bluuebunny/crossref_metadata_2025 huggingface dataset:
Planar nearfield acoustical holography in high-speed subsonic flow.
Authors: Kim Yong-Joe , Kwon Hyu-Sang , Jung Seunghwan
Published: March 2010

The objective here is to develop a nearfield acoustical holography (NAH) theory that includes the effects of high-speed, subsonic flow. Recently, the speed of a transportation means such as aircraft or vehicle has significantly increased, e.g., too close to the speed of sound. As a result, the NAH data measured with a microphone array fixed on an aircraft or vehicle entail significant airflow effects such as a Doppler shift in wave number domain. Here, a convective wave equation is used to define a mapping function. The mapping function is then used to derive a NAH theory that includes the Doppler shift effect by mapping the convectional NAH procedure in the wave number domain. A numerical simulation with a monopole is performed at the high-speed airflow of Mach = 0.7. The reconstructed acoustic fields obtained by applying the proposed NAH procedure to the simulation data match well with the exact fields. Through an experiment with two loudspeakers performed in a wind tunnel at the speed of Mach = 0.1, it is also shown that the proposed NAH procedure can be used to successfully reconstruct the sound fields radiated from the two loudspeakers.
Angle dependent effects for impulse noise reduction for hearing protectors.
Authors: Murphy William J. , Khan Amir , Zechmann Edward L.
Published: March 2010

The proposed U.S. Environmental Protection Agency regulation for labeling hearing protection devices (HPDs) includes an impulsive noise reduction rating . In 2009, the American National Standards Institute Subcommittee for noise approved a revised standard for measuring the impulsive insertion loss of HPDs, ANSI/ASA S12.42-2009. The exposure at the ear in response to a forward-propagating wave depends strongly on the orientation of the head with respect to the direction of propagation. Furthermore, the insertion loss varies with the peak sound pressure level. This paper reports the results of tests performed using an acoustic shock tube to produce peak impulses of approximately 160-dB peak sound pressure level. Two manikins were evaluated: the GRAS KEMAR manikin equipped with 1/2 and 1/4 in. microphone in a GRAS 711 IEC coupler and the Institute de Saint Louis manikin equipped with a Bruel & Kjaer IEC 711 coupler equipped with a 1/4 in. microphone. The manikin heads were rotated through ±90 deg relative to the direction of the oncoming wavefront and impulsive peak insertion loss was measured according to S12.42-2009. [Portions of the research were supported by U.S. EPA Interagency Agreement No. 75921973-01-0.]
Measuring recreational firearm noise.
Authors: Rasmussen Per , Flamme Greg , Stewart Michael , Meinke Deanna , Lankford James
Published: March 2010

Recreational use of firearms in the United States is commonplace. There are 28 × 106 Americans who consider themselves hunters and 13 × 106 went hunting in 2000. Participation in the shooting sports, without the use of properly worn hearing protection, exposes the involved persons to high levels of impulsive noise which may cause hearing loss and/or tinnitus (ear ringing). The present study was initiated to gain a better understanding of the noise exposure created by contemporary firearms using state of the art instrumentation and to ultimately increase our knowledge and awareness of this unique noise hazard. The sound pressure signal created by recreational firearms as used in hunting or target practice is characterized by a high-frequency, short duration impulsive noise. This signal is perceived by the human ear as one single, loud impulse or “shot.” However, when the firearm sound level is measured with microphones capable of sampling wide frequency ranges and combined with high-speed data acquisition computer systems, the impulses can be resolved into a number of different acoustic signals related to different source mechanisms.
Two-substructure, time-domain transfer path analysis of transient dynamic response of mechanical systems with nonlinear coupling.
Authors: Jiang Wenwei , Lim Teik
Published: March 2010

The traditional frequency domain transfer path analysis has become a popular method to detect and diagnose vehicle NVH problems. Unfortunately, due to its reliance on frequency transfer functions, the approach is strictly effective only for linear time-invariant system and steady-state response. This limitation prevents the method from being applied to transient and/or nonlinear behavior such as clunk, shudder, and tip-in and tip-out. In this paper, a novel time domain transfer path analysis is proposed to deal with a class of non-linear transient response problems. It combines the versatility of the transfer path analysis for tracking transmission of vibratory energy between substructures and generality of the time domain analysis for treating transient response that is also nonlinear in nature. The formulation that is derived by combining the spectral-based substructure method and a discrete, piecewise convolution theory is applied to a lumped parameter system, and the results are compared with output from a direct numerical integration of the nonlinear equations of motion. Comparison results show significant promise and appear to be usable for solving real-life vehicle problems that are highly transient with moderate level of nonlinearity present.
Refinement of vehicle interior noise by reduction of driveline vibrations.
Authors: Tandogan Okan , Yapici Tarkan , Doganli Mert , Sevginer Caner
Published: March 2010

Driveline vibrations can be a significant vibration source, which require emphasis in vehicle NVH development studies. In the early design phases, it is usually not easy to predict the vehicle level NVH performance induced by the torsional irregularities of the driveline. Establishing a model with inertia, mass, and stiffness data taken from engine, transmission and driveline suppliers can be possible and useful to initiate preliminary cautions. However, it is first, a challenging job for OEMs to receive all relevant data from suppliers to create a reliable model. Second, driveline vibration-driven NVH response of a vehicle is mostly figured out in real-time testing. Therefore, it is of great importance to treat driveline vibrations as a potential source of customer concern in vehicles and should be investigated throughout the testing phase. In this study, a dissatisfying noise behavior of a coach is determined with objective data and defined by means of engine operating condition, frequency, and excitation orders. As a next step, the problem is cascaded to its possible sources by examining the exciters’ inputs and the transfer paths. Finally, the important parameters in the reduction in driveline torsional vibrations and, as a consequence, the refinement of vehicle interior noise are discussed.
Calculation of optimal damping placement in a vehicle interior.
Authors: Birkett Craig , Tang Poh-Soong , Featherman Dieter
Published: March 2010

A study was performed of a heavy duty truck cab to reduce interior noise with the objective of using a minimum amount of damping material. Several complementary tools were applied to the problem of determining damping material layout. Candidate locations for damping material were first identified by summing A-weighted velocities over the frequency range of interest. These velocities could be additionally weighted by acoustic sensitivity. Then an automatic optimization was performed using structural inputs to determine the optimal damping treatment from the candidate damping patches given weight constraints. Results were confirmed with testing on a vehicle dyno. The study was significant because it compared various practical methods of optimizing a vehicle interior.
Prediction of muffler insertion loss and shell noise by a hybrid finite element acoustic statistical energy analysis model.
Authors: Connelly Terence , Mattson Steve , Labyak Dave , Pruetz Jeff
Published: March 2010

A reactive automotive style muffler was used to evaluate and experimentally validate the numerical predictions of muffler acoustic performance. A CAD model of the silencer was developed and an acoustic FE mesh created. The interior of the muffler included two sections of perforated pipe, which were included in the cavity mesh. A hybrid FE-statistical energy analysis (SEA) numerical model was created from the finite element acoustic mesh and was excited by a diffuse acoustic field at the inlet and coupled via hybrid junctions to SEA semi-infinite fluids on both the inlet and outlet. From the hybrid acoustic model different FE-SEA modeling approaches were investigated to predict the shell noise. The muffler insertion loss and shell noise was measured experimentally using a broadband acoustic source piped into a hemi-anechoic chamber. A straight pipe with simple bends to recreate the path from muffler inlet to outlet was fabricated for comparison. Muffler insertion loss was calculated by means of a simple level difference between the silencer and the straight pipe. Shell vibration and radiated noise were also measured to validate the shell noise modeling. Agreement between experimental measurement and numerical prediction was found to be reasonably accurate up to 3 KHz.
Innovative quieter aspirator design for in-car temperature sensor.
Authors: Humbad Niranjan G. , Silaghi Dan , Morris Matthew
Published: March 2010

Many vehicles use automatic temperature sensor mounted on dash [instrumentation panel (IP)] to sense the vehicle interior temperature for controlling the climate comfort. One type of design requires airflow over the sensor to correctly measure the interior vehicle temperature. This suction airflow over sensor is produced by various means. The present study deals with a widely used aspirator design to draw/suck interior airflow from ventury effect caused by discharging HVAC module flow. Such a design has an inherent drawback of bringing the HVAC module noise and flow noise (generated by aspirator) to an opening mounted on dash (via a connecting tube from sensor to aspirator). In one application, this caused a customer noise complaint; noise levels were higher at frequencies above 2 kHz. This required a separate muffler part between aspirator and sensor to reduce this noise. A new innovative aspirator design was developed to replace the aspirator and muffler by a single part. This one piece assembly was designed to be easy for manufacturing but still keeping the same performance targets of the two part aspirator and muffler design. Test results of the new design are compared to the current design and shows meeting both the airflow and noise targets.
Passenger vehicle exhaust cool down noise measurement and sound assessment.
Authors: Szatkowski Antoni , Butler Brian
Published: March 2010

Passenger vehicle exhaust cool down is getting more attention as NVH vehicles quality is more and more refined. A new test procedure was developed and presented in this paper. Data acquisition, processing, and sound qualifying are presented. Four different metrics were developed that quantify the sound level and sound quality. A few examples of different exhaust systems were analyzed. Presented methodology is a great tool for different exhaust system ranking, benchmarking, comparison, and target setting.
The noise from flow over rough surfaces with small and large roughness elements.
Authors: Glegg Stewart , Devenport William
Published: March 2010

This paper will review theoretical and experimental results for the sound radiation from turbulent boundary layer flows over rough surfaces. Two distinctly different regimes will be considered. The first is hydrodynamically smooth surfaces for which the surface roughness does not impact the boundary layer turbulence. These surfaces have been shown experimentally and theoretically to radiate enhanced sound levels due to the scattering of the hydrodynamic pressure fluctuations by the roughness. The second regime considers large roughness elements that directly impact the boundary layer flow. Numerical calculations show that the flow separates around the large roughness elements and theoretically this implies that the roughness radiates sound in proportion to the unsteady force on each element. It is still an unresolved issue as to whether the unsteady loading is caused by the distortion of the turbulent flow around the element or the unsteady loading associated with the flow separation. This paper will describe the theoretical approaches which have been used to predict roughness noise levels in each of these two regimes and the transition from one regime to the other.
Simulation of acoustic noise in duct systems.
Authors: Prasad M.G. , Rajavel B.
Published: March 2010

Acoustical noise studies of automotive muffler, HVAC, and other duct systems are important in their design and performance. A methodology is developed for simulating the acoustical noise from a duct system which can be modeled in terms of source, duct element, and termination. In this methodology first the transfer function of the preliminary design of the duct system is obtained using system geometry, source, and radiation impedances. Then the impulse response of the obtained transfer function from the preliminary design is convolved with source signal to obtain the acoustic noise output of the system in frequency domain. In order to verify this methodology, the simulated noise is compared with experimentally measured noise for two types of duct systems, namely, a straight pipe and a simple expansion chamber. The results show good agreement between the simulated and measured noise spectra. The proposed methodology is then applied to obtain a simulation of noise reduced due to automotive muffler system. The methodology presented in this work provides the capability of simulating the noise of a duct and muffler system from its design stage before it is actually built. Further, this work could also be used for sound quality studies of duct systems.
Acoustic propagation in three-dimensional, rectangular ducts with flexible walls.
Authors: Lawrie Jane B.
Published: March 2010

Analytic expressions provide valuable benchmarks against which to check sophisticated finite element codes. In this talk some such expressions are presented for two duct configurations. Consideration is given first to the propagation of sound in a three-dimensional, unlined duct formed by three rigid walls, lying along y − 0, −b ≤ z ≤ b and z − ±b, 0 ≤ y ≤ a of a Cartesian frame reference, and closed by a thin elastic plate lying along y − a, −b ≤ z ≤ b. On assuming harmonic time dependence e−iωt, the fluid-coupled structural waves are expressed in the form Bnψn(y,z)e±isnx, n=0,1,2,…, where ψn(y,z) are an infinite set of non-separable eigenfunctions, sn are the admissible wavenumbers, and Bn are the wave amplitudes. An exact, closed form expression for the eigenfunctions is presented. Various properties of the eigensystem are discussed. Second, the effect of incorporating a porous lining into the above model is considered. It is shown how the analysis is extended to include this modification. Numerical results are presented for both situations.
Closed form calculation of reverberant sound propagation in a thin duct with flexible walls.
Authors: Panza Michael
Published: March 2010

An analytical method for calculating the propagation of reverberant sound between two parallel perfectly reflecting planes in a thin duct with flexible side walls is presented. The flexible walls are modeled with a complex wave number to account for dissipation within the wall material. A mathematical model based on the Euler–Maclaurin sum formula provides an approximate closed form Green’s function for the acoustic space. The method gives a set of two coupled integral equations in acoustic pressure and side wall displacement consisting of convolutions with respect to the spatial dimension along the duct. Laplace transforms for the spatial dimension are applied to the integral equations to solve for the acoustic pressure in terms of the spatial Laplace transforms of the Green functions for the reverberant acoustic space and the mechanical wave in the side wall material. A closed form solution is obtained by considering the first term of a binomial series in the Laplace domain and applying a partial fraction expansion leading to the solution in the spatial dimension along the duct. Numerical simulations show the behavior of the reverberant noise reduction provided by the flexible side walls along the duct.
Exploration of a hybrid noise control system in a cylindrical duct.
Authors: Too Gee-Pinn , Chen Shao-Rong
Published: March 2010

The purpose of this study is to explore the effects of sound elimination in a cylindrical duct by combining a reactive muffler and active noise control (ANC) system. Besides the exploration via experiment of the combined noise control system, predictions of desired signals in ANC system are proposed for this hybrid system. These predictions are Grey prediction based on Grey theory and signal processing for path impulse response function. In the experiment, the effects of sound elimination (such as transmission loss and insertion loss) are compared between cases with ANC systems installed before the muffler and after the muffler. The results indicate several conclusions that (1) the sequence of arrangement of muffler can influence the results of active noise control, (2) the effect of noise reduction in ANC system is influenced extremely by reference signal received, (3)the hybrid system has the advantages over a traditional muffler when the muffler is not designed for the frequency of the noise, and (4) predictions of the desired signals such as Grey prediction or path impulse response function could give a better control for the hybrid system.
Optimal microphone placement for active noise control in a forced-air cooling system.
Authors: de Callafon Raymond , Kinney Charles
Published: March 2010

In active noise cancellation systems with relatively small acoustic coupling, feedforward compensation is an effective methodology to create a controlled emission for sound attenuation. Especially for small electronic systems where forced air-cooling is required to control the temperature of large power sensitive components in the system, an active noise cancellation (ANC) system is a viable solution to reduce acoustic emissions. In this paper we discuss the placement of the noise source microphone for feedforward based active noise control in a forced-air cooling system. Noise source microphone placement is directed by the ANC performance of an on-line output-error based affine optimization of a linearly parametrized generalized finite impulse response filter for sound compensation. For the computation of the optimal filter, generalized or orthogonal FIR models are used as they exhibit the same linear parametrization as a standard FIR filter. The procedure is demonstrated on a small portable NEC LT170 data projector. The data projector is equipped with a shielded internal directional pick-up microphone to measure the sound created by the forced-air cooling of the projector’s light bulb. Non-invasive small directional speakers located at the inlet and outlet grill of the data projector are used to minimize acoustic coupling.
Reflection and transmission across partial blockages in fluid-filled flexible, non-thin-walled pipes.
Authors: Dupere Iain D. J. , Duan Wenbo
Published: March 2010

A model is presented for propagation along a flexible pipe whose thickness is not small in comparison with its diameter across a partial blockage with varying sizes and material properties. Comparison is made with Flugge’s well-known thin-shell theory for a propagation along a pipe where it is found that the additional computational complexity found in the current model becomes necessary when the thickness of the shell exceeds 10% of the pipe radius. Comparison is also made with experiment both for the propagation characteristics of the pipe and for the reflection from a partial blockage. Two reflection models are presented: a crude area change model with compensation for the mass of the blockage and a more accurate model using high-order modes and matching to a flexible blockage using co-location. Reasonable agreement is found for both with the more accurate model, giving better agreement but at the expense of computational efficiency. The work is useful both for blockage detection and for detecting stenosis in blood vessels.
Shaped optimization of multi-chamber mufflers with open-ended perforated inlets using a simulated annealing method.
Authors: Chang Ying-Chun , Chiu Min-Chie
Published: March 2010

Recently, research on new techniques of single-chamber mufflers equipped with a non-perforated intruding tube has been addressed; however, the research work on multi-chamber mufflers conjugated with open-ended perforated intruding inlet tubes which may dramatically increase the acoustical performance has been neglected. Therefore, the main purpose of this paper is not only to analyze the sound transmission loss (STL) of a multi-chamber open-ended perforated inlet-tube muffler but also to optimize the best design shape within a limited space. In this paper, the four-pole system matrix for evaluating the acoustic performance is derived by using a decoupled numerical method. Moreover, a simulated annealing method has been used during the optimization process. To appreciate the acoustical ability of the open-ended perforated intruding inlet-tube and chambers inside a muffler, two kinds of traditional multi-chamber mufflers hybridized with non-perforated intruding inlet tubes (one-chamber and two-chamber mufflers) have been assessed and compared. Results reveal that the maximal STL is precisely located at the desired tone. In addition, the acoustical performance of mufflers conjugated with perforated intruding inlet tubes is superior to traditional mufflers. Also, it has been shown that the acoustic performance for both pure tone and broadband noise will increase if the muffler has more chambers.
A subject centered approach to environmental noise effects: revisiting old concepts and proposing new methods.
Authors: Cance Caroline , Dubois Danièle
Published: March 2010

Considering the effects of noise implies that “somebody” is affected by noise. If the noise itself is not problematic regarding its measurement (by physics), the question is less clear regarding WHO is concerned by noise? Humans, animals? Asking such a question entails some other ones: Is any living system similarly affected by noise? Generally as an organism? Or differentially as “subjects”? What scientific domains are concerned with such studies? We would address these questions from our experience and knowledge on soundscapes. Starting from psychophysics that remains within the “endemic antinomy of a world-less subject confronting a thought-less object: the antique dualism of mind and matter” [Shalins (1976)], we will consider the diversity of subjects (animal as well as human “experts” of different types, acousticians, urban planners, politicians, and inhabitants) to propose an alternative conception we name “semiophysics”: it leads to reconsider the concepts of information versus meaning, as well as from a methodological point of view, the concepts of affordance versus Umwelt. Coupling field research and experimental work by accounting for meanings as relationships given to the world by the different subjects calls then for an ecological validity of laboratory investigations.
Predicting acoustic impact: Considering individuals versus populations.
Authors: Southall Brandon L. , Frankel Adam S. , Ellison William T.
Published: March 2010

Predictive models to assess the potential impacts of anthropogenic activities are increasing being used to assess environmental impacts. The most accurate models are, arguably, individual-based models that integrate species-specific biological and area-specific environmental data such as the acoustic impact model. These models simulate the movement of animals in four dimensions and typically include responses to both acoustic and/or non-acoustic environmental variables. The predicted exposures of individuals to sound sources may be assessed with a risk function; however, a recent meta-analysis of behavioral response and acoustic dose [Southall et al. (2007)] did not find meaningful linear relationships that were generally applicable between low to medium received sound levels and behavioral response. There appears to be significant variability in both species-specific and individual animal responses that are mediated by various contextual factors. Since regulatory requirements are often focused on population impact, the simplest approach to considering individual variability in behavioral response is that averaged over the population. Therefore, a mathematically linear dose-response function may be most applicable, at least within species for certain activity patterns, even if it is not supported for individual animals in all conditions.
Modeling the exposure of greater sage-grouse to noise from industrial gas drilling rigs.
Authors: Hooper Stacie L. , Hanser Sean , Patricelli Gail
Published: March 2010

Natural gas and methane extraction is a growing industry in Wyoming, and some greater sage-grouse leks appear to be declining in areas near industrial sites. The goal of this project is to develop a model for understanding whether industrial noise has played a significant role in these reductions in lek attendance. A software package called NMSIM, previously developed by Wylie Laboratories to measure noise exposure from aircraft for the National Park Service, is being used. NMSIM utilizes amplitude measurements, recorded a set distance from the noise source, topographic map data, and measurements of other factors affecting sound propagation such as temperature and humidity, to build a spatially explicit model simulating how noise from the industrial sites propagates over the surrounding terrain. Simulation results are then verified using a set of noise exposure measurements taken from known locations around the gas drilling rigs. In addition to explaining historic lek attendance patterns, this model will also be used to predict how noise from new industrial sites will impact nearby greater sage-grouse leks.
Hospital soundscape modeling.
Authors: Okcu Selen , Ryherd Erica , Zimring Craig
Published: March 2010

Effective soundscape solution considerations for hospital settings can be very complex. Some acoustic qualities of these soundscapes have been shown to have potential negative impacts on occupant outcomes. To enhance these qualities, different acoustic solutions are applied in the hospital settings. Testing the effectiveness of these implications is critical but not always practical in the real settings. In this study, we examined the soundspaces of critical care settings through acoustic models. This paper will discuss the preliminary results regarding the modeled acoustic qualities of various ICU settings such as noise levels and reverb qualities.
Controlling patient room reverberation with a thin acoustical wall treatment.
Authors: Babineau Francis J. , Sparks Amy
Published: March 2010

A study was conducted to explore an alternate method for reducing room reverberation time in a healthcare setting. Reverberation time (RT) is known to play an important role in overall noise levels and speech privacy, both of which are key factors in patient and staff satisfaction. However, RT is difficult to control in healthcare facilities, primarily due to durability and infection control requirements. A private patient room was treated with a thin, acoustically absorptive wall treatment. The wall treatment was not a typical acoustical finish, with absorption coefficients ranging from 0.05 to 0.6. However, several walls of the room were entirely covered with the treatment to achieve reverberation control. Reverberation times were measured before and after the installation, and results were consistent with predicted values. Despite being a small study, the results suggest that a thin acoustical wall treatment that meets durability and infection control requirements can be effective for controlling reverberation in healthcare facilities and creating a more comfortable environment for patients and staff.
Strengthening the healthcare guidelines: About the new online research community.
Authors: Sykes David M. , Cavanaugh William , Tocci Gregory , Carballeira Andrew
Published: March 2010

Myriad challenges and opportunities exist for researchers in the 2010 edition of the Guidelines for the Design and Construction of Healthcare Facilities. The new edition, released in January, contains the first comprehensive acoustical criteria ever included in the 60-year-old Guidelines that are now being adopted as code by most states, federal agencies, and municipalities. Enforcement—and future strengthening—of these Guidelines will require a strong, organized, well-funded research community in acoustics willing to do transdisciplinary research. Since federal agencies do not actively support research on the human impacts of noise in healthcare facilities but some private foundations do, the drafters of the Guidelines recently launched an online research community to enable research teams across the country to interact directly with interested foundations, government agencies, policy groups, and healthcare organizations. The online community has a distinguished Advisory Board of interested professionals in acoustical science, medicine, healthcare architecture, and engineering. It hosts an open database of recent research on acoustics and human health, RFPs and announcements, links to interested groups such as ICBEN, the World Health Organization and UIA-PHG, and other features such as blogs and wikis.
Mack Breazeale and E. A. Hiedemann’s group at Michigan State University.
Authors: Blackstock David T.
Published: March 2010

Mack Breazeale received a Ph.D. degree in physics at Michigan State University in 1957. He was one of 19 doctoral students supervised by Egon A. Hiedemann, who headed a very active group in ultrasonics at Michigan State in the 1950s and 1960s. Mack’s period there, 1954–1961, is reviewed and also the history of the Hiedemann group, which was well known for its contributions to physical acoustics. A particular interest in optical measurement of ultrasonic waves led to many theses and papers in nonlinear acoustics, at that time just beginning to enjoy a renaissance. Among those who, like Mack, went on to have very active roles in the Acoustical Society of America were Laszlo Adler, Bill Cook, Logan Hargrove, and Walter Mayer.
Impact of Mack Breazeale on the ultrasonic studies of interfaces.
Authors: Adler Laszlo
Published: March 2010

Over the last 50 years, Mack Breazeale made very significant contributions to Physical Acoustics. He was a great influence to his students as well as to researchers all around the world who carried on, continued, and expanded the work which was initiated by him. His work is well known on nonlinear studies of liquids and solids, acousto-optics, ultrasonic interaction at liquid-solid interfaces at the Rayleigh angle generating leaky waves, and many others. Nonlinear acoustic techniques improved material characterization of complex materials and structures significantly. The generation and detection of leaky waves opened up several applications in nondestructive evaluation. In this presentation, several of these techniques which were recently developed will be discussed. One of this is the optical detection of leaky waves at an air-solid interface which can be used to evaluate elastic properties of solids as well as surface imperfections. A nonlinear ultrasonic method to study interfaces between solid layers will be also presented. Mack Breazele leaves a legacy of knowledge, wisdom, and kindness and will always be remembered by us.
A diffraction correction for the nonlinearity parameter measured by the harmonic generation technique.
Authors: Yost William T.
Published: March 2010

Practical applications of harmonic generation to determine the nonlinearity parameter Beta generally tend toward the lower drive (fundamental) frequencies. As a result, diffraction effects on Beta become more significant. Derivations of a number of different diffraction correction formulas, which are applied for a piston source and a receiver located some distance away, are in the literature. In the paper by Blackburn and Breazeale [J. Acoust. Soc. Am. 76, 1755–1760 (1984)] the correction formulas were applied to the amplitude of the fundamental frequency and the results on Beta were experimentally tested. By building on this earlier work, a diffraction correction formula that includes a factor from a numerical integration algorithm applied to the harmonically generated wave is provided. The formulation of this algorithm is discussed. Experimental results are given for measurements of Beta in AA 2024 to illustrate the agreement.
Auditory stream segregation using amplitude modulated vocoder bandpass noise.
Authors: Nie Yingjiu , Nelson Peggy
Published: March 2010

We investigated the contribution of amplitude modulation (AM) rate and spectral separation to stream segregation of vocoder bandpass noises. Stimulus sequences were repeated pairs of A and B bursts, where bursts were white noise or vocoder bandpass noise carrying sinusoidal AM (100% modulation depth). Bursts differed either in the center frequency of the noise, or the AM rate, or both. Eight vocoder bands were used. The lowest four bands (1-2-3-4) were combined into one bandpass noise (B bursts) and the higher three bands (3-4-5, 4-5-6, and 6-7-8) were combined to constitute the A bursts. Results show that stream segregation ability increases with greater spectral separation. Larger AM rate separations were associated with stronger segregation abilities, but not when A and B bursts were both white noise. Significant inter-subject differences were noted. Results suggest that, while both spectral and AM rate separation separations could be cues for auditory stream segregation, stream segregation based on AM rate is more successful when combined with spectral separation. Correlations between segregation ability and understanding of vocoded speech will be discussed.
A test battery to assess localization ability in simulated complex acoustic environments.
Authors: Kerber Stefan , Seeber Bernhard U.
Published: March 2010

In complex acoustic environments, following a target sound is made difficult by the presence of noise and reverberation and especially hearing impaired people struggle understanding speech in such settings. Localizing the speaker is important in such situations to follow discussions and to gain additional benefit from visual cues. A test battery is proposed to quantify localization performance in different realistic environments and with laboratory tests when noise and reverberation are present. The aim is to relate real-life performance to that in simplified tests. In the localization tests, participants indicate the sound location with a visual pointer. Sounds are played in an anechoic chamber from loudspeakers across the frontal hemi-field. Localization performance is measured in quiet, in diffuse background noise, and with reverberation of simulated rooms. The ability to cope with a single reflection is assessed in a precedence effect paradigm where participants localize a sound and its delayed copy for various delays and levels. The test battery is completed by questionnaires (e.g., SSQ), a speech, and a cognitive test. By cross-comparing results from the tests, we attempt to predict the performance in real-world environments from outcomes of simplified tests particularly in the presence of hearing impairment.
Psychophysical tuning curves and recognition of highpass and lowpass filtered speech for a person with an inverted V-shaped audiogram.
Authors: Nagaraj Vinay , Moore Brian
Published: March 2010

A single subject whose audiogram resembled an inverted V shape (good hearing at 4000 Hz, poorer hearing at other frequencies) was tested. Results of the TEN(HL) test suggested that a dead region (DR) in the cochlea was present at all test frequencies from 500 to 3000 Hz, but no DR was present at 4000 Hz. Psychophysical tuning curves obtained using signal frequencies of 2000, 3000, 4000, and 6000 Hz showed upward shifted tips for the lowest two signal frequencies and a downward shifted tip for the highest frequency. The results suggested a functioning region extending from 3900 to 5100 Hz, with DRs outside that range. The identification of nonsense syllables, amplified according to the Cambridge formula, was measured as a function of lowpass or highpass filter cutoff frequency. The results suggested that useful speech information could only be extracted from a limited frequency range around 4000 Hz.
The relationship between quiet threshold and the forward-masking temporal effect.
Authors: Strickland Elizabeth A. , Shames Yonit A.
Published: March 2010

Research in our laboratory has shown that the temporal effect (TE) in simultaneous masking is consistent with a decrease in gain, possibly mediated by the medial olivocochlear reflex (MOCR). The TE in simultaneous masking is a decrease in threshold signal-to-masker ratio for a signal at masker onset when a precursor is added. This work has been extended to a forward-masking paradigm. A growth of masking (GOM) function is measured with a short-duration off-frequency masker (which should not activate the MOCR) and a 4-kHz signal. Then the masker level is fixed at a point on the lower leg of the GOM function, and threshold is measured with a long-duration precursor which is intended to activate the MOCR. The estimated input-output function is compared for a precursor at and well below the signal frequency. The difference in thresholds is the TE, which is also a measure of the change in gain. In simultaneous masking, the size of the TE decreases with increasing quiet threshold. In the present study, this relationship was examined for the forward-masking TE. The TE was measured as a function of precursor level for listeners who had a range of quiet thresholds, including listeners with mild cochlear hearing impairment. [Research supported by a grant from NIH(NIDCD) R01 DC008327.]
The effects of development and hearing impairment on the ability to understand speech in temporally and spectrally modulated noise.
Authors: Hall Joseph W. , Buss Emily , Grose John H.
Published: March 2010

This study examines the ability of hearing-impaired children to receive speech recognition benefit from temporal modulation, spectral modulation, or combined spectral and temporal modulation of a background noise. The task involves identification of words within the context of meaningful sentences presented in a speech-shaped noise background. Control groups include normal-hearing adults and children and hearing-impaired adults. The age range of the children is approximately 5–10 years. In the procedure, the masker level is held constant and the speech level is adaptively varied to track a criterion percent correct. Preliminary data suggest that both hearing-impaired children and hearing-impaired adults show a poorer than normal ability to benefit from temporal and spectral modulation. The hearing-impaired children require approximately 2-dB higher signal-to-noise ratio than the hearing-impaired adults for most conditions. The normal-hearing adults and children show better masked thresholds than their hearing-impaired counterparts, with normal-hearing adults generally performing 3–5 dB better than normal-hearing children across conditions.
Horizontal localization and hearing in noise ability in adults with sensorineural hearing loss using hearing aids with binaural processing.
Authors: Mullin Amy R.
Published: March 2010

The purpose of the study was to determine whether hearing aids with binaural processing improve performance during a localization and a hearing in noise task. The study included 15 participants between the ages of 29 and 68 who had a bilateral symmetrical sensorineural hearing loss and who had no prior hearing aid experience. Participants were fitted with Oticon Epoq XW receiver-in-the-ear hearing aids bilaterally. The participants completed a horizontal localization task and a hearing in noise task with three listening conditions: (1) without hearing aids (NO), (2) with hearing aids that were not linked (BIL), and (3) with hearing aids that were linked (BIN). For the horizontal localization task, 1.5-s pink noise bursts were used as the stimulus. Sentences from the Hearing in Noise Test were used as target stimuli for the hearing in noise task. Continuous discourse by one male and two female talkers was recorded and used as maskers. The specific aim of the localization and hearing in noise tasks was to determine which of the listening conditions resulted in the best score for each task. Data are still being collected and data analysis will follow.
Pitch-ranking of electric and acoustic stimuli by cochlear implant users with the HiRes and Fidelity120 speech processing strategies.
Authors: Russell Benjamin A. , Donaldson Gail S.
Published: March 2010

Estimates of place-pitch sensitivity in cochlear implant (CI) users are typically obtained using electric pulse trains presented directly to the implanted electrodes. Such estimates may overestimate the place-pitch sensitivity available to these listeners through their speech processors due to spectral smearing by the analysis filters. To determine the influence of speech processing on place-pitch sensitivity, electric pitch-ranking (EPR) and acoustic pitch-ranking (APR) thresholds were compared in four users of the Advanced Bionics CI. EPR thresholds were obtained for single- and dual-electrode pulse-train stimuli presented to electrodes near the center of the array. APR thresholds were obtained for pure tones having frequencies corresponding to the tonotopic locations of the electric pulse trains, using both the HiRes and Fidelity120 speech processing strategies. Counter to expectation, APR thresholds were similar to EPR thresholds for three of four subjects, and APR thresholds were smaller than EPR thresholds for the remaining subject. APR thresholds did not differ systematically for the HiRes and Fidelity120 strategies, consistent with Nogueira et al. [(in press). EURASIP J Adv Signal Proc]. Findings suggest that CI users can make use of across-channel cues when performing an APR task and that such cues can compensate for spectral smearing by the analysis filters.
Lowering mean fundamental frequency to improve speech intelligibility in noise under simulated electric-acoustic stimulation.
Authors: Brown Christopher A. , Bacon Sid P.
Published: March 2010

We have previously demonstrated that much or all of the benefits of electric-acoustic stimulation (EAS) can be achieved when the low-frequency speech is replaced with a tone that is modulated in both frequency and amplitude with F0 and amplitude envelope cues derived from the target speech. One advantage of this approach is that the frequency of the carrier tone can be lowered with little decline in benefit. Lowering mean F0 has the potential to provide EAS benefit to CI users who have very limited residual hearing. One drawback to this approach is that it relies on the efficacy of the pitch extraction algorithm. This is problematic because pitch extractors have trouble in background noise, an environment in which F0 is particularly useful. Here, an alternative way of lowering mean F0 that is unaffected by the presence of noise is examined under simulated EAS conditions. Speech intelligibility was measured using an algorithm based on resampling and compared to performance with the pitch-based method we have used previously, at frequency shifts of 0, 0.5, and 1 octave. At the 0.5-octave shift, the resampling-based approach provided more benefit than the tone. However, at the 1-octave shift, resampling was less beneficial. [Work supported by NIDCD.]
Decreasing the radiated acoustic and vibration noise of a mid-size, prop-driven, autonomous underwater vehicle.
Authors: Zimmerman Richard , D’Spain Gerald , Orcutt John
Published: March 2010

Previously published efforts at decreasing the radiated acoustic and vibration noise of the propulsion system of an Odyssey IIb autonomous underwater vehicle (AUV) manufactured by Bluefin Robotics, Inc. resulted in noise levels recorded by an AUV-mounted hydrophone array that were at or below typical background ocean noise levels across much of the frequency band from 300 Hz to 10 kHz [IEEE J. Ocean. Eng. 30, 179–187]. The modifications required to achieve this 20–50-dB reduction in propulsion noise levels will be reviewed in this talk. Recently, these modifications have been incorporated into the Bluefin 21 AUV at the Scripps Institution of Oceanography. In addition, the stepper motors in the linear actuators used to steer this AUV’s vectored-thrust tail cone in depth and heading have been replaced. At-sea measurements show that the high-level, broadband transients that previously occurred every 2–3 s due to these actuators are no longer visible in the hydrophone data. Eliminating these sources of self-noise allow the vehicle to be used in marine biological studies without vehicle noise disturbing either the acoustic measurements themselves or the habitats under observation. [Work supported by the Office of Naval Research and British Petroleum.]
Acoustic noise estimates for a quiet unmanned underwater vehicle.
Authors: Cascio Carl A.
Published: March 2010

Acoustical Technologies Inc. (ATI) has been tasked by a number of clients to predict the radiated noise of unmanned underwater vehicles (UUVs). Laboratory, dockside, and at sea measurements have been taken on 21-in.-diameter, 20-ft-long prototype vehicles. Data were obtained during operation of the propulsion motors, control surfaces, and other UUV components. Structural impact hammer testing was also used to estimate propagation path transfer functions. Acoustic noise and structural vibration sensors were recorded on the ATI multi-channel data acquisition system and analyzed to produce narrow and broad bandwidth spectral estimates over the 10-Hz–100-KHz frequency range. Radiated noise predictions from the component source level data and transfer functions were made and illustrate the importance of selecting quiet components and appropriate noise control. This paper takes a look at how quiet a 21-in.-diameter 20-ft-long UUV could be using what is currently known about typical UUV component hardware. This is not an estimate for a real UUV but a radiated noise model based on an ATI concept using quiet components, practical noise control, and generic transfer functions. Radiated noise estimates will be presented at several operating speeds.
Turbulent boundary layers over hydrophone arrays.
Authors: Dolder Craig N. , Haberman Michael R. , Tinney Charles E.
Published: March 2010

The speed at which naval vessels can operate sonar receiver arrays is limited due to the noise produced by the formation of a turbulent boundary layer (TBL) over the hull of the vessel. Despite efforts in the signal processing community to reduce these signatures, flow noise levels continue to surpass the signal to noise ratio needed for effective sonar operation at high-vessel speeds. This study focuses on the hydrodynamic signatures induced by the turbulence and the means by which energy can be removed from the TBL structures to reduce pressure fluctuations on the array elements. The research presented here employs an array of hydrophones with high-spatial resolution to measure the dynamic surface pressure while simultaneously acquiring time resolved single-point velocity field measurements at various positions above the array and within the TBL using laser Doppler velocimetry. Classical statistical quantities are then computed to determine the relationship between the pressure and velocity fields. Further, an analysis of the wave number frequency makeup of the surface pressure provides insight into the convective nature of the pressure filtered flow structures. The findings provide helpful guidance in developing active control methods for reducing the TBL noise.