Acoustic Effects Research Articles

Exploring velar function in speech: An integrated approach using nasometry and high-speed nasopharyngoscopy

It is well established that coupling between the oral and nasal cavities is controlled by velopharyngeal opening and closing movements and that coarticulatory patterns in these movements can affect both the intelligibility and the naturalness of speech. In addition, poor control can cause individuals to develop undesirable compensatory patterns. Most studies of these patterns have relied on indirect methods to assess both extent and timing of movement due to the difficulty of direct observation of the velopharyngeal port. This study focused on the correlation between indirect and direct methods of assessing both timing and magnitude of velopharyngeal opening for coarticulation using complementary data from nasometry and a novel technique – high-speed nasopharyngoscopy. Nasometry measures the ratio of distinct nasal and oral cavity outflow to determine the degree of nasality in speech. High-speed nasopharyngoscopy captures images of the nasopharyngeal region and can resolve velar motion during speech. By aligning these data, we can infer the functional changes of the velopharyngeal port and show the correlation between its status and resulting acoustic effects. Preliminary findings replicate previous work on coarticulatory patterns associated with prosodic structure and low versus high vowels. This work will illuminate how variability in velar function affects phonetic outputs.

Acoustical effects of extreme weather events

The transfer of water from evaporating regions to precipitating regions drives the global water cycle, and understanding its dynamics is essential in determining how weather patterns will respond to changes in global climate. An intensification of the global water cycle has been reported using 50-year sea surface salinity data (Durack and Wijffels, 2010, J. Climate) with the consequence of more frequent extreme weather events. However, data under extreme weather conditions over the ocean are rare and a lot of physics remains to be investigated. As part of the Ocean Climate Stations that NOAA is maintaining, the 1-year data presented here are from Ocean Station Papa (50°N, 145°W), including measurements of wind speed, rain rate, currents, wave height and direction, bubble plume spatial structure and dynamics, and ambient noise for wind speeds up to 25 m/s. This full suite of data enables the study of the statistical properties of bubble plumes, their relation to meteorological parameters, and how to take them into account in ambient noise prediction, especially under severe weather conditions. Knowledge gained through this unique dataset can be critical for understanding air–sea interaction, validating satellite rain products, and predicting the ambient noise field under extreme weather conditions.

Effect of stud dimension and material properties on predicted and tested sound insulation

A common wall design is gypsum wall board (GWB) cladding on each side of a row of steel studs, which may or may not include insulation. Steel studs are available in a range of metal thicknesses, dimensions, and structural properties. Most published laboratory testing on these walls uses a small subset of the available stud types, and the acoustical effect of changes to stud parameters has not been completely studied or documented. As a result, theoretical models of stud walls have not been evaluated over the full set of stud parameters. This work is a continuation of previous laboratory testing programs to systematically investigate the acoustical effects of stud properties. This paper analyzes the effects of stud depth and structural properties on third-octave transmission loss values and single-number ratings and investigates the capability of existing models for wall transmission loss to predict performance of walls with an expanded set of stud parameters. Our findings indicate that the parameters currently used to describe stud walls in acoustical test report are not sufficient to characterize the assembly.

Enhancing heat-driven acoustic characteristics of standing wave thermoacoustic engines by using corrugated stack

The present work considers the heat-driven acoustic characteristics and dynamic thermal-fluid flow fields of a standing-wave thermoacoustic engine (SWTAE) by using sinusoidally shaped corrugated stack surfaces. 3-D numerical SWTAE models are developed and validated, aiming to examine the heat-driven acoustic effects caused by different corrugation amplitudes and wave-lengths of the sinusoidal stack surface. The results demonstrate that corrugated-shaped stack channels increase the contact area of the working gas in the stack area, and the thermos-acoustic conversion is more amplified. Compared to the SWTAE with uniform-shaped stack, the corrugated-shaped stack exhibit enhanced acoustic power output while maintaining a constant acoustic oscillation frequency. With the corrugation peak and wave-length of the sinusoidal stack are 2 and 0.2 mm, respectively, the amplitude and acoustic power of the acoustic pressure oscillations increase by 10.12% and 17.31%, respectively, in comparison with that of the conventional SWTAE. However, when the corrugation peak exceeds 0.4 mm, stronger nonlinear acoustics and flow effects are observed in the stack channels, leading to a reduction in the heat-driven acoustic power output, and thermo-acoustics energy conversion efficiency. The developed model highlights the effects of the corrugated-shaped stack on enhancing acoustic power output and thermo-acoustic conversion efficiency.

FUS and surfactant-based nanocarriers: A combined strategy for nose to brain drug delivery

Brain drug delivery is hampered by the presence of the blood brain barrier and nanocarriers, administered by intranasal route, could represent an alternative and efficient strategy to improve drug localization in the Central Nervous System (CNS). The aim of this work is to design and characterize non-ionic surfactant vesicles (NSVs) and perfluorocarbon gas non-ionic surfactant based nanobubbles (VNBs) suitable for Nose to Brain Delivery (N2B). In particular, Pluronic F127, Span 85 and cholesterol have been employed to prepare NSVs and VNBs. Both systems have been characterized in terms of (a) hydrodynamic diameter, ζ-potential and morphology (b) vesicle bilayer feature (anisotropy), (c) physical-chemical stability and (d) fluorescent model probe release capability. VNBs have been also studied in terms of gas entrapment and acoustic efficiency. In addition, in order to understand optimal ultrasound (US) parameters to obtain in vitro stable cavitation, the acoustic pressure effect on VNBs fluorescent probes release kinetics was evaluated. The obtained results suggest that NSVs and VNBs show a hydrodynamic diameter suitable for N2B delivery. Moreover, in this study, we develop a new kind of protocol to evaluate an in vitro US characterization of VNBs and our data suggest a stable and controlled probe release, encouraging the possibility to deliver VNBs in mixture with NSVs loaded neuroprotective drugs for brain delivery coupled to US obtaining stable cavitation. In this context, extracellular field recordings in specific area of hippocampus (CA1-CA3) have been carried out in order to assure that empty NSVs do not affect synaptic plasticity in the form of long-term potentiation, a molecular mechanism which underlies learning and memory.

Echo

Intelligent audio systems are ubiquitous in our lives, such as speech command recognition and speaker recognition. However, it is shown that deep learning-based intelligent audio systems are vulnerable to adversarial attacks. In this paper, we propose a physical adversarial attack that exploits reverberation, a natural indoor acoustic effect, to realize imperceptible, fast, and targeted black-box attacks. Unlike existing attacks that constrain the magnitude of adversarial perturbations within a fixed radius, we generate reverberation-alike perturbations that blend naturally with the original voice sample 1. Additionally, we can generate more robust adversarial examples even under over-the-air propagation by considering distortions in the physical environment. Extensive experiments are conducted using two popular intelligent audio systems in various situations, such as different room sizes, distance, and ambient noises. The results show that Echo can invade into intelligent audio systems in both digital and physical over-the-air environment.

Mechanistic study of ultrasound-assisted chromatography using plastic and stainless steel columns

Based on the previous ultrasound-assisted chromatography (UAC) studies on plastic and stainless steel (SS) columns, this study explores the UAC mechanism by comparatively analyzing ultrasound effects on plastic and SS columns with C18 stationary phase when separating a mixture of polycyclic aromatic hydrocarbons (PAHs) under various ultrasound intensities. The results showed a substantial difference in H values between the PEEK and SS columns under the influence of ultrasound agitation. Specifically, for the pyrene peak, as the ultrasonic intensity increased from 0% to 100% of 900 W, the H values of the SS column slightly rose from 8.82 μm to 9.86 μm. Conversely, the corresponding values for the PEEK column exhibited a significant 12-fold increase from 11.5 μm to 134 μm. The findings demonstrated poor penetration of ultrasound energy through the SS column, and the temperature rise of the medium induced by the ultrasound was the primary contributing factor to PAH separation. However, ultrasound easily penetrated through the plastic column, resulting in acoustic cavitation within the C18 polyether ether ketone (PEEK) column. Cavitation induced heat generation and contributed to a decrease in retention time and the magnitude of peak broadening or distortion, depending on the specific ultrasonic energy. Based on the estimated change in inlet temperature of the PEEK column due to an acoustic effect, the comparison with temperature effects under non-sonic conditions consistently demonstrated a stronger acoustic effect in reducing the retention time, by 2–9%, depending on specific peaks and pairs. We revisited the previously described separation mechanism of ultrasound-assisted ion chromatography and conjoined with our findings to infer and establish a thorough explanation for the previously unexplained separation mechanism of chiral separation and size exclusion chromatography by UAC using SS columns.

Deflector shape impact on aero-acoustic noise generation and propagation

The acoustic pressure level generated during lift-off and the associated vibrations can significantly affect the payload of a launch vehicle. Optimizing the plume deflector is one of the most effective methods to reduce this noise. Considering the Vega launcher as a case of study, different deflectors are studied: flat, inclined at 30°, and wedge. The approach followed is to use the unsteady Navier–Stokes equations to solve both the noise generation and the propagation. First, it has been observed that the blast wave, due to the ignition overpressure, is independent of the deflector geometry. However, the predominant acoustic waves are due to the impact of the jet with the deflectors. The analysis has shown that the flat deflector generates more shock waves and propagates the acoustic waves equally in all directions so that more acoustic loads reach the fairing. The inclined deflector causes a plate shock and intermediate tail shocks and redirects the flow towards one side of the launcher. Finally, the wedge deflector generates a detached shock wave with a higher pressure increase than the inclined deflector. However, as the flow is redirected towards the two sides, a lower OASPL reaches the fairing. In the same way, the pressure distribution over the fairing surface has shown that the wedge deflector is acoustically more efficient for this case of study. The acoustic effectiveness of deflectors has been demonstrated compared to the case without a deflector. Therefore, deflectors are advised to be included on the launch platform to improve payload comfort and reliability on the launchers.

Acoustic parametric instability in thermo-diffusively unstable CH4/O2/Xe mixtures

Acoustic and parametric instability in downward propagating premixed flames of low Lewis number (∼0.6) mixture of CH4/O2/Xe is studied experimentally and analytically. Seven mixtures of increasing laminar burning velocity (SL) at constant equivalence ratio of 0.7 are considered. Flame front history and pressure measurements are reported. Parametric instability of the flame front due to effect of acoustics is observed for mixtures with SL higher than 27 cm/s. Complex stability diagrams are observed for the mixtures. For mixtures of lower SL, a clear condition of wavenumber and acoustic velocity amplitude for the onset of parametric instability is not found in the stability diagram. Rather a wavenumber, k0B is observed where instability is observed for all the acoustic velocity amplitudes. The experimentally measured wavenumbers at the onset of parametric instability were found to match with k0B. For mixtures of SL> 54 cm/s, wavenumber and acoustic velocity amplitude at the onset of parametric instability were clearly identified in the stability diagram. Experimentally measured wavenumbers were found to lie between critical wavenumber of parametric instability and k0B. This work shows a quantitative agreement between theory and experiments and thus proves the applicability of theoretical analysis for low Lewis number mixtures.

Discontinuous Galerkin method for solving viscoacoustic wave equations with amplitude dissipation and phase dispersion separation in isotropic and anisotropic media

SUMMARY The standard-linear-solid (SLS) theory works well for viscoelasticity. However, the coupling of amplitude dissipation and phase dispersion makes it impossible to investigate their effects separately by the discontinuous Galerkin method (DGM). In this paper, we have derived newly viscoacoustic wave equations with amplitude dissipation and phase dispersion separation in isotropic and anisotropic media, based on a Fourier method, which is suitable for using a time–space-domain DGM on unstructured meshes. The basic framework of DGM is constructed and the amplitude-dissipation effect and the phase-dispersion effect in viscoacoustic wave equations are investigated. The original equation is first transformed into the frequency–wavenumber domain, where the amplitude dissipation and phase dispersion are separated effectively, and then the decoupled formulation is converted back to the time–space domain. The new equivalent and approximate equations can be obtained. Compared with the original equation, the newly approximated equation enables us to separate the amplitude-loss and phase-delay terms, respectively, and experiences four kinds of effects, namely acoustic effect, only amplitude-dissipation effect, only phase-dispersion effect and both amplitude-dissipation and phase-dispersion effect. Moreover, the stability condition and numerical dispersion for using DGM to solve the new and old equations are presented. Several numerical examples are used to verify the correctness and effectiveness of the modified approximate equations in viscoacoustic isotropic and anisotropic media. The numerical results in a cave and SEG/EAGE salt models demonstrate that the new equations combined with DGM have performances on viscoacoustic media with complex geological structures.

Investigation of ultrasonic mechanism and development of tool wear model in ultrasonic elliptic vibration assisted cutting of stainless steel

By analyzing the kinematics and dynamics of ultrasonic vibration under various conditions, the tool wear mechanism in Ultrasonic Elliptic Vibration-Assisted Cutting (UEVAC) were investigated. Two distinct mechanisms for mitigating tool wear emerge: In non-separated UEVAC, the pivotal factor is the reduction of material yield stress through the acoustic softening effect. Conversely, in separated UEVAC, tool wear reduction is attributed to the decrease in average contact stress via stress superposition and the hammer effect. These findings highlight the effectiveness of aligning ultrasonic energy field action times and intensity to reduce stainless steel tool wear rates in non-separated UEVAC. Furthermore, the proposed tool wear model demonstrates robust reliability for separated UEVAC processes.

Validation of an integrated pressure level measured earmold wideband real-ear-to-coupler difference measurement

Objective To validate measurement of predicted earmold wideband real-ear-to-coupler difference (wRECD) using an integrated pressure level (IPL) calibrated transducer and the incorporation of an acoustically measured tubing length correction. Design Unilateral earmold SPL wRECD using varied hearing aid tubing length and the proposed predicted earmold IPL wRECD measurement procedure were completed on all participants and compared. Study Sample 22 normal hearing adults with normal middle ear status were recruited. Results There were no clinically significant differences between probe-microphone and predicted earmold IPL wRECD measurements between 500 and 2500 Hz. Above 5000 Hz, the predicted earmold IPL wRECD exceeded earmold SPL wRECDs due to lack of standing wave interference. Test-retest reliability of IPL wRECD measurement exceeded the reliability of earmold SPL wRECD measurement across all assessed frequencies, with the greatest improvements in the high frequencies. The acoustically measured tubing length correction largely accounted for acoustic effects of the participant’s earmold. Conclusions IPL-based measurements provide a promising alternative to probe-microphone earmold wRECD procedures. Predicted earmold IPL wRECD is measured without probe-microphone placement, agrees well with earmold SPL wRECDs and is expected to extend the valid bandwidth of wRECD measurement.

Internal Cognitive Load Differentially Influences Acoustic and Lexical Context Effects in Speech Perception: Evidence From a Population With Attention-Deficit/Hyperactivity Disorder.

To overcome variability in spoken language, listeners utilize various types of context information for disambiguating speech sounds. Context effects have been shown to be affected by cognitive load. However, previous results are mixed regarding the influence of cognitive load on the use of context information in speech perception. We tested a population characterized by an attention-deficit/hyperactivity disorder (ADHD) to better understand the relationship between attention (or internal cognitive load) and context effects. The use of acoustic versus lexical properties of the surrounding signal to disambiguate speech sounds was examined in listeners with ADHD and neurotypical listeners. Compared to neurotypicals, individuals with ADHD relied more strongly on lexical context for speech perception; however, reliance on acoustic context information from speech rate did not differ. These findings confirm that cognitive load impacts the use of high-level but not low-level context information in speech and imply that speech recognition deficits in ADHD likely arise due to impaired higher order cognitive processes.

Evaluation of advective solute infiltration into porous media by pulsed focused ultrasound-induced acoustic streaming effects.

Acoustic streaming induced by applying transcranial focused ultrasound (FUS) promotes localized advective solute transport in the brain and has recently garnered research interest for drug delivery and enhancement of brain waste clearance. The acoustic streaming behavior in brain tissue is difficult to model numerically and thus warrants an in vitro examination of the effects of using different sonication parameters, in terms of frequency, intensity, and pulse duration (PD). Melamine and polyvinyl alcohol (PVA) foams were used to mimic the porous brain tissue, which contains leptomeningeal fenestrations and perivascular space, while agar hydrogel was used to emulate denser neuropil. FUS was delivered to these media, which were immersed in a phosphate-buffered saline containing toluidine blue O dye, across various frequencies (400, 500, and 600 kHz; applicable to transcranial delivery) in a pulsed mode at two different spatialpeak pulse-average intensities (3 and 4 W/cm2). Image analysis showed that the use of 400 kHz yielded the greatest dye infiltration in melamine foam, while sonication had no impact on infiltration in the agar hydrogel due to the dominance of diffusional transport. Using a fixed spatial-peak temporal-average intensity of 0.4 W/cm2 at 400 kHz, a PD of 75 ms resulted in the greatest infiltration depth in both melamine and PVA foams among the tested range (50-150 ms). These findings suggest the existence of a specific frequency and PD that induce greater enhancement of solute/fluid movement, which may contribute to eventual in vivo applications in promoting waste clearance from the brain.

Structural–fluidic–acoustic computational modelling and experimental validation of piezoelectric synthetic jet actuators

In this study, coupled structural–fluidic–acoustic modelling of piezoelectric diaphragm driven synthetic jet actuators is conducted computationally for the first time. The aim is to demonstrate the importance of piezoelectric diaphragm structural modelling and the effects of acoustics coupling to compute accurate synthetic jet exit jet velocity. Two different synthetic jet actuator orifice–diaphragm configurations are studied in which the orifice is parallel and adjacent to the diaphragm, namely, opposite and adjacent synthetic jet actuators, respectively. In investigating the aforementioned configurations, cavity acoustic and mechanical resonance frequencies are identified within ± 100 Hz, compared to in-house experimental measurements of laser vibrometry and hot-wire anemometry. The numerical peak jet velocity differs from the experimental value at the diaphragm mechanical resonance by 5.4% and 0.3% for opposite and adjacent synthetic jets, respectively. Further analysis of velocity and vorticity fields showed that no vortex formation is observed in the cavity of the adjacent synthetic jets, despite having similar exit jet velocity of the opposite synthetic jet configuration.

Stage as an Expanse of Artistic Research by Director-Author. Part 3. A. Vaida, K. Zanussi: Theatre as an Experimental Field of Activity

The purpose of the article is to identify the problems of creativity of auteur directors who have realised their artistic potential both in auteur cinema and in the field of stage art and to define scientific guidelines that will contribute to a comprehensive analysis of the phenomenon of the film author in the performing arts. Research methodology. Methods of scientific analysis, comparison, generalisation, and self-analysis of the artist were used in the study. In addition, analytical and systematic methods were applied in their unity, which is necessary for the study of the art historical aspect of the problem. The scientific novelty of the study is to define the universality of directing as a specific type of artistic and aesthetic activity; to clarify the mutual influence of stage and screen arts in the use of expressive means; to determine the peculiarities of the film author's activity in the stage space through the adaptation of screen means in theatrical productions, which for the first time became the subject of a special study; in highlighting the universal activities of auteur directors who reformed the cinematic language and the language of stage staging; in identifying original principles of film construction and specific means of cinematic expression that were not only directly embodied in films and contributed to the emergence of outstanding auteur cinematic works, but also had a significant impact on auteur theatre directing, which was distinguished by the search for visualisation of stage images. Conclusions. It is proved that the stage work of film directors-authors questions the theoretical postulates about the harmfulness of the invasion of theatre culture on the screen. It is found that the visual and expressive means that provide the chronology of image creation (long shots, intra-frame editing, acoustic, light and shadow effects), the use of which is considered a high degree of skill in cinema, have their origins in the stage art. Key words: director-author, stage space, directorial means, theatre, stage, screen, performance, television.

Study on effects of ultrasound on microstructure refinement at semi-solid statement of ultrasonic-assisted brazing SiCp/Al composites

Ultrasonic composite brazing uses ultrasonic cavitation and acoustic flow effects to ameliorate the soakage property of SiC particles and brazing material, enabling flux-free brazing of SiCp/Al-MMCs under atmospheric conditions. However, its mechanical properties are limited by the performance of the brazing material, which is often difficult to apply in structures with high strength requirements. In order to break through the limitations of conventional ultrasonic composite brazing of SiCp/Al-MMCs, this paper uses 50 vol.% SiCp/Al MMCs as base material and Zn-16Al brazing material. It applies secondary ultrasound at different times during the solidification of the liquid brazing material to reduce the weld grain size and reinforce the weld intensity by using ultrasonic cavitation and acoustic flow effects. The results show that the addition of secondary ultrasound can reduce the α-Al size and make the SiC particles and α-Al evenly distributed in the joint, which can significantly reinforce the intensity of the weld. The shear performance enhanced with the increase of supersound application second, but too long secondary sonication caused atomization of the brazing material, resulting in unfilled brazing material in the weld, which seriously affected the properties of the weld.

The influences of forward context on stop-consonant perception: The combined effects of contrast and acoustic cue activation?

The perception of the /da/-/ga/ series, distinguished primarily by the third formant (F3) transition, is affected by many nonspeech and speech sounds. Previous studies mainly investigated the influences of context stimuli with frequency bands located in the F3 region and proposed the account of spectral contrast effects. This study examined the effects of context stimuli with bands not in the F3 region. The results revealed that these non-F3-region stimuli (whether with bands higher or lower than the F3 region) mainly facilitated the identification of /ga/; for example, the stimuli (including frequency-modulated glides, sine-wave tones, filtered sentences, and natural vowels) in the low-frequency band (500-1500 Hz) led to more /ga/ responses than those in the low-F3 region (1500-2500 Hz). It is suggested that in the F3 region, context stimuli may act through spectral contrast effects, while in non-F3 regions, context stimuli might activate the acoustic cues of /g/ and further facilitate the identification of /ga/. The combination of contrast and acoustic cue effects can explain more results concerning the forward context influences on the perception of the /da/-/ga/ series, including the effects of non-F3-region stimuli and the imbalanced influences of context stimuli on /da/ and /ga/ perception.

METHODOLOGICAL ASPECTS OF INTERSPECIES EXTRAPOLATION OF EXPERIMENTAL DATA UNDER PULSED ACOUSTIC INFLUENCE ON BIOOBJECTS (REVIEW)

Background. Despite a significant number of theoretical and experimental studies, the issue of determining the threshold levels of pulsed acoustic exposure, when exceeded, their negative effect on the morphofunctional state of a biological object begins to appear. Traditionally, in laboratory conditions, such estimates are obtained in experiments on animals, varying the parameters of exposure, followed by extrapolation of the results obtained to humans. However, the pathophysiological mechanisms of disturbances that develop in experimental animals as a result of impulse acoustic impacts have not been sufficiently studied in this context, and indicators of the state of the physiological systems of a biological object that are sensitive to acoustic impulses are not currently taken into account when determining their safe levels.
 Purpose. The purpose of the work was to analyze the pathophysiological mechanisms of the development of biological effects of pulsed low-intensity acoustic exposure at different levels of the organization of a living system and to develop a methodological approach to obtaining a quantitative assessment and extrapolation of data on such exposure from animals to humans, taking into account the physical parameters of the acoustic factor and characteristics of the state of the experimental biological object.
 Materials and methods. The selection and systematic review of the scientific literature on the topic of research by keywords in specialized bibliographic databases was carried out.
 Results. The analysis and generalization of the existing theories about the pathophysiological mechanisms of the biological action of acoustic impulses at different levels of the organization of a living system have been carried out. An original hypothetical scheme for interpreting the effects of acoustic exposure in animals is proposed, which is suitable for obtaining threshold estimates of the levels of the adverse effect of the factor on clinical parameters in experimental animals, and vulnerable critical links in the regulation of external respiration in mammals that cause the damaging effect of acoustic vibrations are identified. A scientific and methodological approach to interspecies extrapolation of medical and biological effects of exposure to low-amplitude air pressure waves from animals to humans has been developed, taking into account the anatomical and physiological parameters of the respiratory system of experimental animals, as well as the informative characteristics of the acoustic pulse. An empirical model is proposed that makes it possible to predict the threshold levels of the conditional power of adverse acoustic effects in humans using data on the development of lung damage in experimental animals of various biological species, and the features of setting up such a model are formulated.
 Conclusion. It has been substantiated that it is relevant to refine the proposed empirical model and develop a theoretical model for extrapolation of the initial experimental data on the threshold of safe acoustic exposure from animals to humans, taking into account the interspecific patterns of functioning of physiological systems of the body that are critical to the impact.

Modulation Effects of Internal-Wave Evolution on Acoustic Modal Intensity Fluctuations in a Shallow-Water Waveguide

Internal solitary waves evolving with time in shallow water are known to affect sound propagation significantly. Unlike prior work studying the acoustic effects of individual internal-wave properties separately, this paper elucidates and evaluates the influence of a complete evolution process of internal waves on acoustic fields both theoretically and by the coupled ocean-acoustic simulation. Two evolving wave properties considered here are shape deformations including the variations of wave amplitudes and widths and packet dispersion manifested as the increasing wavelength (i.e., the distance between successive solitons). The acoustic modal intensity expressed by the Dyson series solution is reformulated to explicitly reveal the modulation effects induced by the deformation and dispersion of internal waves. Dispersion leads to modal interference and causes the intensity envelope to oscillate with the varying wavelength. Deformation modulates intensity in a non-oscillatory manner that is less predictable due to the complexity of amplitude and width variations. In the environment reconstructed from the field observations of internal waves in the South China Sea, the modal intensity simulated by the parabolic-equation model exhibits pronounced modulation effects, where the modal interference due to dispersion dominates the intensity-envelope shape, and deformation affects the extremum positions of envelopes.