining attention among both self-builders and professionals. The huge amount of straw available worldwide can turn this material into a very interesting resource for the building sector. Nevertheless, the absence of certified or reliable technical data discourages engineers and architects to use it.
This paper aims at investigating the acoustic properties of straw bale constructions. The first section reports a brief summary of straw bale constructions and their energy and environmental performance. Then the state of the art of acoustic properties is presented in more detail. Normal incidence sound absorption coefficient of loose straw is measured using a two-microphone incidence tube in accordance with ISO 10534-2. Five and seven centimetres thick samples with different water contents were investigated. A limited variation of sound absorption with water content was noticed.
Lastly, the results of a façade sound insulation test on a real straw bale wall are reported. The tested wall resulted to be a poor sound insulator, especially at low frequencies, because of the low mass of the structure.
Authors: D’Alessandro, Francesco; Schiavoni, Samuele; Bianchi, Francesco
