Perceived Level Research Articles

The noise dose range of the X-59 estimated from propagation simulations

NASA’s X-59 aircraft will soon be flown in a series of low-boom community noise surveys across the USA. Community test experimental designs will include noise dose schedules, which require an estimate of the noise dose range that X-59 can produce. To determine the dose range, propagation simulations using NASA’s PCBoom code were completed using CFD-generated X-59 C612A near-field pressure data for an on-design condition (Mach 1.4 at 53 200 ft) and two off-design conditions (Mach 1.4 at 46 000 ft and Mach 1.3 at 43 000 ft). Near-field data at four cardinal aircraft headings were propagated through one year of realistic atmospheric profiles from the Climate Forecast System Version 2 database at several USA locations. Statistics of the mean and range of the Perceived Level (PL) of the booms in the inner 40 km of each carpet as well as the carpet width were computed. Results indicate the typical inner carpet mean PL is approximately 70–87dB depending on the aircraft condition. The typical PL range across the inner carpet is 6–8 dB (on-design) and 5–13 dB (off-designs). The carpet widths ranged from 32–55 km. Understanding these quantities for various flight and atmospheric conditions is important for planning X-59 community noise surveys.

Preliminary lasso regression analysis of environmental effects on sonic boom metric variability

NASA’s Low-boom Flight Demonstration mission is a step toward commercial, overland supersonic flight. Certifying low-boom aircraft will require accurate measurement and understanding of uncertainty due to variations in meteorology, aircraft trajectory, and measurement environment. This work describes an analysis of the variability present in the Quiet Supersonic Flights 2018 (QSF18) dataset collected in Galveston, Texas, and an initial effort to correlate this variability with source and environmental factors. Although these data are for an F-18 executing a low-boom dive, no other low-boom dataset over a widespread populated area exists, and this study has the potential to guide future X-59 testing and data interpretation. Although several aircraft and meteorological variables are investigated for possible correlation, no single variable consistently explains the large variation in the measured booms. This has led to the use of lasso regression (LR) to identify the most relevant factors. Thus far, the fact that LR correlates boom Perceived Level (PL) with ambient PL is a strong indication of dataset contamination by significant ambient noise. Additionally, although several meteorological factors can contribute to boom metric variability, low-altitude wind speed is particularly important. [Work supported by NASA Langley Research Center through National Institute of Aerospace.]

Evaluation of numerical predictions of sonic boom level variability due to atmospheric turbulence.

A numerical model of full-scale N-wave sonic boom propagation through turbulence is described based on the nonlinear Khokhlov-Zabolotskaya-Kuznetzov (KZK) propagation equation and the most advanced turbulence model used in atmospheric acoustics. This paper presents the first quantitative evaluation of a KZK-based model using data from the recent Sonic Booms in Atmospheric Turbulence measurement campaigns, which produced one of the most extensive databases of full-scale distorted N-waves and concurrent atmospheric parameters. Simulated and measured distributions of the perceived level (PL) metric, which has been used to predict public annoyance due to sonic booms, are compared. For most of the conditions considered, the present model's predictions of the PL variances agree with the measurement to within normal uncertainty, while about half of the mean value predictions agree. The approximate PL distribution measured for high turbulence conditions falls within about 2 dB of the simulated distribution for nearly all probabilities. These favorable results suggest that the KZK-based model is sufficiently accurate for approximating the N-wave PL distribution, and the model may therefore be useful for predicting public reaction to sonic booms in turbulent conditions.

Simulated X-59 on- and off-design sonic boom levels in realistic atmospheres for noise dose range estimation

NASA is planning several community noise surveys across the USA using the X-59 low-boom aircraft. These surveys require a range of noise levels to resolve a dose-response relationship. The X-59 was designed to produce a shaped sonic boom with a Stevens’ Perceived Level (PL) of 75 dB or less across the boom carpet in a standard atmosphere. However, the X-59’s flight condition can be adjusted to produce levels other than 75 PLdB to obtain a range of doses during community testing. Simulated nearfield pressure waveforms of the X-59 C612A in its on-design condition (Mach 1.4 at 53 200 ft) and an off-design condition at a lower altitude (Mach 1.4 at 46 000 ft) were propagated using PCBoom through realistic atmospheres over the span of one year at several locations across the country. The predicted on-design and off-design boom levels and carpet widths are presented, resulting in a preliminary estimate of the dose range that the X-59 may produce. Future work is planned with additional off-design conditions to assess the true capable dose range of the X-59.

Simulations of X-59 low-booms propagated through measured atmospheric profiles in Galveston, Texas

During NASA's Quiet Supersonic Flights 2018 (QSF18) test, residents of Galveston, Texas and surrounding communities were exposed to low amplitude sonic booms for a community noise survey. Despite the flight test lasting only 11 days, substantial weather variability occurred including snow and record high temperatures. Similar atmospheric variability could occur in future community noise flight tests with the X-59 Quiet Supersonic Technology aircraft that is currently being constructed. X-59 is designed to have a Stevens Mark VII Perceived Level (PL) of 75 dB in a standard atmosphere. In this work, X-59's low-boom performance in real atmospheres was tested by using NASA's PCBoom code to simulate propagation of its nearfield pressure through the atmospheric profiles measured during QSF18. Results indicate undertrack booms would not exceed 75 PLdB in these atmospheres. A range of about 8.5 PLdB between the loudest and quietest undertrack boom was observed indicating adjustments to the X-59 flight condition may be needed to achieve target loudness levels during future sonic boom community noise surveys. Attenuation rate, ray tube area, path length and other quantities throughout propagation of the loudest and quietest booms are presented, which indicate humidity differences below 15kft were a primary driver of the PL differences.

Stevens perceived levels of common impulsive noises, sonic booms, and sonic thumps

NASA’s X-59 Quiet Supersonic Technology low boom flight demonstrator aircraft is being designed to produce a shaped sonic thump of 75 dB Perceived Level (PL) at the ground. The PL metric was chosen because it correlates well with human perception of sonic booms both outdoors and indoors. Members of the public often ask how loud 75 dB PL is. To communicate this level in terms of more familiar sounds, a PL reference scale was developed. Common impulsive sounds were recorded, and their PLs were computed. Some of the various impulsive sounds include distant thunder, basketball bounces, and car door slams (79, 81, and 89 dB PL, respectively). Concorde’s 105 dB PL traditional N-wave sonic boom is also included in the reference scale. Additionally, the impulsive sounds’ energy spectral densities and sone spectra are compared to that of a simulated X-59 ground waveform.

Comparison between predicted and measured Stevens perceived level of sonic booms for community response testing

In 2011, NASA conducted a flight test to study community response and perception of low amplitude sonic booms in the Waveforms and Sonic Boom Perception and Response (WSPR) experiment. Several noise monitors were placed in a 1.6 sq. km area to record the booms. In future sonic boom community response flight tests, it will not be practicable to place noise monitors at the locations of every survey respondent. Therefore, noise predictions are necessary. Using NASA’s PCBoom code, the Stevens Mark VII Perceived Level (PL) was predicted at each noise monitor locations using the real aircraft trajectories and weather balloon data taken during the WSPR test. These predictions are then compared to the measured PL values. This comparison will inform the methodology for estimating noise exposure in future flight tests.

Erratum: Stability of sonic boom metrics regarding signature distortions in atmospheric turbulence [J. Acoust. Soc. Am. 141(6), EL592-EL597 (2017)

In Doebler and Sparrow [J. Acoust. Soc. Am. 141(6), EL592-EL597 (2017)], a collection of five sonic boom metrics were analyzed to see which was the most stable in atmospheric turbulence. After publication, a mistake in one metric calculation was discovered that alters a portion of the results from that work. The purpose of this note is to correct those results-replacing one figure and commenting on another. The correction indicates that the Indoor Sonic Boom Annoyance Predictor (ISBAP) is a stable metric in regards to turbulence. ISBAP and B-weighted Sound Exposure Level (BSEL) are found to be similarly stable. E-weighted Sound Exposure Level (ESEL) is the next most stable followed by Steven's Mark VII Perceived Level (PL) and A-weighted Sound Exposure Level (ASEL).

Patient’s Expectation and Perception for Preorthodontic Treatment Consultation: A Study in a Dental School

ObjectivesThe aim of the study is to explore the desired expectation (DE), adequate expectation (AE), zone of tolerance (ZoT), and perceived level (PL) from the patients attending a preorthodontic treatment consultation at Orthodontic Clinic, Dental School, Prince of Songkla University, Thailand.Materials and MethodsA total of 170 patients aged 15 years and older were asked to express their DE and AE before the consultation and to give their PL after the consultation. Two sets of questionnaires were used in this study. The first set was designed to gain data regarding general information and the measured level of expectation. The second set was used to measure the PL of patients after the preorthodontic consultation. Both questionnaires contained four dimensions of the service: Dentist’s courtesy, dentist’s care and examination, dentist’s communication, and convenience of the services.ResultsThe communication dimension especially information regarding the orthodontic treatment need got rather low PL compared to others.ConclusionThe information regarding the orthodontic treatment need was the main item that patients need to receive in the consultation.

Empathic Accuracy and Observed Demand Behavior in Couples.

Empathic Accuracy and Observed Demand Behavior in Couples.

Evaluation of the effect of aircraft size on indoor annoyance caused by sonic booms

Sonic booms from recently proposed supersonic aircraft designs developed with advanced tools are predicted to be quieter than those from previous designs. The possibility of developing a low-boom flight demonstration vehicle for conducting community response studies has attracted international interest. These studies would provide data to guide development of a preliminary noise certification standard for commercial supersonic aircraft. An affordable approach to conducting these studies suggests the use of a sub-scale experimental aircraft. Due to the smaller size and weight of the sub-scale vehicle, the resulting sonic boom is expected to contain spectral characteristics that differ from that of a full-scale vehicle. To determine the relevance of using a sub-scale aircraft for community annoyance studies, a laboratory study was conducted to verify that these spectral differences do not significantly affect human response. Indoor annoyance was evaluated for a variety of sonic booms predicted for several different sizes of vehicles. Previously reported results compared indoor annoyance for the different sizes using the metric Perceived Level (PL) at the exterior of the structure. Updated results include analyses with other candidate noise metrics, nonlinear regression, and specific boom duration effects.

Effects of short noise bursts on human performance and perception

The goal of this research project is to better quantify human reactions to short bursts of noise, to complement research at NASA Langley Research Center on evaluating human response inside buildings to low-level sonic booms. The project involved exposing participants over 30-minute sessions to 250 ms broadband noise bursts of certain levels, presented in a controlled yet randomized fashion throughout the session, and gathering responses on human perception and performance on an arithmetic task dealing with short-term memory. While previous research has demonstrated effects of noise bursts of varying amplitudes on other types of tasks that study cognitive processing including attention and at louder levels on this arithmetic task (i.e. 100 dB peak), more information is needed to indicate at what level and to what degree such noise bursts may impact human performance and perception. Twenty-seven test subjects were tested over multiple sessions, with four different levels of the noise bursts, ranging from 47 to 77 dBA. The gathered performance and perception results will be presented, with consideration of each subject’s self-reported noise sensitivity. The results will also be correlated to a number of noise metrics, including perceived level (PL) and L1-L99. [Work supported by a NASA Nebraska Space Grant.]

Human response to sonic booms and rattle heard indoors.

Human response to sonic booms heard indoors is affected by the generation of contact-induced rattle noise. The effect of sonic boom-induced rattle noise was studied in a series of psychoacoustics tests. In order to remove the effects of loudness, sounds were equalized to the same perceived level (PL) in each test. Stimuli were divided into three categories and presented in three different studies: isolated rattles at the same calculated PL, sonic booms combined with rattles at the same calculated PL, and sonic booms combined with rattles at three different PL. The sonic booms, both measured and synthesized, were filtered to simulate presentation inside structures with different transmission and reverberation properties. The rattle sounds due to sonic booms or mechanical loading were recorded in a residential home. Subjects listened to sounds over headphones and were asked to judge the level of annoyance of other factors, depending on the test. Annoyance to different rattles is shown to vary, and the combination of sonic booms and rattles can be more annoying than the sonic boom alone. These results show that the PL metric does not fully represent human annoyance to the selected indoor sonic boom and rattle sounds.

Who do we think we are? The effects of social context and social identification on in‐group stereotyping

In this study, in-group stereotyping was examined as a function of variations in social context and perceiver factors. The social context consisted of different comparison groups and different domains of comparison. Comparison group and comparative domain were expected to interact in determining the content of the in-group stereotype. This prediction was confirmed with in-group stereotyping being strongest in conditions where the combination of comparison group and comparative domain made the in-group seem most similar to an out-group. The perceiver's level of in-group identification was also positively related to the level of in-group stereotyping. Moreover, the level of identification was shown to be dependent on the immediate social context and mediated the relationship between social context and in-group stereotyping. This pattern is explained in terms of a search for in-group distinctiveness.

Haptic Perception of Affordances of a Sport Implement: Choosing Hockey Sticks for Power versus Precision Actions on the Basis of “Feel”

The present study investigated how changing the mass distribution of a hockey stick influenced the perceived affordances of a stick's utility for performing either a precision or power action. Top-weighted sticks were preferred for executing precisely controlled movements, both before and after using the stick to complete an interception action task. Initially, participants in the power condition preferred the bottom -weighted stick. However, once participants performed the power condition action task, they preferred a stick with a mass concentration closer to their point of grasp. These results indicate that a held object's perceived affordances are influenced both by its mass distribution, and the perceiver's level of experience using the tool for a given action. Human factors consideration include designing hand-held sporting equipment that capitalizes on people's sensitivity to an object's mass distribution.

Person perception in the heat of conflict: Negative trait attributions affect procedural preferences and account for situational and cultural differences

Disputes by their nature involve contentious behavior. If one attributes such behavior to underlying personality traits, these attributions can be quite damning. The current research investigated negative trait attributions and their impact on dispute resolution decisions. We hypothesized that judging one's opponent to be low in agreeableness and high in emotionality (e.g. stubborn and volatile) shifts one’s preference towards more formal procedures – formal in the sense that a third party judge controls the process and outcome. Drawing on the attribution literature, we hypothesized that two antecedents of these judgments (and consequent preferences) are the perceiver's level of prior information and the perceiver's cultural proclivity to explaining behavior in terms of personal dispositions. Results of an experiment measuring reactions to a hypothetical dispute found that prior information and culture (USA vs Hong Kong) increased trait attributions and preferences for formal procedures. Additionally, expectancy measures showed interaction effects suggesting that disputants dynamically construct expectancies in light of their personality impressions.

Research on a sonic boom evaluation and low-boom and low-drag design

Kawasaki Heavy Industries, Ltd. has been researching on a sonic boom since 1990 toward the development of the next-generation SST (super sonic transport). A small chamber where a similar-sonic-boom could be created was made in 1993, and over 200 tests were carried out to see the reaction of people inside the chamber. As the result, it was found that A-weighted sound-pressure level (ASEL) and Stevens’ Mark VII perceived level (PL) were good metrics for boom evaluation, and the intolerable levels of ASEL and PL were studied. At the same time, an aerodynamic design technique was developed, which was produced by combining the low-boom theory of Darden (NASA) with the low-drag design method of super sonic aircraft. The validity of the design technique was verified by computational fluid dynamics (CFD) and wind tunnel testing. The effect of trim characteristics on a sonic boom has also been studied for more practical investigations. A boom propagation has also been calculated recently by using Hayes’ program for more understanding. The effects of weight, altitude, and Mach number on a propagating boom were investigated by parametric studies using the next-generation SST configurations in Japan.

Women who tell and men who ask: Perceptions of men and women departing from gender stereotypes during initial interaction

An experiment was conducted to determine if behavior that deviated from gender stereotypes during initial interaction produced less positive perceptions of a target than did behavior conforming to stereotype. Thirty-seven males and 38 females (targets) were randomly assigned to conditions where they either enacted a behavior stereotypical to their gender or engaged in a behavior departing from the stereotype during initial interaction with a randomly assigned different-gender stranger (perceiver). All of the participants were raised in the United States. The majority of participants were Caucasian, approximately 30% of the participants were Hispanic. The participants were predominantly middle class. The gender stereotypical condition required the female target to ask questions and the male target to talk about himself during the interaction. A second condition required male and female targets to do the reverse (female tell and male ask). Following the interaction perceivers completed measures of positive affect and social attractiveness. The results indicated that perceptions of targets engaging in behavior opposite of gender stereotypes depend on the perceiver's level of gender-schematicity. The level of gender schematicity indicates a person's tendency to depend on traditional gender stereotypes. While schematics tended to feel less positively or no differently during interactions with gender opposite versus gender norm targets, they tended to evaluate the gender opposite target as more or no differently socially attractive than gender norm targets. Results also suggest that men may have more latitude to engage in gender opposite behaviors than do women.

Loudness evaluation of sounds transmitted through walls—basic experiment with artificial sounds

A basic psycho-acoustic experiment was performed in order to establish a reliable method for evaluating insulation properties of building walls against airborne sound. Eleven models were used to represent actual sound insulation characteristics and three models used for incident noises on walls. Results of a four-step hearing test were arranged according to five well-known measures for noise assessment, and Perceived Level ( PL) was found to be the best among them for assessing the loudness of the sound transmitted through walls. In addition, arithmetic mean values of the sound pressure levels in octave bands from 63 Hz or 125 Hz to 4 kHz were examined. It was found that such simple measures have an unexpectedly high correlation with the loudness, surpassing even the PL. This suggests that the arithmetic mean value of the sound transmission losses in octave bands is a good single-number measure for rating the airborne sound insulation performance of walls.