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Nov 1979

Volume 66, Issue S1, pp. S1-S89

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back to top Session A. Engineering Acoustics I: General
Contributed Papers
FREE

The Green's function of the fluid‐loaded plate (A)

D. G. Crighton

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S1-S1 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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The surface response of an infinite thin elastic plate or membrane to concentrated forcing is considered under the (realistic) condition that the normalized response is specified by three parameters: (1) a ratio Ω of driving frequency to the vacuum coincidence frequency, (2) the product X of distance from the excitation point and the vacuum free wavenumber, and (3) a parameter ϵ characterizing fluid loading at coincidence. We use the fact that in all applications ϵ is small to construct matched asymptotic expansions for the Green's function covering the entire range of frequency and distance (0 < X, Ω < ∞). The method is applicable equally to line or point forcing and to plate or membrane response, significant differences being confined to the nearfield. The farfield for Ω = O (1) consists of free surface or leaky waves plus an acoustic field decaying as X1/2 at moderate X and as X3/2 at very large X, with a transition expressed by parabolic cylinder functions; the description for other Ω is obtained, but is more complicated.
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The saga of the plate‐fluid interaction. II (A)

Mauro Pierucci

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S1-S1 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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Over the last two years, the author [J. Acoust. Soc. Am. 65, 1190–1197 (1979)] and other researchers have reanalyzed the plate‐fluid interaction problem from different perspectives. In this paper the eigensolutions to the fluid‐loaded thick plate equation are presented as a function of modulus of elasticity fluid loading and structural damping. The thick plate equation allows for the inclusion of shear deformation and rotary inertia effects on the vibrational response of the plate. Solutions for loci of the different modes as a function of frequency are presented in the fluid wavenumber plane. It is shown that under certain conditions the roots of the system cross from one Riemann sheet to the other thus changing the basic characteristics of the plate response and also of the radiated acoustic field. Internal structural damping is also shown to have the same effect upon the behavior of the root loci. Some of the phenomena discussed are a result of the rotary inertia terms in the plate equations and, therefore, cannot be explained by the use of the simpler thin plate analysis.
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Random vibration field on a plate (A)

R. V. Waterhouse

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S1-S1 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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The properties of a steady‐state random, or reverberant, sound field in a reverberation chamber with stationary boundaries are fairly well understood. When the driving signal consists of a single‐frequency tone. and many modes are excited, the sound field in the chamber becomes a randomly irregular interference pattern whose statistical properties follow known distributions. For example, the mean‐square pressure values, suitably sampled, follow an exponential distribution, the simplest kind of gamma distribution. It is pointed out that the same gamma distributions held for the vibrational field on a thin elastic plate vibrating in flexure, under the same conditions of pure tone and multimode excitation. Knowing the distribution of the acceleration values on such a plate is of practical value as it allows one to estimate the confidence levels of the average of a limited number of sample values.
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In situ determination of loss and coupling loss factors by the power injection method (A)

David Alan Bies and Shahul Hamid

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S1-S2 (1979); (2 pages)

Online Publication Date: 11 Aug 2005

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Inversion of the linear power balance equations for a two coupled plate model is used to determine the plate loss factors and the coupling loss factors in situ. To accomplish the determinations, injected power at points chosen at random was measured. To ensure effective statistical independence of modes, each plate was driven at five different points in sequence and the response of both plates in each case was determined at ten randomly chosen points. Good agreement is obtained between the predicted and measured coupling loss factors, and between the in situ loss factors and loss factors determined for each plate separately also in steady state from power injection measurements. Loss factors determined by transient decay methods are consistently lower than those determined by either steady‐state method. During reverberant decay, the more lightly damped modes predominate, giving rise to an apparent loss factor which is significantly less than the steady‐state loss factor determined under conditions of essentially equal energy per mode.
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Use of the Prony method in reflection coefficient measurements of acoustic panels (A)

D. H. Trivett and A. Z. Robinson

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S2-S2 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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A modified Prony method is presented for measuring steady‐state reflection coefficients of acoustic panels. The method extrapolates the steady‐state amplitude from the transient portion of the signal allowing time limited measurements. This method is applied to measurements of square panels 76 cm on an edge and 0.95 cm thick of steel, aluminum, and Lucite in the frequency range of 3–10 kHz. The signals were time limited to 200 μ (0.6–2.0 λ) by the arrival of the diffracted signal from the panel edges. Results are compared with theoretical values and indicate that the method is capable of making measurements subject to ambient noise. [Work supported by Target Strength Reduction Program managed by DTNSRDC of NAVSEA 037.]
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On the compressional damping mechanism in the free impedance response of damped three‐layer beams (A)

B. E. Douglas

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S2-S2 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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The transverse free mechanical impedance response of an elastic‐viscoelastic‐elastic beam incorporating the compressional damping mechanism is considered. The work of Douglas and Yang is extended to include shear deformation and rotary inertia in the elastic layers. The effects of nearly incompressional viscoelastic damping cores on the compressional frequency and hence on the spectral range of damping effectiveness for the composite is also discussed. Results of the analysis are shown to compare favorably with experimental results for a damped three‐layer beam which was optimized for compressional damping and in which the influence of the shear damping mechanism was intentionally minimized.
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Determination of sound pressure distributions in liquid‐filled, elastic and viscoelastic tubes by finite‐element method (A)

E. A. Schroeder and L. T. Ho

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S2-S2 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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Based on the finite‐element approach, the elastic tube was represented by the conical shell elements CONEAX, while the fluid was modeled by the solid elements TRAPAX. Matrix equations at grid points for the displacement vectors in the solid and sound pressure field in the fluid were coupled at the fluid‐structure interface. Constraints were applied and material parameters were chosen so that the axial displacements at grid points in the fluid would correspond to sound pressures that satisfy the wave equations. The coupled equations were solved for sound pressures, using structure computer program NASTRAN. Excellent agreement was obtained between the calculated and experimental results of low‐frequency sound pressure distributions in an elastic tube. For the case of a liquid‐filled, rigid tube lined internally with viscoelastic material, both the fluid and the liner elements were represented by the trapezoidal ring elements TRAPRG. Good correlation was observed qualitatively between the calculated and experimental sound attenuation in a viscoelastic tube. [Work supported by Naval Sea Systems Command.]
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Velocimeter for quality control monitoring in rubber production (A)

R. D. Corsaro, J. Jarzynski, L. Burns, and W. B. Moniz

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S2-S2 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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A velocimeter was designed for longitudinal sound‐speed measurements on 3‐mm‐thick (ASTM) rubber samples. Batch‐to‐batch variations in sound speed are detected to 0.1% precision by operators without technical experience. Each measurement required five minutes with the prototype device, and substantial reductions are expected with minor design modifications. The device consists of two ultrasonic transducers with a rubber sample sandwiched between them. During device assembly, the sample is squeezed by the transducers such that a known and reproducible transducer‐transducer separation distance is obtained. A 5‐MHz cw signal is then applied to one transducer. The phase angle difference of the signal received by the other transducer is read on a meter face, and is related to the wave speed in the rubber. By performing a detailed theoretical analysis of this geometry, we are able to meaningfully compensate the value of the meter reading for variations in temperature, thickness (related to the degree of sample squeezing used), and sound absorption, and also use the device for absolute sound speed and attenuation measurements.
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Stoneley waves at an imperfectly bonded interface (A)

Michael Schoenberg

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S2-S2 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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A model for an imperfectly bonded interface between two elastic media has been proposed. Displacement across this surface is not required to be continuous but it is taken to be linearly related to the stress traction which is continuous across the interface. For isotropic interface behavior, there are two independent interface compliances,ηN and ηT, where the component of the displacement discontinuity normal to the interface is given by ηN times the normal stress and the parallel component is given by ηN times the shear stress. Stoneley wave velocities (possibly complex) at such interfaces between two elastic halfspaces are calculated and are found to be dispersive even when the compliances, ηN and ηT, are real and frequency independent. When the interface is purely dissipative such that the stress traction is proportional to the velocity discontinuity, the compliances are pure imaginary and proportional to the inverse of frequency yielding complex, but in this case, nondispersive, Stoneley wave velocities.
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Experimental studies of ultrasonic radiation from cylindrical shells in water (A)

K. Fritsch, C. W. Allen, and E. F. Carome

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S2-S2 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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Studies are being made of ultrasonic waves radiated into water from air‐filled cylindrical metal shells. A shell is directly excited by polyvinylidine fluoride thin film transducers mounted on its inside surface. By using arrays of such transducers it has been possible to excite various normal modes of the cylinder. Both schlieren and acoustic probe techniques are being used to examine the radiated acoustic fields. Data are presented to indicate the applicability of this new technique. [Work supported in part by ONR.]
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Frequency‐wavenumber spectral analysis of borehole acoustic waves (A)

T. L. Marzetta, D. Leslie, M. Schoenberg, and J. Aron

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S2-S3 (1979); (2 pages)

Online Publication Date: 11 Aug 2005

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In a laboratory experiment an acoustic pulse excited waves in a fluid‐filled borehole that had been drilled in a solid block of epoxy. Typical wavelengths were the same order of magnitude as the hole radius. Waveforms were received at many different ranges and conventional and high resolution, maximum likelihood methods (MLM) of frequency‐wavenumber (ω, k) spectral analysis are applied to this data. The spectra obtained are compared to theoretical dispersion calculations. Good agreement is obtained. Encouraging improvements in wavenumber resolution over conventional spectral estimation are obtained by the use of the MLM techniques.
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Surface intensity patterns for a baffled plate (A)

J. Daniel Brito

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S3-S3 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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The spatial characteristics of the acoustic power flow at the surface of a baffled simply supported rectangular plate vibrating in flexural motion are studied to obtain an insight on the process of energy exchange between the plate and the acoustic medium. An expression for the local radiation efficiency as a function of space and frequency is presented and used to compute sound intensity patterns at the surface of the vibration plate, under different types of excitation of the plate‐bending motion. The space average of the local radiation efficiency is compared with published values and with measurements by the reverberant room method. Frequency averages (⅓ octave band) of this local radiation efficiency at points on the plate are compared with measurements by the accelerometer‐microphone method. Satisfactory agreements are obtained in all these comparisons. [Work performed at M.I.T.]
back to top Session B. Noise I and Underwater Acoustics II: Shipboard Noise Control
Invited Papers
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A personal philosophy of design for noise control in ships (A)

J. R. Baylis

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S3-S3 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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This personal philosophy has evolved from eight years of active participation in the research and the design of Navy ships for controlled noise characteristics. The design for the control of noise begins with the establishment of requirements. Noise specifications must serve an understandable operational purpose that can be communicated to the many people that will design and build the ship. The requirements must be capable of being met within the state of the art, and at a cost that is commensurate with the value of the noise control. The cost must be acceptable to the producer as well as the customer, and the producer must understand from the beginning the amount of engineering and test that he is committed to. The techniques for controlling the noise of ships are well known, but there are choices to be made for those techniques to be used in construction, and those that can be used to come up to specification after test. An allowance should be made for the cost of test and for the cost of corrections to be made after test.
FREE

U.S. merchant ship noise: Recent measurements and proposed criteria (A)

R. S. Gales and D. T. Jones

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S3-S3 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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To provide guidance in the regulation of noise on U.S. merchant ships, noise levels and octave‐band spectra were measured on seven ships of the U.S. Merchant Fleet. Ships selected included tankers, ore carriers, general cargo, and container ships; with steam turbine, gas turbine, and diesel propulsion. They ranged in size from 8000 to 36 000 gross tons and in construction date from the 1920's and 1970's. Locations measured included machinery and engine rooms, passageways, berthing spaces, mess and recreation spaces, bridge, radio room, and offices. Noise exposures based on measured sound levels and time spent in various spaces were calculated for individual crew members in various occupational categories. Exposures are compared with various criteria for hearing conservation, including the 24‐h equivalent continuous sound level (Leq 24). A‐weighted sound levels in other ship spaces are compared with various function‐based criteria, such as speech communication, hearing of warning signals, rest and relaxation, and recovery from temporary hearing loss. Recommended criteria for A‐weighted sound level on U.S. Merchant vessels are presented for immediate use and future goals.
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Prediction of noise in ships by the application of “statistical energy analysis.” (A)

John Ødegaard Jensen

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S4-S4 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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If it will be possible effectively to reduce the noise level in the accomodation on board ships, by introducing appropriate noise abatement measures already at an early design stage, it is quite essential that sufficiently accurate prediction methods are available for the naval architects. In general, the structure‐borne noise contribution from the various noise sources may be precalculated with a reasonable accuracy using empirically based calculation models. The prediction very often fails, however, when the empirically based calculation model is applied for an untypical structure or for a special noise abatement measure, e.g., increased structural damping. The paper discusses whether it might be possible to derive an alternative calculation model based on the “statistical energy analysis” approach (SEA). By considering the hull of a ship to be constructed from plate elements connected by combination of L junctions, T junctions, and cross junctions, a SEA‐calculation model has been derived. Examples on application of the SEA model for prediction of the structure‐borne sound transmission are given, partly through simple two‐element structures consisting of stiffened and unstiffened plate panels, partly through a hull section consisting of several stiffened plate sections. The results of the SEA calculations are compared with corresponding results of vibration measurements on the structures.
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The airborne path in shipboard noise control (A)

M. C. Junger

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S4-S4 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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Reverberant noise in living and working spaces other than the machinery room is typically controlled by structure‐borne paths. However, as machinery vibration isolation and foundation damping techniques are perfected, airborne flanking paths discussed in this paper become increasingly important. In contrast to representative masonry walls, the finite extent of shipboard partitioning and bulkheads is an essential factor in determining transmission loss (TL). Consequently, structural damping is beneficial not only near coincidence, but also at higher frequencies. A second distinguishing feature of much shipboard partitioning is frame stiffening. This extends the beneficial effect of damping to frequencies below coincidence. Stiffening frames cause marked TL degradation below the TL of the underlying uniform plate, in spite of the latter's smaller mass. In conclusion, the concept that mass per unit area is the single most important factor in determining TL is not relevant to the shipboard situation.
FREE

Current practices in shipboard airborne noise control and future needs (A)

Daniel L. Nelson

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S4-S4 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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In recent years, shipboard airborne noise criteria have been applied much more stringently than in the past. Further, noise criteria are likely to be lowered for future ship designs. In response to this, more noise sources and transmission paths need to be considered in the acoustical design process. This paper considers noise control treatments which are presently coming into accepted practice in this country and discusses the merits as well as liabilities of these treatments. Needs for future research and development efforts are also presented in light of more restrictive noise criteria.
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Airborne noise reduction of surface ship propulsion gearboxes and forced draft blowers (A)

Edward V. Thomas

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S4-S4 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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Five surface ships were treated with a propulsion gearbox two‐phase cladding—damping treatment. The effects of treatment installation procedures on airborne noise reduction were evaluated as a function of ships speed. Two surface ships were treated with developmental antireflective airborne noise treatments to reduce forced draft blower noise levels. A resonant sound absorber was installed in another ship to reduce forced draft blower noise.
Contributed Papers
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Control of shipboard airborne noise caused by propeller cavitation with a naturally aspirated compliant air layer (A)

Leslie M. Gray

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S4-S5 (1979); (2 pages)

Online Publication Date: 11 Aug 2005

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Propeller cavitation can often be a severe source of shipboard airborne noise, especially in after spaces on high‐speed or high‐powered vessels. Control of this noise source is difficult since the cavitation imparts vibration energy to major hull structure. Typical noise control of this source usually involves such treatments as damping. isolated decks and bulkheads, and added mass. Unfortunately, this additional weight is often unacceptable to the ship designer. This paper investigates control of this source by introduction of a compliant air layer between the water and the hull structure, which will act as a simple springlike isolator. The potential effectiveness of this compliant air layer is outlined. A source of air is proposed which employs the negative pressure reduction due to flow over an emitter on the hull to suck atmospheric air into the ship's boundary layer. An example design is presented for a high‐speed yacht which will provide adequate air for substantial reduction of propeller‐airborne noise for vessel speeds over 15 knots.
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Structure‐borne noise transmission through ship stanchions (A)

C. B. Burroughs, R. W. Fishcer, and F. L. Shiflet

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S5-S5 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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Stanchions provide a path for structure‐borne noise transmission from a noise source space on one level to noise sensitive spaces on another level in commercial and combatant surface ships. Measurements of structure‐borne noise from one level to an adjacent level were made with and without a stanchion in place in the laboratory full‐scale model of ship compartments at Hopeman Brothers. Measured data of the structure‐borne noise transmission loss across the stanchion and the difference in the airborne sound power levels radiated into the compartments with and without the stanchion in place are presented. Results of statistical energy analysis (SEA) are compared to measured data. Methods for reducing structure‐borne noise transmission through stanchions are suggested.
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Airborne noise criteria on naval ships: Estimating crew response (A)

David R. Lambert

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S5-S5 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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Graphs are presented for predicting the response of shipboard personnel to airborne noise when a given compartment type just meets a proposed A‐weighted criterion. The graphs were constructed from the responses of personnel in selected compartments aboard eight U.S. Naval ships. The author used the responses to questions on habitability to rate each compartment on a five point scale ranging from satisfactory to unsatisfactory. These ratings were then plotted as a function of A‐weighted sound pressure level, and parameters for the curves estimated. [Work sponsored by the Naval Sea Systems Command.]
back to top Session C. Physical Acoustics I: Acoustic Remote Sensing I: Atmospheric Science
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The research and application of acoustic radar systems in Australia (A)

N. A. Shaw and I. A. Bourne

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S5-S5 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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Research and development of atmospheric acoustic radar systems have been closely supported by “application” programs associated with industrial needs. To study this interaction, a survey was conducted on (a) the nature and emphasis of acoustic research programs, (b) the degree of successful industrial application of various systems, and (c) the current and anticipated needs of industry for improved acoustic radar performance. Institutions involved in researching atmospheric acoustic radars include universities, colleges of advanced education, and defense establishments. The power, mining, and larger manufacturing industries have used acoustic probes mainly as a tool for either evaluating meteorological parameters conducive to air pollution problems or as part of extensive environmental impact studies. The somewhat qualitative records by single axis systems are still susceptible to interpretation difficulties. Classification of data, at least into categories and formats suitable for further digital analysis, has been sought, but now the greatest interest exists in multiaxis systems which are thought to be capable of measuring wind profiles and dispersion parameters to heights of 1000 m as well as retaining the conventional facsimile display.
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Sodar studied atmospheric temperature inversions of the Salt Lake Valley (A)

G. Davis and D. R. Dickson

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S5-S5 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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Inversional temperature phenomena indigenous to Utah's Salt Lake Valley were observed and studied over a continuous time span of 28 days occurring in December‐January 1976–1977. The phenomena were combined with local topographical barriers to maintain a situation of marked atmospheric stability in the lowest kilometer. The nonturbulent conditions resulting were commonly neutral in character, but composite conditions retained generally stable patterns of inversion genesis and disintegration. Particular attention was given to comparing available rawinsonde raw data (soundings) with their coincidental sodar counterparts obtained from the continuous record. Results implied a compatibility between two techniques of sensing used, one being a remote sensor, the other in situ. Best agreement was discovered in the inversion cases below 500 m and with those of stronger intensities.
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Estimates of surface heat flux from sodar and laser scintillation measurements in the unstable boundary layer (A)

R. L. Coulter and M. L. Wesely

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S5-S6 (1979); (2 pages)

Online Publication Date: 11 Aug 2005

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Measurements of acoustic backscatter in the lower planetary boundary layer and optical line‐of‐sight scintillation in the surface layer are used separately to compute the sensible heat flux in the unstable surface layer. Comparisons with simultaneous low‐level point measurements by eddy correlation show good agreement both in absolute magnitude and response to rapid changes, indicating that acoustic methods may be successful over less homogeneous terrain where conventional surface layer measurement techniques are often inaccurate. Corrections to lake into account the effects of humidity fluctuations are found necessary in order to achieve accuracies within 10%. Free convection is assumed to permit interpretation of the sodar data, while either forced or free convection is assumed for the scintillation data. A systematic overestimate of surface heat fluxes is found from acoustic measurements made during the morning when the convectively mixed layer is rapidly increasing in height. [Work supported by U.S. Dept. of Energy and U.S. Environmental Protection Agency.]
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Preliminary results on observations of chinooks using a Doppler acoustic sounder (A)

S. A. Leelananda, R. B. Hicks, P. J. Irwin, and T. Mathews

J. Acoust. Soc. Am. Volume 66, Issue S1, pp. S6-S6 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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An acoustic sounder array located on a rural site 20 km west of Calgary is described. The array is designed to sense atmospheric turbulence with a working vertical range of 2 km and also to provide information on the vertical wind profile up to 800 m above the site. The array consists of a central, vertically directed, monostatic array (output acoustic power ∼ 100 W), and four passive inclined receivers, each acting as a bistatic receiver for the central monostatic transmitter. The bistatic receivers are arranged along two mutually perpendicular horizontal baselines. On‐line microprocessors are used to retrieve Doppler shift data from all receiver channels, and hence to calculate the wind profile. Typical results from the Doppler acoustic sounder array are presented. It is hoped that by the time of presentation, soundings will have been made during at least one Chinook event (a foehn‐type wind associated with airflow over the nearby Rocky Mountains).
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