Showing papers on "Sound transmission class published in 1992"
TL;DR: Transmission and reception of high-frequency sound in the natural environment of bushcrickets was studied using the activity of an identified neuron in the insect's auditory pathway as a “biological microphone” to confirm the existence of two kinds of excess attenuation.
Abstract: Transmission and reception of high-frequency sound in the natural environment of bushcrickets (Tettigonia viridissima L.) was studied using the activity of an identified neuron in the insect's auditory pathway as a “biological microphone”. Different positions of the receiver within the habitat were simulated by systematic variation of the distance from a loudspeaker and the height above the ground. Attenuation and filtering properties of the habitat were investigated with pure-tone frequencies between 5 and 40 kHz. Sound attenuation in excess of the attenuation due to geometrical spreading alone increased with increasing frequency, distance between sender and receiver, and decreasing height within the vegetation (Figs. 2–4). The data also confirm the existence of two kinds of excess attenuation. The amount of amplitude fluctuations in the sound signals was investigated by analysing the variability of the neuronal responses at a given receiver position. Variability increased with decreasing bandwidth of a noise signal at some distance from the loadspeaker. The variability in the responses to pure tones increased with both increasing frequency and distance from the source (Fig. 7). In the selected habitat, the temporal pattern of the natural calling song of male T. viridissima was very reliably reflected in the activity of the recorded neuron up to a distance of 30 m at the top of the vegetation, and 15–20 m near ground level (Figs. 5, 8). The maximum hearing distance in response to the calling song was about 40 m. Environmental constraints on long-range acoustic communication in the habitat are discussed in relation to possible adaptations of both the signal structure and the behavior of the insects.
145 citations
TL;DR: In this article, a screen perforated by a regular array of parallel slits with a mean bias flow through the slits was investigated, and the interaction between an incident sound wave and this mean flow converted acoustical energy into unsteady vortical motion.
78 citations
Book•
01 Jan 1992
TL;DR: This newly created workbook presents key points and important information from each chapter of the book, and provides students with an opportunity to actively test their mastery of the information presented.
Abstract: Acknowledgments The Nature of Sound Waves Simple Harmonic Motion Logarithms and Antilogarithms Sound Intensity and Sound Pressure: The Decibel Complex Waves Resonance and Filtering Distortion Sound Transmission References Index
54 citations
TL;DR: In this paper, the authors used a time domain least mean square adaptive algorithm with two error sensors to reduce the sound transmitted through an elastic circular plate by point force vibration inputs, while the error information and performance were measured in the radiated acoustic field by microphones.
38 citations
01 Feb 1992-Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology
TL;DR: Although some sound transmission via the interaural canal occurred, the present experiments support the hypothesis 2 above that the starling's peripheral auditory system is best described as consisting of two functionally decoupled pressure receivers.
Abstract: The physical measurements reported here test whether the European starling (Sturnus vulgaris) evaluates the azimuth direction of a sound source with a peripheral auditory system composed of two acoustically coupled pressure-difference receivers (1) or of two decoupled pressure receivers (2). A directional pattern of sound intensity in the free-field was measured at the entrance of the auditory meatus using a probe microphone, and at the tympanum using laser vibrometry. The maximum differences in the sound-pressure level measured with the microphone between various speaker positions and the frontal speaker position were 2.4 dB at 1 and 2 kHz, 7.3 dB at 4 kHz, 9.2 dB at 6 kHz, and 10.9 dB at 8 kHz. The directional amplitude pattern measured by laser vibrometry did not differ from that measured with the microphone. Neither did the directional pattern of travel times to the ear. Measurements of the amplitude and phase transfer function of the starling's interaural pathway using a closed sound system were in accord with the results of the free-field measurements. In conclusion, although some sound transmission via the interaural canal occurred, the present experiments support the hypothesis 2 above that the starling's peripheral auditory system is best described as consisting of two functionally decoupled pressure receivers.
36 citations
TL;DR: In this paper, the effect of including in-plane waves in a statistical energy analysis model of a building is examined and it is shown that the additional waves make little difference close to the source, but large differences can occur far from the source if they are omitted.
24 citations
TL;DR: In this paper, the authors solved the dynamic range and passband problems in cinema sound transmission by using a laser disk (9) read by a Laser Disk player (10, 11, 12) synchronized with the original sound track of the film.
Abstract: Dynamic range and passband problems in cinema sound transmission are solved by using a laser disk (9) read by a laser disk player (10, 11, 12) synchronized (14) with the original sound track of the film. Problems relating to splices in the film are solved by reading the sound in advance, in storing it in a memory (13), in reading it back subsequently from the memory, and, where necessary, in causing the memory read back system to jump (24) in order to avoid reproducing sound that corresponds to images that have been removed from the film.
19 citations
TL;DR: In this article, the authors investigate the influence of stiffening on the acoustic response of corrugated steel plates which are employed in building and determine the radiation efficiency and the transmission loss.
17 citations
TL;DR: In this article, an investigation was conducted of acoustic transmission through a tube subjected to an intense thermal gradient along its axis, where the measured transfer function across a localized heated region in the tube was compared to a computed transfer function based on a theoretical analysis of propagation through strong temperature gradients.
Abstract: An investigation was conducted of acoustic transmission through a tube subjected to an intense thermal gradient along its axis. The results are of interest in the interpretation of acoustic data from probe tube configurations designed to measure fluctuating pressures in high temperature environments. The measured transfer function across a localized heated region in the tube was compared to a computed transfer function based on a theoretical analysis of propagation through strong temperature gradients. Over the frequency range 0.4 kHz to 6.0 kHz, generally good agreement was obtained between the measured and calculated attenuation across the heated region with some discrepancy occurring at the attenuation minima. Agreement between measured and calculated phase difference was excellent to within the measurement resolution.
16 citations
TL;DR: In this paper, the authors used a statistical energy analysis model to predict the acceleration response and sound transmission of plates that are exposed to random acoustic or turbulent boundary-layer excitation.
Abstract: The 'APEPS statistical energy analysis model is used in the frequency range of 315-5000 Hz to predict the acceleration response and sound transmission of plates that are exposed to random acoustic or turbulent boundary-layer excitation. Good agreement was found with measured noise reduction data for aluminum, acrylic, and graphite-epoxy plates with length and width larger than the acoustic wavelength. The VAPEPS predicted acceleration response of a 12 X 8 X 0.040-in. plate, installed in a 1-in. thick rigid plate inside a wind tunnel, agreed well with measured data for a stationary (random acoustic) as well as for a convected (turbulent boundary layer) pressure field. It was found that lowest order plate modal frequencies increase most with free flow velocity U. The overall acceleration level as well as the transmitted sound pressure level due to turbulent boundary-layer excitation were close to a Us.' dependence. Excitation by a laminar boundary layer resulted in a U3.6 dependence. Measured noise reduction data for random acoustic excitation of the plate in the wind tunnel fell between the VAPEPS predicted curves for resonant and nonresonant sound transmission showing the limitations of statistical energy analysis to accurately predict sound transmission at low modal densities. The noise reduction of the plate, when backed by a shallow cavity and excited by a turbulent boundary layer, was predicted using a simplified theory based on the assumption of adiabatic compression of the fluid in the cavity. VAPEPS predicted plate acceleration response was used as input in the noise reduction prediction, and reasonable agreement was found with the measured noise reduction in the frequency range of 315-1000 Hz.
14 citations
TL;DR: The feasibility of using acoustic secondary sources in either the source room, or in the receiving room, to actively control the sound transmitted from one room to the other via a common panel has been investigated in this article.
Abstract: The sound insulation properties of many structures mounted between adjacent rooms are known to be poor at low frequencies. The feasibility of using acoustic secondary sources in either the source room, or in the receiving room, to actively control the sound transmitted from one room to the other via a common panel has been investigated. A theoretical formulation for such low‐frequency sound transmission was first developed. The effects of three different active control strategies were then investigated, using computer simulations with a pure‐tone primary source, for a number of different room and panel arrangements. The first strategy involved minimizing the total acoustic potential energy in the source room using a secondary source in the source room. It was found that this could cause increases in the acoustic energy transmitted into the receiving room at some excitation frequencies. Second, the total acoustic potential energy in the receiving room was minimized using a secondary source in the receiving...
06 Mar 1992
TL;DR: The Second International Congress on Recent Developments in Air and Structure-Borne Sound and Vibration held at Auburn University, March 4-6, 1992 as mentioned in this paper was the first workshop devoted to sound and vibration analysis.
Abstract: : This three-volume book of proceedings includes the written versions of the papers presented at the Second International Congress on Recent Developments in Air- and Structure-Borne Sound and Vibration held at Auburn University, March 4-6, 1992. Topics covered in the Proceedings include Sound Intensity, Structural Intensity, Modal Analysis, and Synthesis, Statistical Energy Analysis and Energy Methods, Passive and Active Damping, Boundary Element Methods, Diagnostics and Condition Monitoring, Material Characterization and Non-Destructive Evaluation, Active Noise and Vibration Control, Sound Radiation and Scattering, and Finite Element Analysis.
Journal Article•
Patent•
12 Nov 1992
TL;DR: In this article, an acoustic flow measurement for measurement of the flow velocities of gases and/or quantities that can be derived from same is presented. But the measurement signal is transmitted into a measurement pipe (10) by two sound detectors (14a, 14b) placed at a specified distance (L) from one another.
Abstract: Method and device of acoustic flow measurement for measurement of the flow velocities of gases and/or of quantities that can be derived from same. Long-wave sound is transmitted into a measurement pipe (10). The sound signals passing in the gas flow downstream and upstream are detected by means of two sound detectors (14a, 14b) placed in connection with the measurement pipe (10) at a specified distance (L) from one another, the flow velocity (v) of the gas that flows in the measurement pipe (10) being determined by making use of polarity correlation (15; 151, 152) of said signals. The frequency of the sound that is transmitted into the measurement pipe (10) is scanned between a certain minimum and maximum frequency (fmin...fmax). The measurement signals (fa^_(t), fb^_(t)) arriving from the two sound detectors (14a, 14b) are passed to a narrow-band filter (17a, 17b) or system of filters (17a1, 17a2, 17b1, 17b2). The passband of said filters (17) is scanned synchronously with the frequency scanning of the sound transmission. The duration of the frequency scanning and the width of the passband of said filters (17) are chosen so that, at the moment of the measurement sequence, the measurement signal detected by each sound detector (14a, 14b) has access through its filter (17) substantially without attenuation, as well as so that the interference frequencies substantially different from the mean frequency (f0) of the filters (17) are attenuated significantly.
01 Jan 1992
TL;DR: In this paper, the authors present transmission loss prediction models for a periodically stiffened panel and stiffened double-panels structures using the periodic structure theory, which is capable of accounting fully for multidimensional wave propagation in such materials.
Abstract: This paper presents transmission loss prediction models for a periodically stiffened panel and stiffened double-panel structures using the periodic structure theory. The inter-panel cavity in the double-panels structures can be modelled as being separated by an airspace or filled with an elastic porous layer in various configurations. The acoustic behavior of the elastic porous layer is described by a theory capable of accounting fully for multidimensional wave propagation in such materials. The predicted transmission loss of a single stiffened panel is compared with the measured data.
Patent•
30 Apr 1992
TL;DR: In this article, a method for frequency-tuning the frequency-modulated sound carriers of multichannel sound transmission signals in a satellite television receiver is presented, where the audio range of the television satellite channel is searched for the desired sound carrier in steps.
Abstract: Apparatus and method for frequency-tuning the frequency-modulated sound carriers of multichannel sound transmission signals in a satellite television receiver. By utilizing digital signal processing, the audio range of the television satellite channel is searched for the desired sound carrier in steps. Then the FM center frequency is determined by calculating the average amplitude density in each measurement interval.
TL;DR: In this article, theoretical expressions have been developed for the finite difference approximation errors that occur in estimating sound intensity in the interference fields of point harmonic and random dipole sources, and the effects of the microphone separation distance, the distance of the measurement location from the source, the geometrical arrangement of the sources, the phase difference between the two point sources.
Abstract: The two‐microphone sound intensity measurement technique has been used extensively over the last 10 years for the determination of sound power of noise sources, the determination and ranking of noise sources, and the sound transmission loss of structures. In this paper, theoretical expressions have been developed for the finite difference approximation errors that occur in estimating sound intensity in the interference fields of point harmonic and random dipole sources. Here, expressions have also been developed for the finite difference approximation error analysis of a simple harmonic point dipole located over a reflecting plane using the method of images. Sample calculations have been included to show the effects of the microphone separation distance, the distance of the measurement location from the source, the geometrical arrangement of the sources, the phase difference between the two point sources, and their relative strengths. These calculations suggest that increasing the microphone spacing incre...
Dissertation•
01 Jan 1992
TL;DR: In this paper, the authors examined the transmission of sound through double walls, (walls that consist of two leaves separated by a narrow air cavity). Statistical Energy Analysis was used to assess the importance of individual transmission paths and to determine the overall performance.
Abstract: This thesis examines the transmission of sound through double walls, (walls that consist of two leaves separated by a narrow air cavity). Statistical Energy Analysis was used to assess the importance of individual transmission paths and to determine the overall performance. An existing theory on tie coupling was examined and found to show good agreement with measured level difference data. Direct measurements of power flow across ties confirmed that the theory was accurate. This theory was modified to provide a simple means of predicting the coupling due to the stiffness of the air in the cavity. This is reasonably accurate in the region above the wall's critical frequency. Transmission via these two paths was found to dominate the low frequency performance of masonry cavity walls, (walls where both leaves are heavy). At higher frequencies, transmission via foundations and via joints around doors and windows, was also found to be important. For dry lined walls (walls where one leaf is heavy and the second is light), the strong structural coupling from line joints was found to be the only structural path that affected airborne transmission. This occurred as nearfield radiation from the surface of the dry lining in the vicinity of the joint. If structural coupling is weak, a path involving transmission via the air in the cavity dominates. The path involves nonresonant transmission between the cavity and the adjoining room via the dry lining and occurs as a result of it's low mass and high critical frequency. Additional transmission paths were examined and when found to be important expressions were presented which successfully predicted their performance. This work has shown that the performance of double leaf construction can be predicted with a reasonable degree of accuracy and the theories will have applications in multiple leaf forms of construction.
01 Jan 1992
TL;DR: In this article, it was shown that the reflection-transmission process of a turbofan engine can be treated as an unsteady aerodynamic problem and the rotor shielding effect of the rotor can yield a reduction from negligible up to the order of 30 dB in acoustic power.
Abstract: The dominant sound of a turbofan engine is usually generated by rotor wakes when they impinge on a downstream stator. Consequently, to reach the intake the sound waves must pass the rotor. The rotating blades represent an obstacle that partly reflects and partly transmits the incident sound field. The present paper discusses the calculation of this process by means of a 3D lifting surface approximation of the rotor. It is shown that the reflection-transmission process can be treated as an unsteady aerodynamic problem. The method used will be illustrated by means of numerical examples. It appears that, depending on the relative angle of incidence of the sound waves, the shielding effect of the rotor can yield a reduction from negligible up to the order of 30 dB in acoustic power.
TL;DR: In this paper, a number of different designs for sound transmission suites are examined and their performance computed for standard walls, and it is found that the performance of the system depends on both the test wall and the design of the chambers.
TL;DR: In this article, a large series of measurements studying sound transmission through double panel walls is presented, where the wall surfaces were of 16mm gypsum board studs of 38.5×89mm wood or 90mm light steel with spacing between stud centerlines varying from 30 to 120 cm.
Abstract: The work to be presented is part of a large series of measurements studying sound transmission through double panel walls The wall surfaces in this work were of 16‐mm gypsum board Studs of 38‐×89‐mm wood or 90‐mm light steel were used with spacing between stud centerlines varying from 30 to 120 cm The spacing between screws used to attach the gypsum board was varied with the smallest separation used being 20 cm Transmission loss was also measured for studless constructions Transmission loss contours showed prominent dips at frequencies influenced by stud and screw spacing Sound absorbing material added to the cavity had only a minor effect on these resonances suggesting that they are associated with panel resonances and not with the cavity between the panels A selection of the data from this work will be presented and discussed
Journal Article•
TL;DR: In this article, the transmissin of an incident plane wave through two parallel plates joined by periodically spaced reinforcing beams of finite mass is solved, and the amplitudes of the spatial spectrum of scattered waves and waves transmitted through the plates are determined.
Abstract: The problem of the transmissin of an incident plane wave through two parallel plates joined by periodically spaced reinforcing beams of finite mass is solved. The amplitudes of the spatial spectrum of scattered waves and waves transmitted through the plates are determined.
Dissertation•
01 Jan 1992
TL;DR: The analysis of place relationship within thechest wall suggested that transmission of the sound across the chest occurred not as a surface wave but as a longitudinal wave, therewith traversing the chest wall directly from the sound source.
Abstract: A spark sound was generated in the canine bronchus and sound waves were observed on the surface (skin) and on each layer (pectoralis major muscle, intercostal muscle and parietal pleura) of the chest wall. The sound wave observed on the surface of the chest wall was 5-10 ms in duration, 400-500 Hz in dominant frequency and 0.6-1.2 ms in the duration of the initial deflection. Reverse dispersion of the waves, i.e., the later components of the wave having longer periods, was also recognized. These characteristics of the wave were similar to those of time-expanded wave-form of crackle, i.e., discontinuous adventitious lung sounds, in clinical cases. Both the spark sound and the sound wave observed on the visceral pleura were of short duration, being 0.7 ms and 1 ms, respectively. therefore, the main component of the sound wave observed on the chest surface was considered to reflect the physical properties of the chest wall itself. The analysis of place relationship within the chest wall suggested that transmission of the sound across the chest occurred not as a surface wave but as a longitudinal wave, therewith traversing the chest wall directly from the sound source. The arrival time of the sound was well correlated with the distance between the sound source and the positions of the pick-ups on the surface of the chest wall. Assuming that the medium between the source and the lung and in the chest wall were 71.5 and 29.6 m/sec, respectively. Further studies will be necessary to clarify the theory of the sound transmission through the living tissue as a viscoelastic body.
01 Jul 1992
TL;DR: In this article, a model of a vibrating plate with arbitrary boundary conditions was outlined and the far field was minimized to radiate acoustic power using secondary force inputs, and experimental results for the combination of a clamped steel plate with four secondary aluminum honeycomb panels were presented.
Abstract: Work was performed on the active control of sound transmission in composite structures. First, a model was outlined of a vibrating plate with arbitrary boundary conditions. Second, the far field was minimized to radiate acoustic power using secondary force inputs. Third, a model of a simple case of freely mounted stiff lightweight panels was used. Fourth, experimental results for aluminum honeycomb composite panels is presented. Fifth, experimental results are presented for the combination of a clamped steel plate and an aluminum honeycomb panel with secondary forces acting between the partitions. Finally, experimental results for the combination of a clamped steel plate with four secondary aluminum honeycomb panels is presented. All materials are shown in viewgraph format.
01 Jun 1992
TL;DR: In this analysis, the features of the image theory are studied from another point of view, based on a collection of acoustic doublets, to solve the sound propagation problem within a wedge-shaped fluid overlying either a slow or a fast bottom.
Abstract: : After several years of research, the image theory has been found acceptable to solve the sound propagation problem within a wedge-shaped fluid overlying either a slow or a fast bottom. Some further observations where done in this research. The primary purpose was the development and computer application of a new analysis, the doublet analysis, based on the image theory. In this analysis, the features of the image theory are studied from another point of view, based on a collection of acoustic doublets.
01 Jan 1992
TL;DR: In this paper, a variety of topics, including sound intensity, structural intensity, modal analysis and synthesis, statistical energy analysis and energy methods, passive and active damping, and boundary element methods, are discussed.
Abstract: The papers presented in this volume cover a variety of topics, including sound intensity, structural intensity, modal analysis and synthesis, statistical energy analysis and energy methods, passive and active damping, and boundary element methods Attention is also given to diagnostics and condition monitoring, material characterization and nondestructive evaluation, active noise and vibration control, sound radiation and scattering, and finite element analysis