Care quality in neonatology has acquired an increasingly relevant role in the latest years for most pediatricians [1]. Noise pollution in neonatal intensive care units (NICU) is a sensitive matter to pediatric entities and doctors, being a medical study target in several articles [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16]. These studies show that the measured noise levels are excessive in most cases. Their aim is to diagnose the environmental noise source as well as various remedies for that excessive noise. The World Health Organization (WHO), in some instances, may qualify it as noise pollution. Noise level studies in pediatric newborn units (NU), which are more prevalent than in NICUs, are also available and conclude the same [17,18]. Some researchers have examined noise in NICUs or nursing homes, but all these studies focus on noise and not on vibrations, with the assessment of frequencies between 100 Hz and 5000 Hz. In terms of sound analysis, in some studies, noise levels were estimated to range between 60 dB (A-weighted) and 73.5 dB (linear) [19]. Other studies set the levels at an average of 56 dB [20]. These data are above recommendations made by the American Academy of Pediatrics (AAP), remarking that the noise must not remain above 45 dB for more than one hour, to be not above 50 dB for more than 10% of the measured time, and there should not be peaks above 65 dB [16]. An optimized design could reduce the sound exposure of the newborn [21]. A difference of +8 dBA has been found when comparing the inside and outside of the incubator [16], especially when using respiratory equipment [20], these facts are supported by studies that question the quality of the isolation of the incubators, establishing high levels of reverberation above the noise at almost all frequencies [22]. Sounds produced from the inside of the incubator create a reverberation effect that amplifies in 2 to 4 dB several measured sounds such as the baby cry or opening and closing of portholes [23]. The infant’s characteristics, the room, the number of medical devices, as well as visits and the level of workload also affect the amount of sound. As an example, preterm infants, although being the most fragile, are often exposed to louder exterior sounds than term-born neonates. Private rooms, low sound-level equipment, and sound-absorbing materials might contribute to the solution to this problem [16].

From the perspective of acoustic engineering, what is being assessed is the sound pressure level or airborne noise. By definition, noise pollution is “environmental vibration or noise, whatever its acoustic origin, which disturbs, endangers or damages people, their activities or property of any kind, or which has a significant negative effect on the environment,” according to environmental commissioners from EU member states [24]. A distinction must be made in the field of acoustics: airborne noise and vibrations. They are distinguished from each other by frequency. The human ear cannot detect waves outside the range of 20 Hz–20 KHz. Waves from 0 Hz to 80–100 Hz should be considered vibrations. Thus, it is undeniable that noise pollution includes both vibration and noise. The major distinction between them is that vibration is felt in the body as opposed to being heard as a noise. Generally speaking, waves with low frequencies are vibrations, and waves with medium-high frequencies are known as airborne noise. Each of their frequency spectra are clearly defined. The Spanish National Institute for Safety and Health at Work determines that, in health prevention, the vibrations that are of interest due to the effects they have on the organism are those with frequencies between 1 and 1500 Hz [25]. Some researchers are focusing on how frequencies between 20 Hz and 80 Hz are perceived, because this range has a major impact on health [26]. Only solids can produce vibrations and present a high percentage of transmission.

The International Standard ISO 2631-2: 2003 [26] issues a warning about the complexity of the physiological reaction to vibration. Regarding vibrations’ negative effects on health, it states that “biodynamic research studies, as well as epidemiological ones, showed indications of an increased risk of health deterioration caused by sustained exposure to vibration.” It also highlights the insufficient information to provide a quantifiable relation between WBV exposure in terms of the probability of the risk depending on several magnitudes and durations of exposure. A Royal Decree [27] in Spain, which approves the list of work-related illnesses covered by the Social Security System, lists among the illnesses brought on by exposure to vibration “Musculoskeletal or cerebrovascular diseases induced by mechanical vibration” or “disorders of the lumbar spine provoked by repeated whole-body vibration”. Acute health impacts from whole-body vibration exposure include pain, disruption of daily activities, changes in physiological functions, neuromuscular, cardiovascular, endocrine, and metabolic systems, as well as sensory disturbances of the central nervous system.

Regarding acoustic zoning, quality goals, and acoustic emissions, one must consider the restrictions set out by Law 37/2003 on 17 November 2003, as well as Royal Decree 1367/2007 [27,28]. The introduction of this act intends to stop, track, and lower the country’s levels of vibroacoustic pollution. The following restriction values are suggested [28,29] in order to meet the European aim of reducing noise pollution.

According to Table 1, legislation requires recorded Law index levels in the health sector to be less than 72 dB with a 5 dB safety buffer. This Law index is useful to estimate the maximum vibration values during the assessment of the interior of buildings.

Presently, it is nearly impossible for anyone to avoid being exposed to vibration. Research and documentation on vibrational negative effects on people have been conducted all around the world. Regarding the biological impacts, exposure might result in significant differences across people. The lumbar spine and its surrounding nerve system are frequently impacted by this exposure. Peripheral veins, the cochleo-vestibular system, the gastrointestinal system, female reproductive organs, and the neck-shoulder region have all been emphasized in other studies [30,31,32]. The effects are difficult to assess and mainly rely on the vibration’s amplitude, frequency, duration, direction, and body part affected. Most of these studies focus on workers who are subjected to prolonged vibration from the equipment and the vehicles used at work, and all have come to the same conclusion: exposure can induce loss of balance, fatigue, discomfort, lack of attention, and even health hazards, including potential damage to some organs when subjected to certain frequencies or amplitudes. In the case of newborns, whole-body vibration is also related to reduced heart rate variability, a marker of sympathetic regulation and high levels of stress [33]. Vibrations might alter the development of hearing and language, also generating disorders in blood pressure, oxygenation, respiratory rate, and sleep. Preterm infants, which are still in earlier stages of development, might be more affected by these disorders [16]. There is a lot of research to be done about the impact of vibrations on a neonate, because most of the research focuses on the detection of vibrations in buildings or workplaces, and there is very little accessible information about the vibrations detected in pediatric contexts [34,35].

Regarding the research on vibrations in the pediatric area, there are studies on vibrations during pregnancy [30], but there is a knowledge gap in neonatal patients. Limited studies have concentrated on the amount of vibration experienced during the transportation of neonatal patients, both by ground (ambulance) and air (helicopter) [36,37,38,39,40], as a cause of morbidity [36,39,41], most concluded that noise exposure during neonatal transport exceeds the published recommendations and neonates are subjected to vibration levels that are higher than acceptable norms for adults. Moreover, some reports have shown an increased rate of death and morbidity after the transportation of preterm neonates [40]. The possible link between brain damage in preterm infants and neonatal transport raises the issue of potential risks from environmental exposure, including vibrations, the translational forces, and rotational moments of inertia during transport, but the exposure to vibration of neonates during hospitalization has been seldom studied. Although the functional auditory and vestibular systems of a newborn are functional at the 28th gestational week, the mechanisms that adapt and habituate the child to sensory stimuli are not completely developed. Therefore, the newborn is unable to adapt to changes in sensory input. Additionally, until 32 to 34 weeks postmenstrual age, preterm newborns are less able to coordinate their autonomic and self-regulatory responses to deal with the stress brought on by external disruptions. Unfortunately, there are no specific legal limitations for any pediatric age.