by Katie Daniel | December 1, 2017 11:51 am
By Sean Browne
Hospitals are inherently noisy for two primary reasons. First, there is the abundance of noise sources, from paging systems and patient monitoring equipment to staff conversations and the bustle of visitors. Second, walls, floors, and drywall ceilings tend to be hard surfaces, designed for durability and cleanliness, but this also creates excessive reverberation in a space. Consequently, they reflect rather than absorb sound, making already noisy spaces noisier. High noise levels in hospitals have implications for the health and well-being of both patients and staff.
The World Health Organization (WHO) guidelines for maximum noise levels in patient rooms are 35 dBA (decibels, A-weighted) during the day and 30 dBA at night. However, when researchers examined the hospital noise levels as reported in a myriad of studies, not a single hospital reported noise levels in compliance with the WHO guidelines. (Visit apps.who.int/iris/handle/10665/66217 to read “Guidelines for Community Noise: In Protection of the Human Environment” by B. Bergland, T. Lindvall, D.H. Schwelaand, and T.K. Goh, published by World Health Organization in 1999.)
Studies validate noise problem
A series of research studies at Johns Hopkins Hospital in Baltimore validates the problem of noise in hospitals. The first investigated noise levels in the facility’s emergency department (ED) where there is a constant flow of patients, doctors, nurses, and moving equipment. (For more information, read “Noise in the Adult Emergency Department of Johns Hopkins Hospital” by D. Orellana, I.J. Busch-Vishniac, and J.E. West, in the April 2007 edition of The Journal of the Acoustical Society of America.)
Researchers found high sound levels day and night, particularly in the speech frequency band, caused by the need to communicate constantly for performing necessary functions. Compared to patient rooms, the ED tends to exhibit sound levels nearly twice as loud. WHO recommends noise levels must be kept as low as possible in intensive care units and operating areas.
Researchers also noted it is likely staff members raise their voices above the background noise level in order to be understood. Medical staff fatigue then becomes a potential issue since speaking in a raised voice is tiring.
A universal problem
Another Johns Hopkins study, much broader in nature in that it looked at noise levels throughout the hospital, observed sound levels significantly exceeded WHO guidelines. (Visit asa.scitation.org/doi/10.1121/1.2118327 to access “Noise Levels in Johns Hopkins Hospital” by I. Busch-Vishniac, J. West, C. Barnhill, T. Hunter, D. Orellana, and R. Chivukula and published in December 2005 issue of The Journal of the Acoustical Society of America.) Moreover, all the measured average sound levels exceeded the typical speech level for communication between two people, once again suggesting staff routinely need to raise their voice to be heard.
According to researchers, the study results not only demonstrate a noise problem in Johns Hopkins Hospital, but also suggest the problem of hospital noise is universal, and noise control techniques would be valuable if applied broadly.
In its conclusion, the study states:
It is important to not only characterize the existing environment, but to understand why it is so noisy. To this end, we note hospitals are notoriously lacking in the materials one normally associates with acoustical absorption. This is largely the result of concerns about infection control, wear, and cost. However, there are materials available that meet hospital standards in these areas as well as in related areas such as flammability and smoke production.
Effect on patients
Numerous research studies also validate the belief noise is annoying to patients, largely because of its impact on sleep. Noise in hospitals has been linked to sleep disturbance and arousals among patients—both can lead to increased pain perception and, consequently, impact patient medications and healing. (Find out more in the article, “Sleep in the Intensive Care Unit,” written by S. Parthasarathy and S.J. Tobin, published in the June 2014 issue of Journal of Intensive Care Medicine.)
Additionally, a study evaluated the effect of reduced reverberation time on sleep by exposing subjects to sound stimuli, with and without sound-absorbing ceiling panels. (Read “Impact of Reduced Reverberation Time on Sound-Induced Arousals During Sleep,” written by S. Berg and published by SLEEP in May 2001.) The study found arousals following specific sound stimuli were significantly reduced when reverberation time was reduced with sound-absorbing ceiling panels. Subjects evidenced far better sleep quality (less sleep fragmentation) in patient rooms with shorter reverberation times compared to those with longer reverberation times.
Healing is affected
A similar study assessed the effect of room acoustics on patients admitted to a coronary care unit (CCU). (The 2005 article,“Influence of Coronary Care Acoustics on the Quality of Care and Physiological States Of Patients” by I. Hagerman, G. Rasmanis, V. Blomkvist, R.S. Ulrich, C.A. Eriksen, and T. Theorell was published in International Journal of Cardiology.) As part of the study, room acoustics were altered by changing ceiling panels throughout the unit from sound-reflecting panels to sound-absorbing panels of similar appearance. Patients were monitored with regard to blood pressure, pulse amplitude, and heart rate. The study indicated significant improvements after the changeover, especially in regard to pulse amplitude, with lower values during the night after the changeover.
Additionally, the study found the incidence of re-hospitalization was lower for patients after the changeover compared to those before it. Patients found staff attitudes had improved and patients were awakened less during the night. The study concludes a poor acoustical environment during acute illness may, therefore, have important detrimental physiological effects on recuperation.
Loud noise levels are also a key concern in healthcare settings such as neonatal intensive care units (NICU) where premature infants have a high sensitivity to noise. Studies show loud noise levels in NICU environments increase the need for oxygen support, elevate blood pressure, increase heart and respiration rates, and worsen sleep. (A.N. Johnson provides extensive information on noise levels in neonatal intensive care units in his 2001 article “Neonatal Response To Control of Noise Inside the Incubator,” published in Pediatric Nursing.)
Effect of noise on staff
Noise can also be a source of annoyance and stress to hospital staff, and interfere with their ability to work effectively, especially in regard to speech intelligibility, which is key in healthcare because nurses and physicians must constantly comprehend and act on many types of auditory information in a high-stress environment. High levels of noise can lead to distractions and a loss of focus. A major concern is patient safety in the form of medical errors caused by compromised oral communication.
A poor acoustical environment also makes it difficult for healthcare staff to understand patients with different languages, accents, and speech patterns. Noise-induced stress is also related to emotional exhaustion and burnout.
To help determine the influence of acoustic conditions in the work environment, a study was conducted to examine their effect on patients in CCU, specifically investigating their impact on staff. (Visit dx.doi.org/10.1136/oem.2004.017632 to read “Acoustics and Psychosocial Environment in Coronary Intensive Care,” written by V. Blomkvist, C.A. Eriksen, T. Theorell, R.S. Ulrich, and G. Rasmanis and published by Occupational and Environmental Medicine.)
In this case, the study noted staff members were surprised by the improved speech intelligibility after the installation of new sound-absorbing ceiling panels as well as the perceived noise level. They reported feeling more relaxed with decreased irritability. Thus, the study raises the possibility important gains in the psychosocial work environment can also be achieved by improving room acoustics.
Hard sound-reflecting surfaces typical of many hospital designs cause sounds to linger and have long reverberation times. When acoustic conditions are characterized by long reverberation times, sounds overlap, resulting in reduced speech intelligibility.
Reverberation time is largely determined by the amount of sound-absorbing materials in the room. Research has shown installing high-performance sound-absorbing ceiling panels results in reduced noise levels, improved speech intelligibility, and reduced perceived work pressure among staff.
To reduce noise levels and reverberation time, acoustical ceiling panels should have a noise reduction co-efficient (NRC) of 0.60 or greater. The NRC indicates the ability of a ceiling panel to absorb sound. It is expressed as a number between 0.00 and 1.00, and indicates the average percentage of sound the ceiling absorbs. An NRC of 0.70 indicates the ceiling absorbs 70 per cent of the sound striking it. The higher the NRC, the better the ceiling acts as a sound-absorber—an NRC of 0.70 or higher is considered high performance and an NRC of 0.50 or lower is considered low performance.
Protecting patient privacy
In current healthcare settings, patients can be exposed to situations where they overhear conversations about other patients, or their own private information is communicated in an environment where it can be heard by others.
This impacts trust and ability to freely discuss health issues with their physicians, which could seriously impact patient care. (Check out www.healthdesign.org/system/files/CHD_Issue_Paper3.pdf to read A. Joseph’s “The Role of the Physical and Social Environment in Promoting Health, Safety, and Effectiveness in the Healthcare Workplace,” published in the November 2006 issue of The Center for Health Design.) It is critical, therefore, private conversations with or about a patient are not overheard.
Acoustical ceiling panels can help ensure patient privacy. To do so, the ceilings panels should have a ceiling attenuation class (CAC) of 35 or higher. This metric indicates the ability of a ceiling to block sound in one space from passing up into the plenum and transmitting back down into an adjacent space sharing the same plenum. The higher the CAC, the better the ceiling acts as a barrier to sound intrusion between spaces. A CAC of 35 or higher is considered high performance, while low performance is less than 25.
Absorption and blocking
In the past, selection of an acoustical ceiling was often dictated by the function of the space. The choice was either a ceiling with good sound absorption to decrease noise levels or one with good ceiling attenuation to block unwanted sound intrusion into a space.
However, some newer ceiling panels feature a combination of both high-performance sound absorption and high-performance sound-blocking in the same panel. Ceiling panels offering this type of performance have an NRC of 0.60 or greater and a CAC of 35 or greater.
By delivering the ability to both reduce noise and keep it from travelling into adjacent areas, the ceiling panels are an ideal choice for today’s healthcare facilities. Typical applications include patient, examination, consultation, meeting and treatment rooms, as well as nurses’ stations and physicians’ private offices.
Quiet and clean
Ceilings installed in healthcare environments are required to be cleanable and must not interfere with infection control practices. They should be water-repellant, washable, and scrubbable. Many high-performance ceilings meeting the acoustical needs of healthcare facilities can be readily cleaned, providing both clean room performance and a smooth, soil-resistant, water-impervious surface capable of being easily washed with disinfecting cleaners.
Lobbies and waiting areas also play an important role in healthcare settings because they can help alleviate the stress and anxiety known to accompany a hospital visit or stay. A facility’s main lobby can set the tone for the entire design theme and personality of a building. Patients and visitors alike want to feel at ease from the moment they enter.
The addition of a wood or wood-look ceiling to a lobby or waiting area imparts a warm, comforting ambiance to the space. Wood ceilings are available in a variety of shapes, sizes, and finishes. In addition, the panels can be perforated and backed with an acoustical fleece to help lower noise levels and create a calmer environment. Perforations vary in size depending on esthetic appeal.
Other acoustical ceiling design opportunities for public spaces include metal ceilings and ‘free-floating’ clouds and canopies. Metal ceilings impart a very high-tech or sophisticated look to a space and can also be perforated for acoustical performance. Perforations vary in size, although it is possible today to have extra microperforated panels in which the holes are so small, they are virtually invisible. Metal ceilings with finishes resembling real wood are also offered.
Acoustical clouds, canopies, baffles, and vertical elements combine an esthetically pleasing visual with sound-absorbing properties by providing good sound absorption in the space below them. Their ability to reduce reverberation makes them ideal for use over spaces such as reception areas and registration desks.
As spot acoustical treatments, but used in 20 to 50 per cent of the space, they can actually provide more sound absorption per unit area than a continuous ceiling because sound is absorbed on both their front and back surfaces.
Acoustical clouds are different in size and look compared to acoustical canopies and vertical panels. Visually, acoustical clouds are flat and horizontal, while canopies are curved and can be installed as hills or valleys. Baffles and other vertical elements come in a variety of shapes and sizes.
The abundant research compiled over recent years shows the dramatic impact of noise and inadequate privacy in the healthcare environment. As a result, the importance of good acoustics in the design and operation of healthcare facilities continues to grow.
A proper acoustical environment has shown to improve patient sleep, increase patient satisfaction and confidentiality, improve the healing environment, reduce staff stress, and improve speech intelligibility among staff members. With thoughtful design comes a positive patient and staff outcome, returning dividends patient after patient.
|To demonstrate the effect sound-absorbing materials can have on lowering noise levels, researchers at Johns Hopkins Hospital conducted a study using one of the facility’s hematological oncology units.* The space has hard-surfaced floors, walls, and ceilings—no sound-absorbing materials are anywhere in the unit. The centre of the unit houses the nurses’ station and service rooms, while patient rooms are located on the outside of the unit.
The nursing staff mentioned that any conversation at the nurses’ station was audible throughout the unit. Acoustical measurements showed the noise level was 55 dBA with a reverberation time of 1.1 seconds.
To help control noise within the unit, sound-absorbing panels were installed high on the corridors’ walls and on half of the corridors’ ceiling areas. An immediate impact of the sound-absorbing panels and their sound-reducing properties was to permit patients, staff, and visitors to lower the level of their speech while still being understood. Additionally, the reverberation time dropped to 0.4 seconds, a reduction of 64 per cent.
The study also notes an important measure of the effectiveness of noise control in a hospital setting is the perception of patients and staff regarding the noisiness of the unit. To determine staff and patient perceptions, the Johns Hopkins researchers also conducted a short survey before and after the acoustical intervention.
Prior to panel installation, nearly two-thirds of the patients and staff viewed the unit as noisy, with the majority of patients viewing it as very noisy. After installation of the panels, more than 90 per cent of the staff and patients viewed the unit as quiet or very quiet.
The study suggests new hospital buildings, particularly those with in-patient units, would do well to incorporate sound-absorbing materials where possible in their design.
* Visit asa.scitation.org/doi/abs/10.1121/1.2723655 to read “Quieting Weinberg 5C: A Case Study in Hospital Noise Control” by M. MacLeod, J. Dunn, I.J. Busch-Vishniac, and J.E. West, published in the June 2007 issue of The Journal of the Acoustical Society of America.
Sean Browne is the principal scientist of Global Acoustics for Armstrong Ceiling Solutions. A member of the Acoustical Society of America (ASA) and ASTM, Browne has engineering degrees from Florida State University and the University of Miami. He holds a patent for a power and signal distribution system for use in interior building spaces, and has been published in the journals of the International Symposium on Room Acoustics and the Acoustical Society of America. He can be reached at email@example.com.
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