Insights

The multiple impacts of acoustics.

The real-world performance of buildings is under scrutiny. But the part that the technical discipline of acoustics plays in supporting both people-centric and planet-conscious design outcomes is not always fully appreciated, yet we know that the role of acoustics impacts on multiple levels.

Good acoustic design is key to bringing buildings to life for people. This imperative is coming into increasingly sharp focus, most recently through the immediate need for resilience against COVID, the need to future-proof against the extremes of climate change and the flexibility to accommodate ever-changing user expectations. It may
not be immediately obvious, but all these factors have acoustic implications. Sitting alongside the focus on human-centred design is the need to be guided by doing right by our planet. The situation demands change so we can either be part of this change, or we can watch it happen without us. The climate emergency has focused minds on the need to reduce the carbon associated with buildings (embodied or operational). If essential climate emergency trajectories are to be met buildings will need to be constructed and operated with operational energy use approximately 60% smaller than has traditionally been the case, with material circularity (reduce-reuse-recycle-recover) also becoming increasingly relevant. Again, the delivery of successful acoustic outcomes has implications on achieving targets for both embodied and operational carbon, and circularity.

Crucially, acousticians understand that human-centred design solutions aren’t always the best choice for the planet and, conversely, achieving net zero carbon and other planet-conscious objectives can result in negative outcomes for building users. Balancing this tension is where the industry problem-solving culture shines. Sound falls into two distinct categories: physical sound and perceived sound. Ultimately it is the perception of sound that matters in delivering a better built environment in terms of human outcomes. It is therefore right we should start with perceived sound as our primary driver in designing buildings that we can declare to be ‘acoustically high performing’. However, to deliver such human outcomes with confidence, while simultaneously delivering better outcomes for the planet, requires an intimate appreciation of the underlying science.

Human health and wellbeing

Somewhat counterintuitively, and excepting buildings such as auditoria or recording studios for which acoustics is their prime function, is where good acoustic design should be ‘silent’. Building users should be immersed in an environment that is subconsciously conducive to them feeling and delivering at their very best. Whatever the building’s prime function may be, it should be taken as read that the very highest performing buildings should provide an optimally designed acoustic environment as standard. Human outcomes are considered at two levels. Firstly, the direct impact of indoor environmental quality on human health and wellbeing. In this regard sound is one of the key indoor environmental factors needing to be considered (not forgetting that vibration also falls within the technical discipline of acoustics). Poorly controlled acoustic environments can lead to disturbance, annoyance and stress leading to raised blood pressure even at relatively low amplitudes, while prolonged exposure to higher levels of sound can cause irreversible damage to hearing.

The second human outcome is the degree to which the acoustic environment promotes productive output. In this context ‘productivity’ may be defined quite differently for any given space or building typology. As a rudimentary example, the prime function of a bedroom is to enhance sleep, whereas promoting sleep in a teaching environment would be the least desirable outcome. Fundamental acoustic design considerations which acoustic designers take for granted as leading to improved human outcomes include the control of:

• Sound levels in rooms, either from noise sources within the building itself such as ventilation systems or the intrusion of external noise (e.g. typically from
transportation sources);
• Reverberant sound build-up within rooms;
• Sound transmission between adjacent internal spaces;
• Sound egress through the building façade.

However, there are some sectors and building types where acoustics should no longer remain a ‘silent’ discipline to good design, but instead should ‘shout’ the
presence of the highest quality acoustic design to become front and centre of the building users’ experience. For such developments it is essential that the aspirations and needs of the user are fully explored and understood. Obvious examples are buildings where the reproduction of sound is their prime function (concert halls, auditoria, sound and film recording studios, etc). There exists, however, a multitude of less obvious building typologies where acoustic design is fundamental to the building functionality. In the science and research sector there is increasing demand for facilities benefitting from ultra-low noise and vibration environments required for undertaking sub-atomic scale measurements. At the other extreme, the space industry is developing new facilities for the testing of propulsion systems and their payloads, both of which involve the generation and control of ultra-high levels of noise and vibration. Regardless of the extremes concerned, these are all design tasks whose successful delivery demands an
understanding of the fundamental physics of acoustics behind the design principles required to drive real-world outcomes.

These outcomes also increasingly demand that acoustics be considered in tandem with other technical disciplines to ensure that truly holistic outcomes are delivered. Our scientific understanding of the pathways to human perception of sound is evolving; traditionally, acoustic specifications have been based around the concept of sound amplitude, often expressed as a single numerical decibel limit. These limits have largely been derived from social surveys which have sought to aggregate the typical subjective response at a community level from the self-reported response of populations. However, it has long been acknowledged that the response to the same sound stimulus can vary widely between individuals. Large variations in response can occur even for the same person when exposed to the same sound stimulus but across different contextual settings. A combination of advances in non-invasive neuroscience coupled with the analytics of large data sets using machine learning techniques is beginning to provide much greater insight into the complexities of human sound perception.

For part 2, I will be discussing about the emerging field of ‘soundscapes’.