By Jeffrey A. Zapfe, Ph.D. and Marc S. Newmark
From the May/June 2015 issue
Whether it’s a new construction project or renovation of an existing structure, the result is often a state-of-the-art facility with exciting new capabilities and opportunities. And while the future may be bright with potential, the construction process itself can be extremely disruptive to ongoing healthcare operations.
Construction vibration and noise can adversely affect staff as well as sensitive equipment and activities. Perhaps, more importantly, it can affect patients. It is well known that patient satisfaction reports1 invariably list noise as the most unpleasant part of a hospital stay. Unfortunately, construction produces noise and vibration.
There are methods that can be used to calculate the expected noise and vibration during construction to help hospital facility stakeholders predict which areas may be affected. This in turn allows the facility staff to plan around the construction and, hopefully, keep most of its operations viable during the construction process. When construction is actually underway, monitoring systems help to keep tabs on the noise and vibration and make sure they are within acceptable limits.
Vibration Concerns
Construction vibration monitoring is required at most building sites and is typically provided by the contractor. The primary purpose of this monitoring is to address structural damage to nearby buildings, and is usually accompanied by pre- and post-construction crack inspections. The vibrations necessary to cause even minor structural damage are quite high and can easily be felt by people. These are not the vibrations that are the subject of this article. The concerns addressed here are activities and equipment that can be affected by extremely low levels of vibration, in many cases far below the level of human perception.
In a hospital environment, vibration concerns relate to sensitive areas, such as operating rooms, procedure rooms, and patient rooms; and equipment, including MRI, NMR, electron microscopes, and lab equipment. The Facility Guidelines Institute (FGI), in Guidelines for Design and Construction of Hospitals and Outpatient Facilities 2014, recommends that floor vibrations be limited to 6,000 micro-inches per second (min/s) in patient rooms and 4,000 min/s in operating and other procedure rooms. As a point of comparison, 4,000 min/s is around the threshold of perception for the most sensitive humans.
The manufacturers of most vibration sensitive equipment typically provide clearly defined criteria for acceptable levels of floor vibration. In many cases, these criteria depend on the frequency of the vibration. For example, the criterion for one particular electron microscope is 130 min/s at 5 Hz, but at 20 Hz it is 1,100 min/s (more than eight times higher). When considering the effects of potentially disruptive vibration, both the magnitude and the frequency are equally important in determining whether or not there may be an issue. This is significant because conventional construction vibration monitors are not typically capable of measuring extremely low levels of vibration, nor are they able to measure vibrations at multiple frequencies simultaneously. Specialized sensors and analyzers are required to do this.
Healthcare campuses with research activity may also have animal facilities. While vibration effects on animals are not extremely well understood, there is anecdotal evidence that vibration from construction can have disastrous consequences on animal populations. The National Institutes of Health recommends that a vibration design criterion of 2,000 min/s be used for vivarium floors. This level can easily be exceeded by construction activity. More recent experience suggests that 3,000 min/s can be a more reasonable level for animal spaces during construction.
Monitoring During Construction
The prediction process provides a very good indication of which sensitive adjacencies may be adversely affected by construction vibration, and when. Many institutions have found it useful to monitor vibrations in real time during the actual construction process. In recent years, wireless connectivity has made it possible to monitor vibrations remotely, and to access this information in real time. Project managers and contractors alike have found the live data feeds to be an invaluable tool in maintaining the noise and vibration environment in nearby sensitive spaces. Furthermore, the users of these spaces take comfort in the knowledge that someone is actively “watching out” for their interests.
A typical monitoring system consists of a set of sensors, an analyzer, and a computer with an Internet connection. The sensors are chosen to match the sensitivity of the instrument or space usage. The analyzer settings are likewise configured to match the applicable criteria. The computer stores the data and can be accessed remotely for download and operation (to change settings, for example). But more importantly, the Internet connection provides the ability to send warning and alarm messages by text or e-mail when pre-set levels are exceeded. Once installed, the systems are hands-off. This can be extremely useful in areas where frequent visits for maintenance or to download data would otherwise be disruptive.
Since the contractor or facility manager can receive the alarm feed, they can anticipate problems and take preemptive steps to stop or modify the activity, and maintain the low-noise and low-vibration environment. As limits are approached or exceeded, the contractor can often adjust their means and methods to reduce or prevent the disturbance. If not possible, the contractor and project manager can inform affected users as to how long the disturbance will persist.
Of course, it is far better to know about disturbances before they happen, which is where the predictive process contributes the most. By and large, facility users understand there will be disruptions, and most can work around these. But when unexpected conditions occur, live monitoring allows them to know before the first complaint.
Zapfe is the president of Acentech, a multidisciplinary acoustics, audiovisual systems design, and vibration consulting firm in Cambridge, MA. He specializes in vibration, structural dynamics, and vibration sensitive facilities. Newmark is a senior consultant at Acentech specializing in acoustics and vibration.
References
1Hospital Consumer Assessment of Healthcare Providers and Systems (HCAHPS). Available through the Centers for Medicare & Medicaid Services (CMS).
