Division of Pulmonary and Critical Care Medicine and Division of Medical and Experimental Ultrasound, Eastern Virginia Medical School, Norfolk, VA, USA.
Pediatr Crit Care Med. 2012 Nov;13(6):685-9. doi: 10.1097/PCC.0b013e31824ea2b7.
High sound pressure levels may be harmful to the maturing newborn. Current guidelines suggest that the sound pressure levels within a neonatal intensive care unit should not exceed 45 dB(A). It is likely that environmental noise as well as the noise generated by the incubator fan and respiratory equipment may contribute to the total sound pressure levels. Knowledge of the contribution of each component and source is important to develop effective strategies to reduce noise within the incubator.
The objectives of this study were to determine the sound levels, sound spectra, and major sources of sound within a modern neonatal incubator (Giraffe Omnibed; GE Healthcare, Helsinki, Finland) using a sound simulation study to replicate the conditions of a preterm infant undergoing high-frequency jet ventilation (Life Pulse, Bunnell, UT).
Using advanced sound data acquisition and signal processing equipment, we measured and analyzed the sound level at a dummy infant's ear and at the head level outside the enclosure. The sound data time histories were digitally acquired and processed using a digital Fast Fourier Transform algorithm to provide spectra of the sound and cumulative sound pressure levels (dBA). The simulation was done with the incubator cooling fan and ventilator switched on or off. In addition, tests were carried out with the enclosure sides closed and hood down and then with the enclosure sides open and the hood up to determine the importance of interior incubator reverberance on the interior sound levels
With all the equipment off and the hood down, the sound pressure levels were 53 dB(A) inside the incubator. The sound pressure levels increased to 68 dB(A) with all equipment switched on (approximately 10 times louder than recommended). The sound intensity was 6.0 × 10(-8) watts/m(2); this sound level is roughly comparable with that generated by a kitchen exhaust fan on high. Turning the ventilator off reduced the overall sound pressure levels to 64 dB(A) and the sound pressure levels in the low-frequency band of 0 to 100 Hz were reduced by 10 dB(A). The incubator fan generated tones at 200, 400, and 600 Hz that raised the sound level by approximately 2 dB(A)-3 dB(A). Opening the enclosure (with all equipment turned on) reduced the sound levels above 50 Hz by reducing the revereberance within the enclosure.
The sound levels, especially at low frequencies, within a modern incubator may reach levels that are likely to be harmful to the developing newborn. Much of the noise is at low frequencies and thus difficult to reduce by conventional means. Therefore, advanced forms of noise control are needed to address this issue.
高强度的声压可能对发育中的新生儿有害。目前的指南建议新生儿重症监护病房内的声压级不应超过 45dB(A)。环境噪声以及培养箱风扇和呼吸设备产生的噪声可能会导致总声压级升高。了解每个组件和来源的贡献对于制定降低培养箱内噪声的有效策略非常重要。
本研究的目的是使用模拟研究确定现代新生儿培养箱（GE 医疗保健公司的长颈鹿 Omnibed；芬兰赫尔辛基）内的声级、声谱和主要声源，该研究模拟了接受高频喷射通气的早产儿的情况（Life Pulse，Bunnell，UT）。
使用先进的声音数据采集和信号处理设备，我们在模拟婴儿的耳朵处和外壳外的头部水平处测量和分析了声级。使用数字快速傅里叶变换算法对声音数据时间历史进行数字采集和处理，以提供声音的频谱和累积声压级（dBA）。在培养箱冷却风扇和通风机开启或关闭的情况下进行了模拟。此外，还进行了外壳侧面关闭且罩子放下以及外壳侧面打开且罩子升起的测试，以确定培养箱内部混响对内部声级的重要性。
当所有设备关闭且罩子放下时，培养箱内的声压级为 53dB(A)。当所有设备开启时（大约比推荐值高 10 倍），声压级增加到 68dB(A)。声强为 6.0×10(-8)瓦/米(2)；该声级大致与高转速厨房排气扇产生的声级相当。关闭通风机会将总声压级降低到 64dB(A)，并将 0 到 100Hz 的低频带的声压级降低 10dB(A)。培养箱风扇产生 200、400 和 600Hz 的音调，使声级升高约 2dB(A)-3dB(A)。打开外壳（所有设备都打开）通过减少外壳内的混响降低了 50Hz 以上的声级。
现代培养箱内的声级，尤其是低频声级，可能达到对发育中新生儿有害的水平。大部分噪声处于低频，因此很难通过传统方法降低。因此，需要采用先进的噪声控制形式来解决这个问题。
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