Decibel Levels Research Articles

Occupancy states forecasting with a hidden Markov model for incomplete data, exploiting daily periodicity

To automatize HVAC energy savings in buildings, it is useful to forecast the occupants’ behaviour. This article deals with such a forecasting problem by exploiting the daily periodicity of the input variables and the ability of the proposed model to learn from missing data. We propose a case study of occupancy behaviour, for which only a history of indirect information is available: CO2 and decibel levels. The unobserved classes are modeled by a Hidden Markov Model (HMM) which emits sensors’ data and periodic variables. The fact that Baum-Welch’s algorithm for HMMs is an instance of the EM algorithm allows the model to learn from incomplete data. In this case, the missing data are the class labels at every instant (past and future) and the sensors’ data in the future, but the time periodic variables are known at every instant: this enables the model to classify both the past instants (history) and the future instants (forecasting). Our method is tested on simulated data sets with 5%, 15%, 25% and 50% missing data that provide respectively an average classification accuracy of 93%, 89%, 85% and 80%. Then, experiments on one-day and one-week forecasting scenarios achieved an average accuracy of 82% and 81%. The proposed method is also applied on a real-life data set which seems to provide promising results.

Efficacy of an Audio-Based Biofeedback Intervention to Modify Running Gait in Female Runners.

A variety of gait retraining interventions are available to modify running mechanics associated with musculoskeletal injuries. These often require specialized equipment and/or personnel to prompt the runner toward specific strategies. To determine whether instructing female recreational runners to "run quietly" could decrease impact force characteristics. Cohort. Research laboratory. Fifteen healthy female recreational runners (24 [7]y) volunteered. Baseline testing occurred on day 1 (baseline), a posttraining assessment occurred on day 2 (training), and a final assessment occurred 1week after training on day 3 (follow-up). A smartphone decibel measuring app was used to provide biofeedback on the decibel level of foot strike on day 2 (training). Peak vertical force, impact transient, peak and average vertical loading rate, ground contact time, and running economy were collected on each day and compared via repeated-measures analyses of variance. Vertical ground reaction force was lower at follow-up (2.30bodyweights [BW]) versus baseline (2.39BW, P = .023) and training (2.34BW, P = .047). Maximal loading rate decreased from baseline (69.70BW·s-1) to training (62.24BW·s-1, P = .021) and follow-up (60.35BW·s-1, P = .031). There was no change in running economy. Our findings demonstrate that simple instructions to "run quietly" can yield immediate and sustained reductions in impact force profiles, which do not influence running economy.

An experimental study of acoustical design, physiological measurements, and repetitive behaviors in children with autism

Researchers have known that sound is an aspect of the environment that can have an effect on children with Autism Spectrum Disorder (ASD) due to hypo or hypersensitivities that are commonly present in this population. What is less known is how sound is specifically correlated to behaviors and physiological phenomenon. In order to build a predictive measure of sound decibel level on behavior, children with ASD were observed in a controlled environment while exposed to varying acoustic levels. Behaviors, heart rate, ECG, and respiration were recorded during experimental sessions and results revealed that the children typically stayed on task consistently throughout the sound stimulation; however, significant ECG, HR, and respiration rate variances occurred at the different sound levels in all behaviors. The results found from this study do point to a predictive relationship when it comes to the influence of sound and physiological readings on behavior in ASD children.

Noise in cesarean deliveries: a comprehensive analysis of noise environments in the Labor and Delivery operating room and evaluation of a visual alarm noise abatement program

Cesarean deliveries are the most common major surgery worldwide. Noise in healthcare settings leads to impaired communication, concentration, and stress among health care providers. Limited information is available about noise at cesarean delivery. Our aim was to achieve a comprehensive analysis of noise that occurs during cesarean deliveries. Sound level meters are used to determine baseline noise levels and to describe the frequency of acute noise that is generated during a cesarean that will cause a human startle response. Secondarily, we will evaluate the effectiveness of a visual alarm system to mitigate excessive noise. We completed a pre-intervention/post-intervention observational study of noise levels during cesarean deliveries before and after introduction of a visual alarm system for noise mitigation between 2/15/2021 to 8/26/2021. There were 156 cases included from each study period. Sound pressure levels were analyzed by overall case median decibel levels and by time epoch for relevant phases of the operation. Rapid increase noise events capable of causing a human startle response, "Startle events" were detected a by retrospective analysis, with quantification for baselines and analysis of frequency by case type. Median noise levels with inter-quartile ranges [I.Q.R.] are presented. Data are compared between epochs and case characteristics with non-parametric two-tailed testing. The median acoustic pressure for all cesarean deliveries was 61.8 [58.8, 65.9] dBA (median [I.Q.R.]). The median dBA for the full case time period was significantly higher during cases with NICU team presence, 62.1 [60.5, 63.9]; neonatal admission to the NICU, 62.0 [60.4, 63.9]; 5-minute APGAR score less than 7, 62.2 [61.1, 64.3]; multiple gestations, 62.6 [62.0, 64.2]; and intraoperative tubal sterilization, 62.8 [61.5, 65.1]. The use of visual alarms was associated with a statistically significant reduction of median noise level by 0.7 dBA, from 61.8 [60.6, 63.5] dBA to 61.1 [59.8, 63.7] dBA, (p<0.001). The noise intensities recorded during cesarean deliveries were commonly at levels that affect communication and concentration, and above the safe levels recommended by the W.H.O. Although noise was reduced by 0.7 dBA, the reduction was not clinically significant to reduce noise a discernible amount (a 3dB change) nor in reducing "startle events". Isolated use of visual alarms during cesarean deliveries is unlikely to be a satisfactory noise mitigation strategy.

The influence of audience participatory noise on sound levels at live events.

The 'audience verbal appreciation' for a worldwide known artist can raise the decibel levels during a show. This can lead to limit violations if there is a decibel limit for the show. In this publication the effect of a yelling audience, known by almost all sound engineers, will be described. The research was done at 18 large live shows in Belgium and the Netherlands in the years 2015..2019. The measurement setup was a single channel measurement with a class 1 sound level meter at FOH. The data was stored as LAeq,1sec and LCeq,1seq and also the 1/3 octave band information per second was logged. The outcome gives more information about the frequencies of yelling, but more important the effect on the decibel level of the total show. Besides measuring at FOH (front-of-house) position, two alternative measurement methods are discussed (2-channel setup and multiple measurement points in the hall).

An Assessment of Noise Pollution and Its Health Implications in Hospitals in Anyigba, Kogi State

Noise pollution undesirable sound capable of disturbing normal activities such as working, sleeping, and conversations. The World Health Organization, 2001 warned that noise pose a serious threat to human wellbeing. But little is known about noise pollution in hospitals in study area. The study is aimed at assessing the level of noise pollution in selected private and public hospitals in Anyigba town, Kogi state. While sound measuring meters were used to measure the sound intensity at the selected hospitals, questionnaires were used to elicit responses from the respondents. Findings shows that 101 (63%) of the respondents indicated that noise pollution has effect on patients in the hospital, stressing that excessive noise in hospitals reduces the intelligibility of speech and impairs communication, causing annoyance, irritation, fatigue and reduction of the quality and safety of healthcare delivery. The paper found that noise levels in some hospitals in Anyigba have exceeded the WHO and EPA recommended noise decibel levels (35dB) in hospital rooms. These hospitals include Kogi State University Teaching Hospital (60dB), Kogi State University, Medical Center, (59dB), Grimard Catholic Hospital (58dB), Good Shepard hospital (58dB), Nebo Multi-Care Hospital (55dB), Pacific Hospital (54dB), and Blue House Hospital (52dB). Hypothesis tested says there is no statistically significant variation in the level of noise pollution between selected hospitals in Anyigba. The paper suggested that hospital noise emission level in the study area should not exceed the WHO and EPA standard (i.e., 35dB).

Intranasal dexmedetomidine versus intranasal midazolam as sole sedative agents for pelviabdominal magnetic resonance imaging in pediatrics: A randomized double-blind trial

Background: The diagnostic effectiveness of magnetic resonance imaging (MRI) resulted in its growing usage among cases of all ages. Nevertheless, children having MRIs are frequently sedated due to the magnetic field’s extremely loud decibel level and to avoid motion artefacts. This research aimed to compare the efficacy and safety of intranasal dexmedetomidine and midazolam in pediatric MRI patients. Materials and Methods: This double-blind, randomized clinical trial involved 60 cases aged 2–8 years, both sexes getting elective MRI. Sixty children were randomly allocated into two equal groups, subjects in group D were sedated with 2 μg/kg intranasal dexmedetomidine, whereas group M were sedated with 0.3 mg/kg intranasal midazolam. Successful sedation was considered when the Modified Observer Assessment of Alertness/Sedation Scale < 4. Results: The 1st and 2nd dose success rates were significantly higher in group D (80% and 90%) as opposed to group M (46.67% and 63.33%) (P = 0.015 and 0.032, respectively). Sedation onset was significantly faster in group D compared to group M (P = 0.037). Sedation time was significantly prolonged in group D than group M (P = 0.044). MRI satisfaction of operator was significantly higher in group D compared to group M (P = 0.022). Conclusion: Intranasal dexmedetomidine provided higher incidence of successful sedation and operator satisfaction with quicker onset and prolonged period of sedation and less adverse events than intranasal midazolam in pediatrics undergoing pelviabdominal MRI.

Ubjective evaluation of noise generated in a dental environment and comparison of sound insulation effects of noise cancelling earphones

Purpose: Various devices such as dental handpieces, ultrasonic scalers, and aspirators exist in the dental clinic, and they generate noise with high decibel levels in a complex way. Through this study, we survey the discomfort and hearing changes on patients and dental staff, and compare and analyze the sound insulation effect of each noise cancelling product for vari-ous noises.Materials and Methods: This study is a multi-faceted evaluation of noise generated in the dental treatment. First, patients and dental staffs were surveyed through the Gallup Korea Research Institute. Afterwards, subjective evaluations of various noise cancelling earphones for dental noises were conducted by VAS scales.Results: In this study, more than 50% of patients, dentists, and dental hygienists feel uncomfortable about dental noise, and more than 70% of the respondents say that they had interrupted in communication due to noise. In both the dentist and non-dentist groups, when noise-cancelling earphones were used for high-speed and low-speed handpieces and suction noise, a decrease in VAS value was confirmed. Regarding the scaler noise, the increase or decrease of the VAS value was different depending on the products.Conclusion: The results of this study indicate that noise generated in a dental treatment can cause emotional discomfort to both patients and dental staff, and both are aware of the possibility of hearing impairment. And it is necessary to consider the sound isolation device optimized for each noise.

Programmable ferroelectric bionic vision hardware with selective attention for high-precision image classification

Selective attention is an efficient processing strategy to allocate computational resources for pivotal optical information. However, the hardware implementation of selective visual attention in conventional intelligent system is usually bulky and complex along with high computational cost. Here, programmable ferroelectric bionic vision hardware to emulate the selective attention is proposed. The tunneling effect of photogenerated carriers are controlled by dynamic variation of energy barrier, enabling the modulation of memory strength from 9.1% to 47.1% without peripheral storage unit. The molecular polarization of ferroelectric P(VDF-TrFE) layer enables a single device not only multiple nonvolatile states but also the implementation of selective attention. With these ferroelectric devices are arrayed together, UV light information can be selectively recorded and suppressed the with high current decibel level. Furthermore, the device with positive polarization exhibits high wavelength dependence in the image attention processing, and the fabricated ferroelectric sensory network exhibits high accuracy of 95.7% in the pattern classification for multi-wavelength images. This study can enrich the neuromorphic functions of bioinspired sensing devices and pave the way for profound implications of future bioinspired optoelectronics.

Experimental study of the influence of coal mine noise on miners

This study explored the influence of underground noise on coal miners' physiological indexes and behavior ability. A system was constructed to measure a miner's physiological indicators and behavioral capacity. This measurement system mainly involved the behavioral and physiological indicators tester, the response tester, and the noise source. A total of 30 subjects were selected for this experimental research, and the ambient noise of 45, 65, 85, and 95 dB (decibels) was considered. The main data sources were three physiological indicators: the subjects' respiratory rate, heart rate, and galvanic skin response. In addition, data from the three behavioral indicators were gleaned, including the response time measured by sound, the response time measured by light, and a few operating errors. The correlation analysis of experimental data was carried out to analyze the correlation between physiological and behavioral indicators. In addition, variance analysis was performed, as ANOVA was used to analyze the experimental data to examine the variability of the physiological and behavioral measures of the subjects under univariate and multivariate interactions. Multiple linear regression analysis was performed to determine the single-factor and multiple-factor interchanges between subjects, considering their physiological and behavioral differences as obtained from the indicators. Based on the coupling effect of the noise level, the different education and age levels and the mathematical relationship with the tested physiological indicators and behavioral ability were established. Predictions can be made regarding the behavioral capability of miners through their age, education levels, and the noise decibel level in the working environment. This may provide a theoretical basis for both the reduction in the unsafe behavior of miners and the improvement in coal mine safety.

An illustrated tutorial for logarithmic scales and decibels in acoustics.

Acoustics is generally defined as the science that deals with the production, transmission, and reception of sound and the understanding and control of its effects. In fact, the fields of acoustics cover an especially broad range of subjects and domains, and comprehensive acoustics textbooks are usually quite thick as a consequence. While they are valuable resources for researchers, these books might appear a little daunting for a young audience or for people who are new to acoustics. This paper is an example of how educational comics can be designed and used to introduce one of the most commonly discussed topics when the basics of acoustics are taught: decibel level. Seven drawn pages constitute a visual support to explain the origin and history of the decibel, together with examples from acoustics and other domains on the use of logarithmic scales and classical decibel calculations. Several comments and comprehensive bibliographical references are also provided for each drawn page to enlarge the range of subjects or exercises that can be discussed in courses and foster further readings.

Maternal Voice Exposure and Its Effect on Premature Infants' Feeding Milestones: A Systematic Review.

Premature infants experience alterations in maternal stimulation (including auditory sensory alteration such as talking or singing to the infant in the neonatal intensive care unit) due to admission to the neonatal intensive care unit. Because of their physiological and neurobehavioral immaturity, infants are at an increased risk of delays in reaching feeding milestones (a key developmental milestone), which often need to be achieved before discharge. This systematic review evaluated the literature regarding the effect of maternal speech on achievement of feeding milestones in premature infants. A systematic search of CINAHL, PubMed, Web of Science, and Google Scholar from 2010 to 2021. Studies were selected if they examined the effect of maternal voice interventions on premature infants' feeding milestones. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used. Six studies were identified. This systematic review of the literature on the effects of maternal voice on feeding milestones in premature infants found equivocal results. Given the inconsistent results, this systematic review does not support a change in clinical practice. However, encouragement of maternal visits is highly recommended as the additional benefits of the mother's presence may extend beyond exposure to maternal voice. More research is needed including use of more homogenous samples, application of recommended decibel levels, and utilization of an adequately powered randomized controlled trial to further examine the effects of maternal voice on feeding milestones.

Assessing speech communication in the operating room

Smooth communication in the operating room (OR) is essential. However, its acoustic environment is typically composed of machine and human caused sounds such as patient temperature monitoring devices, systems, waste management systems, and irrelevant conversations that impede speech communication. These challenges are exacerbated by the need for combinations of facial protective equipment (FPPE) that both attenuate critical speech information as well as obviate relying on visual information for understanding speech. In order to faithfully capture the challenges to speech perception in this environment, we first recorded various interfering sounds based on a qualitative study of over 59 surgeries across different specializations. We analyzed their acoustic characteristics and obtained subjective measures of perceived interference from 60 surgical team members who all worked in the OR. In a follow up study, we assessed the acoustic consequences of different facial ppe combinations on produced speech. In both studies, we identified critical impediments to smooth OR communication. These include high decibel levels of interfering sounds, attention engaging irrelevant speech, and substantial attenuation of speech frequencies when using typical FPPE combinations. These studies constitute our preliminary steps to identifying and alleviating speech perception challenges in the OR.

Risk of Noise-Induced Hearing Loss for Orthopaedic Surgeons.

Noise-induced hearing loss (NIHL) affects the ability of an individual to communicate and can negatively impact quality of life. The risk to orthopaedic surgeons of developing NIHL as a result of occupational exposures in the operating room (OR) is currently unknown. Hearing protection is recommended for levels of >85 decibels (dB), irrespective of length of exposure. The primary goal of the present study was to determine whether orthopaedic surgeons are exposed to harmful noise levels in the OR that puts them at risk for developing NIHL. A prospective review was conducted with use of intraoperative audio recordings across 6 orthopaedic subspecialties. Recordings were made in ORs prior to the surgical start time to serve as baseline controls. Decibel levels were reported as the maximum dB level (MDL), defined as the highest sound pressure level during the measurement period, and as the time-weighted average (TWA), defined as the average dB level projected over an 8-hour time period. Noise doses were reported as the percentage of maximum allowable daily noise (dose) and as the measured dose projected forward over 8 hours (projected dose). Three hundred audio recordings were made and analyzed. The average MDL ranged from 96.9 to 102.0 dB, with noise levels for all subspeciality procedures being significantly greater compared with the control recordings (p < 0.001). Overall, MDLs were >85 dB in 84% of cases and >100 dB in 35.0% of cases. The procedure with the highest noise dose was a microdiscectomy, which reached 11.3% of the maximum allowable daily noise and a projected dose of 104.1%. Among subspecialties, adult reconstruction had the highest dose and projected dose per case among subspecialties. The present results showed that orthopaedic surgeons are regularly exposed to damaging noise levels (i.e., >85 dB), putting them at risk for permanent hearing loss. Further investigation into measures to mitigate noise exposure in the OR and prevent hearing loss in orthopaedic surgeons should be undertaken. Orthopaedic surgeons are at risk for NIHL as a result of occupational exposures in the OR.

Attenuation of EM Waves Emitted From Inset Feed Type Microstrip Rectangular Patch Antenna by Wet Snow

Microstrip patch antennas stand out because of their low cost, smaller size and easy fabrication. The study presents the design of a microstrip rectangular patch antenna operating at 2.6 GHz frequency and the effect of different weather conditions on the antenna. During the antenna design on CST program and manufacturing in the laboratory, it is aimed to perform the measurement at the desired frequency and decibel level. The study includes experiments and results made on different types of snow, apart from the normal measurement with the VNA. A good S11 scattering value was obtained at the desired frequency in the designed microstrip patch antenna as -18.48 dB. This value decreased to around -5 dB when there was wet snow on the antenna due to attenuation and thermal effects. If the snow was removed from the antenna, the old S11 value could not be returned because of the wetness left by the snow, and it remained at approximately -14 dB. Consequently, the attenuation of the electromagnetic waves have been confirmed by the literature under different conditions as wet snow with nano VNA for the first time. Attenuation by wet snow and water is greater than dry snow with voids.

Snoring and aortic dimension in Marfan syndrome

Recent reports suggest that self-reported snoring, which is a feature of obstructive sleep apnea, is associated with aortic enlargement in Marfan syndrome (MFS). Objective assessment of snoring although lacking, could provide a rational for OSA screening in MFS patients. Our goal in this study was to examine the association between objective measurements of snoring with OSA and aortic size in persons with MFS. Consecutive persons with MFS who reported snoring were recruited at Johns Hopkins, completed the Epworth Sleepiness Scale (ESS) and underwent overnight polysomnography during which inspiratory sound was captured. We measured breath-by-breath peak decibel levels and snoring was defined as flow limitation with sound ≥ 40 dB(A). OSA was defined as an apnea–hypopnea-index (AHI) ≥ 15 or AHI: 5–15 and ESS > 10. Participants’ aortic data were collated to ascertain aortic root diameter. Regression models were used to determine the relationship of snoring breath% with OSA and aortic root diameter. In our cohort (M|F:13|16, Age: 37.0 ± 15.5 years, Aortic diameter; 38.9 ± 4.8 mm), a 1-unit increase in snoring breath percentage increased the odds of having OSA by 5% in both the unadjusted (OR = 1.05, p = 0.040) model, and a model adjusted for age and sex (OR = 1.05, p = 0.048). Similarly, a 10-unit increase in snoring breath percentage was associated with a 1 mm increase in contemporaneous aortic-root-diameter in both unadjusted (β = 0.09, p = 0.007), and adjusted (β = 0.08, p = 0.023) models. Objective snoring assessment could provide a means for identifying persons with MFS who need sleep studies, who may also be at risk for more severe aortic disease.

Peace in the PACU

<h3>Introduction</h3> Open-bay Post Anesthesia Care Unit (PACU) environments can be loud and overstimulating for patients, caregivers, and healthcare workers. Literature describes noise interferes with the patient's surgical recovery and increases the need for analgesia. In patients and healthcare workers, physiologic (increased heart rate, blood pressure) and psychologic (sleeplessness, stress) changes are associated with increased noise levels as well as medical errors, miscommunication, and surgical site infections. <h3>Identification of the Problem</h3> Reports of a noisy, loud pediatric PACU environment has been identified as an area of improvement by healthcare workers, patients, and caregivers. <h3>Purpose of the Study</h3> Evaluate the effects of noise-reducing curtains on PACU noise level and noise perception by caregivers. <h3>Methodology</h3> Institutional Review Board approval was obtained. A pre/post- intervention study design was employed to evaluate the effectiveness of noise-reducing curtains on noise level and caregiver perception. Noise decibels were measured with calibrated dosimeters. An acoustical assessment was performed and caregiver perception of noise was measured by anonymous surveys. <h3>Results</h3> Following noise-reducing curtain installation no statistical significance in overall decibel levels was observed, however intrusive noise was reduced by 35% - 50%. Additionally, 54.7% of caregivers reported the area around the bay was never quiet before installation compared to 15.5% after noise-reducing curtain installation. <h3>Discussion</h3> This study was done to validate results from a 2019 study in the same PACU where a statistically significant reduction in decibel levels was observed following noise-reducing curtain installation. This study did not validate an improvement in decibel levels likely due to pandemic-related effects such as decreased surgical volumes and an intentional reduction of caregivers and healthcare workers at the bedside. However, this study does validate the use of noise-reducing curtains to improve noise perception. <h3>Conclusion</h3> Noise and sound are multi-dimensional. Though a statistically significant reduction in noise levels was not observed, sound transmission, speech privacy, and reverberation measurements revealed statistically significant reduction in noise perception. Caregiver surveys supported the use of noise-reducing curtains in providing a more therapeutic environment. <h3>Implications for perianesthesia nurses & future research</h3> Literature describes noisy hospital environments lead to negative outcomes for patients, caregivers, and healthcare workers. Noise-reducing curtains are an evidence-based intervention that can improve noise perception in PACUs.

Series of ultra-low loss and ultra-compact multichannel silicon waveguide crossing.

Ultra-compact waveguide crossing (UC-WC) is a basic component in optoelectronic fusion chip solutions, as its footprint is smaller in the orders of magnitude than that of traditional photonic integrated circuits (PICs). However, a large loss of UC-WC (decibel level) becomes a barrier to scaling and practicality. Here, we propose a series of ultra-low loss UC-WC silicon devices using an advanced hybrid design that combines the adjoint method with the direct binary search (DBS) algorithm. Simulation results show that our 2 × 2 UC-WC has an insertion loss as low as 0.04 dB at 1550 nm, which is about ten times lower than the previous UC-WC results. In the valuable C-band (1530-1565 nm), the insertion loss of UC-WC is lower than -0.05 dB, and the channel crosstalk is lower than -34 dB. Furthermore, for the 3 × 3 UC-WC device, the highest insertion loss in the entire C-band is approximately -0.07 dB, and the highest channel crosstalk is lower than -33 dB. Additionally, the 4 × 4 and more complex 8 × 8 UC-WC devices were also analyzed. The highest insertion loss for 4 × 4 and 8 × 8 UC-WC in the C-band is only -0.19 dB and -0.20 dB, respectively, and the highest channel crosstalk is approximately -22dB and -28 dB, respectively. These results confirm that the designed devices possess two attractive features simultaneously: ultra-compactness and ultra-low insertion loss, which may be of great value in future large-scale optoelectronic fusion chips.

Controling noise from tunnel ventilation fans

Infrastructure projects involving transportation networks underground such as railways and roadways have strict ventilation requirements for fire and smoke and engine exhaust control. The fans used for these projects are often very large and very loud compared to typical building equipment. Transit autorities typically have criteria regarding A-weighted decibel levels in and around the tunnel environment to ensure audibilty of emergency announcements and acceptablility of environmental sound levels. Fan and duct silencers as well as acoustical panels play critical roles in meeting maximum sound level criteria at property lines and at track and platform levels. Due to high airflow rates, the design, placement, and configuration of noise control products must be carefully considered to ensure adequate system performance. This paper will review various issues and considerations encountered in tunnel ventilation noise control projects and present typical solutions and design practices with examples.

Multi-objective, Multidisciplinary Optimization of Low-Boom Supersonic Transports Using Multifidelity Models

A multidisciplinary optimization (MDO) method has been developed to design a computational fluid dynamics (CFD)-based low-boom configuration that can be obtained from a Pareto solution of a low-fidelity multi-objective MDO problem with mission constraints. This paper refines the developed MDO method by using multifidelity models for CFD-based multi-objective MDO and a better method for the system-level trade between the target low-boom ground noise level and the overland range. The refined MDO method can generate a low-boom configuration that satisfies the mission requirements, has the lowest takeoff gross weight and the longest range for the low-boom mission, trims the low-boom cruise flight with fuel redistributions, and has a reversed equivalent area distribution closely matching a low-boom target with ground noise level below 70 perceived level in decibels. The validity of the refined MDO method is demonstrated by a design study of a low-boom supersonic transport that carries 40 passengers, flies a low-boom mission with cruise Mach of 1.7 and range of 3500 n mile, and cruises overwater at Mach 1.8 with range of 3882 n mile. Moreover, the refined MDO method eliminates the difference between the assumed cruise weight for CFD-based low-boom inverse design optimization and the estimated cruise weight of the optimal inverse design solution with respect to the mission requirements.