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Acoustic Comfort

Solutions for improving occupant outcomes in the built environment

When designing a building, why go further than just meeting the basic regulations?

The World Health Organisation (WHO) defines noise as ‘unwanted sound’ (1) and such noise in buildings can have significant effects on the people who occupy them. If a person is subjected to noise for long periods, it can result in physical discomfort or mental distress.

The best defence against noise is to ensure that proper precautions are taken at the design stage and during construction of the building. The correct acoustic climate must be provided in each space, and noise transmission levels should be compatible with the building’s usage. The UK has the building regulations and a number of sector specific guidance documents covering noise (see Approved Document E, Building Bulletin 93, Health Technical Memorandum 08-01 and BS8233, for example). As we explore the effect that noise has on people, we will see that there are strong arguments for considering solutions which go above and beyond just meeting the minimum requirements in these regulations. Using British Gypsum’s range of acoustic ceiling products and partition systems is possible to create environments that offer exceptional acoustic comfort for occupants that will have a positive impact on health, well-being and productivity.

(L1) Which problems does enhancing acoustics solve? How do poor acoustics affect people?

Within the field of Evidence-Based Design, there have been numerous studies published across a wide range of building types and usages. These cover the many effects that poor acoustics have on occupiers and often then go on to demonstrate the positive impact on people’s health, wellbeing and productivity when the acoustic environment is improved.

Effects in Hospitals

Acoustic ceiling in hospitalThe WHO recommends average noise levels of no more than 35 dB in rooms where patients are treated or observed and no more than 30 dB in ward rooms (1 & 2), although a recent landmark study showed that no hospital noise results published since 1960 meet these guidelines (2 & 3). Many studies have demonstrated noise levels far exceeding these guidelines, with ranges cited from 45 to 90dB, with peaks frequently exceeding 85-90dB and some as high as 120dB (4 & 5). There is also a concerning trend where hospital noise levels have increased over time by 5dB per decade (6).

Studies have found that reduced noise levels can improve sleep, reduce annoyance, improve satisfaction, reduce pain and the use of pain medications, decrease psychological and physiological stress, decrease emotional exhaustion, reduce headaches, improve communication, reduce medical errors, decrease heart and respiratory rate, decrease blood pressure, shorten recovery time and hospital stays, and reduce re-hospitalisation (7-13). There is no doubt that excessive noise in hospitals is bad for people’s health and measures taken to improve the situation have a very positive impact.

Excessive noise affects staff as well as patients, with noise implicated in staff stress levels, burnout and emotional exhaustion (4 & 5). A study revealed that noise induced stress could account for 6% of headaches at work, as self-reported by nurses in critical care areas. When noise levels were reduced, staff report less stress and overall better working environments (4 & 14).

Effect in schools

Acoustic ceiling tile range and sound insulation through partition wallsThere is increasing evidence that poor classroom acoustics can create a negative learning environment for many students (15). AII children need good, clear signals and low background noise for full understanding, therefore improving classroom acoustics is important for children in all schools (16). Communication in classrooms often occurs in less than ideal conditions and is complicated by multiple people speaking simultaneously, noisy rooms, reverberant surfaces, and inexperienced listeners. This acoustical complexity confounds the instruction of young students, children learning English as a second language, and children with hearing difficulties (16).

The WHO recommends that to be able to hear and understand spoken messages in classrooms, the background noise level should not exceed 35dB during teaching sessions (1). The same value is also found in Building Bulletin 93; however the evidence shows that this is often not met in practice.

A major effect of noise and poor acoustics in the classroom is the reduction of speech intelligibility. If children are unable to understand the teacher then the major function of a classroom in providing an environment that enables the transfer of information from teacher to pupil is impaired. In addition it is important, both for learning and for social interaction, that children are able to hear and understand their peers in the classroom (17).

Effects in homes

Acoustic ceiling tile range and sound insulation through partition wallsThe WHO estimates that around 50% of the population of the European Union live in areas are exposed to noise levels that do not ensure acoustic comfort to their inhabitants and more than 30% are exposed to noise levels at night which is at a level disturbing to sleep (1).

Within homes, a noisy neighbour can be one of the main problems experienced in attached housing. It’s estimated that up to 4 million people in Britain have had their lives disturbed by noisy neighbours.

Effects in offices

Acoustic ceiling tile range and sound insulation through partition wallsIn the modern workplace, the emphasis is on teamwork, flexibility and communication. For most companies and designers this means open plan work areas. Today’s workplace dictates the need for open and easy communication between staff to provide an environment that promotes the exchange of ideas and an efficient working environment (18).

Despite the many positives of open plan working, two major drawbacks directly related to open plan offices are unacceptable noise levels and poor speech privacy (13). Numerous research studies have confirmed that noise, in addition to causing nuisance and disturbance in an office environment, is a primary cause of reduction in productivity and can contribute to stress and illness which, in turn, can also contribute to absenteeism and turnover of staff (18 & 19).

Studies indicate that even moderate levels of noise in an office environment can cause increased distraction and stress amongst employees this can lead to a reduction in productivity and can ultimately affect a company’s financial performance (18).

What are the solutions? How can a more comfortable acoustic environment be created?

To improve acoustic comfort in buildings acoustical engineers and consultants traditionally use a method called "the A, B, C's” (20). This convenient acronym describes the three factors that need to be controlled to achieve good speech privacy i.e., Absorption of sound waves (such as by using a high performance acoustic ceiling tiles), Blocking (such as by using high performance sound reduction partitions, walls, and windows, etc.) and Covering (such as adding a source of low-level background sound to counter the noise). British Gypsum offers a wide range of solutions for both absorbing and blocking noise.

    Absorption of sound

    Acoustic ceiling tile range and sound insulation through partition wallsStudies around the improvements offered by acoustic ceiling tiles have been carried out in both healthcare and education settings and show significant benefits. In healthcare it is one of the most frequently recommended interventions for sound reduction in wards, with a number of authors endorsing such a strategy (4,7,21-25). In educational settings, when classrooms are acoustically treated, thereby reducing background noise levels and reverberation times, children’s performance on word intelligibility tests improves; this improvement is particularly marked when other pupils are talking in classrooms (15 & 26). In one study pupils correctly identified 10% more words on average in sound intelligibility tests carried out in classrooms with people talking following acoustic treatment of the rooms with sound absorbing ceiling tiles (15).

    Speech intelligibility

    Speech intelligibility (clarity) is now recognised as essential in helping pupils in an educational environment to achieve their full potential. Research has shown that pupils who cannot understand clearly what the teacher is saying have a tendency to ‘switch off’ – limiting their own educational opportunities and creating additional stress for teachers. In a typical classroom with the teacher at one end, sound reaches the pupils both directly from the teacher and via reflections from the ceiling, walls and floor. Refer to figure below.

    Acoustic ceiling tile range and sound insulation through partition walls

    Pupils at the front will generally be able to understand what the teacher is saying, whilst pupils at the back and sides of the room receive a mixture of both direct speech and reflected sound, making it difficult to identify the teacher’s words.

    Reverberation time alone cannot be relied upon to deliver a suitable environment for good speech intelligibility. In any situation where speech communication is critical, e.g. classrooms, conference rooms, or lecture theatres, it is necessary to design the space appropriately using a mixture of sound reflective and sound absorbing surfaces. British Gypsum offers both within its ceiling products and plasterboard ranges.

    The amount of reflection is quantified by the ‘reverberation time’ of the room, which is the time in seconds that it takes for a sound to decay by 60 dB, in effect the time it takes for a sound to become inaudible. The reverberation time can be reduced by increasing the amount of acoustic absorption in the room, for example by installing acoustic ceiling tiles (15). Different buildings and application types have varying optimal reverberation times – see figure below.

    Typical reverberation times

     Type of room/activity   Reverberation time
    (mid frequency)
     Swimming pool   <2.0 seconds
     Dance studio   <1.2 seconds
     Large Lecture theatre    <1.0 seconds
     Small lecture room    <0.8 seconds
     Primary school playroom    <0.6 seconds
     Classroom for hearing impaired    <0.4 seconds

    References:


    (1) Berglund B, Lindvall T, editors. Guidelines for community noise. Geneva: World Health Organization; 1999

    (2) T Hsu, E Ryherd, K Persson Waye, and J Ackerman. Noise pollution in hospitals - Impact on patients. JCOM Vol 19, No 7 July 2012 Pg 301-309

    (3) Busch-Vishniac IJ, West JE, Barnhill C, et al. Noise levels in Johns Hopkins Hospital. J Acoust Soc Am 2005;118:3629–45

    (4) Ampt A, Harris P and Maxwell M. The health impacts of the design of hospital facilities on patient recovery and wellbeing: A review of the literature. 2008 Centre for Primary Healthcare and Equity, University of New South Wales, Sydney

    (5) Ulrich R. and X. Quan. The Role of the Physical Environment in the Hospital of the 21st century: A Once-in-a-Lifetime Opportunity. Designing the 21st Century Hospital Project, The Center for Health Design. 2004

    (6) Ulrich R. Evidence Based Design for better buildings. Welsh Health Estates and IHEEM Conference, Cardiff, 2006

    (7) Ulrich R, Zimring C, Xuemei Zhu,  DuBose J, Hyun-Bo Seo, Young-Seon Choi, Xiaobo Quan, and Anjali Joseph. A Review of the Research Literature on Evidence based Healthcare Design. Health Environments Research & Design, 1(3), 2008.

    (8) H Salonen , L Morawska. Physical characteristics of the indoor environment that affect health and wellbeing in healthcare facilities: A review. Intelligent Buildings International, 2013

    (9) Bayo, M.V., Garcia, A.M. and Garcia, A., 1995, 'Noise levels in an urban hospital and workers’ subjective responses', Archives of Environmental Health, 50 247-251.

    (10) Beyea, S.C., 2007, 'Noise: a distraction, interruption, and safety hazard. AORN Journal.

    (11) Biley, F.C., 1994, 'Effects of noise in hospitals', British Journal of Community Nursing, 3 (3), 110-113.

    (12) Joseph, A., 2010, 'Hospitals that heal’. Hospital design for the 21st century. Asian hospital and healthcare management.

    (13) Hagerman I., Rasmanis G., Blomkvist V., Ulrich R., Eriksen C. A. ,& Theorell T. (2005). Influence of intensive coronary care acoustics on the quality of care and physiological state of patients. International Journal of Cardiology, 98 (2), 267–270.

    (14) Devlin, A.S. and Arneill, A.B., 2003, 'Health care environments and patient outcomes: A review of the literature', Environment and Behaviour, 35 (5), 665- 694.

    (15) Shield B. M & Dockrell J. E. Acoustical barriers in classrooms: the impact of noise on performance in the classroom. British Educational Research Journel. Volume 32, issue 3, 2006

    (16) Nelson P B & Soli S. Acoustical Barriers to Learning: Children at Risk in Every Classroom. Language, Speech & Hearing Services in Schools. Oct 2000, 31, 4

    (17)Shield B. M. & Dockrell J. E. External and internal noise surveys of London primary schools, Journal of the Acoustical Society of America. 2004, 115(2), 730-738.

    (18) Acoustics at work. Noise in Office Environments: Its effects and Means to Reduce and Control it. 2011

    (19) Abbot, D. Calming the office cacophony. The Safety and Health Practitioner, 2004, 22 (1), 34-36.

    (20) Sykes D M. Productivity: How Acoustics Affect Workers’ Performance In Offices & Open Areas. 2004.

    (21) Barach, P. (2008). "Strategies to reduce patient harm: understanding the role of design and the built environment." Studies in Health Technology and Informatics 132: 14-22.

    (22) White, R. D. (2006). "Recommended standards for newborn ICU design." Journal of Perinatology 26(SUPPL. 3).

    (23) Altimier, L. B. (2004). "Healing environments: for patients and providers." Newborn & Infant Nursing Reviews 4(2): 89-92.

    (24) Reiling, J. G., B. L. Knutzen, et al. (2004). "Enhancing the traditional hospital design process: a focus on patient safety." Joint Commission Journal on Quality & Safety 30(3): 115-124.

    (25) Brown, P. and L. T. Taquino (2001). "Designing and Delivering Neonatal Care in Single Rooms." Journal of Perinatal and Neonatal Nursing 15(1): 68-83.

    (26) Medibank. The Health of Australia’s Workforce. 2005

    (27) Aurell J, Elmqvist D. Sleep in the surgical intensive care unit: continuous polygraphic recording in nine patients receiving postoperative care. Br Med J 1985; 290:1029–32

    (28) Chaudhury, H., A. Mahmood, et al. (2006). "Nurses' perception of single-occupancy versus multi-occupancy rooms in acute care environments: an exploratory comparative assessment." Applied Nursing Research 19(3): 118-125.

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