Sound Field Formation Research Articles

The formation of nonlinear sound fields in the boundary region of the bubble medium

The formation of sound fields in the boundary region of a bubble medium under the influence of a powerful sound pulse for different volume concentrations of bubbles is studied. Two characteristic ranges of the volume concentration of bubbles, to the limits of which different types of wave fields are formed, are determined. At low values of volume concentrations in the boundary region, a long-lived space-limited standing sound wave is formed. A standing sound wave contains an order of magnitude more energy than other areas of the bubble medium. At large values of the volume concentration of bubbles in the boundary region of the bubble medium, an excitation zone forms. The structure of the zone is a periodic wave propagating deep into the bubble medium. The wavelength in the excitation zone increases with increasing distance from the boundary.

P‐208: Late‐News‐Poster: Interdisciplinary Research on Acoustic and Human Cognitive Characteristics of Flat‐Panel TVs: Front‐Firing Exciter Speaker Characteristic

Technological advances in the display industry have allowed organic light‐emitting diode panel manufacturers to create ultra‐wider‐screen, high‐picture‐quality, high‐sound‐quality TVs. In the previous research, we have been studied the characteristics of the sound on the screen directly by excite speaker, with the panel of OLED. Unlike LCD, the OLED emits light and composes pictures without complex sheets such as BLU so that the panel can play the role of a diaphragm of a general dynamic speaker.Sound is free to propagate by the vibration of the air. And this air vibration can be information or noise. In this case, when the information is used, the sound is the information required by the listener, and when the opposite listener is not needed or not desired, the noise may be referred to. In addition, the sound is perceived through human auditory organs. At this time, excessively loud volume causes noise‐induced hearing loss. Furthermore, rather degrades information transmission. Depending on the wave motion characteristics of the sound, the phenomenon of refraction, reflection, diffraction occurs, and forms a sound field. As shown in Fig. 1 and Fig. 2, the sound field is distributed differently according to the ordinary dynamic speaker system and exciter speaker system. It is the same thing that occurs in a speaker, but as it propagates, it is different from being concentrated or evenly spread in one place by the effects of refraction and reflection. When the sound is aggregated, the sound quality may be improved by interference between frequencies, but the resolution is often lowered. That is, the down‐firing sound by the existing dynamic speaker has low sound intelligibility. On the other hand, the proposed exciter speaker spreads evenly around the sound sourced directly from the center of the screen and has less influence of the reflected sound source, thus including the information of the original sound well.As shown in Figures 1 and 2, the sound quality of TV sets is also different. Cognitive analysis was performed through listening analysis. Over 150 people watched the same video and conducted a survey. The experiment was to watch TV sitting on the front and side, a group of about ten people at a time. The videos used in the experiments utilized news, classical music, and pop music, and alternately listened and tested for about 30 seconds. After watching the audience, they responded to the cognitive differences in sound quality. The questionnaire asks three kinds of questions. The analysis was performed by factor analysis, reliability analysis, and T‐test. The exploratory factor analysis and reliability analysis results have been fully validated. Cronbach's alpha is above 0.8, and the results are highly reliable. In the T‐test analysis, the t value was significantly obtained as ‐8.684. The sound quality of the two TV sets is different, which means that the average of the indirect sound TV(down‐firing) set is 3.860, and that of the direct sound TV(exciter speaker) set is 4.528, which means the clarity of the direct sound TV set is high.Audiovisual is an essential component of information delivery. The technology of panel makers is improved, and image quality can go beyond HD to achieve ultra‐high resolution of 8K. Sound is also developing through exciter speakers. In this study, Interdisciplinary research was conducted on the information transmission and sound quality of moving images through acoustic and cognitive analysis of down‐ and front‐firing sound sources. In acoustic analysis, the conventional dynamic method is reflected, and the formation of sound fields is disadvantageous. Cognitive analysis showed that the direct sound was easy to understand and accurate. In the future, we will conduct additional studies to improve the objective and subjective sound quality by conducting acoustic and cognitive analysis studies according to various spatial conditions.

FORMATION OF GIVEN SOUND FIELD BY MODELING SOUND REFLECTING SURFACE

A model of a sound reflecting surface is presented that provides the specified character of the sound field formation. According to the pre-planned nature of the sound field for a specific area, the shapes of the reflecting surfaces are modeled, made and installed in a given order. For a point sound source, the shape of the reflecting surface is calculated, which is located at a given distance from the source and ensures the formation of a parallel sound stream in a given direction.

Mathematical model of traffic noise

Reducing noise to acceptable levels is an environmental, social and economic problem of modern cities. To achieve this task, information about the noise conditions of the studied area should be accessible and detailed. That is why the integrated mathematical model for evaluating noise levels at a point of the receiver taking into account the dynamics of vehicles in the flow on the road section, noise reductioneffects, characteristic of modern cities, at its propagation from the source to the receiver and integration of noise levels at the receiving point was developed.This model has allowed taking into account the motion nature of vehicles in the flow depending on the studied road area, the impact of the rugged terrain on the propagation of sound waves from the source to the receiver depending on the position of the receiver, as well as integral evaluation of the noise load levels.The developed model was verified by comparing with the results of experimental studies of traffic flows in two cities. This has allowed to determine the application range of the model and motion features of vehicles in the flow depending on the lane. Mathematical model of traffic noise allows to evaluate noise levels, not only from transport flows on straight roads, but also to simulate the formation of sound fields when approaching traffic lights and intersections.

Acoustic-Wave Hearing Model, The Initial Stage-C:Hydroacoustics of the Inner Ear (Sound Field Formation in the Cochlea)

Acoustic-Wave Hearing Model, The Initial Stage-C: Hydroacoustics of the Inner Ear (Sound Field Formation in the Cochlea) The auditory effect (hearing) is determined by the information coming into the brain from the peripheral part of the auditory analyzer. The signals (nerve impulses) are triggered by the receptors of Corti organ-hair cells .Being secondary structures the receptors themselves create the generator potential due to their interaction with the tectorial membrane and being distant they take sound energy in the cochlea experiencing multiple conversions. The article analyzes theformation ofthe sound fieldon the initial stage(in perilymphaticand the middlescaleof cochlea.

МОДЕЛЮВАННЯ ВПЛИВУ ФАСАДУ БУДІВЛІ НА ФОРМУВАННЯ ЗВУКОВОГО ПОЛЯ

Досліджено методи моделювання звукових полів. Розроблено дві променеві моделірозрахунку впливу фасаду будівлі на формування звукового поля: класичну променеву модельта модель, що враховує функцію автокореляції. Проведено моделювання звукових полів передфасадом будівлі методом скінченних елементів. Проаналізовано доцільність використаннякожної моделі та точність отриманих результатів.Ключові слова: інтерференція, метод скінченних елементів, променева модель, фасад.

Review of formulae for efficiency calculation of noise barriers in streets

Analysis of principal formulae for calculation of diffraction effects on the top edge of noise barrier and interference effects of sound waves after reflection from impedance surfaces was done. Main criteria of noise barriers efficiency assessment were considered. Model for calculation of building façade impact was analyzed. Assessment of building façade impact on sound field formation on the street was done.

The discovery of the underwater sound channel, experimental studies, and regional differences

More than half a century has passed since the discovery of the underwater sound channel. In this period of time, the Acoustics Institute has performed a number of experiments on the long-range propagation of explosion-generated sound signals in different ocean regions. These experiments included the studies of such phenomena as the frequency-dependent sound attenuation in the sea medium and the sound field formation in the underwater sound channel. A combined analysis of the data obtained revealed considerable regional differences in the time structure of the sound field. In the experiments, a number of phenomena were observed that required special explanation and additional theoretical treatment. These phenomena include: the unexpectedly high attenuation of low-frequency sound in the sea medium, the “spectrum-analyzing” properties of the underwater sound channel in the Black Sea, the existence of the reverberation forerunner (the so-called prereverberation), the frequency-independent deviation of the phase shift from the usual value of 90° between the signals in classical quartets differing in the number of contacts with the caustic, the splitting of individual signals into quartets, and the transformation of these quartets into groups of nearly irresolvable signals at long distances. The most interesting data of the aforementioned studies are described in the present paper.

Characteristic features of the sound field formation near the bottom of a shallow sea

Detailed calculated data are presented for the angular, temporal, and energy structures of the sound field at the points of localtion of a horizontal line array of receivers (at 250-m intervals) in a shallow sea. The array is deployed near the bottom of a 200-m-deep waveguide along a sound propagation track, at distances from 20 to 30 km from a source generating a signal in the kilohertz frequency range. The influence of a sand or mud bottom on the intensity of signals arriving along single rays is numerically estimated for winter and summer conditions of sound propagation in a specific region of the Barents Sea.

Some Features of the Sound Field Formation in the Kamchatka Region of the Pacific Ocean

Some Features of the Sound Field Formation in the Kamchatka Region of the Pacific Ocean

Year-to-year variability of the long-range propagation conditions in the Norwegian Sea

On the basis of the experimental data on the sound field formation in the Norwegian Sea, the year-to-year variability of the propagation conditions is estimated. A comparative analysis is performed for the data obtained from two long-range-propagation experiments with explosion-generated signals. The experiments were carried out in summertime (August) on a path crossing the central deep-water part of the Norwegian Sea and were separated in time by a period of four years. Noticeable changes are found to occur in the sound speed fields between the two experiments. These changes are related to a change in the distance between the cores of cold waters (observed in the region of the Norwegian Basin) and warm waters (observed in the region of the Lofoten Basin). According to calculations, the observed changes in the sound speed structure can lead to considerable changes in the propagation anomaly and in the range dependence of the sound field decay. In spite of the noticeable difference in the propagation conditions, the experimental coefficients of low-frequency attenuation differ little for the two experiments.

Comprehensive studies of sound fields in the Kuril-Kamchatka region of the northwestern Pacific

The technique, experimental conditions, and main results of comprehensive studies of sound fields in the northwestern region of the Pacific Ocean are presented. The experiments are carried out on paths up to 2100 km in length. The power-frequency, space-time, and correlation characteristics of the sound fields are studied in sonic and infrasonic frequency bands for long-and extra-long-range propagation with the use of cw and explosion-generated sound signals. Effects of the bottom relief and the spatial distribution of the speed of sound on the frequency characteristics of the sound field are investigated. The role of front zones in the formation of sound fields received at the coastal shelf and in the open ocean is revealed. The loss coefficients are estimated. The space-time stability of the sound field components is studied, and the possibility is shown for the coherent components to be conserved and resolved in frequency at distances up to 2100 km. The phase velocities of these components are determined. The total broadening of the frequency spectra is considered. The correlation characteristics of the total field are obtained for horizontally separated receivers in sonic and infrasonic frequency bands.

Long-range ocean mapping by low-frequency sound

The development of high-power, low-frequency sound sources and methods of acoustical tomography has been enhancing the range of observation of underwater inhomogeneties in the ocean from local to global scale. In this way, the problem of the role of underwater mountains in sound field formation arises. It also looks attractive to apply a low-frequency sound for large-scale acoustic ocean mapping. The characteristic of sound reflection by underwater mountains has not been studied enough until now. A review of experiments made in the Pacific and Atlantic on long-range sound reflections from underwater mountains and continental slopes is presented. During the measurements, continental slopes were sounded by tone-burst signals of about 240-Hz frequency from distances of 600 and 200 km. Receiving systems deployed at 20–90 km apart from the slopes detected both the forward and reflected signals. The reflection coefficient was found to be about −(20–30) dB. This makes it possible to observe the reflections everywhere in the ocean. Different schemes of long-range ocean mapping based on low-frequency echo sounding and on coherent and incoherent aperture synthesis are discussed. [This work was supported by RFBR Grant No. 96-02-1944.]

Effective Modal Density in a Reverberant Sound Field for Finite Sized Sources

Much of the theory concerning the formation of sound fields in reverberant rooms and the measurement of the sound levels produced by these fields has emphasized the statistical aspects. A previous paper [K. M. Eldred, B. H. Sharp, and F. M. Murray, “The Coupling of Finite Sized Sources to a Modal Reverberant Sound Field,” presented at the 76th Meeting of the Acoustical Society of America (Nov. 1968), J. Acoust. Soc. Amer. 45, 338 (A) (1969)] discussed the coupling of finite sized sources to a reverberant sound field and showed that there is a strong dependence between sound level and source configuration in certain frequency ranges. This paper will briefly review these findings and extend the work to examine the relationship between the effective modal density and the calculated modal density as a function of source configuration. On the basis of this relationship, the relevance of statistical methods as applied to reverberant sound fields with finite sized sources will be discussed.