The Journal of the Acoustical Society of America

A theory is developed for the propagation of stress waves in a porous elastic solid containing compressible viscous fluid. The emphasis of the present treatment is on materials where fluid and solid are of comparable densities as for instance in the case of water-saturated rock. The paper denoted here as Part I is restricted to the lower frequency range where the assumption of Poiseuille flow is valid. The extension to the higher frequencies will be treated in Part II. It is found that the material may be described by four nondimensional parameters and a characteristic frequency. There are two dilatational waves and one rotational wave. The physical interpretation of the result is clarified by treating first the case where the fluid is frictionless. The case of a material containing viscous fluid is then developed and discussed numerically. Phase velocity dispersion curves and attenuation coefficients for the three types of waves are plotted as a function of the frequency for various combinations of the characteristic parameters.

During the past decade a number of variations in the simple up-down procedure have been used in psychoacoustic testing. A broad class of these methods is described with due emphasis on the related problems of parameter estimation and the efficient placing of observations. The advantages of up-down methods are many, including simplicity, high efficiency, robustness, small-sample reliability, and relative freedom from restrictive assumptions. Several applications of these procedures in psychoacoustics are described, including examples where conventional techniques are inapplicable.

This paper describes a number of objective experiments on recognition, concerning particularly the relation between the messages received by the two ears. Rather than use steady tones or clicks (frequency or time-point signals) continuous speech is used, and the results interpreted in the main statistically. Two types of test are reported: (a) the behavior of a listener when presented with two speech signals simultaneously (statistical filtering problem) and (b) behavior when different speech signals are presented to his two ears.

The theory of propagation of stress waves in a porous elastic solid developed in Part I for the low-frequency range is extended to higher frequencies. The breakdown of Poiseuille flow beyond the critical frequency is discussed for pores of flat and circular shapes. As in Part I the emphasis of the treatment is on cases where fluid and solids are of comparable densities. Dispersion curves for phase and group velocities along with attenuation factors are plotted versus frequency for the rotational and the two dilational waves and for six numerical combinations of the characteristic parameters of the porous systems. Asymptotic behavior at high frequency is also discussed.

Image methods are commonly used for the analysis of the acoustic properties of enclosures. In this paper we discuss the theoretical and practical use of image techniques for simulating, on a digital computer, the impulse response between two points in a small rectangular room. The resulting impulse response, when convolved with any desired input signal, such as speech, simulates room reverberation of the input signal. This technique is useful in signal processing or psychoacoustic studies. The entire process is carried out on a digital computer so that a wide range of room parameters can be studied with accurate control over the experimental conditions. A fortran implementation of this model has been included.

The mathematical theory of tracking had an early and distinguished start.In 1801, Carl Friedrich Gauss, on the basis of meager observations, computed the orbit of the newly discovered asteroid Ceres.When, a year later, Ceres was rediscovered precisely where Gauss predicted it would be, his fame as a mathematician was secured.In his calculations Gauss em-

Relationships between a listener's identification of a spoken vowel and its properties as revealed from acoustic measurement of its sound wave have been a subject of study by many investigators. Both the utterance and the identification of a vowel depend upon the language and dialectal backgrounds and the vocal and auditory characteristics of the individuals concerned. The purpose of this paper is to discuss some of the control methods that have been used in the evaluation of these effects in a vowel study program at Bell Telephone Laboratories. The plan of the study, calibration of recording and measuring equipment, and methods for checking the performance of both speakers and listeners are described. The methods are illustrated from results of tests involving some 76 speakers and 70 listeners.

We developed a distributed-parameter model (partial differ-ential equations and associated boundary conditions) that de-scribe the coupled torsion and bending motions of the Digital Micromirror Device (DMD) using the extended Hamilton prin-ciple. The work done by the electrostatic field is expressed in the form of a potential energy. It is found that coupling between the torsion and bending motions appears in the boundary con-ditions. The nonlinearity is mainly due to the application of the electrostatic forces and moments. Nonlinear terms appear only in the boundary conditions. The developed model provides a basis for a thorough study of the static and dynamic behaviors of the electromechanical device. The static response of the DMD for different DC loads shows the occurrence of pull-in (snap-down) instability at critical voltage values corresponding to the collapse of the yoke to mechanical stops. Estimates of the voltage, an-gle, and deflection at pull-in are given. The dynamic behavior of the DMD is analyzed by plotting the natural frequencies versus the applied DC voltage. We conducted a study of the sensitivity of the static and dynamic behaviors of the micromirror to vari-ations in the geometric parameters of the DMD. It is found that the thickness and width of the hinges are the key parameters in-∗Address all correspondence to this author

Oral speech intelligibility tests were conducted with, and without, supplementary visual observation of the speaker's facial and lip movements. The difference between these two conditions was examined as a function of the speech-to-noise ratio and of the size of the vocabulary under test. The visual contribution to oral speech intelligibility (relative to its possible contribution) is, to a first approximation, independent of the speech-to-noise ratio under test. However, since there is a much greater opportunity for the visual contribution at low speech-to-noise ratios, its absolute contribution can be exploited most profitably under these conditions.

A method is presented for the translation of acoustic field data from a source to a target region. Field data are represented as spherical harmonic expansions on spheres surrounding the source and target regions, respectively, and expansions are translated using a “point and shoot” method using the Kirchhoff–Helmholtz integral to carry out an axial translation from one sphere to the other. The principal motivation for the method is its use in a time-domain fast multipole method, and test cases reflective of this application are presented. The method converges to six digits for appropriate values of parameters, and for the values of N considered here, computational effort scales approximately as N2, where N is the order of spherical harmonic expansion for the field data. The method is causal and thus avoids artifacts generated in methods that are not based on intrinsically causal formulations.

Our study examines the role of oral motor control in the acquisition of acoustic targets for lingually complex consonants in Estonian by speakers from four age groups. We focus on children's production of secondarily palatalised and non-palatalised consonants where anatomical development and acquisition of motor control skills make differing predictions about the timing and nature of speech production. Our aim is to disentangle the contribution of, on the one hand, speech motor control development and, on the other hand, anatomical growth and articulator change in proportion. We examined oral motor control using a single syllable alternating motion rate diadochokinetic (DDK) task and studied the difference between the second formant (F2) and first formant (F1) using functional principal component analysis. Our results show that palatalised and non-palatalised productions differ significantly across all age groups, indicating children can produce palatalisation contrasts from age 3 years, but consistency in production increases with age. Results also show that children and adults with greater oral motor control skills are better able to produce the palatalisation contrast. These results suggest that anatomical proportions pre-dispose children toward early acquisition of the acoustic properties of palatalisation. However, adult-like production of the phonological contrast also depends on the acquisition of oral motor control skills.

The rapid growth of research in advanced acoustic materials has been enabled by contemporary growth in additive manufacturing advancement and accessibility. This report provides a quantitative evaluation of variability in the elastic vibration response of structures fabricated using fused deposition modeling. The approach in this study involves assembling a sample set from six institutions via an interlaboratory round robin study. Slender beam samples were fabricated using fused deposition modeling and a standardized commercial filament and printed on whichever commercial printers were available at each institution. To quantify variability in fabrication of both bulk material and metamaterial-inspired features, two sample sets were requested and tested, a set of plain beams and a set of beams with embedded resonator. All samples were measured for dimensional accuracy and dynamic performance using a vibration shaker using a laser Doppler vibrometer. Measured resonance response of each set of samples revealed that the variability between printers was roughly 20% in bulk dynamic properties and as large as 280% in coupled resonator-beam dynamic performance. The study provides design bounds for metamaterial design across various printer hardware and highlights the importance of understanding repeatability using this fabrication approach.

The evolution of bubbles released from a submerged nozzle involves coupled hydrodynamic and acoustic effects throughout growth, detachment, and ascent. This study investigates the acoustic emission mechanisms of millimeter-scale bubbles using high-speed imaging and hydrophone measurements over a range of gas flow rates. A spherical-cap-cone correction is introduced into the classical force-balance model to characterize the non-spherical morphology of bubbles detaching from large orifices at low flow rates, improving detachment-diameter prediction. With increasing gas flow rate, the classical Minnaert frequency increasingly overestimates the dominant detachment acoustic frequency. A coupled-bubble oscillator model accounting for interactions between newly detached and rising bubbles reproduces this downward frequency shift. Under stable gas supply and nearly axisymmetric detachment, three satellite-bubble pinch-off modes are observed during bubble ascent. Statistical analysis reveals that the dominant pinch-off mode is governed by the competition between inertial-buoyancy effects and surface tension. These events generate distinct acoustic pulses associated with satellite-bubble volume oscillations and re-excitation of the parent-bubble breathing mode, driven by Laplace-pressure perturbations induced by abrupt changes in interfacial curvature. This study clarifies the unsteady dynamics and acoustic emission mechanisms of nozzle-generated bubbles, supporting acoustic monitoring of gas-liquid two-phase flows.

Semi-occluded vocal tract exercises (SOVTE) are vocal exercises involving partial occlusion in the front part of the vocal tract, often through phonation into a narrow tube. Although SOVTE are widely used in voice therapy and pedagogy, the physiological mechanisms underlying their therapeutic benefits remain unclear. In this computational study, voice production at different vocal fold configurations with and without semi-occlusion was investigated in a three-dimensional model. Semi-occlusion significantly increased phonation threshold pressure under conditions of weak vocal fold adduction. Under conditions of strong vocal fold adduction, semi-occlusion reduced mean glottal area and increased the duration of glottal closure. These findings suggest two possible adaptation mechanisms through which SOVTE may guide speakers toward an efficient phonatory configuration. For speakers with hypofunctional voice, increased respiratory effort associated with elevated phonation threshold pressure may encourage increased vocal fold adduction. For speakers with habitually tight vocal fold adduction, increased duration of vocal fold contact may alter mechanosensory feedback and promote compensatory reductions in vocal fold adduction. Together, these adaptations may facilitate adoption of an intermediate vocal fold adduction configuration, which is associated with high vocal efficiency and reduced risk of vocal fold injury. Such adaptation effects may persist briefly after SOVTE but gradually diminish over time.

Conventional cochlear implant (CI) strategies convey limited tonal information. Although fundamental frequency (F0)-based strategies, such as C-tone, which combines F0 extraction with amplitude envelope modulation, improve Mandarin tone perception, their high computational demands hinder integration into power- and resource-constrained devices. This study evaluates a lexical tone enhancement CI strategy, pk-Ctone, that employs a computationally efficient local extrema-based F0 detection algorithm. Acoustic evaluations on two Mandarin monosyllabic corpora assessed both the coarse-scale robustness and fine-scale fidelity of F0 detection. Computational operations required for F0 extraction were quantified, and a clinical trial with 62 participants compared Mandarin speech recognition using pk-Ctone versus a standard envelope-based baseline. Results showed that pk-Ctone reduced the computational operations for F0 extraction by more than 30-fold compared with C-tone. Although this efficiency gain incurred a penalty in fine-scale precision, pk-Ctone achieved improved coarse-scale robustness, as quantified by Accuracy and F1-score. Clinically, pk-Ctone yielded significant improvements in recognition of monosyllabic tones (+10.1% points, pp), monosyllabic words (+19.2 pp), and disyllabic words (+13.0 pp). These findings indicate that pk-Ctone, by preserving coarse-scale F0 tracking robustness while reducing computational cost, maintains clinical effectiveness despite some loss in fine-scale precision, offering a practical solution for power- and resource-constrained CI processors.

Sensorimotor adaptation within the Directions Into Velocities of Articulators (DIVA) framework (including DIVA, LaDIVA, and SimpleDIVA) is governed by auditory feedback, somatosensory feedback, and feedforward mechanisms. SimpleDIVA provides a reduced three-parameter formulation that enables direct estimation of auditory and somatosensory feedback control gains, as well as the learning rate of the feedforward command from trial-by-trial adaptation data; however, it provides point estimates without uncertainty information. This limitation becomes critical for subject-specific analyses based on noisy data. We introduce a probabilistic inference framework that estimates posterior distributions and quantifies how parameter uncertainty propagates to predicted trajectories. The method uses particle-based likelihood inference, sampling candidate parameter sets from prior distributions and weighting them according to their likelihood. We compare a late-window-only variant with a joint early-late formulation that treats early-window (feedforward-dominated) and late-window (feedback-engaged) responses as complementary observations. Monte Carlo simulations across eight measurement noise levels evaluate the coverage and width of credible intervals, as well as estimation error. Results show robust estimation of feedback gains under both formulations. The joint early-late approach improves learning-rate inference, yielding narrower intervals, reduced bias, and improved trajectory recovery while maintaining near-nominal coverage at empirically relevant noise levels.

The Reflections series takes a look back on historical articles from The Journal of the Acoustical Society of America that have had a significant impact on the science and practice of acoustics.

This paper deals with the modeling of optical fiber Bragg gratings (FBGs) dedicated to ultrasound measurements. It addresses the problem of modeling the impact of acoustic waves on such small transducers, with typical FBG lengths and optical fiber diameters several orders of magnitude smaller than the ultrasound's characteristic wavelength, especially with guided waves. The method adopted to model the behavior of such transducers can therefore severely affect computational performances and results. We propose here the use of a one-way coupling scheme, limiting the impact on the simulation of ultrasonic waves, while reproducing accurately the FBG transducer's response. This model is validated against experimental data, especially regarding the FBG's spectral response with respect to ultrasonic wavelength.

Accurate knowledge of acoustic surface admittance or impedance is essential for reliable wave-based simulations, yet its in situ estimation remains challenging due to noise, model inaccuracies, and restrictive assumptions of conventional methods. This work presents a physics-informed neural operator approach for estimating frequency-dependent surface admittance directly from near-field measurements of sound pressure and particle velocity. A deep operator network is employed to learn the mapping from measurement data, spatial coordinates, and frequency to acoustic field quantities, while simultaneously inferring a globally consistent surface admittance spectrum without requiring repeated evaluations of an explicit numerical forward model during inversion. The governing acoustic relations, including the Helmholtz equation, the linearized momentum equation, and Robin boundary conditions, are embedded into the training process as physics-based regularization, enabling physically consistent and noise-robust predictions. The method is validated using synthetically generated data from a simulation model for two planar porous absorbers under semi free-field conditions across a broad frequency range. Results demonstrate accurate reconstruction of both real and imaginary admittance components and reliable prediction of acoustic field quantities. Parameter studies confirm improved robustness to noise and sparse sampling compared to purely data-driven approaches, highlighting the potential of physics-informed neural operators for in situ acoustic material characterization.