bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection, bearing estimation, and telemetry of North Atlantic right whale vocalizations using a wave glider autonomous vehicle
Authors: Cheyne Harold A. , Key Charles R. , Satter Michael J.
Published: October 2014

Assessing and mitigating the effects of anthropogenic noise on marine mammals is limited by the typically employed technologies of archival underwater acoustic recorders and towed hydrophone arrays. Data from archival recorders are analyzed months after the activity of interest, so assessment occurs long after the events and mitigation of those activities is impossible. Towed hydrophone arrays suffer from nearby ship and seismic air gun noise, and they require substantial on-board human and computing resources. This work has developed an acoustic data acquisition, processing, and transmission system for use on a Wave Glider, to overcome these limitations by providing near real-time marine mammal acoustic data from a portable and persistent autonomous platform. Sea tests have demonstrated the proof-of-concept with the system recording four channels of acoustic data and transmitting portions of those data via satellite. The system integrates a detection-classification algorithm on-board, and a beam-forming algorithm in the shore-side user interface, to provide a user with aural and visual review tools for the detected sounds. Results from a two-week deployment in Cape Cod Bay will be presented and future development directions will be discussed.
Small cetacean monitoring from surface and underwater autonomous vehicles
Authors: Gillespie Douglas M. , Johnson Mark , Harris Danielle , Gkikopoulou Kalliopi
Published: October 2014

We present results of Passive Acoustic surveys conducted from three types of autonomous marine vehicles, two submarine gliders and a surface wave powered vehicle. Submarine vehicles have the advantage of operating at depth, which has the potential to increase detection rate for some species. However, surface vehicles equipped with solar panels have the capacity to carry a greater payload and currently allow for more on board processing which is of particular importance for high frequency odontocete species. Surface vehicles are also more suited to operation in shallow or coastal waters. We describe the hardware and software packages developed for each vehicle type and give examples of the types of data retrieved both through real time telemetry and recovered post deployment. High frequency echolocation clicks and whistles have been successfully detected from all vehicles. Noise levels varied considerably between vehicle types, though all were subject to a degree of mechanical noise from the vehicle itself.
Acoustic seagliders for monitoring marine mammal populations
Authors: Van Uffelen Lora J. , Oleson Erin , Howe Bruce , Roth Ethan
Published: October 2014

A DMON digital acoustic monitoring device has been integrated into a Seaglider with the goal of passive, persistent acoustic monitoring of cetacean populations. The system makes acoustic recordings as it travels in a sawtooth pattern between the surface and up to 1000 m depth. It includes three hydrophones, located in the center of the instrument and on each wing. An onboard real-time detector has been implemented to record continuously after ambient noise has risen above a signal-to-noise (SNR) threshold level, and the glider transmits power spectra of recorded data back to a shore-station computer via iridium satellite after each dive. The glider pilot has the opportunity to set parameters that govern the amount of data recorded, thus managing data storage and therefore the length of a mission. This system was deployed in the vicinity of the Hawaiian Islands to detect marine mammals as an alternative or complement to conventional ship-based survey methods. System design and implementation will be described and preliminary results will be presented.
Effects of environmental uncertainty on source range estimates from horizontal multipath
Authors: Ballard Megan S.
Published: October 2014

A method has been developed to estimate source range in continental shelf environments that exhibit three-dimensional propagation effects [M. S. Ballard, J. Acoust. Soc. Am. 134, EL340–EL343, 2013]. The technique exploits measurements recorded on a horizontal line array of a direct path arrival, which results from sound propagating across the shelf to the receiver array, and a refracted path arrival, which results from sound propagating obliquely upslope and refracting back downslope to the receiver array. A hybrid modeling approach using vertical modes and horizontal rays provides the ranging estimate. According to this approach, rays are traced in the horizontal plane with refraction determined by the modal phase speed. Invoking reciprocity, the rays originate from the center of the array and have launch angles equal to the estimated bearing angles of the direct and refracted paths. The location of the source in the horizontal plane is estimated from the point where the rays intersect. In this talk, the effects of unknown environmental parameters, including the sediment properties and the water-column sound-speed profile, on the source range estimate are discussed. Error resulting from uncertainty in the measured bathymetry and location of the receiver array will also be addressed. [Work supported by ONR.]
Acoustical observation of the estuarine salt wedge at low-to-mid-frequencies
Authors: Reeder D. Benjamin
Published: October 2014

The estuarine environment often hosts a salt wedge, the stratification of which is a function of the tide's range and speed of advance, river discharge volumetric flow rate and river mouth morphology. Competing effects of temperature and salinity on sound speed control the degree of acoustic refraction occurring along an acoustic path. A field experiment was carried out in the Columbia River to test the hypothesis that the estuarine salt wedge is acoustically observable in terms of low-to-mid-frequency acoustic propagation. Linear frequency-modulated (LFM) acoustic signals in the 500–2000 Hz band were collected during the advance and retreat of the salt wedge during May 27–28, 2013. Results demonstrate that the three-dimensional salt wedge front is the dominant physical feature controlling acoustic propagation in this environment: received signal energy is relatively stable under single-medium conditions before and after the passage of the salt wedge front, but suffers a 10–15 dB loss as well as increased variance during salt wedge front passage due to 3D refraction and scattering. Physical parameters (i.e., temperature, salinity, current, and turbulence) and acoustic propagation modeling corroborate and inform the acoustic observations.
Sensitivity analysis of three-dimensional sound pressure fields in complex underwater environments
Authors: Lin Ying-Tsong
Published: October 2014

A sensitivity kernel for sound pressure variability due to variations of index of refraction is derived from a higher-order three-dimensional (3D) split-step parabolic-equation (PE) solution of the Helmholtz equation. In this study, the kernel is used to compute the acoustic sensitivity field between a source and a receiver in a 3D underwater environment, and to quantify how much of the medium change can cause significant consequence on received acoustic signals. Using the chain rule, the dynamics of sensitivity fields can be connected to the dynamics of ocean processes. This talk will present numerical examples of sound propagation in submarine canyons and continental slopes, where the ocean dynamics cause strong spatial and temporal variability in sound pressure. Using the sensitivity kernel technique, we can analyze the spatial distribution and the temporal evolution of the acoustic sensitivity fields in these geologically and topographically complex environments. The paper will also discuss other applications of this sound pressure sensitivity kernel, including uncertainty quantification of transmission loss prediction and adjoint models for 3D acoustic inversions. [Work supported by the ONR.]
Results of matched-field inversion in a three-dimensional oceanic environment ignoring horizontal refraction
Authors: Sturm Frédéric , Korakas Alexios
Published: October 2014

For some practical reasons, inverse problems in ocean acoustics are often based on 2-D modeling of sound propagation, hence ignoring 3-D propagation effects. However, the acoustic propagation in shallow-water environments, such as the continental shelf, may be strongly affected by 3-D effects, thus requiring 3-D modeling to be accounted for. In the present talk, the feasibility and the limits of an inversion in fully 3-D oceanic environments assuming 2-D propagation are investigated. A simple matched-field inversion procedure implemented in a Bayesian framework and based on the exhaustive search of the parameter space is used. The study is first carried out on a well-established wedge-like synthetic test case, which exhibits well-known 3-D effects. Both synthetic data and replica are generated using a parabolic-equation-based code. This approach highlights the relevance of using 2-D propagation models when inversions are performed at relatively short ranges from the source. On the other hand, important mismatch occurs when inverting at farther ranges, demonstrating that the use of fully 3-D forward models is required. Results of inversion on experimental small-scale data, based on a subspace approach as suggested by the preliminary study made on the synthetic test case, are presented.
Measurements of sea surface effects on the low-frequency acoustic propagation in shallow water
Authors: Turgut Altan , Orr Marshall H. , Wylie Jennifer L.
Published: October 2014

In shallow water, spatial and temporal variability of the water column often restricts accurate estimations of bottom properties from low-frequency acoustic data, especially under highly active oceanographic conditions during the summer. These effects are reduced under winter conditions having a more uniform sound-speed profile. However, during the RAGS03 winter experiment, significant low-frequency (200–500 Hz) acoustic signal degradations have been observed on the New Jersey Shelf, especially in the presence of frequently occurring winter storms. Both in-plane and out-of-plane propagation effects were observed on three moored VLAs and one bottom-moored HLA. These effects were further analyzed using 3-D PE simulations with inputs from a 3-D time-evolving surface gravity wave model. It is shown that higher-order acoustic modes are highly scattered at high sea states and out-of-plane propagation effects become important when surface-wave fronts are parallel to the acoustic propagation track. In addition, 3-D propagation effects on the source localization and geoacoustic inversions are investigated using the VLA data with/without the presence of winter storms. [Work supported by ONR.]
Effects of sea surface roughness on the mid-frequency acoustic pulse decay in shallow water
Authors: Wylie Jennifer , Turgut Altan
Published: October 2014

Recent and ongoing efforts to characterize sea bed parameters from measured acoustic pulse decay have neglected the effects of sea surface roughness. In this paper, these effects are investigated using a rough surface version of RAMPE, RAMSURF, and random rough surface realizations, calculated from a 2D JONSWAP sea surface spectrum with directional spreading. Azimuthal dependence is investigated for sandy bottoms and found that the rate of pulse decay increases when the surface wave fronts are perpendicular to the path of acoustic propagation and higher significant wave height results in higher decay rates. Additionally, the effects from sea surface roughness are found to vary with different waveguide parameters including but not limited to sound speed profile, water depth, and seabed properties. Of particular interest are the combined effects of sea bed properties and rough sea surfaces. It is shown that when clay like sediments are present, higher-order modes are strongly attenuated and effects due to interaction with the rough sea surface are less pronounced. Finally, possible influences of sea-state and 3D out-of-plane propagation effects on the seabed characterization efforts will be discussed. [Work supported by ONR.]
Myocardial tissue characterization: Myofiber-induced ultrasonic anisotropy
Authors: Miller James G. , Holland Mark R.
Published: October 2014

One goal of this invited presentation is illustrate the capabilities of quantitative ultrasonic imaging (tissue characterization) to determine local myofiber orientation using techniques applicable to clinical echocardiographic imaging. Investigations carried out in our laboratory in the late 1970s were perhaps the first reported studies of the impact on the ultrasonic attenuation of the angle between the incoming ultrasonic beam and the local myofiber orientation. In subsequent studies, we were able to show that the ultrasonic backscatter exhibits a maximum and the ultrasonic attenuation exhibits a minimum when the sound beam is perpendicular to myofibers, whereas the attenuation is maximum and the backscatter is minimum for parallel insonification. Results from our laboratory demonstrate three broad areas of potential contribution derived from quantitative ultrasonic imaging and tissue characterization: (1) improved diagnosis and patient management, such as monitoring alterations in regional myofiber alignment (for example, potentially in diseases such as hypertrophic cardiomyopathy), (2) improved echocardiographic imaging, such as reduced lateral wall dropout in short axis echocardiographic images, and (3) improved understanding of myocardial physiology, such as contributing to a better understanding of myocardial twist resulting from the layer-dependent helical configuration of cardiac myofibers. [NIH R21 HL106417.]
Quantitative ultrasound for diagnosing breast masses considering both diffuse and non-diffuse scatterers
Authors: Zagzebski James , Rosado-Mendez Ivan , Gerges-Naisef Haidy , Hall Timothy
Published: October 2014

Quantitative ultrasound augments conventional ultrasound information by providing parameters derived from scattering and attenuation properties of tissue. This presentation describes our work estimating attenuation (ATT) and backscatter coefficients (BSC), and computing effective scatterer sizes (ESD) to differentiate benign from malignant breast masses. Radio-frequency echo data are obtained from patients scheduled for biopsy of suspicious masses following an institutional IRB approved protocol. A Siemens S2000 equipped with a linear array and recently a volume scanner transducer is employed. Echo signal power spectra are computed from the tissue and from the same depth in a reference phantom having accurately measured acoustic properties. Ratios of the tissue-to-reference power spectra enable tissue ATT and BSC’s to be estimated. ESD’s are then computed by fitting BSC vs. frequency results to a size-dependent scattering model. A heterogeneity index HDI expresses variability of the ESD over the tumor area. In preliminary data from 35 patients, a Bayesian classifier incorporating ATT, ESD, and HDI successfully differentiated malignant masses from fibroadenomas. Future work focuses on analysis methods when diffuse scattering and stationary signal conditions, implicitly assumed in the power spectra calculations, are not present. This approach tests for signal coherence and generates new parameters that characterize these scattering conditions.
Quantitative-ultrasound detection of cancer in human lymph nodes based on support vector machines
Authors: Mamou Jonathan , Rohrbach Daniel , Coron Alain , Saegusa-Beecroft Emi , Bui Thanh Minh , Oelze Michael L. , Yanagihara Eugene , Bridal Lori , Yamaguchi Tadashi , Machi Junji , Feleppa Ernest J.
Published: October 2014

Histological assessment of lymph nodes excised from cancer patients suffers from an unsatisfactory rate of false-negative determinations. We are evaluating high-frequency quantitative ultrasound (QUS) to detect metastatic regions in lymph nodes freshly excised from cancer patients. Three-dimensional (3D) RF data were acquired from 289 lymph nodes of 82 colorectal-, 15 gastric-, and 70 breast-cancer patients with a custom scanner using a 26-MHz, single-element transducer. Following data acquisition, individual nodes underwent step-sectioning at 50-µm to assure that no clinically significant cancer foci were missed. RF datasets were analyzed using 3D regions-of-interest that were processed to yield 13 QUS estimates including spectral-based and envelope-statistics-based parameters. QUS estimates are associated with tissue microstructure and are hypothesized to provide contrast between non-cancerous and cancerous regions. Leave-one-out classifications, ROC curves, and areas under the ROC (AUC) were used to compare the performance of support vector machines (SVMs) and step-wise linear discriminant analyses (LDA). Results showed that SVM performance (AUC = 0.87) was superior to LDA performance (AUC = 0.78). These results suggest that QUS methods may provide an effective tool to guide pathologists towards suspicious regions and also indicate that classification accuracy can be improved using sophisticated and robust classification tools. [Supported in part by NIH grant CA100183.]
Applications of acoustic radiation force for quantitative elasticity evaluation of bladder, thyroid, and breast
Authors: Fatemi Mostafa
Published: October 2014

Acoustic radiation force (ARF) provides a simple and yet non-invasive mechanism to induce a localized stress inside human body. The response to this excitation is used to estimate the mechanical properties of the targeted tissue in vivo. This talk covers an overview of three studies that use ARF for estimation of elastic properties of thyroid, breast, and the bladder in patients. The studies on thyroid and breast were aimed at differentiating between malignant and benign nodules. The study on the bladder was aimed at indirect evaluation of bladder compliance; hence, only a global measurement was needed. The study on breast showed that 16 out of 18 benign masses and 21 out of 25 malignant masses were correctly identified. The study on 9 thyroid patients with 7 benign and 2 malignant nodules showed all malignant nodules were correctly classified and only 2 of the 7 benign nodules were misclassified. The bladder compliance study revealed a high correlation between our method and independent clinical measurement of compliance (R-squared of 0.8–0.9). Further investigations on larger groups of patients are needed to fully evaluate the performances of the methods.
Rapid simulations of diagnostic ultrasound with multiple-zone receive beamforming
Authors: Nariyoshi Pedro , McGough Robert
Published: October 2014

Routines are under development in FOCUS, the “Fast Object-oriented C + + Ultrasound Simulator” (http://www.egr.msu.edu/~fultras-web), to accelerate B-mode image simulations by combining the fast nearfield method with time-space decomposition. The most recent addition to the FOCUS simulation model implements receive beamforming in multiple zones. To demonstrate the rapid convergence of these simulations in the nearfield region, simulations of a 192 element linear array with an electronically translated 64 element sub-aperture are evaluated for a transient excitation pulse with a center frequency of 3 MHz. The transducers in this simulated array are 5 mm high and 0.5133 mm wide with a 0.1 mm center to center spacing. The simulation is evaluated for a computer phantom with 100,000 scatterers. The same configuration is simulated in Field II (http://field-ii.dk), and the impulse response approach with a temporal sampling rate of 1 GHz is used as reference. Simulations are evaluated for the entire B-mode image simulated with each approach. The results show that, with sampling frequencies of 15 MHz and higher, FOCUS eliminates all of the numerical artifacts that appear in the nearfield region of the B-mode image, whereas Field II requires much higher temporal sampling frequencies to obtain similar results. [Supported in part by NIH Grant R01 EB012079.]
Effects of room acoustics on subjective workload assessment while performing dual tasks
Authors: Boyd Brenna N. , Peng Zhao , Wang Lily
Published: October 2014

This investigation examines the subjective workload assessments of individuals using the NASA Task Load Index (TLX), as they performed speech comprehension tests under assorted room acoustic conditions. This study was motivated due to the increasing diversity in US classrooms. Both native and non-native English listeners participated, using speech comprehension test materials produced by native English speakers in the first phase and by native Mandarin Chinese speakers in the second phase. The speech materials were disseminated in an immersive listening environment to each listener under 15 acoustic conditions, from combinations of background noise level (three levels from RC-30, 40, and 50) and reverberation time (five levels from 0.4 to 1.2 seconds). During each condition, participants completed assorted speech comprehension tasks while also tracing a moving dot for an adaptive rotor pursuit task. At the end of each acoustic condition, listeners were asked to assess the perceived workload by completing the six-item NASA TLX survey, e.g., mental demand, perceived performance, effort, and frustration. Results indicate that (1) listeners’ workload assessments degraded as the acoustic conditions became more adverse, and (2) the decrement in subjective assessment was greater for non-native listeners.
Stick bombs: A study of the speed at which a woven stick construction self-destructs
Authors: McKay Scotty , Slaton William
Published: October 2014

A stick bomb is created by weaving sticks together in a particular pattern. By changing the way the sticks are woven together, different types of stick bombs are created. After the stick bomb is woven to the desired length, one side of the stick bomb can be released causing it to rapidly begin tearing itself apart in the form of a pulse that propagates down the weave. This occurs due to a large amount of potential energy stored within the multitude of bent sticks; however, the physics of this phenomena has not been studied to the authors knowledge. The linear mass density of the stick bomb can be changed by varying the tightness of the weave. Data on these stick bombs, including video analysis to determine the pulse speed, will be presented.
Three-dimensional printed acoustic mufflers and aeroacoustic resonators
Authors: Ferrier John , Slaton William
Published: October 2014

We explore and present the use of 3D printing technology to design, construct, and test acoustic elements that could be used as a low-frequency Helmholtz-resonator style muffler in a ventilation duct system. Acoustic elements such as these could be quickly prototyped, printed, and tested for any noisy duct environment. These acoustic elements are tested with and without mean flow to characterize their sound absorption (and sound generation) properties. It is found that at particular ranges of air flow speeds the simply designed acoustic muffler acts as a site for aeroacoustic sound generation. Measurement data and 3D model files with Python-scripting will be presented for several muffler designs. This work is supported by the Arkansas Space Grant Consortium in collaboration with NASA's Acoustics Office at the Johnson Space Center.
Palate shape and the central tongue groove
Authors: Talbert Coretta M. , Lulich Steven M.
Published: October 2014

It is well known that the center of the tongue can be grooved so that it is lower in the mouth than the lateral parts of the tongue, or it can bulge higher than the lateral parts of the tongue. It has never been shown whether or how this groove or bulge is related to the shape of the palate. In this study, we investigated the shape and size of the palate for several speakers using digitized 3D laser-scans of palate impressions and measurements on the impression plasters themselves. The groove or bulge in the center of the tongue was measured using real-time three-dimensional ultrasound. Pertinent findings will be presented concerning the relationship of the central groove/bulge shape and size to the shape and size of the palate.
Palate-related constraints on sibilant production in three dimensions
Authors: Janssen Sarah , Lulich Steven M.
Published: October 2014

Most studies of speech articulation are limited to a single plane, typically the midsagittal plane, although coronal planes are also used. Single-plane data have been undeniably useful in improving our understanding of speech production, but for many acoustic and aerodynamic processes, a knowledge of 3D vocal tract shapes is essential. In this study, we used palate impressions to investigate variations in the 3D structure of the palates of several individuals, and we used real-time 3D ultrasound to image the tongue surface during sibilant production by the same individuals. Our analysis focused on the degree to which tongue shapes during sibilant productions are substantially similar or different between individuals with different palate shapes and sizes.
New phased array models for fast nearfield pressure simulations
Authors: Stewart Kenneth , McGough Robert
Published: October 2014

FOCUS, the “Fast Object-oriented C + + Ultrasound Simulator,” is free MATLAB-based software that rapidly and accurately models therapeutic and diagnostic ultrasound with the fast nearfield method, time-space decomposition, and the angular-spectrum approach. FOCUS presently supports arrays of circular, rectangular, and spherically focused transducers arranged in flat planar, spherically focused, and cylindrically focused geometries. Excellent results are obtained with all of these array geometries in FOCUS for simulations of continuous-wave and transient excitations, and new array geometries are needed for B-mode simulations that are presently under development. These new array geometries also require new data structures that describe the electrical connectivity of the arrays. Efforts to develop these new features in FOCUS are underway, and results obtained with these new array geometries will be presented. Other new features for FOCUS will also be demonstrated. [Supported in part by NIH Grant R01 EB012079.]
Analysis of acoustic data acquisition instrumentation for underwater blast dredging
Authors: Wallin Brenton , Stott Alex , Hill James , Nohara Timothy , Fullan Ryan , Morasutti Jon , Clark Brad , Binder Alexander , Gardner Michael
Published: October 2014

A team of seniors from the University of Rhode Island were tasked with analyzing the acoustic data and evaluating the data acquisition systems used in Pacific Northwest National Laboratories’ (PNNL) study of blast dredging in the Columbia River. Throughout the semester, the students learned about the unique acoustic signatures of confined underwater blasts and the necessary specifications of systems used to record them. PNNL used two data acquisition systems. One was a tourmaline underwater blast sensor system created by PCB Piezotronics. The second was a hydrophone system using a Teledyne TC 4040 hydrophone, a Dytran inline charge amplifier, and a signal conditioner built for the blast sensor system. The students concluded that the data from the blast sensor system was reliable because the system was built by the company for this specific application and there were calibration sheets showing the system worked properly. The hydrophone data was deemed unreliable because components were orientated in an unusual manner that lead to improper data acquisition. A class of URI graduate students built a new hydrophone system that accurately recorded underwater dredge blasts performed in New York Harbor. This system is a fraction of the price of the blast sensor system.
75th Anniversary of the Shure Unidyne microphone
Authors: Pettersen Michael S.
Published: October 2014

2014 marks the 75th anniversary of the Shure model 55 microphone. Introduced in 1939 and still being manufactured today, the Shure Unidyne was the first unidirectional microphone using a single dynamic element. The presentation provides an overview of the Unidyne’s unique position in the history of 20th century broadcast, politics, and entertainment, plus the amazing story of Benjamin Bauer, a 24 year old immigrant from the Ukraine who invented the Unidyne and earned his first of over 100 patents for audio technology. Rare Unidyne artifacts from the Shure Archive will be on display after the presentation, including prototypes fabricated by Ben Bauer.
Iconic microphonic moments in historic vocal recordings
Authors: Case Alexander U.
Published: October 2014

Microphone selection—the strategic pairing of microphone make and model with each sound to be recorded—is one of the most important decisions a sound engineer must make. The technical specifications of the microphone identify which transducers are capable of functioning properly for any given recording task, but the ultimate decision is a creative one. The goal is for the performance capabilities of the microphone to not only address any practical recording session challenges, but also flatter the sound of the instrument, whether in pursuit of palpable realism or a fictionalized new timbre. The creative decision is informed, in part, by demonstrated success in prior recordings, the most important of which are described for that essential pop music instrument: the voice.
The WE 640AA condenser microphone
Authors: Elko Gary W.
Published: October 2014

In 1916 Edward Wente, working for Western Electric an AT&T subsidiary, invented a microphone that was the foundation of the modern condenser microphone. Wente's early condenser microphone designs continued to be developed until Western Electric produced the WE 361 in 1924 followed by the Model 394 condenser microphone in 1926. Western Electric used the WE 394 microphone as part of the “Master Reference System” to rate audio transmission quality of the telephone network. The WE 394 was too large for some measurement purposes so in 1932 Bell Labs engineers H. Harrison and P. Flanders designed a smaller version. The diaphragm had a diameter of 0.6 in. However, this design proved too difficult to manufacture and F. Romanow, also at Bell Labs, designed the 640A “1 in.” microphone in 1932. Years later it was discovered that the 640A sensitivity varied by almost 6 dB from -650 C to 250 C. To reduce the thermal sensitivity, Bell Labs engineers M. Hawley and P. Olmstead carefully changed some of the 640A materials. The modified microphone was designated as the 640AA, which became the worldwide standard microphone for measuring sound pressure. This talk will describe some more details of the history of the 640AA microphone.
Electret microphones
Authors: West James E.
Published: October 2014

For nearly 40 years, condenser electret microphones have been the transducer of choice in most every area of acoustics including telephony, professional applications, hearing aids, and toys. More than 2 billion electret microphones are produced annually, primarily for the communications and entertainment markets. E. C. Wente invented the condenser microphone in 1917 at Bell Labs while searching for a replacement for the carbon microphone used in telephones; however, the necessary few hundred volt bias rendered the condenser microphone unusable in telephony, but its acoustical characteristics were welcomed in professional and measurement applications. Permanently charged polymers (electrets) provided the necessary few hundred-volt bias, thus simplifying the mechanical and electrical requirements for the condenser microphone and making it suitable for integration into the modern telephone. The introduction of inexpensive condenser microphones with matching frequency, phase, and impedance characteristics opened research opportunities for multiple microphone arrays. Array technology developed at Bell Labs will be presented in this talk.
The phonodeik: Measuring sound pressure before electroacoustic transducers
Authors: Thompson Stephen C.
Published: October 2014

The modern ability to visualize sound pressure waveforms using electroacoustic transducers began with the development of the vacuum tube amplifier, and has steadily improved as better electrical amplification devices have become available. Before electoral amplification was available; however, a significant body of acoustic pressure measurements had been made using the phonodeik, a device developed by Dayton C. Miller in the first decade of the twentieth century. The phonodeik employs acoustomechanical transduction to rotate a small mirror that reflects an optical beam to visualize the pressure waveform. This presentation will review the device and some of the discoveries made with it.
A transducer not to be ignored: The siren
Authors: Maynard Julian D.
Published: October 2014

An historic transducer to which one should pay attention is the siren. While its early application was as a source for a musical instrument, the siren soon became the transducer of choice for long-range audible warning because of its high intensity and recognizable tone. The components defining the siren include a solid stator and rotor, each with periodic apertures, and a compressed fluid (usually air but could be other fluids). With the rotor rotating in close proximity to the stator, and the resulting opening and closing of passageways through the apertures for the compressed fluid results in periodic sound waves in the surrounding fluid; usually a horn is used to enhance the radiation efficiency. The high potential energy of the compressed fluid permits high intensity sound. Some sirens which received scientific study include that of R. Clark Jones (1946), a 50 horsepower siren with an efficiency of about 70%, and that of C. H. Allen and I. Rudnick (1947), capable of ultrasonic frequencies and described as a “supersonic death ray” in the news media. Some design considerations, performance results, and applications for these sirens will be presented.
The slippery path from piano key to string
Authors: Birkett Stephen
Published: October 2014

Everything that contributes to the excitation of a piano string, from key input to hammer–string interaction, is both deterministic and consistently repeatable. Sequences of identical experimental trials give results that are indistinguishable. The simplicity of this behavior contrasts with the elusive goal of predicting input–output response and the extreme difficulty of accurate physical characterization. The nature and complexity of the mechanisms and material properties involved, as well as the sensitivity of their parameterization, place serious obstacles in the way of the usual investigative tools. This paper discusses and illustrates the limitations of modeling and simulation as applied to this problem, and the special considerations required for meaningful experimentation.
Coupling between transverse and longitudinal waves in piano strings
Authors: Etchenique Nikki , Collin Samantha , Moore Thomas R.
Published: October 2014

It is known that longitudinal waves in piano strings noticeably contribute to the characteristic sound of the instrument. These waves can be induced by directly exciting the motion with a longitudinal component of the piano hammer, or by the stretching of the string associated with the transverse displacement. Longitudinal waves that are induced by the transverse motion of the string can occur at frequencies other than the longitudinal resonance frequencies, and the amplitude of the waves produced in this way are believed to vary quadratically with the amplitude of the transverse motion. We present the results of an experimental investigation that demonstrates the quadratic relationship between the magnitude of the longitudinal waves and the magnitude of the transverse displacement for steady-state, low-amplitude excitation. However, this relationship is only approximately correct under normal playing conditions.
Modeling the influence of the piano hammer shank flexibility on the sound
Authors: Chabassier Juliette
Published: October 2014

A nonlinear model for a vibrating Timoshenko beam in non-forced unknown rotation is derived from the virtual work principle applied to a system of beam with mass at the end. The system represents a flexible piano hammer shank coupled to a hammer head. A novel energy-based numerical scheme is then provided and coupled to a global energy-preserving numerical solution for the whole piano (strings, soundboard, and sound propagation in the air). The obtained numerical simulations show that the pianistic touch clearly influences the spectrum of the piano sound of equally loud isolated notes. These differences do not come from a possible shock excitation on the structure, nor from a changing impact point, nor a “longitudinal rubbing motion” on the string, since neither of these features are modeled in our study.
Real-time tonal self-adaptive tuning for electronic instruments
Authors: Wang Yijie , Hsu Timothy Y.
Published: October 2014

A fixed tuning system cannot achieve just intonation on all intervals. A better approximation of just intonation is possible if the frequencies of notes are allowed to vary. Adaptive tuning is a class of methods that adjusts the frequencies of notes dynamically in order to maximize musical consonance. However, finding the optimal frequencies of notes directly based on some definition of consonance has shown to be difficult and computationally expensive. Instead, this paper proposes that the current key of the music is both a good summary of past notes and a good prediction of future notes, which can facilitate adaptive tuning. A method is proposed that uses a hidden Markov model to detect the current key of the music and compute optimal frequencies of notes based on the current key. In addition, a specialized online machine learning method that enforces symmetry among diatonic keys is presented, which can potentially adapt the model for different genres of music. The algorithm can operate in real time, is responsive to the notes played, and is applicable to various electronic instruments, such as MIDI pianos. This paper also presents comparisons between this proposed tuning system and conventional tuning systems.
Evaluation of variability in real-ear attenuation testing using a unique database—35 years of data from a single laboratory
Authors: Berger Elliott H. , Kieper Ronald W.
Published: October 2014

The gold standard in measuring hearing protector attenuation since the late 1950s has been real-ear attenuation at threshold (REAT). Though well understood and standardized both in the U. S. (ANSI S3.19-1974 and ANSI S12.6-2008) and internationally (ISO 4869-1:1990), and known to provide valid and reliable estimates of protection for the test panel being evaluated, an area that is not clearly defined is the variability of the test measurements within a given laboratory. The test standards do provide estimates of uncertainty, both within and between laboratories, based on limited test data and interlaboratory studies, but thus far no published within-laboratory data over numerous tests and years have been available to provide empirical support for variability statements. This paper provides information from a one-of-a-kind database from a single laboratory that has conducted nearly 2500 studies over a period of 35 years in a single facility, managed by the same director (the lead author). Repeat test data on a controlled set of samples of a foam earplug, a premolded earplug, and two different earmuffs, with one of the data sets comprising 25 repeat tests over that 35-year period, will be used to demonstrate the inherent variability of this type of human-subject testing.
Sound field uncertainty budget for real-ear attenuation at threshold measurement per ANSI S12.6 standards
Authors: Voix Jeremie , Lapotre Céline
Published: October 2014

In many national and international standards, the attenuation of Hearing Protection Devices is rated according to a psychophysical method called Real-Ear Attenuation at Threshold (REAT), which averages on a group of test-subjects the difference between the open and occluded auditory thresholds. In ANSI S12.6 standard, these REAT tests are conducted in a diffuse sound field in which sound uniformity and directionality are assessed by two objective microphone measurements. While the ANSI S12.6 standard defines these two criteria, it does not link the microphone measurements to the actual variation of sound pressure level at the eardrum that may originate from natural head movements during testing. This presentation examines this issue with detailed measurements conducted in an ANSI S12.6-compliant audiometric booth using an Artificial Test Fixture (ATF). The sound pressure level variations were recorded for movements of the ATF along the three main spatial axes and two rotation planes. From these measured variations and different head movements hypothetical scenarios, various sound field uncertainty budgets were computed. These findings will be discussed in order to eventually include them for uncertainty budget in a revised version of the ANSI S12.6 standard.
Estimating effective noise dose when using hearing protection: Differences between ANSI S12.68 calculations and the auditory response measured with temporary threshold shifts
Authors: Gallagher Hilary L. , McKinley Richard L. , McKenna Elizabeth A. , Theis Mellisa A.
Published: October 2014

ANSI S12.6 describes the methods for measuring the real-ear attenuation at threshold of hearing protectors. ANSI S12.68 describes the methods of estimating the effective A-weighted sound pressure levels when hearing protectors are worn. In theory, the auditory response, as measured by temporary threshold shifts (TTS), to an unoccluded ear noise exposure and an equivalent occluded ear noise exposure should produce similar behavioral results. In a series of studies conducted at the Air Force Research Laboratory, human subjects were exposed to continuous noise with and without hearing protection. Ambient noise levels during the occluded ear exposures were determined using ANSI S12.6 and ANSI S12.68. These equivalent noise exposures as determined by the ANSI S12.68 “gold standard” octave-band method produced significantly different auditory responses as measured with TTS. The methods and results from this study will be presented.
Fit-testing, training, and timing—How long does it take to fit-test hearing protectors?
Authors: Murata Taichi , Themann Christa L. , Byrne David C. , Murphy William J.
Published: October 2014

Hearing protector fit-testing is a Best Practice for hearing loss prevention programs and is gaining acceptance among US employers. Fit-testing quantifies hearing protector attenuation achieved by individual workers and ensures that workers properly fit and receive adequate protection from their protectors. Employers may be reluctant to conduct fit-testing because of expenses associated with worker time away from the job, personnel to administer the testing, and acquisition of a fit-test system. During field and laboratory studies conducted by the National Institute for Occupational Safety and Health (NIOSH), timing data for the fit-test process with the NIOSH HPD Well-Fit™ system were analyzed. For workers completely naïve to fit-testing, the tests were completed within 15–20 minutes. Unoccluded test times were less than 4 minutes and occluded tests required less than 3 minutes. A significant learning effect was seen for the psychoacoustic method of adjustment used by HPD Well-Fit, explaining the shorter test times as subjects progressed through the unoccluded and occluded conditions. Most of the workers required about 5 minutes of training time. Test times and attenuations were tester-dependent, indicating the need to provide training to staff administering fit-tests in the workplace.
A new perceptive method to measure active insertion loss of active noise canceling headsets or hearing protectors by matching the timbre of two audio signals
Authors: Poncot Remi , Guiu Pierre
Published: October 2014

Attenuation of passive hearing protectors is assessed either by the Real Ear Attenuation at Threshold subjective method or by objective Measurements In the Real Ear. For Active Noise Cancelling headsets both methods do not practically apply. Alternative subjective methods based on loudness balance and masked hearing threshold techniques were proposed. However, they led to unmatched results with objective measurements at low frequency, diverging in either direction. Additionally, they are relatively long as frequency points of interest are measured one after the other. This paper presents a novel subjective method based on timbre matching, which has the originality of involving other perceptive mechanisms than the previous ones did. The attenuation performance of ANC headsets is rated by the change in pressure level of eight harmonics when the active noise reduction functionality is switched on. All harmonics are played at once, and their levels are adjusted by the test subject until he perceives the same timbre both in passive and active modes. A test was carried out by a panel of people in diffuse noise field conditions to assess the performance of personal consumer headphones. Early results show that the method is as repeatable as MIRE and lead to close results.
Inclusion of source extent and coherence in a finite-impedance ground reflection model with atmospheric turbulence
Authors: Gee Kent L. , Neilsen Tracianne B.
Published: October 2014

Acoustic data collected in static rocket tests are typically influenced by ground reflections. Furthermore, the partial coherence of the ground interaction due to atmospheric turbulence can play a significant role for larger propagation distances. Because the rocket plume is an extended radiator whose directionality is the result of significant source correlation, assessment of the impact of ground reflections in the data must include these effects. In this paper, a finite impedance-ground, single-source interference approach [G. A. Daigle, J. Acoust. Soc. Am. 65, 45–49 (1979)] that incorporates both amplitude and phase variations due to turbulence is extended to distributions of correlated monopoles. The theory for obtaining the mean-square pressure from multiple correlated sources in the presence of atmospheric turbulence is described. The effects of source correlation and extent, ground effective flow resistivity, and turbulence parameters are examined in terms differences in relative sound pressure level across a realistic parameter space. Finally, the model prediction is compared favorably against data from horizontal firings of large solid rocket motors. [Work supported by NASA MSFC and Blue Ridge Research and Consulting, LLC.]
Acoustics associated with liquid rocket propulsion testing
Authors: Allgood Daniel C.
Published: October 2014

Ground testing of liquid rocket engines is a necessary step towards building reliable launch vehicles. NASA Stennis Space Center has a long history of performing both developmental and certification testing of liquid propulsion systems. During these test programs, the propulsion test article, test stand infrastructure and the surrounding community can all be exposed to significant levels of acoustic energy for extended periods of time. In order to ensure the safety of both personnel and equipment, predictions of these acoustic environments are conducted on a routine basis. This presentation will provide an overview of some recent examples in which acoustic analysis has been performed. Validation of these predictions will be shown by comparing the predictions to acoustic data acquired during small- and full-scale engine hot-fire testing. Applications of semi-empirical and advanced computational techniques will be reviewed for both sea-level and altitude test facilities.