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Vol. 19, No. 7 July 2012
• Objective:Toreviewtheepidemiologyof noisepollu-
• Results: Using academic search engines such as
PubMed, JSTOR, and JASA, as well as common
internet search engines, 36 papers were selected
bances, cardiovascular response, length of hospital
stay,pain management, woundhealing,andphysio-
posedtonoise;however,conflicting studies arealso
chain in the collected articles by determining which
• Conclusion:Theeffectsof hospitalnoiseon patients
are generally negative but sometimes inconclusive.
Information on specific acoustic metrics/methodolo-
gies used is often limited, few studies examine the
impacts of acoustic interventions, and some patient
orviasmallsubject sample sizes,highlightingareas
Florence Nightingale recognized noise as a health
hazard in 1859 when she wrote “Unnecessary
noise is the most cruel abuse of care which can be
inf licted on either the sick or the well” . Since then, a
growing body of research highlights the potential nega-
tive impacts of noise pollution in hospitals. For example,
links have been developed between sleep disturbances,
such as reduction of sleep depth, continuity, or duration,
cardiovascular response, wound healing, pain manage-
ment, and other patient responses due to hospital noise.
There is also concern for staff and visitors; for example,
noise in general has been shown to alter staff stress lev-
els, impact job performance, induce hearing loss at high
noise levels, generate annoyance, and cause an increased
rate of burnout [2–6]. However, this paper will focus
specifically on patients. For additional information on
staff response, refer to other sources including  and
. In addition to the direct connections between noise
and patient physiology described in this paper, other sec-
ondary relationships between hospital noise and patient
health could be possible. For example, some have voiced
concern over the potential of noise to degrade the abil-
ity of staff to orally communicate [7,8]; this is an issue
potentially related to patient safety but such secondary
effects are not the focus of this review article.
It is important to note that the conclusions drawn by
the authors in this paper are limited due to the concerns
about some of the previous literature, including (1) the
limited subject population both in size and condition type,
(2) the lack of detail about acoustic methodologies, (3)
the presence of some conflicting results, and (4) very few
studies published on some topics (eg, pain management).
Noise is often referred to as unwanted sound. Kryter
states that noise evaluations are useful to “assess, or
predict the unwantedness, disturbance, objectionable-
ness, undesirability, unacceptability, perceived noisiness,
or simply the noisiness of the sound environment in real
life” . Noise can be measured in many ways. A com-
mon unit of measurement is the decibel (dB) which is a
measurement of the energy contained in noise relative
to the very minimum amount of energy average humans
can detect. Often weightings (ie, filters) are applied to
better simulate the human ear’s perception of loudness
across frequency. A-weighting (dBA) is the most com-
Noise Pollution in Hospitals: Impact on Patients
Timothy Hsu, PhD, Erica Ryherd, PhD, Kerstin Persson Waye, PhD, and Jeremy Ackerman, MD, PhD
From the Woodruff School of Mechanical Engineering,
Georgia Institute of Technology, Atlanta, GA (Drs. Hsu and
Ryherd), the Department of Occupational & Environmental
Medicine, University of Gothenburg, Gothenburg, Sweden
(Dr. Waye), and the Department of Emergency Medicine,
Emory University, Atlanta, GA (Dr. Ackerman).
July 2012 Vol. 19, No. 7
mon example and works well for a large range of average
noise levels, whereas C-weighting (dBC) is sometimes
applied to very loud noises. Sound frequency, measured
in hertz (Hz), is related to human perception of pitch.
For example, a piccolo is a high-frequency instrument
and a tuba is a low-frequency instrument. Bandwidth
refers to the range of frequencies included in a particu-
lar sound. If sounds are comprised of a wide range of
frequencies (such as air-conditioning noise), they are
referred to as broadband. On the other hand, a single
note, or tone, would be referred to as narrow-band.
Human perception of loudness is highly complex;
however, some approximations of typical sounds given
for reference are: quiet residence (40 dBA), private of-
fice (50 dBA), conversational speech (60 dBA), vacuum
cleaner (70 dBA), heavy traffic (80 dBA), pneumatic
hammer (100 dBA), jet aircraft (120 dBA) [11,12].
The World Health Organization (WHO) recommends
average noise levels are no more than 35 dBA in rooms
where patients are treated or observed and no more than
30 dBA in ward rooms , although a recent landmark
study showed that no hospital noise results published
since 1960 meet these guidelines .
The noise normally occurring inside rooms is often
referred to as “background noise.” In hospitals, back-
ground noise can result from a variety of sources includ-
ing air-conditioning systems, medical devices such as
respirators, and occupant sounds such as conversation.
Impulsive noises, or very loud, short duration events, are
also commonly found in hospitals (eg, doors slamming,
metal-to-metal contact, alarms). Two other types of noise
sometimes used in acoustics experiments are white noise
and pink noise. White noise has a constant amount of
energy across frequency whereas the energy in pink noise
changes with frequency. Both types of noises sound simi-
lar to TV or radio static (ie, turned on but not tuned to a
station). Another important measure of sound in rooms
is reverberation time (RT). RT is a measure of energy
decay. It is related to volume and absorption; generally
larger spaces with less absorption (harder, reflective sur-
faces) have longer RTs.
Numerous articles show negative relationships between
hospital noise and sleep [13–29]. Methods include
polysomnography (PSG), structured questionnaires, in-
terviews, and electroencephalography (EEG) [13–26].
Although the percentage slightly varies, it has generally
been shown that roughly 11% to 20% of arousals and
awakenings are due to noise . In the experiments
involving sleep disturbance, researchers have often fo-
cused on disturbances that occur within 3 seconds of a
measurable increase in noise, eg, greater than 10 to 15
As early as 1976, investigators studied how the qual-
ity and quantity of sleep in a respiratory intensive care
unit (ICU) was affected by noise . Ten patients were
monitored using PSG, interviews, and observations for
48 hours and exposed to sounds such as speech, equip-
ment noise, alarms, phones, tapping of chairs and rails,
radios, construction noise, and heating, ventilation, and
air-conditioning (HVAC) noise. None of the 10 patients
completed 1 undisturbed sleep cycle, and only 1 patient
had suff icient sleep time for even the possibility of a com-
plete sleep cycle. This study described an average normal
night’s sleep as consisting of 4 to 5 sleep cycles, with each
cycle lasting 90 to 120 minutes. The study concluded
that patients would have difficulty sleeping normally
due to interruptions such as noise caused by personal
and environmental noises. Aurell and Elmqvist studied
9 subjects in a postoperative ICU using PSG, EEG, and
interviews . A reduction of environmental noise was
also made to compare a quiet environment to the noisy
environment. The degree of change was unreported, but
with these acoustical alterations all 9 subjects experienced
sleep def iciencies.
Topf et al studied the interaction between noise and
the suppression of rapid eye movement (REM) sleep
with a sample of 70 women, comparing quiet conditions
with noisy conditions . Approximately one-quarter of
sleep time is normally spent in REM, which consists of
episodic bursts of rapid eye movements along with heart
rate, respiration irregularities, and paralysis of major
muscle groups other than some respiratory muscles .
REM sleep is believed to help with cognitive factors such
as memory retention and learning capabilities. Although
the Topf et al study took place in a sleep lab, the subjects
were exposed to a recording of nighttime coronary care
unit (CCU) noise at 84 dB . Noise affected the
quality of REM sleep compared to patients in quiet con-
ditions; specifically, the subjects exposed to noisy CCU
sounds experienced shorter R EM periods and less REM
activity. The authors concluded that noise acts as a sup-
pressor to REM.
Another study by Carley et al tested 5 adults to see if
acoustic stimulation can cause a sleep disturbance .
Vol. 19, No. 7 July 2012
The acoustic signals consisted of 2 binaural tone bursts:
a 0.5-second 4 kHz tone at 85 dB SPL and a 99-second
interstimulus interval produced by a tone generator. An
EEG arousal could be evoked in non-REM sleep with
an acoustic stimulation. Furthermore, respiratory activity
increased after an acoustic stimulation that was indepen-
dent of general electrocortical arousal.
Aaron et al sought to determine the level and number
of noise peaks needed in order to create a sleep arousal
. In this study, an EEG arousal was def ined as awake
state or alpha rhythm of at least 3 seconds’ duration, oc-
curring following at least 30 seconds of sleep . This
study took place in an intermediate respiratory care unit
and utilized 24-hour PSG measurements. Although this
study only had a sample size of 6 subjects, the research-
ers concluded that noise peaks greater than 80 dB(A)
can correlate to sleep arousals. The authors noted that
follow-up studies were needed to identify the sources of
the noise peaks. Freedman et al used a larger sample size
of 22 patients in a medical ICU where 20 of the patients
were mechanically ventilated . The mean noise level
was measured as 59.1 dBA in the day and 56.8 dBA at
night. They found that environmental noise was not
the main reason for sleep fragmentation, but noise was
partially responsible. Specif ically, 11.5 and 17% of the
total arousals and awakenings were related to noise, re-
spectively. The exact sources of noise were not described.
There has also been investigation into whether the
differences between peak and average background noise
levels are important. Stanchina et al tested 5 subjects and
recorded 1178 arousals using PSG . Subjects were
exposed to recorded sounds from an ICU that included
patient-staff interactions, alarms, ventilators, equipment
noise, and others. Another recording combined these
sounds with white noise. The average level of the ICU
noise-only was 57.9 dB and the combined ICU and white
noise was 61.1 dB. The addition of white noise lowered
the number of sleep arousals caused by ICU noise even
though the average noise level increased.
Another study compared the different contributions
of ICU noise and patient-care activity noise to sleep dis-
ruption . Six healthy male patients and 7 mechanical-
ly ventilated male patients were studied using a 24-hour
PSG and a structured questionnaire was administered to
the healthy subjects. The patient population was already
admitted to an ICU, whereas the healthy population con-
sisted of subjects who volunteered to spend a 24-hour pe-
riod in an ICU. For the mechanically ventilated subjects,
the average daytime and nighttime noise levels were 56.2
and 53.9 dB, respectively. For the healthy subjects in an
open ICU, the average daytime and nighttime levels were
55.6 and 51.4 dB, respectively. For the healthy subjects in
a single room, the average daytime and nighttime levels
were 44.3 and 43.2 dB, respectively. Results showed ICU
noises and patient-care activities accounted for less than
30% of the sleep disruptions. The remaining arousals
and awakenings were caused by opening and closing the
ICU main door, which was located near the patients. The
patients generally slept worse, meaning they generally
exhibited more awakenings and arousals per hour and a
shorter sleep time as compared to the healthy subjects.
For example, patients slept an average of 6.2 hours total,
whereas healthy subjects slept an average of 8.2 to 9.5
hours total depending on if they were in an open bed
location or a single room. They also determined that
about half of the patient’s sleep occurred during the day.
Questionnaire-only studies have also analyzed the
relationships between noise and sleep disturbances in lieu
of direct physiological measurements. Topf et al exposed
60 females to an 8-hour audiotape of coronary care unit
(CCU) noise from monitoring devices, ventilators, suc-
tion machines, drains, oscilloscopes, and staff . The
subjects reported a general negative impact on sleep, in-
cluding longer time to fall asleep, more awakenings, and
fewer hours sleeping. Another survey of 50 general ICU
patients used the Intensive Care Unit Environmental
Stressor Scale (ICUESS) and revealed that high stress-
ors such as pain and noise were also factors in patients’
inability to sleep . Another study of 203 patients
revealed that patients felt their sleep was significantly
worse in an ICU than at home . Specifically, staff
communication and alarms were the most disruptive to
sleep, whereas telephones, televisions, beepers, and equip-
ment noise were not as disruptive.
Observational studies also provide insight. Dlin et
al observed ICU patients and recorded interruptions to
sleep . All but 3 of the patients in the ICU partici-
pated, although specific sample size was not given. Pa-
tients were interviewed and asked about sleeping patterns
at home, in previous hospitalizations, and in the current
hospitalization. Additionally, staff members observed the
patients as “frequently as possible” without structured
questioning, and one final staff observation following
release from the ICU. Each staff observation consisted
of logging interruptions such as discrete events which
impacted the patient in a direct manner (such as the tak-
July 2012 Vol. 19, No. 7
ing of blood pressure) and noted the nature, duration
and response of the interruption. They observed that the
main deterrent to sleep was activity and noise.
Monson and Edéll-Gustafsson implemented vari-
ous changes in a neuro-ICU including noise-reducing
medical and nursing routines and afternoon and night
non-disturbance periods . Two patient groups were
analyzed: 9 before and 14 after. The total number of
sleep disturbance factors over a one-week span before the
behavioral modification program averaged 194.3 sleep
disturbances, as compared to 162.1 after. Another pro-
gram by Walder et al implemented 5 guidelines includ-
ing systematic closure of doors, a reduction of intensity
of alarms, efforts for low conversation, and coordination
and limitation of nursing interventions in sleeping hours
. Results showed a lowering of average and peak
noise levels after the changes, but reported that sleep
patterns could still be disrupted. A similar study by Kahn
et al attempted to reduce peak noise sources in both
medical and respiratory ICUs . An observer was
present in the measurements to note the noise sources.
They recorded noises such as HVAC, medical equipment,
televisions, telephones, intercoms, beepers, and conversa-
tions. The mean peak levels were 80.0 and 78.1 dBA,
before and after behavioral modification, respectively.
There was significant reduction in the total number of
peaks exceeding 80 dBA, from 1363 periods out of 2880
possible periods to 976 periods out of 2811 possible pe-
riods. Specifically, between 6 am and 12 am, there was a
signif icant reduction of noise peaks exceeding 80 dBA.
The authors suggested that sleep can be improved due to
this reduction of noise peaks, but they left the topic for
a future study.
Studies show that factors of the acoustic environ-
ment besides noise can correlate to sleep disruption.
For example, sleep has been related to reverberation
time (RT). A study by Berg, which took place in a re-
furbished former surgical ward, focused on the effects
of RT on noise-induced sleep arousals using EEG for
12 subjects . RT was reduced by an average 26%
after the installation of sound absorptive ceiling tiles.
Noise ranged from 27 to 58 dB(A), coming from both
continuous and impulsive sources such as dropped
plates, traffic noise, fan noise, machine noise, doors
closing, and radios. Results showed that the installation
of the sound absorptive ceiling tiles did not significantly
change noise levels, but did signif icantly reduce the
number of sleep arousals.
Cardiovascular response is also related to the acousti-
cal environment [30–36]. Some of the earliest stud-
ies revealed that heart rate, blood pressure, and other
cardiovascular measures can be affected by noise. Falk
et al studied the relationship between vasoconstriction
and noise intensity and bandwidth . At noise levels
greater than 70 dB there exists a linear relationship
between increases of noise intensity and increases in va-
soconstriction. Further, an exposure to 90 dB of white
noise could cause an immediate vasoconstriction with a
recovery time of about 25 minutes after the white noise
was turned off. The severity of vasoconstriction was a
function of bandwidth of the noise—as the bandwidth
increases, the vasoconstriction worsens.
Conn related heart rate, frequency of arrhythmias, and
state of anxiety during quiet and noisy periods in a coro-
nary care unit (CCU) . Twenty-five male patients
were exposed to 1-minute noise recordings between 3 to
4 pm and 7 to 8 pm. The results showed that anxiety was
heightened and the number of ventricular arrhythmias
rose signif icantly during the “noisy” periods, defined to
be periods of noise greater than 55 dB.
Further research has related changes in heart rate
with types of noise source. One study found that the
average heart rate increased due to the presence of
human sounds (talking) . Another study of 28
patients in a surgical ICU showed an increase in heart
rate due to talking inside a patient’s room . The
average noise levels ranged from 49.1 to 68.6 dBA.
When there were noise events that caused an increase of
3 dBA or greater in overall noise level, 89% of the tests
showed an increase in heart rate more frequently than a
decrease in heart rate. For 46% of the tests, this increase
was statistically significant. When sound pressure levels
showed a 6 dBA increase, the heart rate also rose from
two to twelve beats per minute. Additionally, heart rate
signif icantly increased for impulse noise. A similar study
compared ambient stressors of equipment sounds to
social stressors like conversation in a CCU . Mea-
surements were taken 3 times a day over 2 days with 20
subjects. 55% of the hospital noise was conversation in
the room, 20% of the noise originated from background
sound, 15% from hall conversation, and 10% from envi-
ronmental sound. Although noise did not significantly
affect blood pressure, heart rate was elevated during
social stressor conversations compared to quiet ambi-
ent conditions. Also, heart rate was about 3 beats per
Vol. 19, No. 7 July 2012
minute faster during conversational sounds than during
Similar to the sleep study with variable acoustics
described earlier , Hagerman et al examined blood
pressure and heart rate in a “good” and “bad” acousti-
cal environment . Subjects were 94 patients in an
intensive coronary heart unit. Absorptive acoustical ceil-
ing tiles were added that decreased reverberation time
by 50% in the main work area and by 56% in the patient
rooms. Also, the absorption decreased overall noise levels
by 5 to 6 dB in the patient rooms. Even though there
was no signif icant difference across the entire group in
heart rate, blood pressure, or pulse amplitude, there were
signif icant differences when analyzing the data by type
of disease. Pulse amplitude is the difference between sys-
tolic and diastolic blood pressure . In acute myocar-
dial infarction and unstable angina pectoris groups, the
heart pulse amplitude was higher with the “bad” (ie, less
absorptive) acoustical setting at night. Additionally, pa-
tients in the “bad” acoustic setting were re-hospitalized
more frequently at 1- and 3-month follow-up.
Effects of noise on gastric activity are somewhat unclear.
Sonnenberg et al examined the link between cardio-
vascular response, mental stress, gastric acid secretion,
and noise . One phase tested 10 male subjects and
exposed them to 90 dBA of broadband noise for 1 hour.
Blood pressure, heart rate, and respiratory rate were mea-
sured. The second phase tested the gastric response of 14
male subjects after exposing them to 90 dBA of broad-
band noise and a gastric stimulation. Results showed that
both diastolic and systolic blood pressure increased by 4
and 8 mm Hg, but heart rate and respiratory rate were
not affected. However, the noise did not affect gastric
acid secretion. Another experiment where 50 dyspeptic
subjects were exposed to 95 dB pink noise for 15 minutes
also showed no relationship between gastric secretion
and noise . Sonnenberg et al also reported previously
unpublished results by J.F. Erckenbrecht that found that
noise signif icantly increased small bowel transit time,
stool frequency, and stool volume .
In another study  21 male subjects were exposed
to a 110-minute recording that simulated different noise
sources—hospital noise at 87.4 dBA, conversation at 91.3
dBA, and traffic at 85.6 dBA. Gastric activity was studied
via gastric myoelectrical activity (GMA), which controls
stomach motility. GMA was measured via an electro-
gastrogram (EGG) using standard electrocardiogram
(EKG) electrodes on the upper abdominal wall. Three
cycles per minute (CPM) GMA is common for humans.
Results showed that hospital and traffic noise exposure
signif icantly decreased the percentage of 3 CPM activity.
There was also a nonsignificant decrease in percentage of
3 CPM activity with respect to conversation noise. The
authors concluded that loud noise can alter gastric myo-
Wound healing and noise has thus far primarily been
studied in animals [40–43]. Although some potential
effects on humans can be surmised, it is important to
acknowledge that the response of humans to noise in
general is more complex. One wound healing experi-
ment exposed rats to 80 dB of rock music for a 22-hour
time period and then measured changes of leukocyte
function . The rock music was turned off periodi-
cally to prevent habituation. Lymphocyte function re-
mained unchanged in the presence the noise. However,
short-term noise exposure did cause an alteration of the
superoxide anion and interleukin-1 secretion of neutro-
phils and macrophages, thus decreasing wound healing.
Wysocki measured wound surface area and found
that the wounds healed slower in a group of rats ex-
posed to random white noise at 85 dB . The noise
was played intermittently for 15 minutes for 19.5 days.
Additionally, the average weight of the exposed group
of rats was lower even though food intake was the
same between the exposed and unexposed group. In
another study, 119 mice exposed to temperature and
noise stressors were inflicted with a small wound .
The noise stressor consisted of 99 dBC white noise.
Results showed noise slowed down healing rate (ie,
reduction of wound area) but noise affected the heal-
ing rate less than temperature stressors.
Healing rate can also be measured by the hormone
secretion of the suprarenal cortex . 124 albino rats
had a patch of skin removed from part of the back.
Healing rate was measured by 2 methods: size reduc-
tion of the wound and weight of the suprarenal gland.
The rats were exposed to combined environmental
stressors that included flashes of light, a ringing
bell, and scraping metal wheels. The stressors slowed
wound healing in male but not female rats. Within the
male group, the average difference in total healing was
about 8 days.
July 2012 Vol. 19, No. 7
Only one study relates noise to average length of hos-
pital stay . The study compared the hospital stay
length of 416 cataract patients while the hospital was
and was not under construction. Hospital stay was lon-
ger for patients during the louder construction periods,
with average length increasing about 1 day.
Only one study links hospital noise to patient pain
management . The range of noise levels was related
to the number of patients requiring pain medication,
such as narcotics, in a 10-bed recovery room. Results
showed an increase in noise was related to an increase in
pain medication. On the other hand, noise can poten-
tially be used into reduce pain sensations in certain cases.
Gardner et al exposed 1000 dental patients to ordinary
dental office sounds such as dental drills . The pa-
tients wore earphones and they were able to adjust the
level of either orchestral music or white noise, noting that
the white noise sounded similar to a waterfall. Sixty-five
percent of the patients were able to use this audio-analge-
sic effectively for procedures that usually elicit the use of
nitrous oxide or local anesthesia. The authors theorized
that the music and white noise acted as analgesics due to
their relaxing, soothing nature and because they masked
sounds of dental drills, therefore reducing patient anxiety
DiscussioN of results
It is clear from this literature review that hospital noise
is a serious issue potentially linked to several types of
negative reactions in patients. Table 1 summarizes the
studies described in this review by author and outcome.
Patient sleep has been shown to be negatively af-
fected by the sound environment. A number of research
methods, including PSG, EEG, patient questionnaires,
and observational studies have confirmed relationships
between noise and sleep length, quantity, or quality.
The occurrence rate of sleep arousals tends to rise with
exposure to heightened background or peak levels.
There have been many studies conducted on the number
of noise-induced sleep arousals within different sleep
stages. Previous studies have also determined which noise
sources, such as staff talking and telephone noise, arouse
the patients most frequently and these sources typically
become the targets for noise reduction programs. One
of the major concerns with these studies is that gener-
ally small sample sizes are used in the initial experiments
(eg, as few as 5 patients); thus, the applicability of these
results to larger populations must be scrutinized.
Cardiovascular response has been related to noise
exposure. Occurrences of vasoconstriction and increases
in heart rate and blood pressure due to the presence
of acoustical stimuli have been shown. Additionally,
anxiety and arrhythmia episodes are more frequent in
noisy scenarios. The addition of acoustic absorption can
Outcome Authors Year
Hospital stay Fife&Rappaport 1976
Wound healing* McCarthyetal
Other responses Castleetal
Vol. 19, No. 7 July 2012
potentially help offset the levels of noise and reduce the
negative effects of noise on heart pulse amplitude and in-
cidence of re-hospitalization. However, as a whole, results
are not entirely consistent, with some studies showing
changes and others not. Additionally, it is not yet known
in general whether the presence of noise is directly linked
to the onset of heart disease or other chronic cardiovas-
Research on other health effects has been limited. For
example, there are no known studies of noise and wound
healing in humans. Relationships between noise and
pain management are also unclear. The studies that do
exist suggest the presence of noise may increase the need
for pain medication but conversely, patient control over
sound can potentially limit the need for certain medica-
tions. The field of music therapy is ripe with evidence
suggesting the benefits of pleasing sounds, but was not
the focus of this literature review. Rigorous studies are
needed to relate noise to wound healing and pain.
The literature taken as a whole can be organized in
a way that studies the entire research chain: from the
acoustic metrics being tested through the mechanism
being introduced to the occupant outcomes. For ex-
ample, Berg  focused on how a change in reverbera-
tion time affects patient sleep; thus the acoustic metric
is reverberation time, the mechanism is the addition of
absorptive tiles, and the occupant outcome is the change
in patient sleep arousals. The occupant outcomes shown
in Table 2 were generally negative when the subjects were
exposed to noise, ie, sleep quality was reduced, cardio-
vascular response was heightened, and healing rates were
lowered. When environmental changes or behavioral
changes were made to reduce noise or reverberation time,
the outcomes were generally positive.
It is important to note in Table 2 under the “Metric”
column several studies show blank acoustic metrics. This
does not mean that acoustics were not considered in the
studies; rather, it reveals that specific acoustic metrics
were not systematically altered. For example, in Carley
et al , 85 dB tones were used in the study for noise
exposures. A change in decibel value was not specifically
studied; instead, it is the exposure to noise that was of
interest. Alternatively, in the Hagerman study ,
the acoustic metric that was altered and controlled for
was reverberation time (value reduced by 50% –56%).
The mechanism was that they added absorptive panels.
The outcome was that patients were re-hospitalized at a
higher incidence when the reverberation time was longer.
Hence, the Hagerman study  systematically altered
reverberation time, as opposed to Carley et al  that
drew their conclusion from the exposure itself, not from
an acoustic metric.
This review reveals that hospital noise is a serious
issue linked to several potential negative reactions in
patients. The clinical significance of these results is
not entirely known, but some hypotheses are possible.
Sleep is fundamental to human health in general and
critical to patient recovery. Alertness, mood, behavior,
coping abilities, respiratory muscle function, ventilatory
control, healing time, and length of stay are just a few
of the potential impacts of patient sleep disturbance
or deprivation [25,28,47]. Cardiovascular or other
arousals due to noise stressors can also impede patient
recovery. As Baker states, “stress results in compensa-
tory biological changes, thus redirecting or exhausting
resources that might otherwise be available to combat
the original disease process” . Additional research
is needed to determine the chronic implications of noise
on patient health.
Very few studies examine the entire research chain
(acoustic metrics to mechanism to outcome). Thus,
the conclusions drawn by the authors in this paper are
limited due to concerns such as subject population, lack
of detail about acoustic methodologies, the presence of
some conflicting results, and limited number of publica-
tions on some topics. Regardless, this literature review
concludes that hospital noise is a serious issue that can
negatively affect patient physiology and more research is
The ultimate goal should be to identify ways to improve
the acoustic environment but generally only rudimentary
measures (dBA) have been reported. These acoustic met-
rics may be overly simplistic for hospital environments
[7,8]. Additionally, a number of “mechanism” studies
evaluating changes in the acoustic environment are needed
in order to optimize the effectiveness of acoustic or be-
havioral alterations. Already, the use of absorptive ceiling
tiles has been shown to positively impact patients. Other
acoustical variables such as room shape or equipment se-
lection should also be investigated in detail. With a better
understanding of how inter ventions impact the acoustics
and therefore occupant outcomes, strides can be made
in filling the holes in the research chain and providing a
healthier atmosphere for patients, staff, and visitors.
July 2012 Vol. 19, No. 7
Hospital caregivers and administrators can begin
acting on current knowledge to improve the hospital
noise environment. A combination of administrative
strategies (eg, behavioral modif ications, quiet zones,
changing alarm settings) and design strategies (eg, sound
absorbing materials, architectural layout) are needed. As
described earlier in this paper, administrative approaches
such as behavioral modification programs have been
Patient Outcome Article Acoustic Metric(s) Mechanism* Outcome(s)
Aurell&Elmquist1985 B- Sleepdeficienciesseeninallsubjects
Stanchinaetal2005 Peaklevels AIncreasednumberofsleeparousals
Walderetal2000 LAeqandMaxLevels DSleeppatternsaltered
Kahnetal1998 Peaklevels DNumberofnoisepeaksreducedbutno
Hagermanetal2005 Reverberationtime CSpeechintelligibilityimproved.Patients
Vol. 19, No. 7 July 2012
shown to be effective in improving sleep and reducing
noise levels [26–28]. Other studies discussed earlier
have shown that design strategies such as adding sound
absorption can improve sleep  and reduce incidence
of rehospitalization . Caregivers and administrators
can work with a building acoustical consultant who is
versed in evidence-based hospital design. Ryherd and
Zimring present information on some design strategies
available and provide basic recommendations about how
to facilitate collaborations with acoustic consultants
.The consultant can help incorporate design strate-
gies such as reducing noise from building systems like
air-conditioning, changing communication systems to
reduce overhead paging, using sound absorbing materials
that meet hospital safety requirements, and incorporating
floor plan layouts that are conducive to good acoustics.
Corresponding author: Erica E. Ryherd, PhD, Woodruff
School of Mechanical Engineering, Georgia Institute of
Technology, 771 Ferst Dr., Atlanta, GA 30332, erica.ry-
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