Human Perception of Sonic Booms from Supersonic Aircraft

Alexandra Loubeau Advances in human response research will help pave the way for a new Address: era of commercial supersonic flight. Structural Acoustics Branch NASA Langley Research Center Introduction MS 463 The lure of faster speeds and reduced travel time for commercial flights may Hampton, Virginia 23681 come to fruition soon with advances in low-boom technology. The Concorde USA “was a technological marvel that astounded the world with its beauty of design and speed, halving passenger flight times to distant destinations” (Rogers and Email: Maglieri, 2015). Its last flight on October 24, 2003, ended the first era in supersonic [email protected] commercial travel. Although supersonic flight of the Concorde resulted in loud sonic booms, decades of low-boom research have demonstrated the feasibility of adapting the aerodynamic shape and tailoring the off-body pressure distribution Juliet Page from a supersonic vehicle to decrease or control the sonic boom, a technique Address: known as sonic boom shaping. Sparrow (2006) provides a snapshot of the history Environmental Measurement of sonic boom minimization. With this new technology, research of the human and Modeling response to sonic boom noise is being conducted to better understand the factors Volpe National Transportation that contribute to annoyance from sonic boom sounds so that they can be “shaped” Systems Center for minimal disturbance, thereby potentially resulting in a new era in supersonic US Department of Transportation commercial travel. Indeed, recent advances in understanding and predicting 55 Broadway human perception of sonic booms have coincided with renewed interest from Cambridge, Massachusetts 02142 industry in pursuing development of a new generation of quiet commercial USA supersonic aircraft and have also led to the new lexicon “sonic thump” that reflects their quieter sounds (explained in Unique Qualities of Sonic Booms). Email: [email protected] Low-frequency energy, the transient nature of the sound, and high-frequency energy at shocks are qualities of sonic booms that differ from conventional subsonic aircraft noise. Thus the noise metrics that are currently used for airport noise cannot be used for evaluation of community annoyance and acceptance for sonic booms. Although perceived level (PL; Stevens, 1972) has been identified as a preferred metric (Leatherwood et al., 2002) for describing sonic boom annoyance in outdoor environments, there is no internationally agreed on standard noise metric that can be used to quantify the sonic boom level. Data gathered from planned future community tests with a supersonic demonstrator aircraft will be provided to regulatory organizations such as the International Civil Aviation Organization (ICAO) to provide the scientific basis for development of new noise certification standards for supersonic aircraft. Today’s research will help prepare for this future community testing to ensure gathering of accurate data in an efficient manner.

Unique Qualities of Sonic Booms The transient nature of the sonic boom and large amount of low-frequency energy in the signal result in a sound character that is perceived much differently

volume 14, issue 3 | Fall 2018 | Acoustics Today | 23 Perception of Sonic Booms

a) b) c)

Pa) 120 102 100 Concorde than the sounds from conventional aircraft. Although Shaped boom 100 50 subsonic aircraft noise is a concern near airports, the sonic 80 0 60 0 Concorde 10 booms from supersonic aircraft are created along the entire Shaped boom Pressure (Pa) 40 Difference in levels -50 Loudness (sone) supersonic route and could potentially affect large segments 20 Concorde Shaped boom -100 0 10-2 of the population. Sound Pressure Level (dB re 20 0 0.1 0.2 0.3 0.4 1 10 100 1000 100 102 Time (s) One-third-octave Band Frequency (Hz) One-third-octave Band Frequency (Hz) With advances in aircraft-shaping techniques, modern Figure 1. Comparison of sonic boom waveforms and spectra for the supersonic aircraft designs are predicted to create shaped low- Concorde and an airliner concept designed for low-amplitude shaped amplitude sonic booms heard on the ground that are much booms (J. Klos, personal communication). a: Examples of boom quieter than conventional N-wave sonic booms from the shapes. b: Variation in frequency spectra. c: Variation in loudness Concorde (see Figure 1). The significant reduction in waveform spectra. amplitude and increase in shock rise time lead to a reduction in sound pressure level spectra, particularly at higher frequencies where the reduction can reach 60 dB. Accordingly, the loudness spectra are also reduced by over a factor of 10 in sones over most of the frequency range critical to human hearing. This reduction in the high-frequency content results in a sound like a “thump” rather than a sharp crack or boom. Historically, the maximum overpressure was used to describe the level of sonic booms. Years of research using outdoor sonic boom simulators, however, resulted in identification of PL (Stevens, 1972; Shepherd and Sullivan, 1991) as a noise metric that works best for a variety of signature shapes (Leatherwood Figure 2. Schematic of sonic boom ground exposure (Maglieri et al., et al., 2002). Annoyance to sonic booms experienced indoors 2014). Dark gray, primary boom carpet with an N-wave conven- presents additional factors related to the building itself. tional sonic boom. At the edge of the primary carpet is the lateral The Sonic Boom Carpet cutoff edge with a unique signature that generally does not contain large shocks. Light gray, secondary boom carpet containing wave- Sonic booms are pressure disturbances caused by supersonic forms with indistinct characteristics that sound like rumbles or dis- flight that reach the ground. Figure 2 shows the different tant thunder. The transition from subsonic to supersonic flight creates regions of sonic booms including the primary boom carpet, a focused sonic boom signature with an accentuated high-amplitude the transition focus, and the secondary boom carpet. initial shock. The black and white under the centerline of the flight track and across the carpet indicate the relative overpressure levels (Δp) for the different segments of flight. Sonic Boom Noise Generation for Subjective Studies Laboratory simulators have been used effectively to study boom result in contact-induced rattle noise from elements human annoyance to a broad range of sonic boom signals such as windows, doors, and objects inside rooms. under controlled conditions (Maglieri et al., 2014). Simulators Most outdoor sonic boom simulators consist of an airtight, can reproduce measured booms as well as booms predicted small rigid-walled booth. The cavity is driven with subwoofer for aircraft designs. They can also be used to investigate loudspeakers to reproduce the low frequencies characteristic the human response to different waveform parameters and of sonic booms, whereas midrange loudspeakers fill in the interactions. The majority of simulators reproduce sonic rest of the pertinent spectrum. Another simulator design booms as they would be experienced outdoors, although consists of a mobile trailer that creates a traveling wave using filtered outdoor waveforms or recordings of indoor an array of loudspeakers, a folded horn, and an anechoic waveforms have also been presented to estimate the indoor termination (Salamone, 2005). environment. Most simulators, however, lack indoor realism because there is an absence of space and reverberation as High-quality headphones or earphones are also used to well as of structural vibrations and rattle. These structural reproduce the audible content of sonic booms and secondary vibrations that occur in a building when impacted by a sonic rattle noises typically encountered in indoor environments.

24 | Acoustics Today | Fall 2018 Binaural signals have been used to approximate the auditory of the dive, whereas the second boom is from the earlier part experience of sonic boom and rattle exposure in different- of the dive because the supersonic speed of the aircraft has sized rooms through the use of models and filtering allowed it to outrun the propagating waves! (Giacomoni and Davies, 2013; Loubeau et al., 2013c). Some limitations of this playback equipment are the absence Human Response Studies of experiencing the sounds in a real space with natural Human Response to Outdoor Booms reverberation, the absence of tactile vibration, and decreased Many human response tests were performed in NASA’s realism due to limited low-frequency reproduction. High- outdoor sonic boom simulator in the 1990s (Leatherwood quality systems of amplifiers and headphones have mitigated et al., 2002). These laboratory studies were designed to this last point somewhat, but the systems are still more investigate a wide range of shaped sonic boom signatures restricted than subwoofer systems for reproducing the full and to gather human perception of loudness and annoyance. frequency content of the sonic booms. Shaped booms were rated less loud than symmetric N-waves, and several noise metrics were evaluated for their ability Finally, newer simulators allow for more realistic indoor to predict the subjective response. As a result of PL being soundscapes for investigating causes of elevated annoyance chosen as the best noise metric, it has since been used widely to sonic booms experienced indoors. One configuration to design and assess characteristics of supersonic aircraft. (Naka, 2013) consists of a small booth that can be configured for indoor listening using a partition with a window. Another Evaluation of the realism of outdoor boom simulation was installation called the Interior Effects Room (IER; Klos et al., conducted with simulators and real booms from overflights 2008) at the NASA Langley Research Center consists of a of a supersonic aircraft (Sullivan et al., 2008). PL values were small room configured as a living room with loudspeaker found to be highly correlated between field recordings and playback over arrays adjacent to two exterior walls of the simulator reproduction, and the results increased confidence simulator. The realistic indoor soundscape and environment, in the use of simulators for human response testing. It was augmented with the ability to control secondary rattle noises noted that very low frequency energy (less than 7 Hz) was and vibration, have enabled systematic studies of the factors not significant for assessing realism to booms experienced contributing to human annoyance to sonic booms. in an outdoor environment. Sonic boom subjective studies have also been conducted with Outdoor Versus Indoor Response real supersonic overflights of aircraft. In the past, these studies A field study conducted by NASA compared perception ratings were limited to assessing the response to very loud booms, from test subjects seated inside and outside a house overflown usually produced with military aircraft. However, a special by a supersonic airplane using the low-boom dive maneuver flight maneuver called a low-boom dive has been developed (Sullivan et al., 2010). Although the annoyance ratings (Haering et al., 2006) to mimic the lower amplitudes at the showed that indoor and outdoor annoyance were the same for ground that would be expected from supersonic overflight the same noise exposure, a posttest questionnaire highlighted of future aircraft. By adjusting the location of the dive, and an increase in annoyance indoors. This inconsistency could hence the propagation distance, the ground sonic boom can possibly be attributed to the methodology chosen or to the be varied in level over a geographic area. presence of a rattle indoors. This maneuver has been used successfully in several field A series of subjective tests with playback of measured low- studies to create a variety of boom loudness levels that would amplitude sonic booms was conducted (Miller, 2011) to otherwise not be possible with today’s aircraft in steady, level further explore the inconsistency discovered by Sullivan flight. This dive maneuver is not without limitations for dose- et al. (2010). Three different listening environments were response testing though because it creates a double boom explored, including headphones indoors, headphones of low-amplitude N-waves. In this maneuver, the aircraft outdoors, and an outdoor simulator (Salamone, 2005), and executes an inverted dive from 50,000 feet and transitions the same set of signatures was used in each case. Active to level flight above 30,000 feet (see Sparrow, 2006 for a listeners found indoor signatures more annoying than diagram of the maneuver). The aircraft creates shock waves outdoor signatures regardless of listening environment, continuously while it is moving faster than Mach 1. The first and signatures experienced indoors were considered more boom to arrive at the area of interest is from the latter part annoying.

Fall 2018 | Acoustics Today | 25 Perception of Sonic Booms

A series of simulator tests was also conducted by the Japan the average increase in annoyance due to rattle was equivalent Aerospace Exploration Agency (JAXA; Naka, 2013) to to an increase in exterior boom PL of 4 dB, confirming the evaluate loudness and annoyance ratings of N-waves with headphone test rattle penalty of 3-9 dB. different amplitudes and rise times, using both indoor and Vibration studies were also conducted in the IER (Carr and outdoor configurations. The JAXA tests evaluated loudness Davies, 2015; Rathsam and Klos, 2016; Rathsam et al., 2018) and annoyance and found that indoor ratings were higher using vibration isolators on the test chair legs and shakers than outdoor ratings for a given loudness level. attached to the seat bottom. For vibration levels near the high Human Response to Indoor Booms end of what is predicted to occur in buildings (Klos, 2016), In recent years, sonic boom subjective research has shifted vibration penalties up to 10 dB were observed, indicating to exploring perception of booms experienced indoors. that vibration also plays a role in the indoor perception of Initial studies in NASA’s IER simulator found that boom sonic booms. amplitude and rise time persist as important factors for Startle is another possible factor in the human response an indoor response (Rathsam et al., 2012; Loubeau et al., to sonic booms. Earphone studies examined startle in 2013a). Overall, the longer rise times of low booms result in conjunction with annoyance and loudness for impulsive decreased annoyance. sounds (Marshall and Davies, 2011, 2012) and found that To assess the feasibility of utilizing a subscale flight startle ratings were strongly correlated with annoyance due demonstrator, a comparison of indoor annoyance to sonic to the abruptness of the initial shock and resulting high- booms predicted for subscale and full-scale supersonic frequency energy. Subjective judgments of startle were aircraft (which have different low-frequency energy, even for compared to physiological responses using measured skin the same overall loudness value) was conducted (Loubeau, conductance, heart rate, and electrical activity of three et al., 2013b; Loubeau, 2014). The test used shaped, low- neck muscles. Although subject-to-subject and day-to-day amplitude booms for four classes of aircraft size from variability in the physiological responses were observed, their subscale demonstrator to full-sized airliner. For a given association with startle was rare, and it was concluded that low outdoor PL, the annoyance to subscale aircraft booms was booms are below the threshold of consistent startle responses. not significantly different from that for full-scale aircraft Community Studies booms. This confirmed that outdoor PL can be used to Data relating the response of communities to low-amplitude evaluate supersonic aircraft designs regardless of size. These sonic booms are needed by the international regulatory results show evidence that human response to booms from agencies so they can decide if supersonic overland flight a subscale demonstrator are relevant to a full-size aircraft will be permitted. If so, the regulators will need to establish and help justify plans for use of a subscale demonstrator low-boom criteria for certification of supersonic overland for community studies. However, the results were limited to aircraft. Their decisions will need to be based on both single- isolated booms with no rattle. event and cumulative impacts. Community testing protocols A series of tests was conducted to investigate the human are under development to gather these response data. response to rattle and to combined boom and rattle (Loubeau Historically, noise dose-response testing for transportation et al., 2013c). Using binaural recordings of rattle played back sources and for military installations with impulsive noises over headphones, the study found differences in annoyance such as booms, artillery, and blast noise has related the between rattle sounds for the same PL. Rattle sounds from percentage of community members highly annoyed by the structural elements such as windows, walls, and doors were noise to cumulative metrics such as day-night level (DNL). judged more annoying than rattle from smaller objects, and In 2011, a NASA community study was conducted of the the study confirmed the presence of elevated annoyance response of 100 Edwards Air Force Base (EAFB) California indoors when rattle is present. residents to sonic booms. The waveforms and sonic boom Rattle studies conducted in NASA’s IER facility using a more perception and response (WSPR) program was designed realistic sonic boom playback and indoor environment to test and demonstrate the applicability and effectiveness (Rathsam et al., 2015; Loubeau, 2018) found that rattle of techniques to gather data relating the human subjective increased indoor annoyance. Window rattle sounds response to multiple low-amplitude sonic booms, in essence reproduced for a variety of window types demonstrated that a dose-response test. It included a range of sonic booms from

26 | Acoustics Today | Fall 2018 35 WSPR (2011) 30 Borsky (1965)

25 low amplitude (generated using the low-boom dive maneuver) to higher amplitude from conventional overflight and military 20 operations in the area (Fidell et al., 2012; Page et al., 2014). 15

The WSPR program addressed the following: (1) design 10 Daily % Highly Annoyed and development of an experimental design to expose 5 people to low-amplitude sonic booms; (2) development and implementation of methods for collecting acoustical measures 0 40 45 50 55 60 65 70 of the sonic booms in the neighborhoods where people live; CDNL (dB) (3) design and administration of social surveys to measure Figure 3. Dose-response data from the waveforms and sonic boom people’s reactions to sonic booms; and (4) assessment of perception and response program (WSPR) 2011 study (Loubeau, the effectiveness of various elements of the experimental 2013) compared with data from a 1960s sonic boom field study (Bor- design and execution to inform future, wider scale testing. sky, 1965). CDNL, C-weighted day-night level. Sonic boom measurements were gathered in the residential community and statistical methods were developed for assessing the subjective response to low booms. waves are turned upward before reaching the ground. The speed at which this occurs is referred to as the Mach cutoff The subjective response data-analysis methods allow the and is a function of the atmospheric conditions and flight identification of dose-response curves relating annoyance to altitude. Mach cutoff relies on the fact that the speed of the noise exposure, although this particular dataset reflects sound at flight altitude is lower than that on the ground responses from an acclimated community and might not due to the colder upper air temperatures. The possibility be reflective of people living in areas not routinely exposed is being explored of mixed Mach number conventional to sonic booms. Single-event dose-response curves were N-wave design aircraft that will fly just below Mach cutoff obtained for a variety of noise metrics using measured noise over land (nominally between Mach 1.0 and 1.15) and at levels from a distributed set of noise monitors. Another higher supersonic speeds over water where supersonic flight important element of the WSPR test was the consideration of is not currently prohibited (Matisheck, 2017). Even though not only a single-event response but also a daily cumulative the sonic boom itself does not reach the ground when flying response and hence was designed to take into account the below the Mach cutoff, some of the energy from the sonic number of daily potential future supersonic operations. boom pressure disturbance transitions into an evanescent Past studies (Salamone, 2009; Rachami and Page, 2010) wave, passes into the shadow side, and can reach the ground suggested that a variety in the number of exposures would as an acoustic signal where it often sounds like rumbling be expected across the United States from future operations, or distant thunder. The NASA far-field investigation of no- with a maximum of up to 12 sonic booms daily. boom thresholds (FaINT) test captured an empirical dataset To understand the cumulative impacts, cumulative daily of these evanescent waves (Cliatt et al., 2016). exposures were computed (C-weighted DNL, CDNL) for the Analysis of the Mach cutoff (Plotkin et al., 2008) has WSPR participants and compared with prior sonic boom examined the viability of Mach cutoff flights across the studies in the 1960s and 1970s. An example comparison of these United States, while recent research funded by the Federal data (Loubeau, 2013) to historical data (Borsky, 1965) is shown Aviation Administration (FAA) has explored the sensitivity in Figure 3, which presents the percentage of test subjects who of different atmospheres on overpressure and loudness levels were highly annoyed by the day’s boom events as a function of (Busch et al., 2017). As a consequence, efforts are underway CDNL for each day. Although the WSPR study was primarily to investigate human perception of these Mach cutoff sounds a methodological test in preparation for future studies with a (Ortega et al., 2018) using the FaINT dataset. low-boom demonstrator aircraft, the daily annoyance results are remarkably similar to those from the 1965 Borsky report. Sonic Boom Metrics Mach Cutoff There is a need to identify noise metrics to quantify the It is possible to fly supersonically without creating an noise exposure in dose-response curves of community test audible sonic boom on the ground by taking advantage data. These metrics, which can leverage existing metrics for of atmospheric refraction where the sonic boom pressure commercial, military, and impulsive noise sources, must

Fall 2018 | Acoustics Today | 27 Perception of Sonic Booms

be computed using outdoor signals (even if the majority • CDNL is the DNL calculated with C-weighted sound levels. of people spend most of their time indoors), analogous • PLDN is the day-night average PL that accounts for all noise to the process for subsonic aircraft noise certification and events in a 24-hour period and is based on PL (McCurdy environmental assessments. et al., 2004). A meta-analysis study was conducted to combine results Future Outlook from several years of laboratory testing into a meta-analysis On April 3, 2018, NASA announced a new project with to evaluate candidate noise metrics calculated on outdoor Lockheed Martin to build a low-boom flight demonstrator signals, with the objective of identifying the best subset experimental plane. Now known as the X-59 Quiet of metrics (Loubeau et al., 2015). An exhaustive list of SuperSonic Technology (QueSST) aircraft, this vehicle will approximately 70 metrics was compiled from standards be a purpose-built low-boom aircraft capable of creating and literature; expert judgment, including consideration shaped sonic booms and is intended to provide crucial data of nonacoustic factors, resulted in 25 metrics being chosen that can potentially enable commercial supersonic passenger for quantitative analysis. Three categories of metrics were air travel over land. NASA intends to gather community defined: (1) engineering metrics to describe aspects of response data for delivery to the FAA and ICAO from which the sound, (2) loudness metrics to account for human new rules for supersonic commercial overland flight may perception of sound, and (3) “hybrid” metrics that combine be developed and adopted. Researchers have been actively several metrics into one model. Based on laboratory studies developing the subjective dose-response procedures and of isolated outdoor and indoor booms (Loubeau et al., 2015) protocols for this testing. and incorporation of rattle and vibration effects (DeGolia and Loubeau, 2017), analyses resulted in six single-event Although tremendous progress has been made, two of the metrics: PL, ASEL, BSEL, DSEL, ESEL, and ISBAP (terms areas that have not received significant research attention defined in Single-Event Metrics). This set of metrics will be are the potential for sleep disturbance from low booms and used in the development of single-event and cumulative techniques to model and mitigate the effect of focused booms. dose-response curves from future studies of community As illustrated in Figure 2, a crescent of higher amplitude response to sonic booms. “focused” sonic boom occurs during transition from subsonic Single-Event Metrics to supersonic flight. Preliminary focused boom modeling and • A-, B-, C-, D-, and E-weighted sound exposure levels analysis methods developed as part of NASA’s Superboom (ASEL, BSEL, CSEL, DSEL, and ESEL, respectively) Caustic Analysis and Measurement Program (SCAMP; Page et combine both the intensity of the sound and its duration al., 2015) suggested that shaped booms do remain shaped and and represent the total sound energy in an event accounting retain their loudness reduction benefits even in focal zones. for the spectral weighting factors that amplify the higher The SCAMP also identified the trend that higher altitude and frequency content and deemphasize the lower frequency lower acceleration through transition will help minimize the content to various degrees. focus boom loudness from low-boom aircraft. It is anticipated • PL is the perceived level in decibels based on Stevens Mark that data can be gathered from the flight testing to further VII equal loudness (Stevens, 1972). It includes very low investigate sonic boom focal zones. frequency (1-Hz) energy and accounts for shock rise times and overpressure for N-waves and shaped sonic booms Other factors not considered in the subjective studies to date (Shepherd and Sullivan, 1991). include booms from other parts of the trajectory outside the • Indoor sonic boom annoyance predictor (ISBAP) is a cruise design point, secondary booms, noise in the shadow hybrid metric that applies a low-frequency correction zone beyond lateral cutoff, and sleep disturbance relating to factor to PL and is defined as ISBAP = PL + 0.4201*(CSEL any of these conditions. − ASEL) (Loubeau, 2014). Cumulative Metrics Summary • DNL is the day-night average sound level that accounts for Sonic boom simulators and special aircraft maneuvers have all noise events in a 24-hour period with a 10 dB nighttime been used to investigate human annoyance to sonic booms noise penalty for events occurring between 10 p.m. and 7 in outdoor and indoor environments. The most important a.m. local time. factors have been studied separately to shed light on the role

28 | Acoustics Today | Fall 2018 they each play in human perception. Studies have confirmed 2008 and 3rd Sound Quality Symposium, SQS 2008, Dearborn, MI, July the viability of using an outdoor metric to predict human 28-30, 2008. https://doi.org/10.1121/1.3587708. Leatherwood, J. D., Sullivan, B. M., Shepherd, K. P., McCurdy, D. A., and response indoors despite differences in noise dose indoors. Brown, S. A. (2002). Summary of recent NASA studies of human response Results indicate that low sonic booms, or sonic thumps, to sonic booms. The Journal of the Acoustical Society of America 111(1), are much less annoying than conventional sonic booms, 586-598. https://doi.org/10.1121/1.1371767. although annoyance levels need to be confirmed with Loubeau, A. (2013). Community response to low-amplitude sonic booms. Proceedings of Meetings on Acoustics 19, 040048. https://doi. community testing. org/10.1121/1.4799997. Loubeau, A. (2014). Evaluation of the effect of aircraft size on indoor an- Laboratory test results have been used in meta-analyses noyance caused by sonic booms. The Journal of the Acoustical Society of to evaluate candidate noise metrics, and six metrics are America 136(4), 2223. https://doi.org/10.1121/1.4900073. recommended for further consideration in development of Loubeau, A. (2018). Evaluation of the effect of aircraft size on indoor annoy- a new sonic boom noise certification standard. This subset ance caused by sonic booms and rattle noise. The Journal of the Acoustical Society of America 143(3), 1936. https://doi.org/10.1121/1.4922535. of metrics will be used in future analyses of community field Loubeau, A., Naka, Y., Cook, B. G., Sparrow, V. W., and Morgenstern, data using a purpose-built low-boom flight demonstrator. J. M. (2015). A new evaluation of noise metrics for sonic booms us- Present efforts at NASA are geared toward preparations ing existing data. 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Design of an indoor of America 143(3), 1936. https://doi.org/10.1121/1.5036332. sonic boom simulator at NASA Langley Research Center. Proceedings of Page, J. A., Hodgdon, K., Krecker, P., Cowart, R., Hobbs, C., Wilmer, C., the 23rd National Conference on Noise Control Engineering, NOISE-CON Koening, C., Holmes, T., Gaugler, T., Shumway, D. L., Rosenberger, J. L.,

Fall 2018 | Acoustics Today | 29 Perception of Sonic Booms

and Philips, D. (2014). Waveforms and Sonic Boom Perception and Re- BioSketches sponse (WSPR) Program Final Report: Low Boom Community Response Program Pilot Test Design, Execution and Analysis. Technical Report NASA/CR-2014-218180, National Aeronautics and Space Administration, Alexandra Loubeau is a research aero- Washington, DC. space engineer at the NASA Langley Page, J. A., Plotkin, K., Hobbs, C., Sparrow, V., Salamone, J., Cowart, R., Research Center, Hampton, VA. She Elmer, K.,Welge, H. R., Ladd, J., and Maglieri, D. (2015). Superboom Caus- received her MS and PhD in acoustics tic Analysis and Measurement Program (SCAMP) Final Report. Technical Report NASA/CR-2015-218871, National Aeronautics and Space Admin- from The Pennsylvania State University, istration, Washington, DC. State College, and has been researching Plotkin, K. J., Matischeck, J. R., and Tracy, R. R. (2008). Sonic Boom Cutoff sonic boom acoustics since then. As the Across the United States (AIAA-2008-3033). Proceedings of the 14th AIAA/ CEAS Aeroacoustics Conference (29th AIAA Aeroacoustics Conference), team lead for sonic boom community-response research American Institute of Aeronautics and Astronautics, Vancouver, BC, Can- at NASA, she is involved in the planning, execution, and ada, May 5-7, 2008. https://doi.org/10.2514/6.2008-3033. analysis of experimental, modeling, and psychoacoustics re- Rachami, J., and Page, J. A. (2010). Sonic boom modeling of advanced su- search. Alexandra enjoys playing the violin in a local orches- personic business jets in NextGen (AIAA 2010-1385). 48th AIAA Aero- space Sciences Meeting Including the New Horizons Forum and Aerospace tra, swimming, and learning languages. Exposition, Aerospace Sciences Meetings, Orlando, FL, January 4-7, 2010. https://doi.org/10.2514/6.2010-1385. Juliet Page, a physical scientist with the Rathsam, J., and Klos, J. (2016). Vibration penalty estimates for indoor an- US Department of Transportation Volpe noyance caused by sonic boom. The Journal of the Acoustical Society of America 139, 2007. https://doi.org/10.1121/1.4949897. Center, Cambridge, MA, has spent the Rathsam, J., Klos, J., Loubeau, A., Carr, D., and Davies, P. (2018). Effects last 32 years conducting and directing of chair vibration on indoor annoyance ratings of sonic booms. The theoretical and experimental research Journal of the Acoustical Society of America 143(1), 489-499. https://doi. org/10.1121/1.5019465. programs in acoustics for the aviation Rathsam, J., Loubeau, A., and Klos, J. (2012). A Study in a New Test Facility on In- and transportation sector. As a leading door Annoyance Caused by Sonic Booms. Technical Report TM-2012-217332, expert in the field of sonic boom, she has directed numer- National Aeronautics and Space Administration, Washington, DC. ous NASA, Federal Aviation Administration (FAA), Airport Rathsam, J., Loubeau, A., and Klos, J. (2015). Effects of indoor rattle sounds on annoyance caused by sonic booms. The Journal of the Acoustical Society Cooperative Research Program (ACRP), and Department of America 138(1), EL43-EL48. https://doi.org/10.1121/1.4922535. of Defense environmental analysis, measurement, research, Rogers, P. H., and Maglieri, D. J. (2015). Concorde booms and the mysteri- and NextGen programs and has been instrumental in the ous east coast noises. Acoustics Today 11(2), 34-42. development of acoustic measurement protocols. She is a Salamone, J. (2005). Portable sonic boom simulation. AIP Conference Pro- ceedings 838, 667. https://doi.org/10.1063/1.2210441. member of several US and international standards and tech- Salamone, J. (2009). Recent sonic boom propagation studies at Gulfstream nical committees. In her spare time, Juliet enjoys boating on Aerospace (AIAA 2009-3388). Proceedings of the 15th AIAA/CEAS Aero- Chesapeake Bay and making glass beads. acoustics Conference (30th AIAA Aeroacoustics Conference), American Institute of Aeronautics and Astronautics, Miami, FL, May 11-13, 2009. https://doi.org/10.2514/6.2009-3388. Shepherd, K. P., and Sullivan, B. M. (1991). A Loudness Calculation Proce- dure Applied to Shaped Sonic Booms. Technical Paper TP-3134, National The ASA's Women in Acoustics Committee was Aeronautics and Space Administration, Washington, DC. created in 1995 to address the need to foster a Sparrow, V. W. (2006). Lowering the boom. Acoustics Today 2(1), 20-28. supportive atmosphere within the Society and Stevens, S. S. (1972). Perceived level of noise by Mark VII and decibels (E). The Journal of the Acoustical Society of America 51(2), 575-601. https://doi. within the scientific community at large, ultimately org/10.1121/1.1912880. encouraging women to pursue rewarding and Sullivan, B. M., Davies, P., Hodgdon, K. K., Salamone, J. A., III, and Pilon, A. (2008). Realism assessment of sonic boom simulators. Noise Control En- satisfying careers in acoustics. gineering Journal 56(2), 141-157. https://doi.org/10.3397/1.2919547. Sullivan, B. M., Klos, J., Buehrle, R. D., McCurdy, D. A., and Haering, E. A., Learn more about the committee at Jr. (2010). Human Response to Low-Intensity Sonic Booms Heard Indoors and Outdoors. Technical Report TM-2010-216685, National Aeronautics http://womeninacoustics.org. and Space Administration, Washington, DC.

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