Published on : June 22, 2010
The Sound of Health and Healing
Of the myriad of issues and concerns involved in the design, construction, and operation of hospitals and healthcare facilities, there should be little debate that patient health and recovery, along with staff and visitor comfort should be paramount. Although there are constant improvements in the healthcare industry, growing evidence shows that these concepts are being compromised in particular ways. One of the main culprits deteriorating the state of our healthcare facilities is poor acoustics.
The Nature and Impact of a Growing Noise Problem
In healthcare environments, a multitude of sources such as human voices from medical professionals, patients, visitors, medical equipment (many with beeping alarms), paging systems, heliports, and building systems, such as HVAC, plumbing, and elevators, provide challenges and create barriers between good acoustics and the health and comfort of patients, staff, and visitors.
Available evidence indicates that sound levels from these, as well as other sources, have been rising for the last several decades. One recent study of several sets of published hospital noise level data indicates that average daytime equivalent sound levels1 have risen from 57 dBA2 to 72 dBA between 1960 and 2005; whereas, nighttime levels have risen from 42 to 60 dBA in the same time period. This is an increase of 15 decibels3 during daytime hours and 18 decibels during nighttime hours. An increase of 10 decibels is often cited as a subjective doubling of loudness. Thus, one can reasonably say that sound levels have at least doubled (and have come close to quadrupling in the case of nighttime levels) in the last 45 years. This increase in sound level clearly yields negative impacts upon patients, staff, and visitors of healthcare facilities.
The detrimental effects of noise on humans are many and complex and manifest themselves as both behavioral and medical indicators. These detrimental effects of noise in healthcare facilities include interference with spoken communication, reduction in task performance, sleep disturbance, and psychological and physiological effects.
Speech intelligibility is governed largely by the relationship between the sound level of speech and that of any interfering noise. The average sound level for casual speech at a distance of three feet in low-noise environments is typically 50 to 55 dBA while that of normal speech is typically 55 to 60 dBA. Where the ambient sound level is above 50 dBA, persons with normal hearing typically begin to raise their voice; this increase, on average, is three to six decibels for every 10 decibel increase in noise level above 50 dBA. Among other detrimental effects, decreased speech intelligibility yields the potential for increased medical errors.
Noise can lead to reduction in task performance by serving as a distracting stimulus which reduces cognitive abilities and producing startle responses in the case of impulsive or sporadic noises. This applies, not only to tasks which rely on auditory cues, but also to mental tasks. Among the impacts on cognitive function, noise has the greatest effect on reading, attention, problem solving, memory, and analytic processes. In general, noise has a greater effect on complex tasks than simple ones and tends to degrade accuracy more than total quantity of work. These negative effects are more pronounced with noises that occur in a random, intermittent, or unpredictable fashion.
Another detrimental effect of noise is sleep disturbance. Sleep disturbance comprises, among other effects, difficulty falling asleep, frequent awakenings, alteration of sleep stages or depth, and increased body movements. Measurable effects from noise begin at a continuous nighttime level of approximately 30 dBA. For non-continuous noise, sleep disturbance effects have been observed with individual maximum sound levels of 45 dBA. Such disturbances hinder the recuperative properties of sleep.
Finally, research has established many links between sound and physiological and psychological well-being. Negative effects of noise related to cardiovascular arousal, extended hospital stays, and the need for higher levels of pain medication have been established and documented. Furthermore, evidence suggests that increased noise exposure may result in decreased rates of wound healing.
Certainly this degree of noise elevation cannot be sustained without marked detrimental effects to the quality of care of patients and the perception of workplace quality on the part of staff. Fortunately, action is being taken to curb the cacophony and provide better healthcare environments for all.
Measures to Address the Growing Noise Problem
In recent years, there has been much progress made toward bringing the importance of acoustics in healthcare environments to the attention of designers and operators. At the forefront of the recent movement, the development of the Interim Sound and Vibration Design Guidelines for Hospital and Healthcare Facilities, a process which was initiated in 2005, has laid out, in a detailed format, provisions for exterior noise (e.g., heliports, emergency power generators, outdoor mechanical equipment, and building services), interior room finishes, room noise levels, sound isolation, paging and call systems, clinical alarms, masking systems, sound reinforcement, and building vibration.
Subsequently, the Green Guide for Healthcare, a voluntary, self-certifying document and system has, in Version 2.2 released in January of 2007, adopted the Interim Sound and Vibration Design Guidelines for Hospital and Healthcare Facilities as the basis for two credits under its system. This has led to the United States Green Building Council (USGBC) adopting the language of that same document as the basis of two credits in their Leadership in Energy and Environmental Design (LEED) rating system for healthcare facilities. Furthermore, as part of the American Recovery and Reinvestment-Health Information Technology for Economic and Clinical Health Act (ARRA-HITECH), there is now a $1.5 million penalty for non-conformance with the Health Insurance Portability and Accountability Act (HIPAA), which contains acoustical provisions related to privacy.
The most recent development is the inclusion, for the first time in its 60-year history, of extensive and comprehensive acoustic criteria in the new 2010 edition of the Facility Guidelines Institute (FGI)-American Society for Healthcare Engineering (ASHE) Guidelines for Design and Construction of Health Care Facilities. The acoustics-related content of this document which, at present, forms the basis of the regulatory code in at least 42 states and 7 federal agencies, is culled from, and uses as reference standard, the updated Sound and Vibration Design Guidelines for Hospital and Healthcare Facilities (which was simultaneously published in January 2010). The majority of the relevant criteria is contained in Section 1.2-6.1 and relates to exterior noise, interior room finishes, interior noise levels, sound isolation, electro-acoustic systems, and vibration.
Practical Means to Mitigate the Growing Noise Problem
To address exterior acoustic considerations, the FGI Guidelines begins with an assessment of present and future exterior noise sources, whether or not they are controlled by the facility. The assessment must consider each source’s potential impact on the facility as well as its potential impact on the surrounding community (in the case of facility-controlled sources). For various site noise exposures, building envelope acoustical performance requirements are prescribed in terms of Sound Transmission Class (STC)4. Special care should be taken to address facility-related sources such as heliports, emergency power generators, outdoor mechanical equipment, and building services, both in terms of their impact on the facility as well as on the surrounding community.
Interior acoustics, specifically as it relates to aural comfort and reverberant noise buildup is influenced to a large extent by the finishes chosen within the facility, with acoustically absorbent finishes yielding lower noise levels than reflective ones. Examples of acoustically absorbent finishes can include wall and ceiling panels, draperies, furniture, and, to a lesser extent, carpeting. Their judicious use can reduce noise buildup due to voices, medical equipment, service carts, footsteps, HVAC systems, and paging systems. Some of these materials may need to be cleanable depending on location (e.g., NICUs). Recommendations are made within the FGI Guidelines concerning the average acoustical absorption in various rooms such as waiting areas, corridors, physicians’ offices, and private patient rooms.
In order to provide an environment conducive to health and healing, the sound emitted by sources such as building mechanical systems, elevators, and MRIs also needs to be controlled. Background sound criteria for building mechanical systems are given in terms of Noise Criteria (NC)5, Room Criteria (RC)6, and A-weighted decibels2 for spaces such as patient rooms, NICUs, operating rooms, labs, conference rooms, auditoria, and public spaces. In addition to being measurable in existing facilities, sound levels from most sources can be predicted and calculated during design to ensure compliance with the published criteria.
Speech privacy, acoustic comfort, and a reduction in noise-produced annoyance are also highly dependent on adequate sound isolation between spaces within the facility. The easiest way to ensure appropriate sound isolation is to consider it in the planning stages by avoiding acoustically incompatible adjacencies (e.g., patient room next to an elevator shaft) and using buffer spaces such as corridors and storage rooms judiciously. Recommendations are given for demising constructions (e.g., floor/ceiling and wall partitions) in terms of composite Sound Transmission Class (STC) given various adjacencies. Features such as ceiling plenums, windows (e.g., laminated, insulating), doors (e.g., acoustically sealed, solid), and other penetrations (e.g., outlets, conduits, and ducts) need to be considered in meeting these criteria. In general, the weakest link for sound transmission will be the biggest determining factor in the performance of the overall construction. Thus, holes, gaps, or penetrations, which allow the passage of air, will often result in poor sound isolation. In addition, speech privacy, which is an issue included in the HIPAA guidelines, is defined using a number of metrics.
The metrics provide guidance in achieving appropriate levels of privacy in various spaces by recommending sound isolation characteristics of demising constructions as well as background sound levels within rooms.
The acoustic environment within a healthcare facility is also impacted by electro-acoustic systems. Electro-acoustic systems are addressed in the FGI guidelines by specifying minimum audibility criteria for paging and call systems, alarms, sound masking, and sound reinforcement in terms of metrics such as Speech Transmission Index (STI)7, Common Intelligibility Scale (CIS)8, and A-weighted decibels. While these systems can impact the acoustic environment within a facility, the acoustic environment, in turn, can impact the operation of the systems. Therefore, mutual and concurrent consideration needs to be given to both.
Finally, vibration needs to be addressed and controlled in healthcare facilities to ensure suitable conditions for procedures such as microscopic surgeries and MRI scans as well as for physical perception. Potential sources for vibration include exterior sources such as parking garages and road and rail traffic, as well as interior sources such as building systems (e.g., mechanical, electrical, plumbing, and elevators), medical equipment, and footfalls. Best practices, including the placement of vibration-sensitive and vibration-producing equipment on grade and the use of vibration isolation mounts, should be followed in isolating all vibrating equipment. In the case of footfalls, the building structure should be designed to adhere to the published maximum limits for footfall vibration peak velocity. It should also be noted that while medical equipment may produce vibrations that may propagate throughout a building, certain equipment (e.g., MRIs, microscopes, and scanning equipment) may also be sensitive to vibration from other sources.
For the first time, designers, owners and operators of healthcare facilities now have a comprehensive set of acoustic criteria for the design of healthcare facilities. These criteria are objective, quantifiable, and measurable. They can be designed to and planned for. Most importantly, they are achievable through well-established methods with available materials and techniques. Through diligent planning and implementation, this acoustic criteria can be used to reverse the trend toward increasingly noisy environments. With a well-designed acoustic environment, future healthcare facilities can better serve patients, staff, and visitors by providing improved health and comfort which, after all, should be the main goal of any healthcare facility.
About the author
Jesse J. Ehnert has been an acoustic consultant since 1998 and is a principal with Arpeggio Acoustic Consulting, LLC. Throughout his career, his work has focused primarily on architectural acoustics and noise control. He has worked on over 300 projects and has managed projects including the design of health care, performing arts, worship, convention, educational, courtroom, industrial, residential, and athletic facilities. Mr. Ehnert received his Master’s degree in Mechanical Engineering, specializing in acoustics, from the Georgia Institute of Technology and his Bachelor’s degree, also in Mechanical Engineering, from the University of Florida. He is a member of the Acoustical Society of America, where he is a member of the technical committees on architectural acoustics and noise, and the Institute of Noise Control Engineering. He has been published and has organized sessions and presented papers at national acoustics conferences. He can be reached at firstname.lastname@example.org or 404-277-6528.
Established in 2000 in Atlanta, Georgia and comprising 6 principals, Arpeggio Acoustic Consulting, LLC, draws upon a wealth of experience and expertise and offers more than 75 years of combined practice in all areas of acoustics including architectural acoustics, mechanical and electrical system noise and vibration control, environmental noise, industrial noise, product noise, forensic acoustics, and expert witness testimony. A unique balance of creativity and analytical objectivity, combined with a proactive and responsive management philosophy, has positioned Arpeggio as leaders in their field. Arpeggio, LLC is a member firm of the National Council of Acoustical Consultants. Visit www.arpeggioacoustics.com for more information.
1 Equivalent sound level: The level of a steady sound which, for a stated time period, has the same sound energy as the actual time-varying sound over the time period.
2 dBA (A-weighted decibel): A sound level, expressed in decibels, to which a frequency-dependent weighting has been applied to reflect the sensitivity of human hearing at low to moderate levels.
3 decibel: A logarithmic measure of the ratio of two quantities proportional to power, often used in acoustics to describe the loudness of a sound.
4 Sound Transmission Class (STC): A single-number rating used to quantify the sound isolating properties of building components such as walls, doors, windows, ceilings, and floors where a higher value denotes a greater ability to block the transmission of sound.
5 Noise Criteria (NC): A rating system used to quantify and assess the background sound level in an interior space.
6 Room Criteria (RC): A rating system used to quantify and assess the background sound level in an interior space.
7 Speech Transmission Index (STI): A rating system used to quantify and assess the intelligibility of speech which takes into account both background noise and reverberation.
8 Common Intelligibility Scale (CIS): A standardized rating system used to quantify and assess the intelligibility of speech.