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Perception of Benin Beams
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 €V9i'iis in 3 24'h°“1' P91'i°d and is based 01" PL (MCC“1'dY
environmental assessments. 5‘ ii-— 2004)-
A meta-a.nalysis study was conducted to combine results
from several years of laboratory testing into a meta-a.nalysis Fu‘-Mr: outlook d _ _th
to evaluate candidate noise metrics calculated on outdoor 0“ Apr 3' 2918’ NASA announce a _new Pmlecl M
. . . _ _ _ _ Lockheed Martin to build a low-boom flight demonstrator
signals, with the ob;ective of identifying the best subset ex erimemal [me Now known as the X69 Quiet
of metrics (Loubeau et al., 2015). An exhaustive list of S P S _ T in 1' (Q SST) _ ft th_ aha 11
approximately 70 metrics was compiled from standards buyer omc e: no Tgy b “E _ marfim ’ bl“ vf ‘ 2 
and literature; expert judgment, including consideration e a Purpllsei “ l ow‘ _°(_’m air“ Cap? e 0 Crealmg
. . _ _ shaped sonic booms and is intended to provide crucial data
of nonacoustic factors, resulted in 25 metrics being chosen _ _ _
for quantitative analysis. Three categories of metrics were tint can Potentially Enable colflmercial supersonic i’“"“g_"
defined: (1) engineering metrics to describe aspects of air travel over land.‘ NASA intends to gather community
the sound) (2) loudness marks to account for human response data for delivery to the FAA and ICAO from which
perception of sound, and (3) “hybrid” metrics that combine new rules for supersonic Commercial overland flight _may
several metrics into one model. Based on laboratory studies be deveioped and a‘_l°P_ted‘ Researchers have been actively
of isolated outdoor and indoor booms (Loubeau et al., 2015) developing the_ subléctwe dose-response Procedures and
and incorporation of rattle and vibration effects (DeGolia Protocols for ‘his testmg
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
sl."gIe_Event Metrics to supersonic flight. Preliminary focused boom niodeling and
- A—, B-, C-, D-, and E-weighted sound exposure levels am'lys_'5 meth°_ds developed as Part °f NASA5 S“i7"b°°m
(ASEL, BSEL, CSEL, DSEL, and ESEL, respectively) Caustic Analysis and Measurement Program (SC-‘W11’: Page et
combine both the intensity of the sound and its duration 3-iv 2015) 5“ggesled thal sh“Ped booms d° “main sh“Psd and
and represent the tmai sound energy in an event accouming retain their loudness reduction benefits even in focal zones.
for the spectral weighting factors that amplify the higher Thfi SCAMP 8150 identified the “End thai higher 81'-iiildfi 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 invgsfiga(g sonic boom focal zones‘
frequency (1-Hz) energy and accounts for shock rise times
and overpressure for N_Waves and shaped sonic boom Other factors not considered in the subjective studies to date
(Shepherd and S“]_1ivan_ 1g91)_ include booms from other parts of the trajectory outside the
- Indoor sonic boom annoyance predictor (ISBAP) is a Ci'“is9 design P°iflL S€C0n€i81'Yh00mS, noise in the Shadow
hybrid metric that applies 3»equei-icy convection 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).
CumuIxtiveMetrics 5‘-"'"“"5"'V
. DNL is the day-night average sound level that accounts for S°“iC boom sim“1“i°i's and sP9Ci3i aiicmfi ma-“s“V"s haw
all noise events in at 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.i-i-i. and 7 in outdoor and indoor environments. The most important
am. local time. factors have been studied separately to shed light on the role
as 1 AI:uuII:lr:I Tbday 1 mi 2013

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