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|Year : 2011
: 13 | Issue : 50 | Page
|The sound of operation and the acoustic attenuation of the Ohmeda Medical Giraffe OmniBed TM
Stephanie M Wubben, Paul M Brueggeman, Dennis C Stevens, Carol C Helseth, Kristen Blaschke
Department of Communication Disorders, Center for Disabilities of the Sanford School of Medicine, University of South Dakota, South Dakota, USA
Click here for correspondence address
|Date of Web Publication||15-Dec-2010|
The neonatal intensive care unit (NICU) is an environment that provides premature and fragile infants with health provisions needed to make a complete recovery. Premature infants are often born before their auditory systems have had an opportunity to fully mature. Research has shown that the ambient acoustic environment in the NICU exceeds the maximum noise level recommended by the American Academy of Pediatrics, even after measures have been taken to decrease noise levels. The purpose of this study is to evaluate noise levels inside an Ohmeda Medical Giraffe TM OmniBed TM , the natural attenuation of the incubator, and the effects of modifications on attenuation and reverberation within the Giraffe TM OmniBed TM . The normal operation of the Giraffe TM OmniBed TM is 41.7 dBA which indicates a lower noise of operation than previous studies. The Giraffe TM OmniBed TM naturally attenuates 12 dBA. Leaving an access latch or portal door open causes a statistically significant (P=.001) increase in sound within the bassinet. All modifications in the no-noise and the noise conditions showed a statistically significant (P=.001) drop in Leq when compared to baseline.
Keywords: Neonatal intensive care unit design, prematurity, sound attenuation, dBA
|How to cite this article:|
Wubben SM, Brueggeman PM, Stevens DC, Helseth CC, Blaschke K. The sound of operation and the acoustic attenuation of the Ohmeda Medical Giraffe OmniBed TM. Noise Health 2011;13:37-44
|How to cite this URL:|
Wubben SM, Brueggeman PM, Stevens DC, Helseth CC, Blaschke K. The sound of operation and the acoustic attenuation of the Ohmeda Medical Giraffe OmniBed TM. Noise Health [serial online] 2011 [cited 2013 May 23];13:37-44. Available from: http://www.noiseandhealth.org/text.asp?2011/13/50/37/73999
| Introduction|| |
Noise in the neonatal intensive care unit (NICU) has been recognized as potentially harmful to the developing premature infant. While a fetus first begins to respond to low frequency sounds as early as 19 weeks  the cochlea continues to mature in its response to sound between 24 and 35 weeks gestation with little data available documenting the course of human cochlear development prior to 28 weeks gestation. ,, When infants are born prematurely, their auditory systems are underdeveloped and are not able to adapt to the extrauterine acoustic environment in the same manner as a full-term infant.  Animal studies indicate that the neural components of the auditory system cease to develop normally when they are prematurely exposed to loud noise. 
Premature neonates often remain in the NICU until between 35 and 40 weeks' gestation, while the respiratory, nervous, and auditory systems continue to develop.  In addition to the direct auditory effects of noise, noise also influences the cardiovascular system, the respiratory system, sleep patterns, and stress levels of neonates. When sound intensity is greater than 80 dBA, the heart accelerates causing a stress response. ,
Infants as young as 8 weeks of age can experience apnea or an irregular respiratory pattern when presented with 1 or 2 s of 80 decibels (dB) of white noise, in which all frequencies are equally weighted, on the A-weighted scale (dBA).  Acoustic disturbances have been shown to evoke a crying response from infants in the NICU which may result in decreased blood-oxygen level, increased intracranial pressure, and potentially intracranial hemorrhage. , Multiple stimuli are capable of disturbing an infant's sleep in the NICU. Such disruption may occur as often as 130 times within a day.  In considering such interruptions, half of neonates will awaken following exposure to 75 dBA for 3 min and all will awaken after 12 min of such exposure.  While it is true that the propensity to awaken may vary depending upon the sleep state, this is difficult to measure clinically and was not reported in the above studies. ,
Noise levels in the NICU have been consistently reported between 50 and 90 dBA when average sound equivalents (Leq ) were measured over a period of time. ,, Sources of noise include monitor alarms, incubators, respiratory equipment, crying infants, and hospital staff. Researchers found that the highest intensity of sounds corresponded to the occurrence of physician rounds  and the conversations of other staff, whereas NICU staff perceived that the greatest noise was related to equipment.  Comparisons between traditional NICUs and those that have been updated with acoustic paneling, and in which staff have been educated about the effects of noise, found that the acoustically treated unit was 4 to 6 dBA quieter than the traditional design. Even after measures were taken to decrease noise levels within the NICU, sound-level recordings made at the baby's ear showed that noise levels produced an Leq of approximately 60 dBA. 
In 1974, the American Academy of Pediatrics recommended that manufacturers of incubators reduce the sound level produced by their equipment to less than 58 dBA.  Subsequently, this recommendation for the NICU and incubators has been decreased to 45 dBA.  In 2007, a national consensus committee recommended that hospitals decrease the levels of NICU environmental noise to less than an hourly Leq of 45 dBA.  The use of sound-reducing materials  and the single-family room NICU design  have also been advocated in achieving these sound goals.
Although incubators have vastly improved in recent years, they may still produce noise levels greater than recommended. ,,,,,, Conventional incubators can produce 65 dBA when the built-in fan is running and no other respiratory devices are being used.  Within an incubator, infants themselves can produce sounds as loud as 83 dBA. Noise-absorbing panels within the incubator can decrease internal reverberation. 
Most noise level and sound attenuation studies have evaluated four models of incubators ,,,,,,,, The most widely studied incubator produces between 37 and 43 dBA externally and 50 dBA internally.  When the alarm sounds, the sound level rises to 58 dBA externally and 56 dBA internally. 
The purpose of this research was to explore the operational noise and the sound attenuation capabilities of a relatively new and commonly used neonatal incubator (Ohmeda Medical GiraffeTM OmniBedsTM, GE Healthcare, Waukesha, WI; GOmB). This particular model of incubator was selected for this investigation due its current widespread use in neonatal intensive care units and the investigators' familiarity with its care, use, and operational characteristics. The widespread use of this incubator is because of its ability to function as both a closed incubator and an overhead radiant warmer combined into one unit, thus eliminating the need to replace equipment because of a change in the neonate's clinical condition or care needs. The GOmB also has a variety of features which are quite different than the standard neonatal incubator. These include a bed which swivels and motors for raising and lowering the entire incubator and the top of the incubator while providing radiant warmth for care.
| Methods|| |
The current study involved three parts. First, the noise of operation of the GOmB in air control mode (ACM) and in boost air control mode (BAC) was investigated. ACM is a setting which regulates the temperature inside the GOmB in response to readings from a servo-control sensor inside the compartment wall. ACM is generally regarded as normal operation. BAC is a mechanism by which the fan speed in the GOmB increases to regulate the internal temperature when the door of the GOmB is open for an extended period of time.  The second section of this study investigated the natural attenuation of external sound by the GOmB. The third and final component evaluated the effects that a variety of modifications have on sound attenuation by the GOmB.
These evaluations were performed within an Industrial Acoustics Company sound-treated audiology booth calibrated to ANSI S3.1-1999 standards (Model 404-A, Industrial Acoustics Company, Winchester, England). Sound booth dimensions were 274 × 254 × 195 cm. To provide additional acoustic control, all attenuation recordings were obtained within a quasi-diffuse sound field of 70 dBA pink noise. Pink noise was selected because it has equal energy in each octave frequency. The A-weighted scale was used because it measures sound intensities in a manner which mimics sound perception by the human ear, emphasizing frequencies between 1,000 Hz and 4,000 Hz.  Pink noise was created with Adobe Audition (Adobe Systems, Inc., San Jose, CA) and produced by four matched speakers (Sony SS-B3000, Sony Corporation of America). The speakers were placed on stands with the top of the speaker at 98 cm, a height equal to the center of the mattress of the GOmB and were positioned at the center of each wall, 30 cm from the wall. The signal was produced via a Memorex CD-R (Memorex Products, Inc., Cerritos, CA) produced from an Onkyo Compact Disc Changer (DX.C106, Onkyo USA Corp., Upper Saddle River, NJ). The signal was then transmitted to an Optimus 2-Channel Mixer (Radio Shack Corporation, Fort Worth, TX) pre-amplifier, which served as the volume control, and then to a Harmon/Kardon Amplifier (hk 770 Twin Toroidal Power Ultra Wide Band DC Amplifier, Inc., Woodbury, NY), which allowed for the signal to be routed to the speakers.
Sound measurements were made with a Quest 1900, Sound Level Meter and an OB-100 Octave Filter (Quest Technologies, Oconomowoc, WI). All recordings were obtained in A-weighted frequency scale (dBA) with a slow response time for 5 min intervals.  A slow response time is recommended when human hearing is of interest  because it produces stable readings that averages noise over 1 s intervals.  The sound level meter was calibrated before and after each recording. Noise spikes which occurred during the recordings were removed from the data.
The microphone was placed within the incubator at the geometric center (274 × 253 × 195 cm) of the sound booth and the center of the quasi-diffuse sound field. It was threaded through a tubing access port and placed on a stand 18 cm from the bottom of the incubator and centered between the rear and front sides of the incubator hood.
Octave band measurements and Leq were obtained to ensure that the sound field was within 0.4 of 70 dBA. Signs were also placed around the facility to ensure that only necessary personnel had access to the test site. Measurements were obtained during four separate sessions. Statistical significance was determined by using univariate analysis of variance with post hoc Games-Howell analysis (P<0.05).
Measurement of the noise of operation
All recordings were made at octave bands of 250, 500, 1,000, 2,000, 4,000, 8,000, and 16,000 Hz. Due to size limitations of the sound booth, frequencies ≤ 125 Hz were not assessed.  Octave bands and 5 min Leq recordings were recorded in a no-noise condition to determine the sound levels produced in normal operation ACM and in BAC. To allow for easy access of an infant within the GOmB, clear side access panels can be lowered. Each access panel contains two smaller portholes so that staff can care for the neonate with minimal disruption of the environment inside of the incubator. Each access panel is fastened by two side door latches.  Leq recordings and octave band measurements were obtained to assess the effect of leaving a porthole open and one or two access panel latches open.
Measurement of noise attenuation
The natural insertion loss (IL) of the GOmB was determined in a quasi-diffuse 70 dBA pink noise sound field. IL is the difference in noise levels recorded from the exact same location with and without the use of noise reduction methods. Insertion loss can be found with the following formula: IL = Lp - Lp'- Lp indicates the noise levels before modifications and Lp' indicated the noise levels after modifications have been made.  In this scenario, octave bands and Leq data were recorded at the geometric center of the sound booth without the GOmB inside the sound booth and with the GOmB inside the sound booth.
Measurement of noise reduction using incubator modifications
The third component evaluated the influence of acoustic modifications on insertion loss within the GOmB. A 5.0 × 60.9 × 121.9 cm sheet of acoustic foam (Anechoic Wedges) was purchased from All Noise Control (Green Acres, FL). The manufacturer's reported absorption coefficients are presented in the [Table 1]. After a review of various materials, this acoustic foam was selected because it had the greatest sound absorption coefficients for low frequencies. The manufacturer stated that the acoustic foam is safe for all environments with the exception of clean-rooms for the production of computer chips. In order to optimize sound attenuation in low frequencies, the thickest amount of this soft, porous foam  that could be added to the incubator was selected. A maximum of 5 cm of foam could be added to the walls of the GOmB.
|Table 1: Absorption coefficients for anechoic wedges by octave bands (Hz)|
Click here to view
The effects of modifications on the internal noise produced by the GOmB and the attenuation of the 70 dBA pink noise source were evaluated for multiple scenarios. Modifications included gaskets (1.58 cm 3M weather stripping tape) placed along the hinges of the side panels; tape (4.4 cm Polyken carpet tape Covalence Adhesives, Franklin, MA) placed over the unused tubing access covers; acoustic foam panels placed along the bottom, head, foot, and along the top panel at the head of the inside of the GOmB. Real world foam is the use of top foam, bottom foam, and side foam at the head of the GOmB. For the real world foam scenarios, acoustic foam was not placed along the back sides of the GOmB to allow for maximum visibility of the incubator. Two of the scenarios included covering the GOmB with a commercially available quilted GOmB cover (Children's Medical Ventures, Murrysville, PA).
| Results|| |
Noise attenuation characteristics of the GOmB
When no noise was present, the Leq at the geometric center of the sound booth was 11.6 dBA. In ACM, the Leq inside of the incubator was 41.7 dBA. In BAC mode, the Leq increased 12.4 dBA to 54.1 dBA. The octave band data for the normal operation of the GOmB are presented in [Figure 1]. When the incubator was turned off, 11.6 dBA was recorded across all octave bands; however, this was the lowest level which could be detected by the sound meter in use.  In ACM, most of the noise within the incubator was low frequency. Activation of the BAC feature caused an increase in sound levels for all frequencies with the exception of 16,000 Hz. The increases were especially pronounced at 4,000 (20.2 dBA increase) and 8,000 Hz (14.5 dBA increase) when compared to ACM. Opening a porthole while the BAC was activated created less than 1 dBA increase in sound across octave bands.
|Figure 1: Plot of sound levels in dBA for octave bands inside of incubator in no-noise and pink noise conditions|
Click here to view
In ACM, the 70 dBA pink noise was decreased to 58.9 dBA within the incubator. This indicates that the GOmB naturally attenuated approximately 12 dBA in ACM without any modifications. [Figure 1] also shows the natural attenuation of the incubator at octave bands between 250 and 16,000 Hz. When the GOmB is running in ACM mode the greatest increase in sound levels occurs between 4,000 and 8,000 kHz.
Assessment of clinical variations in sound attenuation pattern in pink noise condition
The side panels of the incubator can be lowered to allow staff to access the neonate inside of the incubator. Leaving a single door latch open increased the Leq from 58.2 to 59.7 dBA. The Leq increased to 60.5 dBA when two latches are open on opposite sides. A porthole left open increased the Leq to 60.3 dBA. With the porthole left open, the greatest loss in attenuation occurred between 1,000 and 4,000 Hz. The presence of a gap or opening around the side access panels created a minimal increase in sound level in the low frequencies (250 to 500 Hz) and at the highest frequency (16,000 Hz). The greatest increase in sound within the incubator occurred between 1,000 and 8,000 Hz.
Evaluation of alterations in sound attenuation pattern in no-noise condition
In the no-noise condition there was very little variability of the effect of acoustic foam when the top, bottom, and side panels were used individually or in pairs [Figure 2]. The Leq data from the side and bottom foam combination is not reported because of inconsistencies in the data. The tape and gasket alone scenarios were not evaluated in the no-noise condition. The use of the top foam panel was the least effective (0.9 dBA decrease). The top and bottom foam combination, bottom foam alone, side foam alone, and top and side foam combination each decreased the sound load by less than a 0.5 dBA. The greatest reduction of sound levels were seen in combination scenarios, which involved all individual foam pieces together, or in combination with gaskets, tape, and the incubator cover. Real world foam scenarios were tested in combination with the use of gaskets and tape over the unused access ports with and without the cover. The commercial incubator cover decreased the noise level by 0.1 dBA in the no-noise scenario. The all foam condition created the greatest attenuation, decreasing the sound levels by 4.1 dBA within the incubator. When compared to no modifications, all modifications were statistically significant (P=0.001). When modifications were compared to each other, all modifications were statistically significant (P=0.001) with the exception of the following: real world foam, gasket, and tape compared to real world foam, gasket, tape, and cover (P=1.0); side and bottom foam compared to all foam, gasket, and tape (P=0.442); and side and bottom foam compared to all foam, gasket, tape, and cover (P=0.222).
|Figure 2: Sound levels inside of incubator using various modifications in the no-noise and pink noise conditions. Gasket and tape alone modifications were not studied in the no-noise condition|
Click here to view
Octave band data were obtained for all modification conditions in the no-noise scenario. A trend was seen with all modifications that mirrored the results in the Leq data. The greatest impact on octave bands were in the all foam only condition with a decrease of zero to 11.3 dBA at all octave frequencies. The greatest impact occurred between 1,000 and 2,000 Hz (7.2 and 11.3 dBA, respectively). This trend was consistent for all modifications.
Evaluation of alterations in sound attenuation pattern in pink noise condition
In the pink noise condition, the GOmB naturally decreased the pink noise by 11.4 dB (Leq 58.2, [Figure 2]). All other modifications were compared to the natural attenuation of the GOmB in ACM. The use of gaskets and tape in combination only provided an additional 1.3 dBA of attenuation. When used independently, both gaskets (Leq 56.9 dBA) and tape (Leq 56.0 dBA) yielded a greater reduction in sound levels within the incubator than when used in combination. This inconsistency may be due to application error when the modification was put in place. Consistent with the no-noise scenario, the panels of acoustic foam were most effective when used in combination. When used alone, the additional benefit provided by the acoustic panels ranged from 1.3 to 2.2 dBA. Placing tape on the unused access ports proved to be just as beneficial as placing acoustic foam on the sides or on the bottom of the incubator. The use of tape alone provided an additional 2.2 dBA to the natural attenuation of the GOmB in ACM. The all foam condition and top and side foam condition varied by only 0.1 dBA providing an additional 4.2 to 4.3 dBA of attenuation. As with the no-noise condition, the greatest reduction in noise levels within the incubator resulted when the acoustic foam was used in combination with gaskets, tape, and the cover. In the real world foam, gasket, and tape with and without the cover, the use of the cover provided an additional 0.6 dBA benefit. This was not seen in the no-noise condition which may indicate that the cover was more effective for decreasing external noise than internal noise produced by the GOmB. Placing tape over the unused incubator ports was more effective than placing the cover over the incubator. The most effective modification was the all foam, gasket, tape, and cover condition (Leq 51.6 dBA) which provided an additional 6.6 dBA of attenuation. When compared to no modifications, all modifications were statistically significant (P=0.001). When modifications were compared to each other, all modifications were statistically significant (P=0.001) with the exception of tape compared to side and bottom foam (P=0.987).
Similar to the no-noise condition, the octave band data for all of the modifications in the pink noise condition mirrored the Leq results. In general, octave band data suggest that all modifications were most effective at frequencies greater than 2,000 Hz. In the high frequencies, all modifications were more effective than they were in the low frequencies. Similar to the no-noise condition, the all foam, gaskets, and tape with and without the cover and the real world foam, gaskets, and tape with and without the cover combinations most efficiently lowered the sound levels inside of the GOmB. Combination scenarios were most effective because the acoustic foam reduced the internal noise produced by the GOmB and the tape and gaskets decreased external noise sources.
In the pink noise scenario, the use of the cover has a greater impact on reducing the sound levels within the incubator between 2,000 and 16,000 Hz. For the all foam, gasket, tape condition, the addition of the cover resulted in an increase in attenuation ranging from 0.4 to 4.1 dBA across octave bands of 2,000 to 16,000 Hz. In the real world foam, gasket, tape combination in the pink noise condition, the addition of the commercial cover had an impact on the octave bands 2,000 to 16,000 Hz resulting in an increase in attenuation ranging from 1.3 to 4.8 dBA. The benefit of the cover was not seen in the no-noise condition.
| Discussion|| |
The youngest neonates who receive care in an NICU may be as early as 23 weeks gestation with birth weights of less than 500 g.  The auditory vulnerability of these neonates was previously discussed. The research finding that the GOmB in ACM operates at 41.7 dBA is compelling, especially in light of the sound level of operation of previously studied incubators. ,,,,,,,, New single-family room NICUs, which comply with the current recommendations and standards , may have ambient sound levels as low as 37 dBA  potentially allowing the tiny neonate to receive additional benefit from the lower level of the noise of operation of the GOmB.
Given a quiet NICU environment, many factors contribute to the sound burden placed upon the neonate. Staff and visitor conversations, bedside rounds,  monitor alarms, and respiratory equipment , can produce continuous sound levels as high as 67 dBA.  The sound attenuation of the GOmB is a significant factor in reducing these levels. The potential short-term impact for the neonate is improved physiologic stability. In the long term, better neurodevelopmental outcomes are hopefully anticipated. Providing care with the GOmB in the open mode, like an overhead radiant warmer, denies the neonate of these potential benefits and allows for continuous direct exposure to high sound levels as with conventional overhead radiant heating devices.
While all measurements in the present study were obtained within a controlled noise environment, recent publications describe similar Leq levels, ranging between 53 and 56 dBA, for the GOmB when used clinically in the NICU in conjunction with respiratory support equipment.  Few other investigations have reported data regarding the GOmB incubator. ,, Only one of these studies concerns sound attenuation but from the standpoint of the application of sound-cancellation technology.  Aside from the present research, no independent data regarding the noise of operation or sound attenuation characteristics of the GOmB are available with the exception of those available from the manufacturer.  As described by Lasky  the GOmB is the newest and technologically most advanced incubator available. In their studies, its noise of operation was also much less than conventional incubators. Because of this incubators' unique and multifunctional capability, data regarding other incubators ,,,,,,,, cannot be generalized to the GOmB.
When used in BAC mode, sound measurements exceed the recommended standard at 54.1 dBA. , BAC is activated by opening the GOmB doors, or it may be manually activated for intervals of 20 min. Unfortunately, the most vulnerable tiny neonates very frequently require this additional support. Fortunately, this level of noise exposure is not continuous and may be modified by the bedside nurse using alternate procedures depending on the needs of the neonate. The authors wish to emphasize the importance of staff education in employing alternative methods so as to reduce the sound exposure of fragile neonates.
The present investigation also explored the application of a variety of materials to the GOmB incubator to assess their potential to reduce neonatal noise inside of the incubator. It has been shown that the Leq inside of the GOmB can be significantly reduced, but at the expense of adding multiple layers of cumbersome sound-attenuating materials to an already complex care area. From a clinical standpoint, it is most important to note the potential sound load imposed on the neonate by minor departures in care. For instance, leaving an access panel door unlatched may contribute one dBA to the sound load inside of the incubator. Leaving two access panel latches open, or a porthole door open may increase the sound load by more than 2 dBA. Conversely, simply taping over the access ports used for intravenous tubing and monitor wires can reduce the sound exposure by 2.2 dBA, more than that realized by the application of acoustic foam to the inside of the incubator.
Limitations of this investigation
There are a number of limitations to this investigation. As previously noted, the sound meter used in this investigation could not measure less than 11.6 dBA. This is the minimum sound pressure which may be measured by the equipment,  rather than experimental error.
Second, there were possible errors in the application of some of the sound attenuating materials to the incubator which may have lead to erroneous measurements. Inconsistent measurements were obtained when gaskets and tape were each applied alone and yielded a greater reduction in sound levels within the incubator than when used in combination. Additional inconsistencies were noted in the data obtained when the side and bottom foam were used in combination. These data were not reported.
Third, the authors cannot condone the use of any of the theoretic modifications employed in this investigation because their impact on the primary functions of the incubator has not been investigated. Further, the authors have concerns that some of the modifications may alter airflow, heating, and humidification characteristics of this device. In addition, the porous surface of the acoustic foam could harbor bacteria and pose the risk of nosocomial infections upon tiny and immunologically compromised neonates.
The last limitation is that this investigation was performed in a calibrated sound-proof booth rather than the neonatal intensive care environment. This allows more precise measurement of sound attenuation at calibrated levels of exposure; however, the sources, direction, and frequencies of the noise exposure may be quite different in the NICU. These questions remain, even though the investigators attempted to simulate the NICU as closely as possible (speaker height and distance, microphone position, noise intensity).
In spite of the above limitations, the results of this investigation were consistent with those of one recent clinical investigation;  however, further investigation involving incubator functions in the environment of the NICU need to be completed. In addition, the reader needs to be aware, that studies by this group  and elsewhere  have demonstrated that sound attenuation characteristics of the incubator may have little clinical impact on the neonate when respiratory support is in use. Having information regarding the sound attenuation of the incubator in conjunction with information regarding the sound load generated by various types of respiratory support equipment may be helpful to the clinician in securing the best sensory environment for the tiny preterm neonate.
| Conclusions|| |
When no noise was present, the Leq at the geometric center of the sound booth was 11.6 dBA, which was the lowest measure with the equipment in use. In ACM, the noise related to incubator operation increased to 41.7 dBA. With the use of the optional BAC mode, the Leq of operation of the incubator increased to 54.1 dBA. When the GOmB is running in ACM mode the greatest increase in sound levels occurs between 4,000 and 8,000 kHz. In ACM, 70 dBA pink noise was attenuated by the GOmB to 58.9 dBA within the incubator (12 dBA reduction) without modification. All modifications of the GOmB showed statistically significant reductions in the noise level inside of the incubator but no statistically significant differences were demonstrated between the methods of sound reduction. One commonly used clinical method to reduce sound of placing a commercially available cover over the incubator did not significantly reduce the internal sound. All studied modifications used simultaneously reduced sound load by a maximum of 6.6 dBA, but only with the addition of complex modifications of the incubator which are of unknown potential clinical consequences.
| Acknowledgments|| |
Ms. Wubben was sponsored as a trainee of the South Dakota Leadership Education in Neurodevelopmental Disabilities Program (SD LEND) of the Center for Disabilities of the Sanford School of Medicine of the University of South Dakota, funded by Health Resources and Services Administration (Grant # T73MC000037). This work was also supported by a loan of equipment by GE Healthcare.
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Dennis C Stevens
Attending Neonatologist, Sanford Children’s Hospital and Specialty Clinic, 1600 West 22nd Street, Sioux Falls, South Dakota 57117-5039
[Figure 1], [Figure 2]
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