Acoustic Design Criteria in Naturally Ventilated Residential Buildings: New Research Perspectives by Applying the Indoor Soundscape Approach

Abstract

The indoor-outdoor connection provided by ventilation openings has been so far a limiting factor in the use of natural ventilation (NV), due to the apparent conflict between ventilation needs and the intrusion of external noise. This limiting factor impedes naturally ventilated buildings meeting the acoustic criteria set by standards and rating protocols, which are reviewed in this paper for residential buildings. The criteria reflect a general effort to minimize noise annoyance by reducing indoor sound levels, typically without a distinction based on a ventilation strategy. Research has developed a number of solutions, discussed here, that try to guarantee ventilation without compromising façade noise insulation, but, currently, none have been adopted on a large scale. This concept paper highlights the main limits of the current approach. First, a fragmented view towards indoor environmental quality has not included consideration of the following acoustic criteria: (i) how buildings are designed and operated to meet multiple needs other than acoustical ones (e.g., ventilation, visual, and cooling needs) and (ii) how people respond to multiple simultaneous environmental factors. Secondly, the lack of a perceptual perspective has led acoustic criteria to neglect the multiple cognitive and behavioral factors impinging on comfort in naturally ventilated houses. Indeed, factors such as the connection with the outside and the sense of control over one’s environment may induce “adaptive acoustic comfort” opportunities that are worth investigating. The mere use of different sound level limits would not be enough to define criteria tailored to the complex user–building interaction that occurs under NV conditions. More holistic and human-centered approaches are required to guarantee not only neutrally but even positively perceived indoor acoustic environments. For this reason, this paper considers this apparent conflict from a soundscape viewpoint, in order to expose still unexplored lines of research. By underpinning a perceptual perspective and by contextualizing it, the indoor soundscape approach provides a framework capable of overcoming the limits of the traditional noise control approach. This could provide the opportunity to foster a wider adoption of NV as a passive design strategy that enhances user health and well-being, while enabling low-cost, and low-energy cooling and ventilation, thereby contributing to current climate change challenges.

Active Control of Low-Frequency Noise through a Single Top-Hung Window in a Full-Sized Room

“…Moreover, the ANC window also provides an avenue for the indoor soundscaping of naturally ventilated buildings, whereby unwanted noise can be removed using selective algorithms [11,12] and wanted sounds can be introduced or amplified via the same loudspeakers that deliver the anti-noise. This element of controllability with an ANC system aligns well with the concept of adaptive acoustic comfort, suggested by Torresin et al [9], which could be worth further investigation.…”

“…Although the indoor acoustic environment for naturally ventilated buildings is dependent on context, there has been some evidence showing a preference of some external sound sources (e.g., natural sounds, human voices) over others (e.g., heavy traffic) while no indoor sound sources were present [5]. With the introduction of international standards on soundscapes [6][7][8], it is imperative that indoor acoustic comfort is approached with a perceptual perspective [9]. One overlooked factor in an indoor environment is the concept of control, which is challenging for naturally ventilated buildings.…”

Acoustics for Supportive and Healthy Buildings: Emerging Themes on Indoor Soundscape Research

“…Unintended consequences occurring as a result of a fragmented approach very often jeopardize the success of design actions. For example, the lack of integrated design in addressing the topics of acoustics and overheating currently result in building occupants having to decide whether to give priority to acoustic or thermal comfort [40,68]. Perceptual and multisensory research on the one side and integrated participatory design practices on the other would enable a holistic view of the complex building-user interrelations and reduce the risk of mismatches between expected and real building experiences [4].…”

“…As a consequence, façades and ventilation systems might be reinterpreted as filters able to transmit, block, or modify outdoor sounds in order to provide a connection with the outdoor environment, reduce unwanted sounds, and enhance the wanted ones, as proposed in Torresin et al [40].…”

“…As far as acoustics is concerned, IEQ models have been traditionally based on the objective measurement of A-weighted (decibel) continuous sound pressure levels, and on surveys for the self-reported evaluation of noise levels and, sound privacy; eventually integrating the identification of annoying sources [5,6,38,39]. External sound has been typically considered as unwanted (i.e., noise) and eliciting annoyance, as such a "waste" to be reduced through sound insulation, regardless of the spectral and temporal composition of the outdoor acoustic environment and the meaning attributed to sound sources [40,41]. Wanted sounds or sounds of preference are not addressed either in IEQ models or in POE surveys, reflecting the general effort to minimize noise annoyance by reducing indoor sound levels.…”