5 minute read
A Quieter Life for Healthcare Buildings
Effective acoustic performance is important in any public sector building, but controlling noise in healthcare sites is absolutely crucial. Noise levels have a significant impact on patient recovery times, quality of care, and staff wellbeing, says Chris McElroy, Altro Specification Consultant.
Ineffective management of noise is typically responsible for poor sleep quality in patients, affecting the patient’s ability to rest, heal and recover, and has also been linked to ICU psychosis, hospitalisation-induced stress, increased pain sensitivity, high blood pressure and poor mental health – increasing pressure on the NHS.
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For this reason, guidelines on background noise levels have been issued by both national and international health bodies. The World Health Organisation (WHO) states that, for a good night’s sleep, background noise levels should not exceed 30 dB, with no peaks over 45 dB. For the UK specifically, the Department of Health Technical Memorandum 08-01: Acoustics provides recommended maximum noise levels for specific zones across the hospital, to take into account the needs of different groups of patients and the activities carried out.
Hospitals face significant challenges; however, when trying to meet these recommended levels. Researchers at John Hopkins University identified that average daytime sound pressure levels in hospitals increased from 57 dB in 1960 to 70 dB in 2006, with a rise in average night-time levels from 42 dB to 60 dB. These levels have exceeded WHO guidelines for many years, and continue to worsen. The problem also impacts on hospital staff. A separate study, by researchers at Heriot-Watt University, has associated excess noise with elevated levels of stress among staff, affecting performance and wellbeing, compromising caring behaviour, and contributing to burnout.
So what practical measures can those involved in the creation of public sector buildings take, to assist healthcare teams in their efforts to create peaceful environments for hospital patients, staff and visitors?
Acoustic performance is, of course, taken into consideration when designing new hospital buildings. In the UK, the overall requirements are outlined in the Health Building Note 00- 01: General Design guidance for healthcare buildings. This document should be consulted alongside the Department of Health Technical Memorandum 08-01: Acoustics, which explains the requirements in greater detail. It states, for example, that washable, acousticallyabsorbent materials may be required in some areas to support the hospital’s infection-control regime. It requires that impact sound is controlled at source, advising that internal planning of buildings should ensure that heavily-trafficked corridors are not placed near wards. A weighted standardised impact sound pressure level (L’ nT,w) of 65 dB is considered a reasonable maximum value for floors over noise-sensitive areas. It also recommends that individual areas may require additional sound reduction (for example, floors over multi-sensory rooms).
In older hospital buildings, however, alteration to the fabric of the building to improve acoustic performance may not be feasible. Acoustics is, of course, a specialist field, and an acoustician will be able to calculate the acoustics of the site, so that you can be confident that improvements will comply with Building Regulations. Alongside specialist advice, it is useful for all parties to have an understanding of how sound behaves, to determine how day-to-day decisions, such as the types of floor and wall surfaces employed across the site, can assist this process.
Saint-Gobain Ecophon explain that sound behaves in different ways according to the types of floor and wall surfaces in the room:
Transmission: Sound flows through and between materials
Absorption: Sound energy is lost when sound waves come into contact with, for example, walls and floors, and is not reflected back into the space
Reflection: Sound is reflected back into the space
Diffusion: Rough surfaces reflect sound, scattering it in all directions.
Hard interior surfaces such as floors can reflect rather than absorb sound. This causes noise to bounce around, overlap, echo and reverberate. Reverberation causes noise to prolong and echo in the environment, meaning it takes longer before the sound stops.
There are two types of sound – airborne and impact. Airborne sound travels through air – examples include speech and music. Impact sound occurs when one object impacts another, resulting in the generation and transmission of sound into the floor below – even through solid structures and cavities. Footsteps are a good example of this. How loud this sound is depends on how hard the impact was, what made the impact and the type of structure that is being impacted.
A quietly comfortable room should ideally have surfaces which absorb sound and reduce reverberation time. Surfaces of this type will also help to mitigate the problem of escalating noise, described by the Lombard effect. This is the involuntary tendency of speakers to increase their vocal effort when speaking in noisy spaces to enhance the audibility of their voice.
When reducing impact sound, installing flooring with noise reduction capabilities is an effective solution. This helps to reduce transmission of sound, breaking the auditory ‘vicious circle’ of escalating noise due to Lombard effect. There are two key methods, both of which are suitable for areas where equipment needs to be moved on a routine basis. Firstly, acoustic flooring products are available with different sound absorption characteristics. These are typically of a greater thickness than standard floorcoverings, delivering sound reductions of up to 19 dB, for example, and providing comfort underfoot for staff who spend much of the time on their feet. Some flooring ranges combine slip resistance with sound reduction features, and the wide choice of colours and effects make it possible to bring enhanced acoustic performance throughout the healthcare site – even in high traffic areas. The second option is to fit an underlay beneath a traditional vinyl floor to enhance its impact sound reduction performance. This improves the overall impact sound performance from just 5 dB, for example, to around 17 dB. Combining underlay with safety flooring could be particularly helpful in areas with high slip risk, such as bathrooms or kitchens.
An acoustician will, of course, be able to consider the full range of noise reduction opportunities for the healthcare site. Careful consideration of flooring is an important part of the solution; however, creating a quieter environment for patients, visitors and staff.