Volume 133, Issue 6, June 2013
- jasa express letters
- letters to the editor
- general linear acoustics 
- nonlinear acoustics 
- aeroacoustics, atmospheric sound 
- underwater sound 
- ultrasonics, quantum acoustics, and physical effects of sound 
- transduction 
- structural acoustics and vibration 
- noise: its effects and control 
- architectural acoustics 
- acoustic signal processing 
- physiological acoustics 
- psychological acoustics 
- speech production 
- speech perception 
- speech processing and communication systems 
- music and musical instruments 
- bioacoustics 
- acoustical news
- book reviews
- reviews of acoustical patents
Index of content:
- JASA EXPRESS LETTERS
133(2013); http://dx.doi.org/10.1121/1.4802903View Description Hide Description
Magnetic resonance imaging has been widely used in speech production research. Often only one image stack (sagittal, axial, or coronal) is used for vocal tract modeling. As a result, complementary information from other available stacks is not utilized. To overcome this, a recently developed super-resolution technique was applied to integrate three orthogonal low-resolution stacks into one isotropic volume. The results on vowels show that the super-resolution volume produces better vocal tract visualization than any of the low-resolution stacks. Its derived area functions generally produce formant predictions closer to the ground truth, particularly for those formants sensitive to area perturbations at constrictions.
133(2013); http://dx.doi.org/10.1121/1.4802896View Description Hide Description
Custom-molded earplugs (CMEPs) whose canal segments extend beyond the second bend of the ear canal can provide excellent attenuation but can sometimes be uncomfortable. Attenuation was measured for CMEPs whose canal segments were shortened in 2-mm increments. The within-subjects design permitted illustration of the form of the function relating attenuation to canal segment length for individuals. Reduction of attenuation due to canal segment shortening was generally more pronounced for frequencies ≤1000 Hz. Some regions of the canal segments were more critical than others in maintaining attenuation. The relationship between comfort and canal segment length was not straightforward.
133(2013); http://dx.doi.org/10.1121/1.4802892View Description Hide Description
Older talkers speak slower than young ones, but speech tempo has increased in the last decades. Have present-day older talkers slowed down with age or have they sped up with their community? This study investigates longitudinal patterns in articulation rate in formal speeches presented annually by Queen Beatrix between her ages 42 and 74. Her tempo decreased first and then increased in the last decade. Within a speech, acceleration and shortening increased longitudinally. These results suggest that this talker's preferred tempo has not decreased but increased longitudinally, presumably in accommodation to an increasing tempo in the Dutch language community.
133(2013); http://dx.doi.org/10.1121/1.4802913View Description Hide Description
Meaningful use of the autocorrelation in jet noise analysis is examined. The effect of peak frequency on the autocorrelation function width is removed through a temporal scaling prior to making comparisons between measurements or drawing conclusions about source characteristics. In addition, a Hilbert transform-based autocorrelation envelope helps to define consistent characteristic time scales. Application of these processes to correlation functions based on large and fine-scale similarity spectra reveal that the large-scale noise radiation from an F-22A deviates from the similarity spectrum model.
133(2013); http://dx.doi.org/10.1121/1.4802183View Description Hide Description
Underwater acoustic recordings of six Floating Production Storage and Offloading (FPSO) vessels moored off Western Australia are presented. Monopole source spectra were computed for use in environmental impact assessments of underwater noise. Given that operations on the FPSOs varied over the period of recording, and were sometimes unknown, the authors present a statistical approach to noise level estimation. No significant or consistent aspect dependence was found for the six FPSOs. Noise levels did not scale with FPSO size or power. The 5th, 50th (median), and 95th percentile source levels (broadband, 20 to 2500 Hz) were 188, 181, and 173 dB re 1 μPa @ 1 m, respectively.
133(2013); http://dx.doi.org/10.1121/1.4802900View Description Hide Description
This study addresses whether there is a threshold, some particular length of silent gap between two speakers' turns, at which negative social attributions emerge. The effect of such inter-turn silence was tested by constructing dialogues where responses to requests were identical and affirmative so that study participants' (n = 380) ratings about “willingness” would be colored by lag time, not semantics. 100 ms intervals between 200 and 1200 ms were tested in a between groups design. There was a notable drop-off in ratings at 600 ms and a statistically significant difference in ratings between 700 and 800 ms.
133(2013); http://dx.doi.org/10.1121/1.4804942View Description Hide Description
This letter describes an ultrasound imaging assessment of novel contrast agents that are detectable by both medical ultrasound and magnetic resonance imaging. Such agents are created by including superparamagnetic particles in polymer-shelled microbubbles through two different approaches. The reduced echogenicity and nonlinearity of the microbubbles are observed, depending on the strategy used to include the particles and the resulting density. The best results are obtained using imaging techniques that exploit the third-order nonlinear term, which is especially true when the microbubbles are excited by means of chirp pulses.
133(2013); http://dx.doi.org/10.1121/1.4807306View Description Hide Description
This study reports a wave-controlled sonic crystal switch device that exhibits a destructive interference-based wave to wave reverse switching effect. By applying control waves, this acoustic device, composed of a two-dimensional square lattice sonic crystal block, reduces acoustic wave transmission from input to output. The finite difference time domain simulation and experimental results confirm the wave-to-wave reverse switching effect at the peak frequencies of the second band. The proposed sonic crystal switch prototype provides a contrast rate of 86% at 11.3 kHz frequency. This wave-to-wave switching effect is useful for controlling wave propagation for smart structure applications.
133(2013); http://dx.doi.org/10.1121/1.4807307View Description Hide Description
Spatial properties of noise statistics near unheated, laboratory-scale supersonic jets yield insights into source characteristics and near-field shock formation. Primary findings are (1) waveforms with positive pressure skewness radiate from the source with a directivity upstream of maximum overall level and (2) skewness of the time derivative of the pressure waveforms increases significantly with range, indicating formation of shocks during propagation. These results corroborate findings of a previous study involving full-scale engine data. Further, a comparison of ideally and over-expanded laboratory data show that while derivative skewness maps are similar, waveform skewness maps are substantially different for the two cases.
- LETTERS TO THE EDITOR
133(2013); http://dx.doi.org/10.1121/1.4802650View Description Hide Description
Existing secondary-edge-source methods based on the Biot–Tolstoy solution for diffraction from an infinite wedge compute multiple-order diffraction by cascading the integration over secondary sources used to determine first-order diffraction from the edge. It is demonstrated here that this approach errs in some important cases because it neglects slope-diffraction contributions. This error is illustrated by considering the case of an infinite slit in a thin, hard screen. Comparisons with measurements for this case and analytical solutions for the case of a circular aperture in a thin, hard screen are used as a basis to gauge the magnitude of the error.
133(2013); http://dx.doi.org/10.1121/1.4803517View Description Hide Description
This study tested the hypothesis that the reduced spatial release from speech-on-speech masking typically observed in listeners with sensorineural hearing loss results from increased energetic masking. Target sentences were presented simultaneously with a speech masker, and the spectral overlap between the pair (and hence the energetic masking) was systematically varied. The results are consistent with increased energetic masking in listeners with hearing loss that limits performance when listening in speech mixtures. However, listeners with hearing loss did not exhibit reduced spatial release from masking when stimuli were filtered into narrow bands.
- GENERAL LINEAR ACOUSTICS 
133(2013); http://dx.doi.org/10.1121/1.4802654View Description Hide Description
A formulation of the problem of scattering from obstacles with edges is presented. The formulation is based on decomposing the field into geometrical acoustics, first-order, and multiple-order edge diffraction components. An existing secondary-source model for edge diffraction from finite edges is extended to handle multiple diffraction of all orders. It is shown that the multiple-order diffraction component can be found via the solution to an integral equation formulated on pairs of edge points. This gives what can be called an edge source signal. In a subsequent step, this edge source signal is propagated to yield a multiple-order diffracted field, taking all diffraction orders into account. Numerical experiments demonstrate accurate response for frequencies down to 0 for thin plates and a cube. No problems with irregular frequencies, as happen with the Kirchhoff–Helmholtz integral equation, are observed for this formulation. For the axisymmetric scattering from a circular disc, a highly effective symmetric formulation results, and results agree with reference solutions across the entire frequency range.
133(2013); http://dx.doi.org/10.1121/1.4802648View Description Hide Description
The use of phased array methods are commonplace in ultrasonic applications, where controlling the variation of the phase between the narrowband emitters in an array facilitates beam steering and focusing of ultrasonic waves. An approach is presented here whereby emitters of alternating polarity arranged in a one-dimensional array are pulsed simultaneously, and have sufficiently wide, controlled bandwidth to emit a two-dimensional wave. This pulsed approach provides a rapid means of simultaneously covering a region of space with a wave-front, whereby any wave that scatters or reflects off a body to a detector will have a distinct arrival time and frequency. This is a general wave phenomenon with a potential application in radar, sonar, and ultrasound. The key result is that one can obtain a smooth, continuous wave-front emitted from the array, over a large solid angle, whose frequency varies as a function of angle to the array. Analytic and finite element models created to describe this phenomenon have been validated with experimental results using ultrasonic waves in metal samples.
133(2013); http://dx.doi.org/10.1121/1.4802741View Description Hide Description
This paper presents a method to identify the surface areas of a vibrating structure that contribute to the radiated sound power. The surface contributions of the structure are based on the acoustic radiation modes and are computed for all boundaries of the acoustic domain. The surface contributions are compared to the acoustic intensity, which is a common measure for near-field acoustic energy. Sound intensity usually has positive and negative values that correspond to energy sources and sinks on the surface of the radiating structure. Sound from source and sink areas partially cancel each other and only a fraction of the near-field acoustic energy reaches the far-field. In contrast to the sound intensity, the surface contributions are always positive and no cancelation effects exist. The technique presented here provides a method to localize the relevant radiating surface areas on a vibrating structure. To illustrate the method, the radiated sound power from a baffled square plate is presented.
- NONLINEAR ACOUSTICS 
Anisotropy of dynamic acoustoelasticity in limestone, influence of conditioning, and comparison with nonlinear resonance spectroscopy133(2013); http://dx.doi.org/10.1121/1.4802909View Description Hide Description
Anisotropy of wave velocity and attenuation induced by a dynamic uniaxial strain is investigated by dynamic acoustoelastic testing in limestone. Nonlinear resonance spectroscopy is performed simultaneously for comparison. A compressional resonance of the sample at 6.8 kHz is excited to produce a dynamic strain with an amplitude varied from to . A sequence of ultrasound pulses tracks variations in ultrasonic velocity and attenuation. Variations measured when the ultrasound pulses propagate in the direction of the uniaxial strain are 10 times larger than when the ultrasound propagation occurs perpendicularly. Variations consist of a “fast” variation at 6.8 kHz and an offset. Acoustically induced conditioning is found to reduce wave velocity and enhance attenuation (offset). It also modifies “fast” nonlinear elastodynamics, i.e., wave amplitude dependencies of ultrasonic velocity and attenuation. At the onset of conditioning and beyond, different excitation amplitudes bring the material to non-equilibrium states. After conversion of velocity-strain dynamic relations into elastic modulus-strain dynamic relations and integration with respect to strain, the dynamic stress-strain relation is obtained. Analysis of stress-strain hysteresis shows that hysteretic nonlinear elasticity is not a significant source of the amplitude-dependent dissipation measured by nonlinear resonance spectroscopy. Mechanisms causing conditioning are likely producing amplitude-dependent dissipation as well.
133(2013); http://dx.doi.org/10.1121/1.4802742View Description Hide Description
The paper describes an approximate but rather general derivation of the acoustic threshold for a subharmonic component to be possible in the sound scattered by an insonified gas bubble. The general result is illustrated with several specific models for the mechanical behavior of the surface coating of bubbles used as acoustic contrast agents. The approximate results are found to be in satisfactory agreement with fully non-linear numerical results in the literature. The amplitude of the first harmonic is also found by the same method. A fundamental feature identified by the analysis is that the subharmonic threshold can be considerably lowered with respect to that of an uncoated free bubble if the mechanical response of the coating varies rapidly in the neighborhood of certain specific values of the bubble radius, e.g., because of buckling.
133(2013); http://dx.doi.org/10.1121/1.4802906View Description Hide Description
A mathematical model describing dynamics of the cluster of gas bubbles in an acoustic field is presented. According to this model a cluster is considered as a large drop with microbubbles inside. The proposed model is used as a basis (1) for an analytical study of small bubble oscillations in mono- and polydisperse clusters and (2) for numerical investigations of nonlinear bubble oscillations and of the diffusion stability of gas bubbles in the cluster. A synchronization of the collapse phases of bubbles with different radii and collapse intensification for bubbles of one size in the presence of bubbles of other size is found. These effects are explained by the interaction between the bubbles of different radii in the cluster. For the cluster with one radius bubbles the numerical values are obtained for the initial gas concentrations in the liquid at which the bubbles tend to one of two equilibrium states because of rectified diffusion. It is found that the cluster with the bubbles of two different radii tends to become a cluster with the bubbles of one radius due to rectified diffusion.
- AEROACOUSTICS, ATMOSPHERIC SOUND 
133(2013); http://dx.doi.org/10.1121/1.4803891View Description Hide Description
Wind noise reduction (WNR) is important in the measurement of infrasound. Spatial averaging theory led to the development of rosette pipe arrays. The efficacy of rosettes decreases with increasing wind speed and only provides a maximum of ∼20 dB WNR due to a maximum size limitation. An Optical Fiber Infrasound Sensor (OFIS) reduces wind noise by instantaneously averaging infrasound along the sensor's length. In this study two experiments quantify the WNR achieved by rosettes and OFISs of various sizes and configurations. Specifically, it is shown that the WNR for a circular OFIS 18 m in diameter is the same as a collocated 32-inlet pipe array of the same diameter. However, linear OFISs ranging in length from 30 to 270 m provide a WNR of up to ∼30 dB in winds up to 5 m/s. The measured WNR is a logarithmic function of the OFIS length and depends on the orientation of the OFIS with respect to wind direction. OFISs oriented parallel to the wind direction achieve ∼4 dB greater WNR than those oriented perpendicular to the wind. Analytical models for the rosette and OFIS are developed that predict the general observed relationships between wind noise reduction, frequency, and wind speed.
133(2013); http://dx.doi.org/10.1121/1.4803863View Description Hide Description
The current work aims at developing a linearized Euler equations solver in curvilinear coordinates to account for the effects of topography on sound propagation. In applications for transportation noise, the propagation environment as well as the description of acoustic sources is complex, and time-domain methods have proved their capability to deal with both atmospheric and ground effects. First, equations in curvilinear coordinates are examined. Then time-domain boundary conditions initially proposed for a Cartesian coordinate system are implemented in the curvilinear solver. Two test cases dealing with acoustic scattering by an impedance cylinder in a two-dimensional geometry and by an impedance sphere in a three-dimensional geometry are considered to validate the boundary conditions. Accurate solutions are obtained for both rigid and impedance surfaces. Finally, the solver is used to examine a typical outdoor sound propagation problem. It is shown that it is well-suited to study coupled effects of topography, mixed impedance ground and meteorological conditions.
133(2013); http://dx.doi.org/10.1121/1.4802894View Description Hide Description
The attenuation of sound waves due to interaction with low Mach number turbulent boundary layers in internal flows (channel or pipe flow) is examined. Dynamic equations for the turbulent Reynolds stress on the sound wave are derived, and the analytical solution to the equation provides a frequency dependent eddy viscosity model. This model is used to predict the attenuation of sound propagating in fully developed turbulent pipe flow. The predictions are shown to compare well with the experimental data. The proposed dynamic equation shows that the turbulence behaves like a viscoelastic fluid in the interaction process, and that the ratio of turbulent relaxation time near the wall and the sound wave period is the parameter that controls the characteristics of the attenuation induced by the turbulent flow.