Sonic Boom Impact Research Articles

Hyplane: a single-stage suborbital aerospaceplane.

This paper has the aim to report the status of the HYPLANE project to date. HYPLANE is a horizontal take-off and landing Mach 4.5 bizjet-size aerospaceplane conceived by Trans-Tech and University Federico II of Naples and under study within the industrial-academic ecosystem of the Campania Aerospace District (DAC). HYPLANE has the aim to offer very fast suborbital flight for space tourism, microgravity experimentation and training, and also shortening time to connect two distant airports within a door-to-door scenario. The concept is based on the access to stratospheric altitudes (30km) for either point-to-point stratospheric or suborbital flights as safe as today's commercial air transportation, by integrating enhanced state-of-the-art aeronautical and space technologies. Essentially, HYPLANE is mostly based on already relatively high TRL technologies which guarantees a sufficiently short time to market. The low wing loading configuration and designed ability to manoeuvre along the flight trajectories at small angles of attack, allow HYPLANE to guarantee accelerations and load factors of the same order as those characterizing the present civil aviation aircraft (FAA/EASA specifications). Thanks to its technical features, it may operate from/to more than 5000 airports all over the world needing short runways to take-off and land, which for point-to-point business aviation is paramount. Furthermore, characteristics such as small dimension, configuration and high cruising altitude determine reduced noise in the airports surrounding and low sonic boom impact on ground. These conditions will further facilitate not only the development of the commercial use of such kind of transportation mean, but also its social acceptability.

Development of computer code and calculation of the propagation of sonic boom to the ground in a real atmosphere

One of the main problems in the development of a supersonic aircraft of the second generation is to ensure a safe level of the sonic boom impact on the environment. Achieving such level at the preliminary design stage is possible with the help of reliable methods for calculating the characteristics of the sonic boom due to impossibility of tube experiments at far field and expensiveness of real flight tests. This paper presents method for determining the shape of the overpressure signatures in the generalized form of an augmented Burgers equation for the case of disturbances propagation in a moving medium (atmosphere with wind). Based on the presented method, the computer code “vBoom” has been developed. The calculation results of the sonic boom characteristics (overpressure waveforms, the loudness in different metrics and the sonic boom carpet on the ground) are presented in comparison with the results obtained by NASA within the international seminar SBPW3 [1] (Sonic Boom Prediction Workshop).

Tribute to Lou Sutherland

This will be a brief tribute to Lou Sutherland who I first met in 1989. Although Lou Sutherland recognized that I had no acoustics background back then, he treated me with utmost respect and professionalism. Lou mentored, guided, and challenged me while I was program director for the Noise and Sonic Boom Impact Technology Advanced Development Program Office for the Air Force’s Armstrong Medical Research Laboratory. I sought his wisdom as I faced critical decisions for my Service’s research program. Over these past 25 years, we haven’t had many occasions to work together, but the times we have had were significant and I will always cherish them.

Interaction of Sonic Booms with Isolated and Multiple Buildings

The sonic boom an aircraft generates when it travels faster than the speed of sound is the last environmental obstacle to the economic viability and widespread development of a commercial supersonic transport. One important aspect to consider in this problem is the impact of sonic booms at the ground level, and in particular their interactions with buildings. With this objective in mind, acoustic data was collected at Virginia Tech around and on the exterior surfaces of a simplified building structure exposed to simulated sonic booms, where an explosive technique was used to generate the desired pressure waveforms. These experiments were simulated with a three-dimensional numerical model by combining the image-source method for the reflected field with an extension of the Biot-Tolstoy-Medwin method for the diffracted field. This numerical model is verified against a boundary element solution and validated against experimental data. The key advantages of this modeling approach are pointed out such as the ability to model large three-dimensional domains over a wide frequency range and also to decompose the sound field into direct, reflected, and diffracted components, thus allowing a better understanding of the physical mechanisms involved in the sound propagation. This validated numerical model is also used to study the sound propagation around a cluster of six rectangular buildings, for a range of elevated source positions.

The impact of including diffraction when predicting the effect of listener environment on the perceived loudness of outdoor sonic booms

The human impact of sonic booms varies with listening environment. Given the incident sonic boom waveform, the specular field around a realistic geometry has been predicted via a C++ implementation of image source method (ISM) tailored to outdoor applications. This work explores the necessity of including the diffracted field when predicting time series and PLdB, both in and out of shadow zones. The impulsive nature of the excitation, and the sensitivity of the PLdB to temporal details, constrains appropriate diffraction modeling techniques to those capable of time domain accuracy. Uniform Theory of Diffraction (UTD) and Biot Tolstoy Medwin (BTM) approaches are considered. The benefits and challenges of each approach are explored, particularly with regards to scalability and bandwidth. The importance of accurately predicting diffraction in this application is evaluated through comparison with booms recorded around a building corresponding to the simulated geometry. [Work supported by the FAA/NASA/Transport Canada PARTNER Center Excellence and the Applied Research Laboratory. Experimental data courtesy of NASA.]

Metrics including time-varying loudness models to assess the impact of sonic booms and other transient sounds

Aircraft manufacturers have proposed that it is possible to build supersonic business jets that create low amplitude sonic booms that may be less objectionable to the public than those that led to the ban of civil supersonic flight over the US. Not only do the proposed sonic boom signatures differ from traditional sonic booms in amplitude, they also differ in shape. Due to the differences between these �low� booms and traditional booms, there has been increased interest in which metrics should be used to quantify the impact of these sounds. A semantic differential experiment, conducted over high quality earphones, was designed to determine the number of independent attributes people perceived and how these attributes influence acceptability or annoyance and to investigate what metrics were correlated to these factors. The work described here is focused on the performance of various metrics in predicting participants� ratings of impulsive sounds. It was found that statistics of and calculations derived from the output of Moore and Glasberg�s time-varying loudness model were the best predictors of participant-rated loudness, startle and annoyance. Performance of other commonly used metrics is also discussed.

Synthesis of sonic boom noise inside structures: An innovative experimental approach.

Current approaches to evaluate the impact of sonic booms on structures are rather few and limited. In this work, an innovative approach was developed and experimentally validated. It consists in simulating the distributed boom load on the structure using an array of discrete forces. Each discrete point force is the integrated sonic boom pressure loading (from experimental data or a diffraction code) over an area associated with that force. Under the assumption that the structure behaves linearly, each discrete force is applied sequentially and the desired vibro-acoustic responses recorded simultaneously with the applied force. The vibro-acoustic responses due to all forces applied simultaneously (and simulating the sonic boom load) can then be obtained simply as a linear superposition of the individual responses. Since the actual force time history due to the sonic boom does not need to be generated, the approach can be implemented using a shaker or modal hammer. Thus, it is sufficient to measure the transfer function between the input force and the vibro-acoustic response of interest. The vibro-acoustic data are then synthesized using the measured transfer functions and the loading on the structure to estimate the time histories of the forces due to the booms.

Sonic boom: From bang to puff.

For almost 40 years commercial supersonic flight over land has been prohibited because of the negative impact of sonic booms. During that time, technology advances have raised the possibility of a muted sonic boom—a sonic “puff”—that could be acceptable over populated areas. This paper reviews the physics of sonic boom generation and propagation, and why booms from conventional aircraft are usually N‐waves with unacceptably large shock waves. The low‐boom shaping technology that can minimize shocks, thus reducing sonic boom loudness to acceptable levels, is presented. The success of the DARPA/NASA Shaped Sonic Boom Demonstrator in validating shaping theory is discussed. Concepts for attaining practical aircraft configurations, versus ideal optimal shapes, are described.

Sonic boom environmental impact prediction methods and issues

Concerns over the environmental impact of sonic booms include their effect on humans, other animals, and fabricated structures. Over the past few years, CAA has been involved in a number of projects focusing on the latter two concerns. Specifically, working with Hubbs Sea World to supplement previous empirical studies, an analytical model was developed for estimating the sonic boom induced response of fertilized tern eggs and evaluated the potential for damage. Working with Wyle Laboratories, Inc., both direct and reciprocal structural-acoustic testing techniques were developed for simulating structural responses in order to assess damage. These methods were validated by comparison with data from actual flyovers. Curently, with Marine Acoustics, Inc., the authors are involved in a project to assess testing and other issues associated with predicting the subsea penetration of sonic booms for assessing marine mammal impacts. Here at issue are those physical processes that may transform from second to first order in light of the evanescent attenuation of the typically subsonic, ‘‘primary’’ acoustic wave that penetrates to depth. These three projects are reviewed in this talk. Particular attention is given to idealizations in the prediction process, the associated uncertainties, and their effects on the overall impact evaluation process. [Work supported by The Armstrong Laboratory of The U.S. Air Force.]

Sonic boom acceptability studies at NASA Langley Research Center

As part of the High Speed Research Program at NASA, Langley Research Center conducted a series of studies during the period 1990–1995 to evaluate human responses to sonic boom impact. This work, in combination with aircraft configuration design efforts, was aimed at determining the feasibility of overland supersonic flight. NASA conducted a three part program, comprising laboratory studies, in-home field experiments and community surveys. The laboratory studies used a sonic boom simulator and were designed to quantify relative loudness and annoyance response to a wide range of shaped boom signatures that might be produced by advanced aircraft configurations. The primary conclusion was that several common noise metrics were able to reliably predict judged loudness/annoyance. Field experiments were conducted in people’s homes using a noise simulation system. A controlled sound environment of booms of known level and number was introduced into a realistic home setting and human responses to a variety of boom exposures were assessed. It was found that the ‘‘equal energy’’ hypothesis was applicable to these boom exposures. Community surveys were conducted in two areas routinely impacted by sonic booms from military aircraft. Relationships between boom exposure and residents annoyance were developed for the two survey areas.

Validation of launch vehicle sonic boom predictions

Concern has been raised about the sonic boom levels generated by launch vehicle operations. To address this concern the USAF recently monitored the sonic boom generated by the launch of a Titan IV rocket and the reaction of the local wildlife. The sonic boom generated by this launch intersected the Channel Islands off the coast of Southern California. The sonic booms were recorded by the USAF Boom Event Analyzer Recorder and by DATs with low-frequency microphones on San Miguel, Santa Rosa, and Santa Cruz islands. Before the launch, predictions were made to assess the sonic boom impact on the islands. The prediction model used in this comparison was PCBoom3, a single-event sonic boom model developed by the USAF. This model has been updated to model sonic booms generated by launch vehicles and includes the effect of the rocket plume on the generation of the sonic boom. The measured sonic boom signatures are compared to predictions.

Transonic equivalence rule involving lift and shocks

For aerodynamic configurations with sufficiently high lift, the transonic equivalence rule must be modified for both linear and nonlinear lift contributions. The latter analyses show that for a thin wing having swept leading edges, with smooth lift and thickness distributions, the outer-flow region has a nonlinear structure determined principally by an equivalent line source and a line doublet. Apart from serving as a helpful guide to conceptual aerodynamic design, the equivalence rule and its extension can be useful in transonic wind-tunnel corrections, as well as studying sonic-boom impact at low-supersonic flight speed. We re-examine the inner and outer solutions and their matching and clarifie the accuracy levels of the theory with consideration of the higher order corrections and shock discontinuities in the outer flow.

Effects of aircraft noise on humans: Overview of NSBIT research program

The U.S. Air Force Noise and Sonic Boom Impact Technology (NSBIT) Program is conducting a comprehensive set of research projects on the effects of military aircraft overflight noise on humans. As the requirements for low-level, high-speed military training flights increase and the general public becomes more aware of possible impacts from these flights, it is becoming more important that improved models are developed to predict potential impacts on individual and community annoyance, sleep disturbance, human health, and other potential negative effects of aircraft noise. The problems inherent in using existing models for predicting human impacts are especially difficult when they are applied to military flying training activities because of the sporadic nature of these flights, their rapid onset rates, low altitudes, and high speeds. The NSBIT research program has been ongoing for several years and is yielding new data and improved environmental impact analysis models addressing several human effects issues. The presentation will provide an overview of the NSBIT human effects research program and will focus on the technical approaches being taken in each of the specific topic areas for both current and planned research.

The influence of nonacoustic factors on judgments of the annoyance of noise exposure

A theoretical model recently developed under sponsorship of the U.S. Air Force Noise and Sonic Boom Impact Technology Program treats annoyance judgments as the outcome of rational decision-making processes. Self-reports of the annoyance of noise exposure are partitioned into two components: one attributable to acoustic factors and one attributable to nonacoustic factors. This approach makes it possible to quantitatively estimate the contributions of nonacoustic factors (referred to collectively as “response bias” to judgments of the annoyance of noise intrusions. Application of this model to predicting the prevalence of annoyance due to different community noise sources is described.

Revision of a dosage‐effect relationship for the prevalence of noise‐related annoyance

More than a decade has passed since Schultz (1978) derived a relationship between noise exposure and the prevalence of annoyance from the findings of various social surveys of community response to general transportation noise sources. Numerous measurements of the prevalence of noise‐related annoyance have been published in subsequent years. A least‐squares quadratic fitting function to a set of 427 data points (developed by addition of 266 new data points to the original set of 161 data points) differs little from the third‐order polynomial fit to the original data set. [Work supported by U.S. Air Force Noise and Sonic Boom Impact Technology Program under Contract F33615‐86‐C‐0530.]

A theoretical model of the annoyance of individual noise intrusions

Self‐reports of noise‐induced annoyance can be modeled as the product of a rational, decisionlike process in which people discriminate among annoying and nonannoying noise intrusions heard in the presence of a reference distribution of noise exposure. This view, developed under the sponsorship of the U.S. Air Force Noise and Sonic Boom Impact Technology program, can assign explicit roles to both acoustic and nonacoustic variables in a probabilistic decision‐making process. The model, expressible in spreadsheet form, permits identification of two components of annoyance judgments: direct annoyance, based on sensitivity to the immediate characteristics of acoustic signals, and response bias. The model also provides insight into the extent to which acoustic variables may be considered to cause annoyance.

A theoretical interpretation of a dosage‐effect relationship for the prevalence of annoyance in a community

A dosage‐effect relationship by Schultz [“Synthesis of social surveys on noise annoyance,” J. Acoust. Soc. Am. 64, 377–405 (1978)], that relates community noise exposure to the prevalence of annoyance, has become a widely used tool in assessing environmental noise effects. Because Schultz's relationship is applied to a broad range of exposure conditions, and because it is entirely empirical, its application to specific situations is frequently challenged. A simple mathematical model can account not only for the shape of the relationship synthesized by Schultz, but also for the differences between Schultz's relationship and that proposed by Kryter [“Community annoyance from aircraft and ground vehicle noise,” J. Acoust. Soc. Am. 72, 1222–1242 (1982)]. A single parameter, representing response bias, suffices for this purpose. [This work was sponsored by the U.S. Air Force Noise and Sonic Boom Impact Technology program under Contract F33615‐86‐C‐0530.]