High-risk neonates are newborns who are at serious risk due to their own physiological defects or pathological changes, or due to high-risk factors during maternal pregnancy. The NICU is a full-care management ward with advanced medical and technical equipment in the neonatal department. The purpose is to provide a safe, comfortable, simple and hygienic medical environment for high-risk newborns, accompanied by doctors and nurses 24 hours a day, and the living and eating supplies of the children are provided by their families after admission. However, in the NICU, there are many cases where the infant is not well fed. However, in the NICU, there are some unfavorable factors such as noise generated by treatment and care, which have unpredictable effects on the development and later rehabilitation of high-risk neonates who need to receive long-term treatment in the NICU. 1, NICU noise characteristics Noise is the sound emitted by the occurrence of irregular vibration, all sounds that prevent people from resting, learning and working normally, as well as sounds that interfere with the sounds that people want to hear can be classified as noise. NICU’s noise is mostly broadband noise, which is a combination of different frequencies and has the characteristics of wide range and high sudden volume. And the summary of recent studies shows that most of the sounds in the NICU environment fluctuate around 50 to 140 decibels. In 1997, the American Academy of Pediatrics Committee on the Environment recommended that the safest sound level in the NICU was below 45 db. In 2002, the American Board of Environmental Investigation recommended a sound level of below 50 db for the NICU environment, with a sudden sound level of no more than 75 db. The fifth U.S. neonatal intensive care unit design report proposed that: it is recommended that the NICU continuous noise be limited to ≤50 dB (A) and the burst noise be limited to ≤55 dB (A), and there is no domestic standard or recommendation in this regard. If the sound level cannot be maintained below the above-mentioned safest level, it will lead to a large number of high-risk newborns affecting their health due to noise. 2, NICU noise sources NICU noise comes from the noise of instruments and equipment, including the sound of newborn incubators, monitors, ventilators, suction machines, infusion pumps and other instruments working and alarming, the sound of crying newborns, the sound of the telephone at the nursing station, the sound of medical and nursing staff activities and operation treatment, etc., and the noise brought by medical and nursing staff is the main source of noise. Noise decibel value of neonatal care room 45dB 50dB 55dB 60dB 65dB 70dB 75dB 80dB 85dB 95dB Routine noise in neonatal incubator Nurse bedside shift Moving chairs, cries of other neonates Carefully closing the panel door of neonatal incubator Loud talking, coughing, monitor alarm Neonatal incubator alarm, closing medicine cabinet Closing the panel door of neonatal incubator Roughly closing the panel door of the incubator, talking in the newborn’s ear, laughing, unintentionally bumping into the incubator, placing bottles and other objects on top of the incubator, crying in the incubator 2.1 Health care workers There is a large body of literature on physical sources of noise in the NICU environment. relatively little has been reported on the noise generated by health care staff during treatment and care behaviors. It has been suggested that staff conversations and behaviors can increase ambient noise levels by 10 to 20 decibels. Because of the high base sound level in the NICU environment, health care workers’ voices are involuntarily raised when they talk, and therefore the noise level in the NICU increases. During medical and nursing operations, medical and nursing staff open and close the incubator door and ward door with force, bump the incubator and other hard objects or drop them on the floor, throw garbage, place hard objects such as medicine bottles or milk bottles on the top of the incubator, wash hands with too much water in the NICU, knock the incubator with force when the premature infant is in respiratory arrest, and fail to respond in time to various instrument alarms and crying noises of newborns, etc. all lead to various noises. Some staff forget to turn on the cell phone to mute also cause sudden environmental noise. 2.2 Instruments and equipment in the NICU Over the past few decades, great progress has been made in emergency and medical technology for high-risk newborns. However, with the invention of various new equipment, the NICU has also gradually become a noise-filled place. Most of the sounds that occur during normal use and alarm of many therapeutic instruments exceed the safest sound levels in the NICU, such as neonatal incubators, monitors, ventilators, suction machines, infusion pumps, etc. 2.3 Cries of newborns In fact, newborns on do not respond to their own cries, but show symptoms of distress to the cries of other newborns and cry with them, which is known as the most basic expression of emotional contact in early life. 3. The effect of NICU noise on high-risk newborns Studies have shown that high-risk newborns who have been treated in the NICU may have a different level of brain maturation than normal newborns. Damage to high-risk newborns from higher noise levels includes: changes in respiratory rhythm, such as apnea or shortness of breath; changes in heart rhythm, such as bradycardia or tachycardia; and changes in blood pressure and oxygen saturation. Long-term effects include potential reduction in growth hormone; increased risk of hearing loss; inattention, learning disabilities, and emotional disturbances due to attention deficit hyperactivity. 3.1 Hearing impairment of high-risk neonates by NICU noise The development of the human auditory system begins in utero, and it has been shown that the fetus begins to respond significantly to sound at 23 weeks of gestation. As the embryo develops, the auditory system matures until the newborn is born, during which time the full-term infant has acquired at least 15-17 weeks of hearing experience. Thus, the infant’s sensitivity to noise is gradually established from 23 weeks of gestation until a fixed threshold is reached 2-3 months after birth. High-risk neonates, especially premature infants, are more susceptible to environmental noise because of their immaturity. Continued exposure to instrument alarms, incubator noises, medical and nursing sounds, and sudden noises make preterm infants more susceptible to sensorineural hearing loss than full-term and non-custodial care newborns. The American Board of Neonatal Hearing states that noise in the NICU is the most significant physical contaminant. The American Academy of Pediatrics Committee on Environmental Health has cited numerous studies demonstrating that continuous exposure of preterm infants to NICU noise can lead to noise-induced hearing impairment, primarily in the form of abnormal development of sound frequency discrimination. Because in a noisy environment, the width of the newborn’s ear to receive sound is actually greatly increased so that they will not be able to discriminate sound frequencies as children or adults. Noise and these potential ototoxic factors have a synergistic effect when aminoglycosides have to be administered. Foreign literature reports a 20-40% incidence of hearing loss in newborns in the NICU. Sun et al. reported a 40% incidence of hearing impairment in critically ill and high-risk infants receiving mechanical ventilation in the NICU. Li, Wei-Guang et al. found that the incidence of hearing loss in high-risk infants treated with ventilators and control infants without earmuffs to isolate noise was 5% higher than the high limit reported abroad. roizen concluded that NICU noise is one of the high-risk factors for the development of deafness based on the results of research in the NICU. grote, J. J study pointed out that unless high-risk neonates are screened earlier in the neonatal period and receive treatment before 6 months of age, it causes a severe lack of excitatory effects on relevant auditory mechanisms and allows for inadequate or slow development of language skills that play a very important role in the developmental refinement of psychological, social and other important behaviors. 3.2 Effects of NICU noise on the physiological and behavioral responses of high-risk neonates Studies have found that loud noise in the NICU can significantly alter the behavioral and physiological responses of neonates. Prolonged exposure to high intensity noise in the NICU can reduce the developmental level of physiological and behavioral aspects of newborns. Bursts of noise can produce a fear response mediated by a subcortical stimulus response system, a catecholamine-mediated reflex and a hormonal regulatory system, and have an effect on the respiratory system. High-intensity noise generated by alarms, ringing telephones, high staff speech, or other infant cries can cause a significant decrease in oxygen saturation and a transient increase in heart rate in high-risk neonates, manifesting as excitement, crying, and sleep disturbances; it can also affect the already unstable physiological balance of high-risk neonates, causing behavioral changes from a quiet state to a state of fear. Gerhardt KJ [19] et al. found that when all newborns were given an auditory stimulus in a quiet environment in the basal state, they showed a significant behavioral response. Their behavior was disturbed and restless long after the stimulus disappeared, and they were unable to return to their initial quiet state. High-risk neonates are particularly vulnerable, as numerous factors affect their central nervous system making them less capable of autoregulating to deal with stress and unable to selectively limit or prevent the intrusion of noise stimuli and other noxious stimuli from having a significant impact on physiological homeostasis. 3.3 Effects of NICU noise on sleep in high-risk neonates High-decibel and high-frequency noise can cause physiological changes during sleep in neonates, such as increased heart rate, pauses or increased respiration, and transient decreases in blood oxygen levels. These changes affect the sleep of newborns, whether they are awakened by noise stimulation or forced to alter their sleep state, putting at-risk newborns under additional stress and loss of already insufficient sleep time. However, as far as sleep rhythms are concerned, there are no monitoring methods available for research that do not disrupt the sleep of the neonates themselves. 3.4 Effects of NICU noise on the humoral system of high-risk neonates The prolonged awakening time of neonates caused by environmental noise in the NICU and the consequent crying and noise are potential causes of neonatal disease and hypoxemia. Fluctuations in arterial oxygen pressure, blood pressure and intracranial pressure can lead to hypoxic brain injury; decreased oxygen saturation may affect normal growth and development of vital organs and metabolism. Some studies have shown that newborns may experience numerous severe effects of noise if they stay in the NICU during their rapid brain development, with potential outcomes including increased cerebrovascular fragility. 3.5 Effects of NICU noise on auditory and emotional development of high-risk neonates Recent studies have shown that stimuli generated by the auditory environment play an important role in the emotional and auditory development of neonates, for example, affectionate conversation with the neonate and other beneficial sounds can have a positive effect on the developmental promotion and recovery of high-risk neonates. The female voice, especially the mother’s voice, and soft voices enhance the newborn’s physiological response and promote growth. However, the environmental noise in the NICU reduces the quality of sound that is beneficial to the at-risk newborn, resulting in difficulty in distinguishing the mother’s voice from that of the caregiver in the early stages of home care, with the resultant impairment of the newborn’s emotional development later in life. 4. Proactive noise reduction measures that can be taken by NICU health care workers Although the noise in the NICU environment cannot be effectively controlled because of the different instruments that must be used to keep the NICU high-risk newborns alive and some human factors, many ways to reduce noise levels in the NICU have been identified so far. Raising awareness of health care workers about the dangers of noise to newborns and teaching them that their inappropriate behavior can increase the noise level in the NICU environment can effectively reduce the NICU noise level. 4.1 Improve the environment and layout of NICU Lay flooring or floor cloths or carpets on the floor of NICU to reduce the sound made by staff walking; set the hand washing sink in the non-medical operation area and turn on the water as little as possible when washing hands to reduce the impact of the sound of running water; use plastic garbage cans to separate medical and domestic garbage and throw garbage at close range to avoid noise from collision; turn the sound of telephone ringing Use plastic garbage cans to separate medical and household garbage and throw garbage close together to avoid noise from collisions; turn down the telephone and place the telephone away from the bed at the nursing station; post signs on the side of the crib and outside of the incubator to keep it quiet. For example, I am asleep; please don’t wake me up, etc. In addition, a study by Hsin-Li Chen et al. in Taiwan suggested that separating each incubator placed in an open space in the NICU with wooden boards could make the noise inside the incubator decrease significantly. 4.2 Clinical interventions by medical staff 4.2.1 Alarm sounds The alarm sounds generated by various instruments in the monitoring room are one of the most important sources of environmental noise. However, if staff respond quickly to alarms and reduce them as much as possible, and turn off the alarm sounds before performing operations that may cause instrument alarms (e.g., the ventilator alarm can be turned off in advance during aspiration), the frequency of the alarm sounds can be greatly reduced thereby reducing The frequency of alarms can be greatly reduced, thus reducing their adverse effects. Responding promptly to a crying baby and soothing, feeding, changing diapers, or repositioning the baby can reduce the impact of crying on other newborns. 4.2.3 Behavior of medical and nursing staff Before entering the NICU, change soft-soled slippers in strict accordance with the requirements and walk with heels on the ground first; turn on the cell phone to the vibrate or silent position; avoid talking loudly at the bedside of the baby and writing, placing objects on the top of the incubator or hitting the incubator with force; perform nursing operations gently and concentrate on operations as much as possible to reduce opening and closing of the incubator door; press the spring buckle of the incubator door before closing it to reduce the impact of closing the incubator. The spring buckle of the incubator door can be pressed to reduce the sound from the door of the incubator. 4.2.4 Selection of equipment and instruments When purchasing or upgrading equipment, attention should be paid to the sound control of the instruments and try to select equipment and instruments that produce lower levels of noise. 4.3 Several simple settings for noise reduction 4.3.1 Soundproof earmuffs Neonatal soundproof earmuffs, which protect the sensitive ears of at-risk neonates in noisy environments and provide a more tranquil environment, can reduce the noise level of the surrounding environment by about 7 dB and reduce the sound pressure by about 50%, resulting in fewer behavioral state changes and thus prolonging the sleep time of neonates. 4.3.2 Floppy hats In addition to wearing ear muffs, another effective measure for unavoidable noise is to reduce persistent, repetitive noise (e.g., sounds from a ventilator) by putting a hat on the newborn. 4.3.3 Covering the incubator with a small sheet The Saunders study showed that partially covering the outer walls of the incubator with a small sheet prevented noise from outside the incubator from penetrating the glass walls and affecting the neonate, and this method reduced the noise level inside the incubator by about 4.8 dB. 4.3.4 Sound absorbing devices Many relevant studies have now proposed many ways to protect newborns in the NICU from noise, while the higher noise level inside the incubator, mainly due to crying and noise of newborns, has been less noticed. In contrast, recent studies have pointed out that the sound pressure level of sudden noise in open spaces is less than that of sudden noise in closed spaces. Therefore, the installation of sound absorption devices in the newborn incubator is not a simple and feasible solution. In a study by E. Altuncu et al. in Turkey, the measured ambient base noise was reduced from 56 dB to 47 dB, the noise of the incubator temperature alarm was reduced from 82 dB to 72 dB, the noise of the monitor alarm was reduced from 64 dB to 56 dB, and the noise of the closed incubator door was reduced from 80 dB to At the same time, the neonate’s own cries were reduced from 79dB to 69dB. 5. Summary The noise in the NICU is distinctive, has a wide range of sources, and has a real long-term impact on high-risk neonates. On the one hand, constant, repetitive, high-intensity noise stimulation can hinder the physiological homeostasis of high-risk newborns and have serious long-term effects on them; in addition, it may increase their morbidity and mortality. On the other hand, the noise environment is one of the negative factors on the communication and work efficiency of health care staff, thus making the treatment of high-risk newborns suffer from secondary effects. Therefore, medical and nursing staff should thoroughly and correctly assess the noise level in the NICU environment and look for sources of noise, and achieve the goal of reducing the noise level in the NICU by consciously improving the NICU environment and their own behavior.