Noise In The NICU: How Sound Affects Premature Babies - Caregiver’s hand rests on premature baby in the NICU

Noise In The NICU: How Sound Affects Premature Babies

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Noise has a number of negative effects on premature babies, including hearing damage and developmental delays. Nevertheless, the noise level in many NICUs is still too high. Noises that are loud or that have a high frequency, such as clatter from metal objects or alarms, are especially harmful. Measures to reduce noise in the NICU are therefore essential. These measures could include behavioural changes such as speaking more quietly and turning down the volume settings on alarms. However, there are also some beneficial sounds that babies do respond well to – like the mother’s heartbeat and voice. So when is loud too loud? What is negative noise and what is a healthy stimulus?

What are the negative effects of noise on premature babies?

Premature baby rests in the NICU

Noise intervenes with a baby’s development

The extent to which noise exposure has an effect on babies has crept into ever increasing focus in neonatal research in recent years. It is now known that excessively loud noise can have a negative impact on parameters such as blood pressure, breathing, heart beat and oxygen saturation. Sleep is interrupted, which in turn impedes development. The stress also increases energy consumption, which means that fewer calories go towards growth. Even in the long term, noise plays a role: the risks of hearing damage, developmental delays, periventricular leukomalacia and bleeding increase with a continuously high noise level.1,2

Nurse works in the NICU

Noise affects caregivers, too

In addition to risks to the baby, noise also affects people caring for the baby. A high noise level is associated with a higher error and accident rate and a generally lower standard of performance. A low noise level is therefore not only directly beneficial for a baby's development, but also indirectly beneficial in that it increases a caregiver’s ability to concentrate and deliver the best care possible to the newborns.

What’s important when assessing the noise environment?

Everyday noise

A Swiss-French working group has researched the effects of everyday noise on the development of premature babies' tactile perception.3 Babies were randomly assigned to a loud group and a quiet group, with the noise coming from feeding pump alarms. According to the study, a high noise level not only negatively affects tactile perception but also sensory learning capacity in general. As such, the authors recommend avoiding unnecessary noise in intensive care units to the greatest extent possible, for example by adjusting the alarms on feeding pumps, which typically only indicate the fill level and are not vital.

Noise levels

In spite of these findings, noise is still often excessively loud in the majority of neonatal intensive care units. According to one study, the average NICU noise level throughout the day is Leq = 60.05 dBA and overnight Leq = 58.67 dBA,4 with premature babies exposed to frequencies greater than 500 Hz, 57 percent of the time. Other studies have demonstrated that simple actions often produce extreme levels of noise.5 Simply setting down an object on the incubator or knocking on the incubator can give rise to extreme levels of noise from 74 to 116 dBA, which can be compared to the level of noise produced by a hammer drill.

A side note: understanding noise levels

In contrast to other units of measure, such as distance or weight, noise can’t be measured on a linear scale – but instead logarithmically. For example, an increase in noise level from 100 to 110 decibels does not represent a ten percent increase, but rather a doubling of the decibel level. Looking at it a different way: under certain conditions, a person is even able to detect a one decibel decrease. Noise is sometimes measured in decibels, shortened to dB, and sometimes in dB(A). In these cases, a process known as A-weighting of the frequencies is carried out and the measurement is weighted. This is applied because higher and lower than normal frequencies are perceived as quieter and therefore given a lower weighting.

How can noise be reduced in the NICU?

Caregiver adjusts device in the NICU

Behavioural changes and training

One option could be for employees to carry noise meters in order to raise more self-awareness when carrying out particularly noise-intensive activities. One study which utilised such devices showed a significant increase in the time during which the noise level remained below 50 dB.6 Regular repeat training can help caregivers to remain continually aware of the importance of noise reduction.7 Hospitals should also be encouraged to distribute flyers detailing rules for noise reduction. 

In addition, it can be beneficial to educate caregivers on the negative effects of noise, so that they understand how changes to their behaviour could make a difference. Information about the consequences of noise leads to noise reduction being seen as part of the care process, rather than a burden.

Parent interacts with baby in the NICU

Behavioural measures for noise reduction

Some important points to consider: speak more quietly, do not speak to one another across the room, switch rooms to hold discussions and handle objects with care. Where possible, metal objects like bowls, for example, can be replaced by plastic objects and trash bins can be equipped with sound absorbers. Alarm management on intensive care units should focus on a general avoidance of monitor alarms and other technical noises. Alarms should be set to no louder than 55 dB or switched to vibrate mode. The number of alarms should also be reduced to the absolute minimum required.

Noise Display SoundEar device in use

Additional measures for noise reduction

Behavioural changes can significantly reduce noise levels, but often not enough to reach the National Recommended Safe Sound Level.8 To this end, further measures may need to be taken with regard to the room itself. Some examples include a reduction in echo, erecting sound barriers or separations between individual rooms and even counter-noise measures. 

A less expensive idea is hearing protection for premature babies, which could be used occasionally during busy periods in the NICU. One study observed that the use of hearing protection reduced noise intensity for the babies by 7 dB.9 This study also noted the importance of not re-introducing babies to audio stimulation too abruptly.

Beyond volume: types of sound matter

High-frequency noises

There isn’t absolute silence in the womb. From around week 22, a foetus can discern low frequency noises like blood flow, intestinal activity, the mother's voice and ambient sounds such as music, which can reach levels as high as 85 dB.10 The abdominal wall mutes high frequencies over 200 Hz – while in neonatal units, such noises are common and can occur from things like metal containers, trash bins or loud alarm noises. The ability of an embryo in utero to discern high-frequency noises first develops around week 33 of pregnancy. But such noises in the womb are primarily transmitted through the bones as well as through fluids. Whereas, after birth, noise is transmitted through the air, offering less frequency damping. In addition, the "separating wall" between the embryo and the outside world becomes increasingly thinner as the foetus grows, which exposes the embryo to louder high-frequency noises very gradually. In the event of a premature birth, this gradual adjustment can’t take place, making it all the more essential to avoid loud high-frequency noises in the NICU.11

And then, there’s good noise

Many studies show that premature babies respond well to "good" sounds. For example, prematurely born babies are deprived of the rhythm of their mother’s heartbeat, which could explain why very small babies respond well to music. "The Original Sound" study looked at precisely this aspect.12 The title is the name given to a specifically compiled MP3 file which reproduces sounds like a heart beating, blood flowing through the veins, breathing and other suitable ambient noises. Thirty-four babies were exposed to either these sounds or the normal noises in the intensive care unit for twenty minutes, three times a day. Those babies exposed to the sound file showed a significant reduction in heart rate. This study supports the increasing efforts of music therapists like Haslbeck, who develop supportive measures for premature babies from the 32nd week of gestational age. According to therapy observations, music therapy together with the right care, can promote communication abilities and advance overall development.13

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1 American Academy of Pediatrics, Noise: A Hazard for the Fetus and Newborn. (Stand 13.04.2016)

2 S. Swathi S, Ramesh A, Nagapoornima M et al. Sustaining a “culture of silence” in the neonatal intensive care unit during nonemergency situations: A grounded theory on ensuring adherence to behavioral modification to reduce noise levels. Int J Qual Stud Health Well-being. 2014; 9: 10.3402/qhw.v9.22523. 

3 Lejeune F, Parra J, Berne-Audéoud F et al. Sound Interferes with the Early Tactile Manual Abilities of Preterm Infants, Sci Rep. 2016; 6: 23329.

4 Lahav A1.Questionable sound exposure outside of the womb: frequency analysis of environmental noise in the neonatal intensive care unit. Acta Paediatr. 2015 Jan;104(1):e14- 

5 Thoma R, Fischer C. Lärmexposition des Frühgeborenen im Inkubator auf der neonatologischen Intensivstation. Z Geburtshilfe Neonatol 2007; 211 - PV5 

6 Wang D, Aubertin C, Barrowman N. Reduction of noise in the neonatal intensive care unit using sound-activated noise meters. Arch Dis Child Fetal Neonatal Ed. 2014 Nov;99(6):F515-6. 

7 Swathi S, Ramesh A, Nagapoornima M et Al. Sustaining a “culture of silence” in the neonatal intensive care unit during nonemergency situations: A grounded theory on ensuring adherence to behavioral modification to reduce noise levels Int J Qual Stud Health Well-being. 2014; 9. 

8 Laubach V, Wilhelm P, Carter K. Shhh… I'm growing: noise in the NICU. Nurs Clin North Am. 2014 Sep;49(3):329-44

9 Abdeyazdan Z, Ghassemi S, Marofi M. The effects of earmuff on physiologic and motor responses in premature infants admitted in neonatal intensive care unit Iran J Nurs Midwifery Res. 2014 Mar-Apr; 19(2): 107–112. 

10 Gerhardt KJ., Abrams RM.. Fetal exposures to sound and vibroacoustic stimulation. J Perinatol. 2000;20(8 Pt 2):S21-30 

11 Lahav A, Skoe E. An acoustic gap between the NICU and womb: a potential risk for compromised neuroplasticity of the auditory system in preterm infants. Front Neurosci. 2014; 8: 381. 

12 Tandoi F1, Francescato G2, Pagani A et al. "The Original Sound": a new non-pharmacological approach to the postnatal stress management of preterm infants. J Matern Fetal Neonatal Med. 2015 Nov;28(16):1934-8. 

13 Haslbeck, F: Creative music therapy for premature infants: An analysis of video footage. Nordic Journal of Music Therapy 2013;23(1): 5-.35