The AcouReVe Project aimed to improve the knowledge and the quality of acoustic calculation in ventilation ductworks. Such calculations are based on simplified models and the main issue is the input data. For each component of the ductwork, acoustic insertion loss and/or sound generation due to air velocity has to be known. Some components are well described by manufacturers, such as terminal devices, silencers, but others are not known. Sometimes, literature exists and can help to assess the input data, but the values may be out of date or no longer reflect current practices. This paper focuses on several component characterisations, such as attenuation in T or Y-shaped junctions, attenuation in straight ducts, attenuation and generation in bends and dampers and finally the acoustic behaviour of a manifold.
Noise remains a key issue for most building occupants, who wish to live in a relatively quiet indoor environment. Ventilation is one of the noise sources in buildings and efforts are made by most manufacturers to design silent solutions, both for components and ductwork. Acoustical consultants implement calculations to predict the sound levels in the rooms taking into account the ventilation system and ductwork but they often face to several issues:
- Lack of information about the acoustical characteristics of ductwork components, both for noise attenuation and regeneration
- Lack of confidence in the calculation process: it usually uses a simplified approach in which each ductwork component is considered independently from the others without interaction,
- Lack of confidence in the literature results: simplified tables or empirical relations are used but their field and limits of application are not well known.
The goal of the AcouReVe research project (2015-2018) was to make the ductwork noise calculations more reliable by providing answers to many of these issues.
Several ductwork geometries for bends and branches have been investigated to assess their acoustical characteristics (generation of noise and insertion loss), both numerically and experimentally. Losses in straight rigid circular ducts have been measured and analysed, as well as acoustical characteristics of components, such as for example acoustical behaviour of manifolds for balanced ventilation systems.
Laboratory tests allowed to check how the assumption of independent components used in the classical noise calculation methods leads to differences between calculation and measurements.