bluuebunny/crossref_metadata_2025 huggingface dataset:
Community noise from waste treatment plants
Authors: Russell G. A. , Hicks A.
Published: October 2005

Various waste treatment plants are discussed in terms of noise emission levels, sources of noise, and possible noise abatement measures. Field measurements are reported for several types and capacity of plant. Particular attention is given to the problem of selecting measurement locations in order to obtain a valid measure of total radiated acoustic power and major source identification. Results are shown in terms of total emitted sound power versus plant type and capacity and illustrate the expected conclusion that noise levels generally increase with increasing plant capacity.
Short-term complaint system concerning community noise near a fossil fuel power station
Authors: Thompson A. R. , Hoover R. M.
Published: October 2005

A communication system by which local residents living near a fossil fuel power station could complain about the types of sounds propagating across their properties is described, as are the results of the program. This complaint system was in operation 24 hours a day for one month during which time a consultant lived in one of the residences surrounding the station. In this way, he was situated in the same environment as the complainants and was able to make observations and measurements on a continual basis. Thirty-one complaints were received during the monitoring period with calls coming from each of the three nearby residential areas. The 31 calls were identified to be principally due to four noise sources—high-pressure safety valves venting steam to the atmosphere, large induction motors driving the station circulating water pumps, induced draft fans, and main power transformers.
Noise of steam-injection water heaters
Authors: Wilby John F.
Published: October 2005

Steam is used as a heating agent in many industries, especially those associated with food processing. Several of the applications, such as steam injection into water in food blanchers, can create noise problems. Noise and vibration levels were measured for several blanchers where steam was injected through holes in pipes running through the blanchers or through steam ejectors. Subsequently, several ejector systems were investigated in a test tank. Parameters such as water temperature, steam pressure, ejector mixing length, and air injection were studied. Variations of up to 50 dB were observed in noise and vibration levels within an operating range of 50–200 °F for water temperature and 20–100 psig for steam pressure. The use of ejector mixing tubes and air injection were found to be more effective in reducing noise at low water temperatures than at high. The results are interpreted in terms of noise from the collapse of steam bubbles at low water temperatures and jet noise at high temperatures. [Sponsored in part by Northwest Food Processors Association.]
Construction site noise level impact
Authors: Yus B. K. , Kessler F. M.
Published: October 2005

Nuclear power plant construction noise impact has been quantified by use of the Equivalent Population Impact (Peq) concept recently used by the federal Environmental Protection Agency to assess the effect of portable air compressor regulation. Numerous construction scenarios, consisting of the constructinn of coal-fired and nuclear power plants with and without cooling towers, were studied. These scenarios were studied using two approaches which considered both the ambient sound level and the change in ambient sound level. An additional method is discussed using a “normalized” Ldn as suggested in EPA “Levels Document” (EPA 550/9-74-004 (1974)). These methods are exemplified using a case study of a recent environmental assessment undertaken for a public utility.
On the evolution of hearing
Authors: Stebbins W. C.
Published: October 2005

The comparative approach provides an additional perspective on the study of hearing. A behavioral account of hearing function supplies a necessary complement to the morphologist's description of the evolution of the ear. The behaviorist relies on the judgment of the morphologist with respect to homology and of the vertebrate paleontologist with regard to phylogenetic sequence. Selective pressures have produced structural adaptations in the auditory system of the evolving vertebrates which have led to enhanced auditory sensitivity over an extended frequency range, improved frequency resolution, more accurate sound localization, specialization for echolocation, and finally the ability to send, receive, and decode the signals of conspecifics—a major factor in the provenance of language and social organization. It is these functional aspects of the hearing process which will be discussed within a comparative context in this symposium. The development of an efficiency conducting apparatus together with changes in the inferior part of the labyrinth led to improved acoustic sensitivity in the advanced and highly specialized ostariophysine fish. In the ancestral lineage of the land vertebrates, leading eventually to the mammals, a middle ear derived from gill supports and jaw bones, an inner ear as an elongated and coiled extension of the vestibular labyrinth plus considerable elaboration of the afferent pathway has resulted in high-frequency hearing and, in some, a marked increase in sensitivity to the low frequencies. Some consequences of these and other evolutionary developments will be discussed in the papers which follow.
Evolution of sound localization
Authors: Masterton R. B.
Published: October 2005

Although there is not yet sufficient comparative data on sound localization acuity to reconstruct its probable evolution, some idea of its long-range trends can be gained by combining currently accepted behavioral, physiological, and comparative neurological information about the auditory system. The variation in the ear and hindbrain auditory nuclei among mammals suggests that there are at least two chief adaptations for sound localization that are understandable by reference to the cues used to determine the aximuth of sound sources. Apparently one source of selective pressure for accurate sound localization has been translated into pressure for refined analyses of binaural differences in time or sound spectra. The phylogenetic history of the structures contributing to these analyses, in turn, yields insight into the evolution of sound localization. Conversely, if the auditory system is viewed as the evolutionary product of selective pressures for accurate sound localization, constrained only by head size on one hand and the physics of sound on the other, several diverse structural variations in auditory systems and behavioral variations in hearing seem to have plausible explanation.
Calculator-based digital system for underwater acoustical measurements
Authors: Kodosky J. L. , Nowlin W. C. , Truchard J. J.
Published: October 2005

An underwater acoustical measurement system has been developed around a Hewlett-Packard 9830 Programmable Calculator. This system includes a pulsed ac voltmeter, a real-time spectrum analyzer, a phase meter, a programmable time-base generator, a frequency synthesizer, a synchro-to-digital converter, and a digital plotter. Much of the plotting and recording previously done with analog instruments can now be done with this digital system. Furthermore, data can be recorded on digital cassettes for further processing and use at a later time. The programmable feature of the calculator allows flexible formatting, labeling, scaling of data, and other types of data reduction. This system is relatively easy to program and to use. One major difficulty with this particular measurement system is that processing time is very slow. This is especially troublesome where continuous plots or recordings, such as directivity patterns, are being made. Continuous plots require a large amount of data to be processed and plotted and the processing time is objectionably long in some cases. These difficulties can be overcome by using a high-speed processor such as a mini-computer.
Adaptive array tracking detection
Authors: Liu C. S. , Nolte L. W.
Published: October 2005

Adaptive arrays for signals with uncertain spatial information have been proposed in the literature which weigh the outputs of a multibeamformer. A difficulty in designing the adaptive array is obtaining the optimal weighting function for detection and/or estimation. An optimal approach to deriving the weighting function sequentially is shown in this paper for a moving signal source example in which the motion of the signal source is modelled as a Markov stochastic process. The close relationship between the optimal weighting function, the a posteriori probability of the target position and the Markovian statistics of the motion are presented. A computer simulation illustrates the inherent sequential adaptive tracking property of the Bayes optimal array processor. [Supported by Office of Naval Research, Code 222.]
Use of calculated sound fields and cross spectral matrix detection to locate sound sources in shallow water
Authors: Bucker H. P.
Published: October 2005

The calculated complex sound field cj for sensor j at depth zj and range rj from a sound source of frequency ω and depth z0 can be written in the normal mode as cj = (2π/rj)1/2  ∑ m Um(z0)Um(zj) exp[(kmrj − ωt)]. Here, km is the horizontal wavenumber of mode m and Um is the depth function for the mth mode. It is proposed that the detection factor DF =  ∑ j=1J  ∑ k=1≠jJ cjck* 〈(cj0ck0*)*〉 is a reasonable measure for determination of whether a set of sound pressure measurements {cj0} for j = 1, 2, …, J is a good fit to calculated values of {cj} for an assumed location of the sound source. Here 〈〉 denotes a time average and * denotes complex conjugate. Several examples are shown where a set of {cj0} are calculated for a given source location in a typical shallow water channel, and values of DF are then calculated for a grid of range depth or range azimuth locations.
Hydrodynamic instabilities of a layered elastic medium in the presence of a flow field
Authors: Pierucci M.
Published: October 2005

The stability of a finite thickness layered medium being excited by a flow field is examined and results with experiments presented. The dynamics of the compliant layer is assumed to be governed by the basic elasticity equations. On the lower surface, the layer is assumed to be fixed to a rigid surface. On the upper surface, a potential flow field is assumed to provide the exciting force. A solution to the linearized set of elasticity and fluid mechanics equation is obtained and when all of the boundary conditions are satisfied, a comparability equation is obtained: F(ω, α, h, σ, ρf, ρe, Fe, U∞) = 0. Complex or imaginary values of ω and/or α indicate either a temporal or a spatial instability of the compliant layer fluid System. Roots of this exact equation for different thickness, Poisson's ratio, Young's modulus, and flow velocity have been obtained. In the limit as the plate thickness goes to infinity and as the fluid density goes to zero, the classical Rayleigh surface waves are recovered. The results have been compared with experiments conducted in a rotating cylinder facility. Different compliant coatings have been tested and the experimental results have been compared with the theory.
Automatic tracking of speech parameters for parallel formant synthesis
Authors: Olive J. P. , Macchi M. J.
Published: October 2005

A speech synthesis model in which the formant resonators are connected in series does not produce satisfactory speech quality for sounds produced with a narrow constriction in the vocal tract or with the velum lowered so that the nasal cavity is coupled to the oral cavity. These latter cases are better handled by a parallel connection of formants, in which the amplitudes of the individual formants can be controlled independently. An existing analysis-synthesis method for a series model of speech [J.P. Olive, “Automatic Formant Tracking by a Newton-Raphson Technique,” J. Acoust. Soc. Am. 50, 661–670 (1971)] has been adapted to a parallel formant model of speech. The analysis procedure derives pitch and four formant frequencies and amplitudes from natural speech which are then used to control a speech synthesizer. The quality of synthetic speech produced in this manner is a substantial improvement over that produced according to a series model.
Steady-state measurements of loss factor
Authors: Swift P. B. , Bies D. A.
Published: October 2005

Apparent loss factors for reverberant mechanical structures are most commonly determined experimentally from measurements of the stored energy decay rate. The decay-rate method is satisfactory for thin plates at high frequencies and especially for fairly well damped plates, but for other situations which are frequently encountered no single decay rate exists. Rather time dependent, decay traces are frequently served which have two or more slopes or even a continuously varying slope. Presumably, the initial slope is to be associated with the apparent loss factor which determines steady-state response, but frequently the initial slope is very hard to determine. An alternative steady-state method which follows from direct measurement of the input power to the structure is described. The simultaneous measurements of force and velocity is accomplished with careful preservation of phase to allow the continuous determination of the input power to the system under test. Some experimental results for plates obtained with the system also will be presented.
Modal damping determinations from resonance spectral shape measurements
Authors: Douglas B. E.
Published: October 2005

A normal-mode interpretation is given to the mechanical impedance spectra of complex structures to evaluate medal loss factors. Standard bandwidth methods are generalized as to the selection of the off-resonance response measurement for application to impedance and radiation factor spectra. The effects of modal density on such an approach are investigated to gain understanding of the limitations of single-degree-of-freedom methods in evaluating the damping of multimodal systems. The sensitivity of this method to damping capacity and mode separation (i.e., modal overlap) is examined utilizing the Snowdon model for the impedance of transversely vibrating, internally damped beams. The application of the method to both analog and digitally generated spectra is investigated. These generalized bandwidth methods were found to have increased the measurement range and flexibility of the standard half-power bandwidth method as well as provided a method for evaluating the damping in resonances arising from degenerate modes in which structural irregularities act as perturbations.
Results of a design effort to control building HVAC equipment noise
Authors: Salter C. M. , Rodkin R. B. , Rosenfeld S. I.
Published: October 2005

An Acoustical Society paper [J. Acoust. Soc. Am. 54, 273(A) (1973)] delivered in Boston on 10 April 1973 discussed the noise control design for a building requiring the exterior installation of its major mechanical and electrical equipment. Our primary concern was noise impact from three aircooled chillers, a transformer, and an emergency engine-generator located in an open outdoor equipment yard across the street from a quiet residential neighborhood. This study was particularly note-worthy because of the extensive interaction required between the architect, mechanical and electrical engineer, mad acoustical consultant. The systems configuration engineered by our firm two years ago is now in operation. For the major equipment we compare our predicted noise levels to the measured noise levels, both nearfield and in the community. We also appraise community opinion to the new noise source, and compare it to our predicted community response. Costs information for the noise control treatment is also presented.
Entrance conditions to air terminals: How important are they from a noise standpoint?
Authors: Jones Robert S.
Published: October 2005

In normal field installation of grilles, registers, and diffusers for air-handling systems, optimum entrance conditions to terminal units are seldom or never realized. This paper discusses differences in generated noise level, as related to duct connections at terminal devices, between optimum laboratory test conditions and actually installed configurations, dictated by job conditions. Examples are used to describe the effect of properly designed and installed ducts leading to air terminals and, by contrast, what happens when optimum or recommended conditions are compromised and air-volume control devices are misapplied. Examples of remedial treatment and the resulting noise reduction are described.
Review of the environmental impact process on land-use planning
Authors: Bragdon Clifford R.
Published: October 2005

Beginning in 1970, the United States enacted legislation that required assessing the potential environmental consequences of impending Federally funded projects, programs and policies. This and subsequently enacted federal, state, and municipal legislation has a profound impact on the land use planning process. Central to the theme of such environmental legislation is a concern for the preservation of land uses compatible with health and welfare objectives and the general quality of life. The acoustical quality of the human environment is becoming of paramount concern in the planing process. This paper outlines the established administrative and legal requirements pertaining to environmental impact, the application to land use planning, and the consideration of environmental noise. It is recommended that the assessment of environmental noise continue to be an integral element in identifying and solving land use planning problems. Examples of effective programs will be described.
Effectiveness of environmental impact statements in abating noise
Authors: Mudarri David H.
Published: October 2005

Producing good Environmental Impact Statements is but a means to an end but not an end in itself. EISs reflect one event in a long chain of decisions spanning the planning, construction, and operation stages of projects having potential noise impacts. The National Environmental Policy Act reflects the need to have the environment elevated as a higher priority concern in the planning and decision process. But the requirement for EISs per se represents a tactical rather than a strategic approach to that end. As an administrative requirement, the EIS is an incentive to avoid and/or abate projects with significant environmental impact because such impacts will be subject to critical review. Also, it has served as a learning device and a context for communicating good environmental assessment and planning techniques. But ultimately, it is the appropriate consideration of environmental noise impact through good noise assessment techniques, and noise abatement devisions, that is, the criteria upon which judgments concerning its success may be made. In this context, Environmental Impact Statements have made significant contributions. However, there remain problems in methodology, particularly as they relate to forecasting future impacts, and areas of traditional neglect, such as construction noise impact and land use planning, that should be examined in some detail.
Air installation compatible use zone (AICUZ) program
Authors: Vest Gary D.
Published: October 2005

Aircraft noise, as a land-use planning determinant, promises to be one of the major land-use planning issues in the next few years. The increased public awareness of this problem and new Federal, state and local legislation, standards, criteria, and affirmative action programs dictate the need for substantial efforts at all levels of government and the private sector. The military approach to this problem is the Air Installation Compatible Use Zone (AICUZ) program. This paper will cover the AICUZ method of land-use planning with regard to aircraft noise by addressing the following topics: (a) subject overview, problem identification, and program justification; (2) federal policy; (3) brief history; (4) preparing an AICUZ Plan; (5) safety considerations; (6) Noise Descriptors Systems; (7) program management; (8) other planning approaches and methodologies; (9) relationship to broad-based environmental planning; (10) trade-offs with source reduction and flight operational changes; (11) legislation; (12) federal programs and relationships; (13) implementation methods; (14) case study summaries; (15) problems; and (16) future directions.
Acoustics, music and noise: General education courses in acoustics
Authors: Rossing Thomas D.
Published: October 2005

Some of the author's experiences during 18 years of teaching acoustics courses of a non-technical nature are described. Laboratory instruction is considered to be a most desirable feature of such courses. Some favorite laboratory and demonstration experiments are described, as well as course materials.
Critical band effects for prestimulus change masking
Authors: Puleo J. S. , Pastore R. E.
Published: October 2005

In a recent experiment [J. Acoust. Soc, Am. 57, 55 (1975)] we demonstrated a two stage interference function in the detectability of a signal (1000 Hz, 20 msec) caused by a prestimulus shift in the frequency centroid of an otherwise continuous, bandlimited (100–1900 Hz) masking noise. The shift did not alter either the total power of the noise (68.5 dB A) or the spectrum level in the frequency region of the signal. The effect occurred regardless of the direction of the shift. This paper reports on the effects of prestimulus decreases in the width of a bandlimited masking noise centered at the signal (1500 Hz, 15 msec) frequency as a function of the unchanged portion of the noise. The results are discussed in terms of a critical band for prestimulus change interference effects. [This research was supported by grants from the SUNY Research Foundation and NINDS.]
Time course of loudness enhancement and intensity discrimination
Authors: Elmasian R. , Morgan R. , Galambos R.
Published: October 2005

When a tone burst is played close in time to another tone burst, each can affect the perception of the other. In particular, the loudness of the less intense tone can be enhanced [e.g., Elmasian and Galambos, J. Acoust. Soc. Am. 58, 229–234 (1975)]. As interstimulus interval is reduced from 500 to 25 msec, the loudness of the less intense tone burst as measured by loudness matched with a variable intensity tone burst can increase as much as 20 dB. Loudness, however, is a subjective attribute. In order to more objectively assess the loudness information available to a listener, subjects were asked to discriminate between two intensities of the less intense tone burst at various interstimulus intervals from the more intense burst. As expected, performance declined as interstimulus interval was reduced below 500 msec. The decrease in discriminability, however, was not enough to account for enhanced loudness on the basis of reduced perceptual information alone.
Temporal integration of threshold and suprathreshold signals
Authors: Ahaus W. H. , Stokinger T. E.
Published: October 2005

A loudness summation study from this laboratory, using signal durations from 10 to 500 msec, failed to demonstrate a definite critical duration (i.e., a straight-line fit to the data gave r's:⩾0.97). A more extensive investigation, involving a number of durations beyond 500 msec, was undertaken to examine the problem in more detail. Employing 12 signal durations (from 10 msec to 3 sec) and using a transformed up/down procedure to collect the data, temporal integration functions at 1000 Hz were determined on six normal-hearing listeners both at threshold and at three suprathreshold intensities: 30, 60, and 90 dB SL. For the suprathreshold conditions listeners balanced the loudness of each tone to that of a 1-sec reference tone. Group data showed (1) evidence of a critical duration of somewhere between 150 and 300 msec at all levels, although this value was highly dependent upon how the critical duration was determined, and (2) some tendency toward reduced steepness of the loudness summation function below the critical duration with increasing level. [Work supported by the Research and Education Committee, Oklahoma City, V.A. Hospital.]
Geometry effects on STOL engine-over-the-wing acoustics with 5:1 slot nozzle
Authors: von Glahn U. , Groesbeck D.
Published: October 2005

The effect of nozzle roof (kickdown) angle and nozzle location relative to the wing trailing edge on noise was determined at model scale with a 5:1 slow nozzle (equivalent diameter, 5.1 cm) for several OTW configurations. Nozzle roof angles of 10° to 40°, with and without cutback at the nozzle sides were tested. Also included, for comparison, was a 5:1 slot nozzle with external deflector. Three wing chord sizes were used: standard (33 cm), 23-standard, and 32-standard. Flap deflection angles used were 20° and 60°. The nozzle was located at 20% and 35% of chord. In addition, velocity maps were obtained at the trailing edge of the wings. With increasing wing size, representing a variety of airframe/engine installations, low-frequency noise was increasingly attenuated and shielding benefits increased directly with wing size. With increasing nozzle roof angle, the jet velocity at the trailing edge was decreased, causing a decrease in trailing-edge noise; however, the jet impingement noise on the wing increased. Cutback of the nozzle sides improved flow attachment and reduced the trailing-edge velocity and noise. The best flow attachment and least trailing-edge noise was obtained with the external deflector configuration.
On the effect of external flow on sound transmission into a thin cylindrical shell
Authors: Koval L. R.
Published: October 2005

In the context of the transmission of airborne noise into an aircraft fuselage, a mathematical model is presented for the transmission of an oblique plane sound wave into a thin cylinder, including the effects of external air flow, internal pressurization, and different fluid properties outside and inside the cylinder. Numerical results are presented for different incidence angles at flow Mach numbers varying from M=0 to M=1.0 with acoustic properties taken at standard atmospheric conditions. It is shown that at M=0, the cylinder transmission loss has dips at fR (cylinder ring frequency) and fc (critical frequency for a flat panel of same material and thickness as shell). Below fR, cylinder resonances affect TL. Between fR and fc, cylinder TL follows a mass-law behavior. Flow provides a modest increase in TL in the mass-law region, and strongly interacts with the cylinder resonances below fR. At normal incidence, TL is unaffected by flow. Although internal pressure does affect cylinder modal resonances, its effect on sound transmission into the cylinder appears to be small. [Work supported by NASA Langley Research Center.]
Preparation for research funding in acoustics
Authors: Kerlin R. L. , Oslac M. J.
Published: October 2005

It is suggested that the formal syllabus for graduate study in acoustics, not unlike those for other disciplines, may be remiss in providing certain background that may be found essential for the successful postgraduate career. Of the many endeavors that will subsequently be considered and/or attempted by the acoustician, funded research offers unique opportunities for personal development and contribution to the field. As they have been found to exist in the academic setting, the processes involved in being successful in obtaining funding for acoustical research from either the public, private, or foundational support sectors are addressed. It is suggested that ample opportunity exists during the education experience to become exposed to these processes and that the student be encouraged to do so. Such encouragement might well be formalized along with other aspects of professional activity considered to comprise the essentials for a successful career in acoustics.
Explaining the intrinsic pitch of vowels
Authors: Ewan William G.
Published: October 2005

High vowels have a higher intrinsic pitch of voice than low vowels all other things being equal. In order to find the cause for these intrinsic pitch differences, two experiments were performed. The first was a study of the movement of the larynx using a photocell/computer tracking technique. The most common pattern found for larynx position during vowel production was /i/ most superior and relatively anterior, /a/ intermediate and posterior, and /u/ always lowest and generally most anterior, relative to /i/ and /a/. These results may possibly suggest that changes in vocal fold length contribute to intrinsic pitch differences between vowels. The low larynx position for the vowel /u/ apparently helps to enlarge the pharyngeal cavity to meet the acoustic requirements for this vowel. Larynx lowering with pharyngeal wall expansion should increase vocal fold tension and elevate pitch slightly. Inferior pharyngeal muscle constriction may account for the posterior position and low intrinsic pitch of the vowel /a/. A second experiment was designed to shed light on this possible mechanism. The effects of Arabic pharyngeal approximates on vowel pitch vis-a-vis the effects of Arabic stops were investigated, since pharyngeal constriction is a key feature for their production. Arabic pharyngeal approximates were found to cause a significantly lower pitch on following vowels than Arabic bilabial, alveolar, and velar stops. This is evidence that pharyngeal constriction and tongue retraction lower pitch. If pharyngeal constriction and tongue retraction vary inversely with vowel height, the same forces may act to automatically lower vowel pitch. Other hypotheses to account for intrinsic pitch differences between vowels are reviewed in the light of these pitch and larynx movement results and in the light of the Arabic pharyngeal effects observed. [This research is supported by the National Science Foundation.]
Electromyographic study of velopharynoeal function
Authors: Bell-Berti F. , Niimi S.
Published: October 2005

A proposed model of velopharyngeal function in speech, based on electromyngraphic (EMG) data from velopharyngeal musculature for open and close vowels, oral stops, and nasal stops, states that the levator palatini is the primary effect or of velopharyngeal port closure and that its activity for oral segments varies directly with oral cavity impedance [F. Bell-Berti, Ph.D. thesis, City University of New York (1973)]. An EMG study of the velopharyngeal musculature was conducted, to test the model. The experimental utterances included oral fricative sod frictionless continuant consonants in addition to the previously studied oral and nasal stop consonants. The model predicts that levator palatini EMG activity will be greatest for oral stop consonants, and will decrease through the series fricative consonants, frictionless consonants, high vowels, low vowels, sod that it will be lowest for nasal consonants, to facilitate nasal coupling. [Supported by NIDR grant DE 01774.]
Vibration response of a fluid-loaded infinite plate with symmetric or asymmetric stiffeners
Authors: Vogel W. H. , Feit D.
Published: October 2005

The velocity distribution along a rib-stiffened thin plate immersed in a fluid and driven by a temporal harmonically varying line force is considered. To solve the coupled fluid-elastic equations of motion, the Fourier transform approach is used. The resulting integrals are numerically integrated directly without the aid of contour integration. Previous studies have primarily dealt with the radiated acoustic field from plates reinforced with symmetric stiffeners. The presence of an asymmetric stiffener provides a mechanism whereby flexural wave energy can be converted into longitudinal wave energy or vice versa. The significance of this energy conversion due to inertia coupling between the flexural and longitudinal motions of the plate is investigated. Results are presented for symmetric and asymmetric stiffeners with and without fluid loading. In addition, the effect of structural damping and fluid loading on the velocity field of a uniform infinite plate is discussed.
Experimental verification of intrinsic structural tuning concept
Authors: SenGupta G. , Small E. F.
Published: October 2005

The fuselage of an aircraft is exposed to convected random pressure fields due to noise from the jet engines and turbulent boundary layer. In addition to satisfying static strength requirements, the fuselage structure should be designed to have a high transmission loss at low and mid frequencies and also a long sonic fatigue life. A new concept called ”Intrinsic Structural Tuning“, (IST) for optimizing the fuselage structure for minimum cabin noise and sonic fatigue has recently been invented for this purpose. [G. SenGupta, Shock Vib. Digest (Oct. 1975)]. According to this concept, the skin panel response and acoustic radiation can be minimized by designing the structure so that the skin and stringers are tuned to each other, and then applying damping treatment on the stringer flanges. The concept was previously verified by using analytical methods. The present paper describes the results of laboratory tests on a group of skin-stringer panels designed and built for verifying the concept. One of these panels was intrinsically tuned. Identical damping treatment was applied on each panel. The panels were tested in a reverberant-anechoic facility and were excited electromagnetically by multipoint random excitation and also by a reverberant random acoustic field. The strain and acceleration responses and the sound radiation from the panels were recorded and analyzed on-line using a FFT analyzer. The PSD of strain, acceleration and sound Tadiation were plotted and the rms and overall levels were recorded. These results were used to assess the potential of the IST concept.
Self-consistent approach to the problem of membrane-fluid coupling in condenser microphones
Authors: Zuckerwar Allan J.
Published: October 2005

The operation of a condenser microphone is characterized by strong coupling between membrane displacement and excess pressure of the fluid between the membrane and backplate. In solving the equation for the excess pressure [I.G. Petritskaya, Sov. Phys.—Acoust. 12(2), 193–198 (1966)], we assume a simple expression for the membrane displacement, containing a single unknown η0; then we calculate the membrane displacement from the membrane equation of motion, using the resulting solution for the excess pressure (which still contains η0). By requiring the assumed and calculated expressions to yield the same average membrane displacement, we find the unknown η0 and insure self-consistent solutions to the membrane and fluid equations. We express the average membrane displacement and lumped parameters in terms of the physical properties of the microphone, including the configurations of holes and slots in the backplate. Effects of variation of microphone properties are demonstrated, both theoretically and experimentally. [Supported by NASA.]
Transducer radiation pattern modification
Authors: Hayre H. S. , Putcha M. S.
Published: October 2005

Ultrasonic transducers were used to simulate radiation patterns of an electromagnetic cavity-backed slot antenna when mounted on a flat ground plane as well as by itself in free space. A 12-in. spherical transducer excited in radial mode was selected to provide essentially isotropic coverage generated by the antenna. The radiation coverage of this transducer was significantly distorted, when mounted on a flat surface just like the antenna. This distortion was caused by both the presence of the plane in the near field as well as due to reflection of the energy from the lower half of the spherical transducer by the plane surface, resulting in the interference or distorted pattern. Then the plane surface immediately underneath the spherical transducer was treated with a synthetic rubber adhesive, “Miracle Seal,” and the resulting surface was randomly shaped in order to diffuse the incident ultrasonic radiation; thus, utilizing our background in scattering, and reverberation of sound, was used in a reverse fashion in order to obtain a very smooth isotropic pattern. The resulting pattern did not contain any sharp nulls which were reduced to less than forty percent of the original number and were significantly attenuated (in decibels) by 75% on the average.
Role of acoustical technology in the development of new energy sources
Authors: Jhaveri A. G.
Published: October 2005

During the past five years, considerable progress has been made in the control and abatement of excessive and/or harmful noise as well as vibration associated with the transportation, construction and industrial activities and systems. This has been a definite contribution of acoustics towards improving the quality of our environment and community life alike. A similar kind of concerted effort is required whereby the know1edge of acoustics can be advantageously utilized in the development of much-needed new energy sources. Among the more challenging acoustical technologies available during exploration, detection, and identification of new conventional and non-conventional energy sources are those utilizing ultrasonic, electroacoustics, underwater acoustics and geoacoustics, principles and/or disciplines. For example, echo-sounding has been effectively used in the detection and assessment of marine resources. In the same way, acousti-coring and seismic reflection techniques have been successfully employed during the exploration and detection phases associated with “mining geology” and “marine sediments.” However, the most attractive area of new energy source development, where acoustical technology can best be utilized, appears to be in the exploration of active "geothermal" sites. The ground noise (seismic) measurements utilizing sensitive and precision acoustical instrumentation can tremendously accelerate development of this important untapped and nonpolluting form of natural energy. This paper reviews the interaction of acoustics with new energy resource development programs.
Land use planning and environmental noise
Authors: Chambers D. B.
Published: October 2005

Noise from stationary industrial sources is becoming more important in determining compatible land uses in adjoining areas. Prediction of environmental noise levels is an essential tool in assessing the impact of a proposed development on a community. Moreover, sound-level prediction can also aid the plant designer in identifying and abating environmentally significant noise sources. In view of recent sound level criteria proposed by the Ontario Ministry of the Environment, which are based on land use types, increased emphasis will be given to control of noise in new industries. The prediction of industrial sound levels and the implications to land use planning are discussed through two case studies.
California Noise Element: The Orange County experience
Authors: Lamoureux Susan D.
Published: October 2005

The purpose of the California Noise Element is to provide an outline for noise control at the planning level in the community. The Noise Element emphasizes a land use planning approach to the abatement of noise as noise-source and transmission-path control is preempted by the Federal and State governments. The Orange County approach in developing a noise element involved all interested County agencies (e.g., Health, Road, Airport, Building, and Safety, Planning) in the preparation of the Element for two reasons: (1) to obtain their support in planning decisions directed at abating noise; and (2) to ensure that all agencies involved in community noise control utilized the same noise standards and criteria. The plan concepts and strategies of the Noise Element were aimed directly at the large areas of undeveloped land that exist in Orange County. These strategies include land use noise compatibility guidelines, a zoning noise sensitivity matrix, and a noise referral zone. These implementation plans serve as triggering mechanisms for potential noise problem areas in the planning process.
Statistical shortcut for the determination of railroad CNELs in proximity to main line tracks
Authors: Benjamin Kaplan O.
Published: October 2005

A statistical analysis of published data [Wyle Lab. Rep.WCR73-5 (1973)] reveals that railroad CNELs (at 100 ft, flat grades, no obstructions) are given by the formula CNEL (dBA) = 54.5 ± 10 log10 N, where N is the equivalent number of daily operations. The confidence level for CNEL ± 1 dBA is better than 95%. The formula obviates the need for time-consuming data gathering and calculations, and it does not result in decreased accuracy. Simple corrections are given for upgrade and downgrade movement, for track conditions, and for other factors.
Noise provisions for an AEC Environmental Report
Authors: Nugent R. E. , Brittain F. H.
Published: October 2005

Specific but somewhat ambiguous requirements have been set by the AEC for incorporating noise provisions into Environmental Reports (ER) for nuclear projects. The noise provisions that should appear in the ER are discussed and guidelines are given for ambient noise measurement, noise prediction, noise monitoring, and noise evaluation, as well as how this information should be presented in the ER.
Improved asymptotic solution of the one-dimensional Helmholtz equation
Authors: Mitchell Stephan K.
Published: October 2005

In a medium in which the sound velocity depends upon depth z only, the principal task in solving for the sound field is finding the solutions to the separated depth part of the wave equation d2U/dz2 + q(z)U = 0. An important asymptotic (valid at high frequencies) solution is the WKBJ, which, however, is not useful at or near turning points. It will be shown that an improved asymptotic solution is U(z) = W(z)(αAi(− φ) + βBi(− φ)), where Ai, Bi are Airy functions, φ = {32 ∫ ztz [q(z)]1/2 dz}2/3, zt is a turning point, W(z) = constx|dφ/dz|−1/2, and α and β are chosen to satisfy boundary conditions. This solution is useful near the turning point, as well as within the sound channel; thus, it obviates the connection formula considerations of the WKBJ solution. [Work sponsored by Office of Naval Research.]
Asymmetrical sound channel axis propagation
Authors: Cybulski J. , Wright E. B.
Published: October 2005

An acoustic experiment was conducted utilizing the asymmetrical sound channel axis propagation paths of the Mediterranean within the Algero-Provencal Basin. Acoustic transmission loss in 94-Hz bands from 94 to 2250 Hz was obtained as a function of range using shipboard deployed explosive caps, half and one pound charges, and a fixed receiver in the channel. The experimental results are compared with the output of an acoustic model at 94 and 562 Hz. A measure of the attenuation coefficients is obtained over the frequency range which is independent of the acoustic model and is in agreement with data from other investigators. This axis data was transformed to develop the acoustic field for the case of off-axis source locations by a procedure devised to decrement the signal intensity as a function of arrival time. Estimates of the arrival time are based upon an inverse sound speed gradient representation of the medium. The resulting range-depth contours for 281 Hz are compared with outputs from NRL acoustic model TRIMAIN.[Work supported by NAVSEA, Code 06H1.]
Large room acoustics versus music
Authors: Weir Robert , Garcia Jerry , Healy Dan , Wickersham Ron
Published: October 2005

Too many large, music performance facilities around the country have acoustical characteristics which are not suitable for concert tours, particularly when electronic sound amplification is required. This paper concentrates on the acoustical problems affecting the musician and his performance. The various problems encountered and corrective procedures utilized by The Grateful Dead are discussed and include electronic instrumentation and measurement techniques, sound system applications, and room treatments.
Fluctuations in the signal response of vertical arrays caused by source motion
Authors: Jensen E. P. , Cox H.
Published: October 2005

The variation with range to the source of the angular distribution of energy received by a vertical array is examined by computer modeling. For a source at a fixed depth, a wave solution for the acoustic field at each point in space in a horizontally stratified medium was generated by the Fast Field Prugram (FFP). Beamforming for different apertures and array depths was accomplished by weighted spatial Fourier transforms of the monochromatic acoustic field at each range step. Results are presented for the variation of beam output power and array signal gain as the range to the source changes. A computer generated motion picture presents the angular distribution of signal energy as it would be perceived by vertical arrays at different depths as the range to the source is gradually increased by about 35 NM or one cycle of a deep refracted ray. Small changes in range are vividly shown to lead to large variations in beamformer output response. [This project was funded by Advanced Research Projects Agency.]
Coherence function for speech
Authors: Young Lamar L. , Parker Cheryl , Carhart Raymond
Published: October 2005

It is well known that the lateralization of an auditory image depends upon the difference in the time of arrival of the signals at the two ears. Based upon modifications of the procedure used by Cherry and Sayers [J. Acoust. Soc. Am. 28, 889–895 (1956)], a two-alternative forced-choice experiment was employed to investigate the DL for lateralization of an ongoing speech stimulus. In one of the stimulus intervals the binaural speech signal was presented diotically, and in the other interval interaural time disparities of 0.0, 0.015, 0.030, 0.060, 0.075, 0.090, 0.250, and 1.0 msec were created between the binaural signals. The listener's task was to indicate the interval in which the Δt was present. The results show that listeners were able to detect small interaural time differences with 75% performance being reached at a Δt of 0.021 msec. The data has been plotted in terms of a coherence function for speech which is discussed. [Supported by a grant from NINCDS.]
Some auditory illusions reheard: dichotic listening to discrete frequencies
Authors: House A. S. , Wohlford R. E.
Published: October 2005

Listeners heard competing (dichotic) discrete-frequency stimuli [D. Deutsch, Nature, 251, 307–309 (1974); J. Acoust. Soc. Am. 56, Suppl., S25 (1974); Op. Cit. 57, 1156–1160 (1974)]. Frequencies, energy levels, phase conditions, harmonic relations, temporal alignments, etc., were manipulated in a number of different listening and response configurations. Findings indicate that one pattern of response predominates: In general, when the signals to the two ears are of equal amplitude, the percept (1) sounds like one of the two signals presented (i.e., is unfused), (2) is lateralized to the side receiving the signal that has a loudness advantage, and (3) has a pitch more appropriate to the signal presented to one ear (independent of ear report), with the left-ear signals showing a preference. This response pattern is sensitive to listener hearing characteristics and, in part at least, to listener handedness. The response phenomena are relatively insensitive to signal manipulations, except that that change loudness characteristic and/or involve channel delays.