- Research article
- Open Access
The characterization of noise levels in a neonatal intensive care unit and the implications for noise management
- Juan Carlos Fortes-Garrido1Email author,
- Andres Mauricio Velez-Pereira†2,
- Manuel Gázquez†2,
- Montserrat Hidalgo-Hidalgo†3 and
- Juan Pedro Bolívar†2
© Fortes-Garrido et al.; licensee BioMed Central Ltd. 2014
- Received: 21 May 2013
- Accepted: 30 June 2014
- Published: 22 July 2014
The effects of noise are particularly harmful for the newborns, and therefore this study assesses and characterizes noise levels in a neonatal intensive care unit (NICU) in a medium-size hospital in the city of Huelva with the aim of optimizing the management and quality of care for newborns.
The equivalent continuous sound level was recorded as A-weighting curves using Type I sound level meters with levels measured during 100 milliseconds along to 15-day period in the both critical (in and out of incubators), and intermediate care units from a medium-size hospital. These devices were attached to a central beam 80 cm below the ceiling and into one of the incubators.
The maximum noise levels measured for critical (C-in), C(out) and intermediate (I) were: 88.8 dBA, 97.2 dBA and 92.4 dBA, respectively, while for the equivalent noise levels for the total measuring period (15 d) were 57.0 dBA, 63.7 dBA, and 59.7 dBA, respectively. The Fourier frequency analysis has demonstrated several typical periods related to both work activities and family visit, which were: 7 days, 24 h, 12 h, and 3 h.
The statistical analysis revealed a clear correlation between the noise level, the kind of care room, and the time of the day. The results show that the values recommended by international bodies and agencies (AAP, WHO) are surpassed by a large margin, thus making it crucial that certain norms are followed in order to reduce the noise level in the NICU, by means of physical alterations to the layout, and raising awareness of health care personnel and visitors in order to encourage noise prevention in the daily care work and conversation. And finally, has been demonstrated that by applying the t-Student test the mean noise values in both wards are significantly different, which leads us to state that the noise level for the critical wards are higher than in the intermediate care ward.
- Noise Level
- Neonatal Intensive Care Unit
- Sound Level
- High Noise Level
- Health Care Personnel
Recent studies on the quality and risks associated with admission to a medical center have established a relation between the increase in morbidity and mortality, in addition to alterations in the quality of life following discharge from the health center which are usually linked to greater exposure to environmental pathogens, a lowering of the body’s defenses and an increase in invasive techniques, among other reasons. Many authors have found a high correlation between noise levels in NICU and adverse effects arising from sleep disorders, underdevelopment of responses to stimuli, deterioration of the nervous system, etc. [1–6]. The noise that occurs in the NICU is linked to the monitoring and follow-up processes of the newborn’s state of health, such as alarm systems, electro-medical equipment and incubators, and the general human ambient noise .
Several studies have measured the noise levels in NICU, finding very different values depending on the management of the work activities or customs of the place, with equivalent continuous levels in ranges from about 55 up to 83 dBA. These noise levels are high enough to stimulate the newborn’s endocrinal and cardiovascular systems, resulting in significant alterations in sleep patterns [8–11]. Bushch-Vishniac et al.  determined that the average noise level for the John Hopkins Hospital has risen in the last 45 years by around 0.40 dBA a year, mainly due to the increase in audible alarm systems, the installation of air conditioning, control and surveillance systems and electro-mechanical therapeutics.
In terms of the legal framework, the World Health Organization (WHO) recommends that the newborn inside an incubator should not be exposed to noise levels higher than 35 dBA at night and 40 dBA during the day . As proposed by the US Environmental Protection Agency and supported by the American Academy of Pediatrics (AAP) Committee of Environmental Health, noise levels within the NICU should be kept below 45 dB . More specifically, the AAP recommends that hourly, a NICU’s loudness equivalent (LAeq) should be below 50 dBA, the sound level that is exceeded 10% of the time (L10) should be at or below 55 dBA, and the maximum sound (Lmax) should be below 70 dBA . In Spain, the Standards Committee of the Neonatology Society of the Spanish Pediatrics Association recommends a total background noise level in NICU of no more than 55 dBA, and should not exceed 70 dBA . However despite these recommendations, noise levels routinely oscillate between 65 dBA and 85 dBA, normally at low frequency .
In this study are correlated the temporal variations of the noise with its causes (Monitoring Systems, work activities, family visits, medical rounds, etc.). Spain is the second noisiest country in the world after Japan , according to the World Health Organisation (WHO), so this study is particularly important due to customs and the high noise level in the daily activities of the Spanish people.
With this in mind, the aim of our study is to identify, assess and make a space-time characterization of the noise levels in the NICU of a typical medium-sized hospital in Spain to find the main correlations with the noise sources, and, as consequence, to establish the right protection measures for noise reduction and elimination.
Two noise level meters used were the Type I Brüel & Kjäer model 2270 and 2250. The technical characteristics for two meters are: 4.2 HZ broadband linear frequency range with supplied microphone Type 4189, 16.6 – 140 dB A-weighted dynamic range with supplied microphone Type 4189. Outputs: Generator and Headphone. The third was the Rion NL-31, and the technical characteristics are: A weighting: 28-138 dB, C weighting: 33-138 dB, flat: 38-138 dB, Peak sound level: 141 dB, Ranges 100 dB dynamic, frequency 20-12,500 Hz (including microphone).
The sampling period lasted 15 days in order to ensure that the averages were representative and to offset the Hawthorne effect  of attention bias in which the study participants alter their behavior when they are aware they are being observed, and avoid interferences that can cause another unexpected variable to influence the study.
The collected data (individual data were for time intervals of 0.1 s) were recorder in the Secure Digital (SD) by Memory Card inside of the level meters and downloaded to PC and were treated and processed in the XLSTAT code developed by Addinsoft and SPSS 13.0.
Obviously there are more instances of intervention, monitoring and follow-up of newborns in the NICU-C ward where the most critical care takes place, with a consequently greater noise level throughout the day. The NICU-C-out ward recorded LAeq,1 h of 69 dBA at 08:00, which is when the biggest number of health care personnel starts work. Hence, the high noise level is directly attributed to talking by the staff, again verified by the second peak which occurs at 15:00 when the majority leaves work. This Figure also shows the close relation between the activities of the health care personnel in the NICU and the noise level in each ward.
By contrast, if we take a specific hourly period such as 00:00-01:00 in NICU-I, the resulting data set (N = 6 · 15 = 90 data) still has a normal distribution with 95% confidence. Likewise, if we apply the Shapiro-Wilk test we get W = 0.838 (p-value = 0.159), so the null hypothesis is acceptable at a significance level of 5% (alpha = 0.05) since the p-value obtained (0.159) is greater than the alpha considered (0.05). This result confirms our hypothesis that the noise level has a normal distribution if the sampling period is restricted to 1 hour, which is less than the shortest of the characteristic periods of the data series (3 hours or the newborns’ feeding time).
The results are consistent with those of other authors [20–28] in which the hours with the highest levels of noise are between 08:00 and 15:00, when care activity around the newborn in NICU is at its busiest. In terms of the maximum, minimum and average noise levels recorded, the studies in NICU that we have analysed present a wide range of values oscillating between 36-80 dBA [21–25]. The results of our study show that the noise levels in NICU at HJRJ fall within a similar range. However, our study recorded maximum values that exceeded those of other researchers, at 80 dBA in LAeq,10 min averages. The equivalent sound level in other studies has a broader range (between 40 and 90 dBA) than the one recorded in our study (between 48.8 and 72.2 dBA), and with an integrated hourly average of LAeq,24 h noise of 64.5 dBA, which easily surpasses international standards and recommendations for newborns in NICU [13, 14]: LAeq,1 h = 45 dBA, L10 (hourly) = 50 dBA and Lmáx = 65 dBA, which is a considerable problem that remains unresolved [29, 30].
The behavior of the hourly noise level in our study is consistent with that of Mackenzie , who established that the level of noise increased as the working day progressed and decreased in the afternoon. This is in accordance with Argote et al.  and Brandán et al.  who stated that noise levels rise at those times when the ward is cleaned in the mornings, and when relatives visit in the afternoons. Another characteristic that influences noise level relates to the health care work performed by personnel in shifts, with the night shift (22:00 – 08:00) showing the lowest levels and the morning and afternoon shifts registering the highest values, which is in line with various other studies [20–26].
This study has demonstrated the high levels of noise pollution that newborns and health professionals are exposed to in NICU. Noise varies according to the shift, with levels at their highest during the morning and falling substantially at night. The critical care unit endures the highest noise levels. Measures to reduce these high noise levels in NICU include sound insulation (design, walls, closed doors with silent locking), drawing up an preventative maintenance equipment programme, placing the newborn as far as possible from machines, which could also be removed from the ward (fridges, computers, medical case history trolleys, etc). It would be advisable to raise awareness among personnel of the noise they make during work, and achieve a gradual decrease in the noise emanating from alarms to acceptable levels. Also needed is a reduction in conversational noise among personnel and visitors to the wards, which could be achieved by hanging the appropriate warning signs in these areas. In addition, it would be needed to develop a guideline for noise mitigation, and educational preparation of the staff and patient’s visitors with the implementation of protocols and to assess the progress.
We would like to thank Dr Ricardo Hernández of the University of Cádiz for his support in obtaining the equipment and technical support necessary for this study, and Dr José Ceballos, Director of the Pediatrics Department at HJRJ, for allowing us to use its installations for our research.
- Brandon DH, Ryan DJ, Barnes AH: Effect of environmental changes on noise in the NICU. Adv Neonatal Care 2008, 8(5):S5-S10.View ArticleGoogle Scholar
- Pinheiro EM, Guinsburg R, Nabuco MA, Kakehashi TY: Noise at the neonatal intensive care unit and inside the incubator. Rev Lat Am Enfermagem 2011, 19(5):1214–1221.View ArticleGoogle Scholar
- Bahadori RS, Bohne BA: Adverse effects of noise on hearing. Am Fam Physician 1993, 47(5):1219–1230.Google Scholar
- Bremmer P, Byers JF, Kiehl E: Noise and the premature infant: physiological effects and practice implications. J Obstet Gynecol Neonatal Nurs 2003, 32: 447–454.View ArticleGoogle Scholar
- Miller RW, Brendel WB, Brent RL, Chisholm JJ Jr, Doyle JL, Ebbin AJ, Knutti SH: Noise pollution: neonatal aspects. Pediatrics 1974, 54: 476–479.Google Scholar
- Morris BH, Philbin MK, Bose C: The full-term and premature newborn: physiological effects of sound on the newborn. J Perinatol 2000, 20: S54-S59.View ArticleGoogle Scholar
- Slevin M, Farrington N, Duffy G, Daly L, Murphy JF: Altering the NICU and measuring infants’ responses. Acta Paediatr 2000, 89: 577–581.View ArticleGoogle Scholar
- Passchier-Vermeer W: Noise and Health of Children. Leiden: TNO Prevention and Health; 2000:17–19.Google Scholar
- Falk SA, Woods N: Hospital noise: levels and potential health hazards. N Engl J Med 1973, 289: 774–781.View ArticleGoogle Scholar
- Bentley S, Murphy F, Dudley H: Perceived noise in a surgical ward and an intensive care unit: an objective analysis. Br Med J 1977, 2: 1503–1506. doi:10.1136/bmj.2.6101.1503View ArticleGoogle Scholar
- Hilton BA: Noise in acute patient care areas. Res Nurs Health 1985, 8: 283–291. doi:10.1002/nur.4770080311View ArticleGoogle Scholar
- Busch-Vishniac I, West JE, Barnhill C, Hunter T, Orellana D, Chivukula R: Noise levels in John Hopkins Hospital. J Acoust Soc Am 2005, 118: 3629–3645. doi:10.1121/1.2118327View ArticleGoogle Scholar
- World Health Organisation WHO: Community Noise- Environmental Health Criteria Document, External Review Draft. Geneva: WHO Publishing; 2002.Google Scholar
- American Academy of Pedriatrics AAP Committee on Environmental Health: Noise: a hazard for the fetus and newborn. Pediatrics 1997, 100: 724–727. doi:10.1542/peds.100.4.724View ArticleGoogle Scholar
- Byers JF, Waugh WR, Lowman LB: Sound level exposure of high-risk infants in different environmental conditions. Neonatal Network 2006, 25(1):25–32.View ArticleGoogle Scholar
- García del Río M, Sánchez Luna M, Doménech Martínez E, Izquierdo Macián I, López Herrera MC, Losada Martínez A, Perapoch López J: Revisión de los estándares y recomendaciones para el diseño de una unidad de neonatología, 2007. An Pediatr 2007, 67: 594–602. doi:10.1016/S1695–4033(07)70810-XView ArticleGoogle Scholar
- Fernández P, Cruz N: Noise effects in neonatal hospital environment. Ciencia &Trabajo 2006, 20: 65–73.Google Scholar
- Desteban Alonso A: Noise pollution and health. Observatorio Medioambiental 2003, 6: 73–95.Google Scholar
- Wickström G, Bendix T: The “Hawthorne effect” – what did the original Hawthorne studies actually show? Scand J Work Environ Health 2000, 26: 363–367.View ArticleGoogle Scholar
- Blomkvist V, Eriksen C, Theorell T, Ulrich R, Rasmanis G: Acoustics and psychosocial environment in intensive coronary care. Occup Environ Med 2005, 62: 318–323. doi:10.1136/oem.2004.017632View ArticleGoogle Scholar
- Christensen M: Noise levels in a general intensive care unit: a descriptive study. Nurs Crit Care 2007, 12: 188–197. doi:10.1111/j.1478–5153.2007.00229.xView ArticleGoogle Scholar
- Brandán R, Halloy N, Sanchez M, Sappia L, Sueldo J, Rocha L, Herrera M, Rotget V, Olivera J: Contaminación Acústica en salas de neonatología. XVII Congreso argentino de bioingeniería web. Accessed January 25, (2013) http://rosario2009.sabi.org.ar/uploadarchivos/p100.pdf
- Lasky R, William A: Noise and light exposures for extremely low birth weight newborns during their stay in the neonatal intensive care unit. Pediatrics 2009, 123: 540–546. doi:10.1542/peds.2007–3418View ArticleGoogle Scholar
- Argote LA, Fajardo DL, Gallego SY: Niveles de ruido en la unidad de cuidados intensivos neonatal «CIRENA» del Hospital Universitario del Valle, Cali, Colombia. Colombia Medica 2007, 38: 64–71.Google Scholar
- Centeno D, Apac A, Sánchez J, Raffo M, Centeno C: Niveles de ruido y fuentes asociadas en una unidad de cuidados intensivos neonatal. Revista peruana de pediatría 2005, 58: 12–14.Google Scholar
- Christensen M: Noise levels in a general surgical ward: a descriptive study. J Clin Nurs 2005, 14: 156–164. doi:10.1111/j.1365–2702.2004.01040.xView ArticleGoogle Scholar
- Maxwell-Armstrong C, Mclaren E: Noise pollution on an acute surgical ward. Ann R Coll Surg Engl 2008, 90: 136–139. doi:10.1308/003588408X261582View ArticleGoogle Scholar
- Álvarez AA, Terrón A, Boschi C, Gómez M: Review of noise in neonatal intensive care units- regional analysis. J Phys Conf Ser 2007, 90: 1–6. doi:10.1088/1742–6596/90/1/012038Google Scholar
- Berg AL, Chavez CT, Serpanos YC: Monitoring noise levels in a tertiary neonatal intensive care unit. Contemp Issues Commun Sci Disord 2010, 37: 69–72.Google Scholar
- Jousselme C, Vialet R, Jouve E, Lagier P, Martin C, Michel F: Efficacy and mode of action of a noise-sensor light alarm to decrease noise in the pediatric intensive care unit: a prospective, randomized study. Pediatr Crit Care Med 2011, 12(2):69–72.View ArticleGoogle Scholar
- MacKenzie DJ, Galbrun DL: Noise levels and noise sources in acute care hospital wards. Building Serv Eng Res Technol 2007, 28: 117–131. doi:10.1177/0143624406074468View ArticleGoogle Scholar
- Pelton HK, Ryherd E, Martin M: Acoustical design of a burn acute care unit for enhanced patient comfort. Noise Contr Eng J 2009, 57(1):32–41.View ArticleGoogle Scholar
- Philbin MK, Evans JB: Standards for the acoustic environment of the newborn ICU. J Perinatol 2006, 26: S27-S30.View ArticleGoogle Scholar
- Philbin MK: Planning the acoustic environment of a neonatal intensive care unit. Clin Perinatol 2004, 31: 331–352.View ArticleGoogle Scholar
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