bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of the Khokhlov–Zabolotskaya–Kuznetsov equation and Fourier-continuation for modeling high-intensity focused ultrasound beams.
Authors: Cheung Theresa , Cleveland Robin O. , Albin Nathan , Bruno Oscar P.
Published: March 2010

High-intensity focused ultrasound (HIFU) employs acoustic amplitudes that are high enough that nonlinear propagation effects are important in the evolution of the sound field. A common model for HIFU beams is the Khokhlov–Zabolotskaya–Kuznetsov (KZK) equation which accounts for nonlinearity and absorption of sound beams. The KZK equation models diffraction using the parabolic or paraxial approximation. For many HIFU sources the source aperture is similar to the focal length and the paraxial approximation may not be appropriate. Here we compare results obtained using the “Texas code” a time-domain numerical solution to the KZK equation to a new method of solving nonlinear differential equations: the Fourier-continuation (FC) method. Here the FC method solves the underlying fluid dynamics equations and does not invoke the paraxial approximation. Results were obtained for a 1.1-MHz focused HIFU source. The medium parameters were taken to either be hyperviscous water or to match human liver. For a low focusing gain transducer (focal length 50λ and radius 10λ) the KZK and FC models showed excellent agreement through the focal region. As the source radius was increased, discrepancies started to appear and for a radius of 30λ, the KZK model did not capture diffraction of the HIFU source accurately. [Work supported by NSF 0835795.]
Modeling diagnosis of the human middle ear.
Authors: Parent Pierre , Allen Jont
Published: March 2010

Tympanic membrane (TM) and ossicular (OSC) models have been studied for many years. Most are implemented in the frequency-domain via Kirchhoff’s equations. However, the frequency domain is less intuitive than the time-domain models and does not apply given non-linear phenomena. This research presents a human time-domain TM+OSC implementation, extending our cat model [J. Acoust. Soc. Am. 122, 918–931 (2007)] as a cascade of slightly missmatched transmission lines. The canal plane-wave volume velocity is uniformly distributed across the canal cross-section, and updated at ≈1 MHz (to accurately simulate sound propagation). The time-domain model includes both forward and backward waves, enabling for the first time, the computation of one-way delays, thus explaining why multi-modal propagation observed on the TM are not critical. Results are validated with data from normal and pathological ears. Additionally, comparisons between the acoustic impedance in living and dead (temporal bones) ears shows significant temporal-bone artifacts. Because of ear-dependent impedance missmatch, canal standing waves are observed. It is frequently assumed that the umbo pressure is the best reference pressure. In fact the “forward-pressure” P+ is a better estimate of the ideal reference, the cochlear pressure [J. Acoust. Soc. Am. 125, 1605–1611 (2009)].
An eardrum impedance simulator for use with physical replicas of the human ear canal.
Authors: Stinson Michael R. , Daigle Gilles A.
Published: March 2010

An eardrum impedance simulator has been incorporated into life-size replicas of the human ear canal. The simulator branches off from the ear canal at the center of the nominal eardrum position. It has been designed so that sound pressure distributions in an ear canal will have the same standing wave ratios as those measured previously in human subjects over the 4–10-kHz range. The key component of the eardrum simulator is a micro-perforated plate, whose holes provide damping through viscous and thermal boundary layer losses. The optimum design specifies 109 holes of 0.06 mm diameter in 0.003-in. shim stock. Measurements of sound pressure distribution in replica ear canals are underway to evaluate the acoustical performance of the eardrum simulator. The sound field is generated by an occluding hearing aid test fixture.
Forward-pressure level for in-the-ear calibration.
Authors: Neely Stephen T. , Gorga Michael P.
Published: March 2010

When acoustic impedance of the ear canal is known, sound pressure measured by a microphone in the ear canal can be decomposed into forward and reflected components. This decomposition provides a means to overcome problems associated with standing waves that may cause in-the-ear sound level calibration to be unreliable at high frequencies. Compared to total pressure measured at the sound source, we have demonstrated that forward pressure provides a more reliable estimate of sound quantity entering the ear, especially at frequencies above 4 kHz. Specifically, we have demonstrated increased reliability in measurements of distortion-product otoacoustic emissions (DPOAEs) when we use forward-pressure level (FPL) calibrations. Also, we have shown that behavioral threshold measurements for stimuli calibrated in FPL are more reliable than conventional calibration methods in the 4–10 kHz range. FPL calibration may provide advantages at high frequencies (1) for assessing hearing status with DPOAEs and (2) for fitting hearing aids using real-ear measurements. Objective methods of assessing hearing loss and fitting hearing aids at high frequencies are needed because the 6–12 kHz range is known to be important to young children for learning speech. [Work supported by Grants DC2251, DC8312, and DC4662 from the NIH/NIDCD.]
Capturing low-frequency cochlear impedance in time domain models: The role of viscosity.
Authors: Rapson Michael J. , Tapson Jonathan C.
Published: March 2010

Viscous effects in the cochlear fluid have been shown to be negligible for frequencies greater than 100 Hz [M. Viergever, Ph.D. thesis]. However, they become important at lower frequencies; hence viscous damping is sometimes included in helicotrema models [S. T. Neely and D. O. Kim, J. Acoust. Soc. Am. 79, 1472–1480 (1986)]. Modeling viscosity in time-domain computational cochlear models for wide-band input signals is problematic. Since the boundary layer thickness is inversely proportional to frequency, Navier–Stokes formulations require fine spatial resolutions, and fluid potential formulations are inherently inviscid models. Lumping all viscous effects into the helicotrema is not physiologically accurate as “the helicotrema does not appear to be a dominant constriction” [Lynch et al., J. Acoust. Soc. Am. 72, 108–130 (1982)]. An alternative is proposed whereby a fluid potential formulation is augmented with frequency dependent viscosity corrections that are based on prior analysis of the cochlear geometry and become negligible at higher frequencies. For simplified fluid boundary conditions, the predictions of this fluid model are compared to Navier–Stokes, potential, and lumped viscosity models for frequencies in the range 10 Hz–10 kHz. The simulations are also compared to physiological data for the input impedance of the cochlea.
What is known about banjo science and what is not yet known.
Authors: Rossing Thomas D.
Published: March 2010

Banjos generally come in three differrent types: five-string banjo with a resonator, five-string banjo without a resonator, and four-string banjo with a resonator. Only recently have banjos been the object of much scientific study, and most of these studies have been directed at the American five-string banjo. These investigations have considered the modes of vibration of the principal parts, how they couple together, and how they radiate sound. In general, peaks in the driving point mobility correlate well with modes of vibration in the banjo head and with the radiated sound. Systematic modifications of some of banjo parts have been made by various investigators, and the effects of these modifications are considered.
Time-resolved studies of banjo head motion.
Authors: Moore Thomas R. , Stephey Laurie A.
Published: March 2010

Almost all of the radiated sound from a banjo can be attributed to the motion of the membranic head. This motion depends critically on the physical properties of the membrane as well as which string is plucked and the direction of the initial displacement. We present time-resolved studies of the motion of the membrane of an American five-string banjo after plucking and discuss the interaction between the string and the vibrating membrane.
Sound transmission through double wall aircraft structures/mounting effect.
Authors: Pascale Neple , Noureddine Atalla , Maxime Bolduc
Published: March 2010

In the context of noise control treatment identification for turbulent boundary layer excitation, the main objective of this work is to assess the impact of mechanical links on the sound transmission loss through a double wall aircraft structure. An assembly of a stiffened panel made of composite fiber reinforced plastic (with a critical frequency around 6000 Hz) and a trim panel with a honeycomb core (with a critical frequency around 3000 Hz) has been considered in the whole study. The transmission loss of this double panel filled with glass wool blankets has been measured under diffuse sound field and point force excitation in the 100–10000 Hz frequency range for a fully decoupled configuration and a totally coupled one (rigid mounting). Extensive simulation using transfer matrix methodology has been conducted on the double panel for different glass wool filling rates, density, sound barriers, and add-on damping patches, for fully decoupled and rigid configuration. The main result is that the rigid mounting decreases significantly (up to 10 dB at 1000 Hz) the double wall transmission loss compared to a fully decoupled mounting and the acoustic efficiency of the passive treatments as well, whatever the excitation field.
Analysis of sound transmission through periodic structures typical for aircraft fuselages.
Authors: Cotoni Vincent
Published: March 2010

A novel numerical method is applied to calculate radiation properties and sound transmission loss of periodic structures typical for aircraft structures. The concept rests on that an accurate statistical energy analysis representation of the structure is determined from a small finite element (FE) model consisting of one or a few cells of the periodic structure. The FE model can be kept small and computationally efficient and can for this reason be used for parametric studies of the effect of design changes. Four different structures are analysed: a flat and a curved rib-stiffened panels typical of an aircraft fuselage, and an aluminium honeycomb inner floor panel. Calculated transmission loss results are found to compare well to measured data. Also mechanical power inputs due to point force excitations as well as radiation efficiencies are calculated and compared to measured data.
Prediction of the cabin noise of business jet using statistical energy analysis.
Authors: de Lima Washington , Ravindran Apoorv
Published: March 2010

The application of deterministic method (FEM and BEM) to predict vibroacoustic response of complex system like an aircraft fuselage is limited to low frequency due to large size of computational model for high frequency and the high frequencies modes are very sensitive to variation in the system properties which introduces substantial uncertainty. Energy based method such as energy statistical analysis (SEA) is an alternative that avoid these difficulties. This paper presents the vibroacoustic response of business jet using SEA. The SEA model is validated using in-flight tests with the aircraft in various acoustic package configurations.
Modeling freighter aircraft interior number.
Authors: Moeller Mark , Allen Albert
Published: March 2010

A freighter version of a commercial passenger airplane platform was developed. The new architecture includes an occupied space immediately aft of the flight deck and forward of the cargo space. A bulkhead separating the occupied space from the cargo space is designed to protect people from being compromised by cargo during a hard landing. Occupied space noise requirements affect the bulkhead design as it is a primary path of noise transmission from the cargo bay. Statistical energy analysis (SEA) noise models were developed to evaluate the noise performance of the bulkhead. Models were developed for ground test, flight test, and component configurations, respectively. The component model is described in a companion paper. A fourth, requirements model, was developed to demonstrate bulkhead noise compliance. The model development and correlation efforts are detailed in this document. SEA model results are shown to correlate reasonably well with the test data.
Acoustic assessment of pneumatic and electric jackleg drills used in the mining industry.
Authors: Camargo Hugo , Peterson J. Shawn , Kovalchik Peter
Published: March 2010

Hearing loss is the most prevalent disease among miners. A study of U.S. western hard-rock mines revealed that 96% of machine operators were overexposed to noise, with jackleg drill operators having the most rapid noise dose accumulation. Traditionally, jackleg drills have been driven by pneumatic power. However, there are currently available rotary hammer drills powered by electricity. This paper presents an acoustic assessment of pneumatic and electric jackleg drills that involved noise source identification (NSID), penetration rate and operator’s cumulative noise dose measurements, and determination of sound power levels. NSID using microphone phased array technology revealed two dominant noise sources for the electric drill, one located at the drill and one located at the drill steel-rock interaction place. In contrast, NSID for the pneumatic drill showed only one dominant noise source located at the drill. Penetration rate and noise dose measurements were combined to estimate the accumulated dose and time required to drill a reference depth hole. Sound power level measurements yielded overall 115 and 125 dB(A) for the electric and pneumatic drills, respectively. The results show that the acoustic performance of the electric drill, despite its slower penetration rates, overcomes the benefits of traditional pneumatic drills.
The development of a damped drill steel to reduce roof bolting machine drilling noise.
Authors: Peterson J. Shawn , Camargo Hugo , Goetchius Greg
Published: March 2010

Among underground coal miners, hearing loss remains one of the most common occupational illnesses. In response, the National Institute for Occupational Safety and Health (NIOSH) conducts research to reduce the noise emission of various underground coal mining equipment, an example of which is a roof bolting machine. Field studies support the premise that, on average, drilling noise is the loudest noise that a roof bolting machine operator would be exposed to and contributes significantly to the operators’ noise exposure. NIOSH has determined that the drill steel radiates a significant amount of noise during drilling. NIOSH has conducted research to evaluate a damped drill steel to reduce noise radiation. With this reduction in drilling noise, the noise exposure of the roof bolting machine operator is reduced. This paper documents the research to date of this damped drill steel. Laboratory testing confirms that the concept of a damped drilll steel reduces sound levels generated during drilling, and by extension, operator noise dose exposure.
An investigation of the noise dynamics in a southern illinois underground coal mine.
Authors: Szary Marek , Chugh Yoginder , Bell William , Hirschi Joseph
Published: March 2010

Noise in an underground coal mine has dominant components generated mainly from three sources: (1) continuous mining machine (CMM), (2) roof bolters, and (3) cars/vehicles which are transporting personnel end/or coal. Each of these three noise sources also has a number of well defined sub-sources with their own noise characteristics. The CMM noise is comprised mainly of noise generated by coal cutting drum, wet scrubber for dust control, and coal transport conveyor (called also the CMM’s tail). Roof bolter’s noise is generated during the drilling of the roof bolt holes in the bolting process. Personnel and coal transportation vehicles generate noise from the power driven system. The personnel most exposed to these noises are operators of these machines and associated support personnel. Three selected techniques with appropriate instrumentation were used to monitor exposure of the personnel to the noise and noise energy over a period of time. The most common technique is based on the use of personal noise dosimeters. The sound level meters (both pressure and power) were also used to collect noise data in form of instantaneous readings and also to check calibration of other sound measuring instruments. Most useful information was obtained from continuous recordings of the noise over time. This paper discusses the variability or dynamics of the generated noise in both frequency and time domains
Vibration impact of 150 MW cogeneration power plant on a semiconductor fabrication facility.
Authors: Bayat Ahmad , Davis Jon Byron
Published: March 2010

A 150 MW cogeneration power plant construction was planned next to an extremely vibration-sensitive semiconductor fabrication facility in Taiwan. Both facilities were under construction simultaneously. We were asked to evaluate the impact of the power plant vibration sources on the semiconductor facility and determine that they can coexist at only about 30 m separation distance. Some of the power plant sources included large rotating equipment such as 7000-HP heat extraction blowers, turbines, and pumps. Dynamic forcing functions were extracted from a similar plant. In situ transfer function mobilities were obtained using seismic load drop equipment. Predictions were made which were in-line with the as-built results with the exception of two blowers. Their foundation design had to be retrofitted with deep pile foundations to transfer their vibration to deeper stiffer soil.
Techniques for measuring the propagation speed of vibration waves in the ground.
Authors: Nash Anthony
Published: March 2010

Characterizing the transmission of ground vibration is important for assessing impacts upon buildings located adjacent to a rail right-of-way. This type ground-borne vibration transmission is typically dominated by surface or “Rayleigh” waves. When predicting the impacts, it is helpful to understand the attenuation of vibration from one location to another along the surface of the ground. In many cases, measuring the time-averaged rms vibration at spaced locations away from a line source is sufficient if one wishes only to quantify the reduction in ground borne energy density. For other purposes, however, it is essential to know the speed (and length) of the propagating wave front. This paper discusses successful (and not so successful) techniques for measuring the propagation speed of Rayleigh waves in the ground using both steady state and transient “point” sources. In terms of meaningful data, the steady state vibration method was found to be inferior to the transient vibration method. The steady state technique generated contradictory information on phase and amplitude at the spaced measurement locations. In contrast, the transient technique always indicated that (1) the Rayleigh wave propagated outward from the source and (2) the vibration amplitudes decreased between the near and far measurement locations.
Variation in measured force density levels of light rail vehicles.
Authors: Rajaram Shankar , Saurenman Hugh
Published: March 2010

The procedure recommended by the Federal Transit Administration for detailed predictions of ground-borne vibration is based on measurements at an existing rail system and measurements at the target site. A force density level (FDL) is derived from train vibration and line source transfer mobility (LSTM) measurements at the existing system. This FDL is then combined with the LSTM measured at the target site to develop predictions. This empirical procedure usually provides more reliable predictions than computer modeling procedures. FDL is assumed to characterize the trains and track support system and LSTM is assumed to characterize the effects of local geology. Implicit assumptions when applying this procedure are that FDL is independent of the local geology and that the vehicle and track support system will be the same at the target site as they are at the vehicle test site. This paper considers the differences in FDLs measured at light rail systems in Los Angeles, Minneapolis, Phoenix, and Portland. Issues discussed are how to adjust for train speed, why the speed adjustments are system specific, causes for FDL variations when the vehicles and track support systems are nominally the same, and procedures for obtaining consistent FDL measurements.
Navy aircraft carrier near-field jet noise and flight deck crew hearing protection.
Authors: Janousek James A. , Bjorn Valerie S. , McKinley Richard L. , Wilt James K.
Published: March 2010

Military jet operations on board US Navy aircraft carriers produce excessive acoustical noise fields in which personnel work. For those working in these noise environments, hearing impairment generally starts and worsens as they continue to perform countless high-stakes jet aircraft launch and recovery missions. Several noise measuring surveys were completed to characterize near-field jet noise on US Navy flight decks. These data set the foundation for numerous efforts to improve personal hearing protection and reduce jet engine noise.
Near-field noise of high-performance military aircraft and required hearing protection.
Authors: McKinley Richard L.
Published: March 2010

The near-field acoustic environment of a high-performance military jet aircraft is very complex and intense. The overall sound pressure levels at high-engine power settings can exceed 170 dB very near the aircraft and can be in the 130–150 dB range at personnel locations. This paper describes the measured near-field noise environments from several Air Force and Navy high performance aircraft such as the F-14, F-15, F-16, F-18, and F-35. This paper will also describe a technique of calculating the hearing protection requirements in octave bands using a baseline exposure criterion and noise dose.
Characterization of near- and far-field nonlinearity in high-performance military jet aircraft noise.
Authors: Neilsen Tracianne B. , Gee Kent L. , Downing J. Micah , James Michael M.
Published: March 2010

This study addresses the characterization of nonlinearity in military jet aircraft noise data in both the near and far fields. Previous work [Gee et al., J. Acoust. Soc. Am. 123, 4082–4093 (2008)] showed using a generalized Burgers equation-based model that nonlinear propagation effects were significant in far-field, ground run-up data from the F-22 Raptor for different engine powers and propagation angles. In this investigation, those findings are further vetted using data collected from the F-35 Joint Strike Fighter over greater propagation ranges and angles. The nonlinear nature of the near fields of the F-22 and F-35 jet noise is characterized through the calculation of maps of the waveform and waveform time derivative skewness as well as the crest factor. These results provide insights regarding short-range shock formation and the apparent origin of the nonlinearity-producing region of the plume. [Work supported by the Air Force Research Laboratory.]
Unique challenges for hearing protection in military noise environments.
Authors: Brungart Douglas S. , Cord Mary T. , Block Kim L.
Published: March 2010

Military noise environments, and, in particular, the noise environments faced by dismounted soldiers on the battlefield, are characterized by wide variations in ambient level. Situations can quickly and unexpectedly change from quiet conditions where the sound of a snapping twig might alert the listener to hostile enemy activity to extreme noise conditions where firefights, explosions, or loud machinery create levels of noise that can cause hearing loss in a matter of minutes or seconds. This poses a unique challenge for the designers of military hearing protection, who must produce systems that provide enough comfort and acoustic transparency to convince users to consistently wear them in quiet conditions to ensure that they will be in place if an unexpected blast or other potentially damaging noise exposure occurs. In this talk, we discuss some of the issues that can influence the willingness of listeners to wear hearing protection for extended periods in quiet environments, including acoustic factors that have been shown to influence situational awareness while wearing hearing protection. Additionally, lessons on the factors impacting the comfort of hearing devices drawn from studies of how consistently hearing aids are worn by hearing impaired listeners will be discussed.
Improved system for detection, localization, and classification of military impulse noise.
Authors: Allanach Jeffrey , Borodinsky Justin , Vipperman Jeffrey , Rhudy Matthew
Published: March 2010

Impulse noise monitoring systems are needed for quantifying the magnitude and time of impulsive noise events to ensure compliance and to provide an archival record of noise emanating from military installations. Currently, there are several commercial systems; however, they report an overwhelming number of false events generated by windborne noise and distant non-military acoustic events. This can bias noise statistics to the point where a meaningful assessment of the acoustic sound levels from a site is not possible. APS, in collaboration with the University of Pittsburgh, have developed an improved noise monitoring system for mitigating windborne and other sources of non-military noise. This system includes a collection of remote sensors capable of detection, localization, and classification. Each sensor uses an acoustic array and real-time signal processing codes to estimate the noise source location. Mitigation of windborne events is accomplished using cross-channel correlation analysis, beamforming, and classification. A prototype of this system is installed at the Marine Corps Base Camp Lejeune where it has been automatically reporting and archiving detected impulse noise. In this paper, we will present the specialized array processing algorithms, system design, and its performance as determined by months of detection statistics accumulated in the field.
Aircraft jet source noise measurements of a Lockheed Martin F-22 fighter jet using a prototype near-field acoustical holography measurement system.
Authors: James Michael M. , Gee Kent L. , Wall Alan T. , Downing J. Micah , Bradley Kevin A. , McInerny Sally Anne
Published: March 2010

Military jet aircraft generate high levels of noise which require innovative measurement and analysis methods to characterize the jet noise. A near-field acoustic holography (NAH) system is being developed to provide model refinement and benchmarking, evaluate performance of noise control devices, and predict ground maintenance personnel and community noise exposure. A prototype NAH system was used to perform jet source noise measurements of an F-22 at Holloman AFB, NM. This NAH system utilizes a patch and scan measurement approach using a 90 channel microphone array and over 50 reference microphones. The microphone array was used to make pressure measurements on a planar surface extending from the jet nozzle to 75 ft along the plume and over 6 ft in height. These measurements were made parallel either to the shear layer or to the nozzle center line of the jet plume at three different offset distances. Measurements were made every 6 in. on the surface which results in over 1800 measurements per offset distance. The ground based fixed reference microphones were located parallel to the nozzle center line. The measurement approach and pressure measurements for four power conditions detailing the source size, frequency content, and ground effect will be detailed. [Work supported by AFRL SBIR.]
An overview of issues concerning loudness measurement versus time.
Authors: Bray Wade R.
Published: March 2010

An overview of present methodologies for loudness measurement, especially considering time-varying sounds, is given. An ideal loudness-measuring method would mimic both the spectral and temporal acuities of human hearing including the relationship of those acuities at all audible frequencies. Due in part to practical considerations in their development history, none of the present set of loudness-measurement tools offers fully accurate representation of subjective time-frequency impressions. The most general limitations are insufficient spectral resolution and frequency-dependent time resolution. A recently standardized method well matches the temporal behavior of subjective loudness perception but only above a certain frequency due to lower-frequency time-resolution limits imposed by prior standards necessitating compliance. Examples will be shown of trade-offs and varying balances among several critical factors: time and frequency resolution at all audible frequencies, representation of temporal masking and growth/release effects, and appropriate spectral representations over varying combinations of broadband and narrowband signals.
Loudness models applied to technical sounds.
Authors: Sottek Roland
Published: March 2010

Loudness evaluation has become a central focus for assuring better consideration of subjective sound intensity phenomena than frequency-weighted levels such as dB(A). Different standards are available for evaluating loudness of stationary sounds (ANSI, ISO, and DIN). In principle, standards are very helpful in daily life, even if the method does not consider the most recent research results. But a variety of standards generating different results, at least for the most important technical or industrial sounds, may lead to confusion. Considering that most of these sounds are time variant, a single model of time-varying loudness is preferable. At present the recently published extension of the German standard for time-varying loudness (DIN 45631/A1) is the sole standardized method, applicable also for stationary sounds. There are other models allowing for loudness evaluation of time-variant sounds. Some years ago, a Hearing Model was borne out of a widespread interest to have a single standardized psychoacoustic model describing and explaining many phenomena at once. The Hearing Model is based on the physiology of human hearing and has been validated by testing against previously conducted psychoacoustic research results. The different methods will be compared and validated with subjective tests using technical sounds.
Safe lifetime occupational exposure-1 LONE (lifetime occupational noise exposure).
Authors: Bruce Robert D. , Bommer Arno S. , Lefkowitz Kimberly A. , Hart Noel W.
Published: March 2010

For many years, it has been recognized by those working in the field of industrial noise that understanding how much noise is needed to cause hearing loss over a lifetime is difficult to communicate to most people, even those who have an understanding of logarithms. The concept of expressing noise exposure in industrial situations without decibels is the focus of this paper. Eldred (“Sound Exposure without Decibels” Internoise-86) discussed this approach for community noise. ANSI Standard S3.44-1996 defines sound exposure with units of Pascals squared seconds, or PASQUES, as noted by Eldred. This paper proposes that a safe value for lifetime occupational exposure to noise be expressed in terms of PASQUES. The authors will discuss the pros and cons of such an approach and offer 11.5 × 106 million PASQUES as the upper limit for a safe lifetime exposure to occupational noise.
Earmuff noise attenuation by microphone in real ear technique.
Authors: Gerges Samir N. Y. , Agurto Danilo A. , Arenas Jorge , Coelho Jose Bento , Neves Miguel M.
Published: March 2010

When using a hearing protector at the workplace, it is necessary to quantify its noise attenuation by laboratory measurements. This paper aims at developing an objective methodology for measuring hearing protector noise attenuation of earmuff type using “microphone in real ear” (MIRE) method. The methodology uses the “insertion loss” (IL) as parameter, which is the difference between the sound pressure level with and without the hearing protector, using MIRE, and then calculating the hearing protector IL. The results for four different hearing protectors are compared with the subjective method “real-ear attenuation at threshold” (REAT). Factors such as physiological noise and bone conduction are quantified using the relation between MIRE and REAT method. Results are compared with values obtained from the literature.
Laboratory measurements of sound transmission at low frequencies.
Authors: Fuller Chris , Kondylas Kathleen , Levit Natalia
Published: March 2010

The ability of acoustic materials to attenuate sound is usually determined in accordance with ASTM E-90 or ISO 140-3, both based on the diffuse field theory. However, the reality is that the size of typical reverberant chambers does not provide a sufficiently diffuse field at low frequencies. As a result, there is significant variation in sound transmission data of tested materials below 150 Hz. Several attempts were undertaken to improve the accuracy of measuring TL such as increasing field diffuseness by using reflecting surfaces, installing near-field array of loudspeakers, and using sound intensity probes on the receiving sides. None of these proved totally satisfactory. This work presents studies on using various approaches to more accurately determine acoustic mitigation of low-frequency transmitted noise. A metal box consisting of a very rigid frame supporting elastic panels on all sides was acoustically excited by a loudspeaker suspended inside of the box. The panels and box interior were designed to have very low-fundamental frequencies. The box was suspended by its frame in an anechoic room. An intensity probe was used to measure the transmitted sound from the box panels. The acoustic performance of various acoustic materials was compared for frequencies below 500 Hz.
Acoustic impedance of Earth’s ground surface at infrasonic frequencies.
Authors: Zuckerwar Allan J.
Published: March 2010

The acoustic impedance of Earth’s ground surface is known to have a significant impact upon measurements of outdoor infrasound, e.g., sonic boom rise times. Current acoustic impedance models assume a rigid frame, or a no-slip condition, and thus lead to unbounded values of the real and imaginary parts of the acoustic impedance as the frequency approaches zero. The model of Tarnow [J. Acoust. Soc. Am. 105, 234–240 (1999)], on the other hand, considers relative motion between a porous frame (soil) and the air in the pores. It is shown here that this model yields finite values of the ground impedance in the limit to zero frequency. Further, extrapolation of selected experimental data to zero frequency by the method of the Richardson extrapolation also leads to finite values of the acoustic ground impedance. Finally, it is shown that the reflection of long-wavelength infrasound from bedrock may reveal resonance effects that will impact the ground impedance.
Research into the human response to vibration from railways in residential environments.
Authors: Waddington David C. , Moorhouse Andrew T. , Woodcock James , Whittle Nathan , Henning Sharron , Peris Eulalia , Sica Gennaro , Steele Andy , Brown Phil A. , Adams Mags D.
Published: March 2010

This paper describes progress in research being carried out at the University of Salford to develop a method by which human annoyance to vibration in residential environments can be assessed. The objective of this study is to yield a robust relationship between vibration exposure and human response, therefore providing a reliable basis for the development of standards and guidance for the assessment of vibration in residential buildings. The vibration sources to be considered are those affecting residents that are outside their control, such as construction, road, and rail activities. Noise is also a consideration. The protocol involves the measurement of vibration outside and inside individual residences and a social study questionnaire based on face-to-face interviews with householders. Work so far has concentrated on the response of people in their own homes to railway noise and vibration. Approximately 1000 case studies have been obtained, and examples of early field measurements and results are presented. This work is likely to be of interest to acoustical consultants and environmental health officers involved in the assessment of vibration complaints and to planners and practitioners involved in the design of buildings. [Work funded by the Department for Environment, Food and Rural Affairs (Defra) UK.]
Measurements of exploding balloon demonstrations.
Authors: Vernon Julia A. , Gee Kent L. , Macedone Jeffery H.
Published: March 2010

Exploding balloons are popular demonstrations in introductory chemistry and physical science classes and as part of outreach programs. However, as impulsive noise sources, these demonstrations constitute a possible hearing damage risk to both the demonstrator and the audience. Measurements of various hydrogen, hydrogen-oxygen, and acetylene-oxygen balloons were made in both a large lecture hall and an anechoic chamber. Condenser microphones (6.35 and 3.2-mm diameters) were placed at various angles, and distances from the balloon and time waveform data were collected at a sampling frequency of 192 kHz. For all balloon sizes tried, hydrogen-only balloons were found to produce peak sound pressure levels less than 140 dB at distances greater than or equal to 2 m. On the other hand, large (but reasonably sized) hydrogen-oxygen and acetylene balloons can result in peak levels exceeding 160 dB at a distance of 2 m, which constitutes a significant hearing risk for unprotected listeners at typical distances.
A comparison of wide-angle and narrow-angle progressive wave equations for modeling sonic boom propagation through turbulence.
Authors: Piacsek Andrew , McDonald B. Edward , Sparrow Victor
Published: March 2010

The high-angle formulation of the nonlinear progressive wave equation model (NPE2) [McDonald, Wave Motion 31, 165–171 (2000)] has been adapted for atmospheric propagation and is used to perform numerical simulations of sonic boom propagation through atmospheric turbulence. Turbulence is incorporated into the model as perturbations of the local ambient sound speed, which have a random spatial distribution determined by a von Karman energy spectrum. Wave forms, peak overpressures, and wavefront profiles computed at fixed ranges from the onset of turbulence are compared to corresponding solutions produced by the original (narrow-angle) version of the NPE in order to quantitatively assess the importance of wide-angle accuracy for sonic boom propagation.
The influence of non-standard atmospheric conditions on the potential number of acoustic signature occurrences in the continental United States.
Authors: Salamone Joe
Published: March 2010

The potential number of supersonic flight operations and their resulting acoustic signature occurrences are important components for assessing the overall impact of supersonic flight over populated areas. Gulfstream Aerospace has recently published estimates for the number of acoustic signatures that would occur per day, on average, over the continental United States based on actual flight movements from large cabin business jets. The previous analysis of the flight movement data assumed propagation from a supersonic vehicle flying at a constant altitude and Mach number through a standard atmosphere and also assumed great circle routing between the origin and destination airports. The present work will examine the influence that realistic flight profiles and non-standard atmospheric conditions have on the location and extent of the acoustic signature occurrences. The non-standard atmospheric conditions will consist of seasonally averaged, upper-air profiles from nearly 100 locations across the continental United States. The realistic flight profiles will be based on estimates for the climb capability of the supersonic vehicle and possible air traffic routing trajectories.
Prediction of shaped sonic boom focusing.
Authors: Pilon Anthony R.
Published: March 2010

The focusing effects of aircraft maneuvers and accelerations on shaped, or minimized, sonic boom signals have been investigated. The spectrally accurate boom prediction methodology of Pilon [AIAA J. 45, 2149–2156 (2007)] has been enhanced to include the effects of focusing through an implementation of the nonlinear Tricomi equation solver of Auger and Coulouvrat [AIAA J. 40, 1726–1734 (2002)]. The newly enhanced prediction tool was used to predict boom focus from aircraft accelerations, turns, and dives. Idealized near-field shaped boom signals were used as inputs to the code. Both fully resolved, continuous boom signals and booms containing zero-thickness shock waves were used as inputs to the focusing algorithm, in order to highlight the differences in perceived loudness on the ground. The new tool and results of the study will be used to help design accelerations and maneuvers for future supersonic cruise aircraft.
A combined ray-tracing and radiosity method for propagation and diffraction of sonic booms in urban landscapes.
Authors: Lefkowitz Kimberly , Sparrow Victor W.
Published: March 2010

Civil supersonic flight over land will only be allowed when sound levels are low enough to be acceptable to the public, and thus the sound field inside buildings needs to be well understood. To understand the field inside buildings, the sound field outside the buildings as well as the diffraction and loading on the building must be determined. A model to propagate sonic booms in urban landscapes was developed using a combined ray tracing and radiosity method. This model includes both diffuse and specular reflections for a single building configuration. The impact of diffuse reflections on the propagating and diffracting sound field will be examined, and multiple building configurations are also considered. The model results will be compared with data from NASA’s SonicBOBS (sonic booms on big structures) experiment conducted in September of 2009. [Work supported by NASA.]
Vibro-acoustic response of a simplified residential structure exposed to sonic booms. Part I: Numerical model.
Authors: Remillieux Marcel , Corcoran Joseph , Haac Ryan , Burdisso Ricardo , Reichard Georg
Published: March 2010

This paper presents a numerical model to predict the vibro-acoustic responses of simplified residential structures exposed to sonic booms. The model is validated experimentally in a companion paper. The dynamics of the fluid-structure system, including their interaction, is computed in the time domain using a modal-decomposition approach. In the dynamic equations of the system, the structural displacement is expressed in terms of summations over the in vacuo modes of vibration. The pressures inside the interior volumes are expressed as summations over the acoustic modes of rooms with perfectly reflecting surfaces. The structural modes are computed numerically using the finite element method. A shell element was specifically derived to model the structural components of typical residential buildings, e.g., plaster-wood walls, windows, and doors. The acoustic modes are computed for rectangular geometries using analytical expressions. Using modal decomposition, the dynamics of the fluid-structure system may be formulated by a finite set of ordinary differential equations (modal equations). These equations are then integrated with a Newmark algorithm to solve for the vibro-acoustic response of the system in the time domain. The system response may also be predicted in the frequency domain, by taking the Fourier transform of the time-domain response.
Vibro-acoustic response of a simplified residential structure exposed to sonic booms. Part II: Experimental validation.
Authors: Remillieux Marcel , Corcoran Joseph , Haac Ryan , Burdisso RicardoBurdisso , Reichard Georg
Published: March 2010

In a companion paper, a model was derived to predict the vibro-acoustic responses of simplified residential structures exposed to sonic booms. In the present paper, the experimental validation of the numerical model is presented. First, the experimental setup is described, including the structure, instrumentation, and external pressure loading. The structure was a single room made of plaster-wood walls and includes two double-panel windows and a door. The structure was extensively instrumented with accelerometers and microphones to record its vibro-acoustic response. Sonic booms with realistic amplitudes and durations were generated by an explosive technique. Subsequently, numerical predictions on the vibration of the structure and pressures inside the room are compared to experimental data, showing a fairly good agreement overall.
Distributed field measurements of low amplitude sonic booms.
Authors: Gavin Joseph , Arnold Jack , Nadeau Bryan , Klos Jacob , Haering Edward A.
Published: March 2010

Quiet supersonic flight over land appears increasingly viable, based on significant advancements in aircraft shape optimization. One of the next critical milestones will involve community scale surveys, measuring the public response to events that sound as benign as distant thunder. The present paper describes a measurement infrastructure to reduce the field costs associated with those tests. Specifically, a scalable grid of NI CompactRIO data acquisition systems has been developed and deployed in a risk reduction test. Highlights of the system include communications via a wireless rf network and synchronization using low cost GPS receivers. This paper highlights some of the development challenges, solutions, and recent results from component and system level risk reduction testing at the NASA Dryden Flight Research Center.
Generating correlated noise.
Authors: Hartmann William M. , Cho Yun Jin
Published: March 2010

Research on binaural hearing frequently presents partially correlated noise to a listener’s two ears. Experimentally, there are two classic methods to generate noise with a controlled amount of cross-correlation: the two-generator method and the three-generator method [J. C. R. Licklider and E. Dzendolet, Science, 107, 121–124 (1948)]. Analytic formulas were developed and numerical experiments were done to study the properties of the two methods, particularly to determine how well the actual correlations approach targeted correlations. It was found that both methods give very similar results, with variance that is greatest when the targeted cross-correlation is zero and which decreases monotonically to zero as the targeted value increases to 1.0. The variance decreases inversely as the first power of the number of degrees of freedom in the noise, whatever the targeted correlation. Paradoxically, a far less popular method, the symmetrical generator method, is far more successful. The variance is zero when the targeted cross-correlation is either zero or 1.0, and the variance decreases inversely as the square of the number of degrees of freedom. The symmetrical generator method is a reasonable alternative to the summing of digitally orthogonalized noises. [Work supported by the NIDCD DC-00181.]