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Understanding detection range is a key factor for the use of acoustic telemetry in fisheries research. Lakes have strong seasonal changes in thermal stratification, as well as short-term changes due to internal seiches. These thermal gradients in lakes imply strong sound-speed gradients that can refract and diverge acoustic signals, leading to acoustic attenuation and smaller detection range. Using field-based range testing and the Bellhop acoustic model, we investigated how changes in stratification lead to changes in detection range within Hamilton Harbour, Ontario, Canada. During the summer stratified period, the detection range was less than 350 m, whereas in the isothermal fall, range was up to 500 m. Range test data from three separate field observations showed a good correlation with Bellhop predictions. Owing to the intense internal seiches in Hamilton Harbour, the stratification in the shallower littoral regions essentially switched between stratified and isothermal conditions over short timescales, which is predicted to lead to high temporal variability in detection range that must be accounted for during the analysis and interpretation of telemetry-derived data. La comprehension de la portee de detection est un aspect cle de l'utilisation de la telemetrie acoustique dans la recherche sur les peches. Les lacs presentent de fortes variations saisonnieres de leur stratification thermique, ainsi que des variations a court terme decoulant de seiches internes. Ces gradients thermiques dans les lacs sous-entendent d'importants gradients de la vitesse du son qui peuvent entrainer une refraction et une divergence des signaux acoustiques, produisant une attenuation acoustique et une reduction de la portee de detection. Nous avons examine, en utilisant des essais de portee sur le terrain et le modele acoustique Bellhop, les modifications de la portee de detection decoulant des variations de la stratification dans le port de Hamilton (Ontario, Canada). Durant la periode de stratification estivale, la portee de detection est inferieure a 350 m, alors que durant la periode d'isothermie automnale, elle peut atteindre 500 m. Les donnees d'essais de portee issues de trois observations distinctes sur le terrain montrent une bonne correlation avec les predictions du modele Bellhop. En raison des intenses seiches internes dans le port de Hamilton, la stratification dans les secteurs littoraux moins profonds alterne entre des conditions stratifiees et des conditions isothermiques sur de courtes periodes, ce qui, selon les predictions, devrait produire une grande variabilite dans le temps de la portee de detection, dont l'analyse et l'interpretation de donnees issues de la telemetrie doivent tenir compte. [Traduit par la Redaction], Introduction Acoustic telemetry is an important tool that is being used to advance and improve conservation and management of fishes in lakes and coastal regions. Acoustic telemetry enables ecologists to [...]

FATIGUE CRACK MECHANISMS A team of researchers from Cornell University made advancements in better understanding how materials break. Using atomic modeling, the researchers identified the mechanism that causes fatigue cracks [...]

55 miles per hour--THE AVERAGE INCREASE in the speed of sound by the end of the century in the Greenland Sea and a section of the Atlantic Ocean under a [...]

To monitor and understand the temporal variations of sound speed due to the changes of soil physical properties such as soil water potential, moisture content, and soil temperature under natural conditions, a long-term field soil survey has been conducted. In this study, transmitter and receiver acoustic probes, consisting of ten (five pairs) and five transducers respectively, were inserted into a prepared trench containing a soil-sand mixture in an outdoor test site. Five time domain reflectometers, five tensiometers, and five thermocouples were buried during the trench-filling at the same depths as the acoustic transducers. Measurements of sound speed, soil temperature, soil moisture content, and water potential were performed continuously, along with the measurements of surface temperature and precipitation over a period of 2 yr. Analysis of the data shows that there is a power law relationship between the sound speed and water potential. It is also found that the water potential is the dominant influence on the sound speed whereas the moisture content and temperature have relatively minor impacts. Brutsaert and Luthin's theory was employed to calculate the sound speed as a function of the effective stress. The theoretical predictions were compared with the experimental data and they are in good agreement. The study suggests that sound speed measurement could be used as a new and effective tool for water potential measurement. Abbreviations: LVD, laser doppler vibrometer; MASW, multi-channel analysis of surface waves.

We present a simple technique to actively stabilize the optical path length in an optical fiber. A part of the fiber is coated with a thin, electrically conductive layer, which acts as a heater. The optical path length is thus modified by temperature-dependent changes in the refractive index and the mechanical length of the fiber. For the first time, we measure the dynamic response of the optical path length to the periodic changes of temperature and find it to be in agreement with our former theoretical prediction. The fiber's response to the temperature changes is determined by the speed of sound in quartz rather than by slow thermal diffusion. Making use of this fact, we succeeded in actively stabilizing the optical path length with a closed-loop bandwidth of 3.8 kHz. OCIS codes: 060.4080, 060.2270.

The speed of sound in a bubbly liquid is strongly dependent upon the volume fraction of the gas phase, the bubble size distribution, and the frequency of the acoustic excitation. At sufficiently low frequencies, the speed of sound depends primarily on the gas volume fraction. This effect can be audibly demonstrated using a one-dimensional acoustic waveguide, in which the flow rate of air bubbles injected into a water-filled tube is varied by the user. The normal modes of the waveguide are excited by the sound of the bubbles being injected into the tube. As the flow rate is varied, the speed of sound varies as well, and hence, the resonance frequencies shift. This can be clearly heard through the use of an amplified hydrophone and the user can create aesthetically pleasing and even musical sounds. In addition, the apparatus can be used to verify a simple mathematical model known as Wood's equation that relates the speed of sound of a bubbly liquid to its void fraction. [DOI: 10.1119/1.2907773]

Recent near-sonic and low-sonic boom transport aircraft development studies have sparked a renewed interest in the nature of the aerodynamics about configurations at near-sonic or low-supersonic speeds. The validity of the wind-tunnel test facilities and the computational methods are challenged by the flow characteristics at near-sonic speeds. Fundamental aerodynamic studies were conducted to assess the ability of the TRANAIR full potential code to predict pressure distributions, drag, and flow characteristics around a family of sting- mounted truncated parabolic bodies of revolution at near-sonic and low-supersonic speeds by comparisons with an extensive existing wind-tunnel database. The analyses included both inviscid and viscous coupled boundary layer analyses. The investigations also included assessments of wind-tunnel wall interference effects as influenced by the various body geometries and test conditions. Extensive test versus theory comparisons of surface pressure distributions, flowfield pressures, and drag forces are presented for subsonic through low-supersonic Mach numbers for the family of test configurations. An additional objective of these studies was to demonstrate the value of using existing and even rather historic experimental data. The experimental data used in the current studies were obtained from NACA wind-tunnel tests reported in 1958. DOI: 10.2514/1.30028

The adiabatic bulk ([K.sub.s]) and shear (G) moduli of mantle materials at high pressure and temperature can be obtained directly by measuring compressional and shear wave velocities in the laboratory with experimental techniques based on physical acoustics. We present the application of the current state-of-the-art experimental techniques by using ultrasonic interferometry in conjunction with synchrotron x radiation to study the elasticity of olivine and pyroxenes and their high-pressure phases. By using these updated thermoelasticity data for these phases, velocity and density profiles for a pyrolite model are constructed and compared with radial seismic models. We conclude that pyrolite provides an adequate explanation of the major seismic discontinuities at 410- and 660-km depths, the gradient in the transition zone, as well as the velocities in the lower mantle, if the uncertainties in the modeling and the variations in different seismic models are considered. The characteristics of the seismic scaling factors in response to thermal anomalies suggest that anticorrelations between bulk sound and shear wave velocities, as well as the large positive density anomalies observed in the lower mantle, cannot be explained fully without invoking chemical variations. elasticity | mantle composition | mantle heterogeneity | ultrasonic interferometry | pyrolite

An approach for accurate Doppler angle estimation for vector flow measurements is introduced, in which two ultrasound beams with known relative orientation are directed towards the same vessel, with one beam committed to perform a Doppler measurement and the other reference beam having the specific task of detecting the beam-flow angle. Validation of the method reveals that the beam-flow angle can be estimated with high accuracy and repeatable velocity magnitude measurements are possible.

Byline: Lian-Gang Lu (1,2,3), Hong-Xia Chen (3), Ye-Li Yuan (3) Keywords: Sound speed; PN section; Kuroshio Abstract: Gridded sound speed data were calculated using Del Grosso's formulation from the temperature and salinity data at the PN section in the East China Sea covering 92 cruises between February 1978 and October 2000. The vertical gradients of sound speed are mainly related to the seasonal variations, and the strong horizontal gradients are mainly related to the Kuroshio and the upwelling. The standard deviations show that great variations of sound speed exist in the upper layer and in the slope zone. Empirical orthogonal function analysis shows that contributions of surface heating and the Kuroshio to sound speed variance are almost equivalent. Author Affiliation: (1) Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China (2) Graduate School of the Chinese Academy of Sciences, Beijing, 100039, China (3) Key Lab of Marine Science and Numerical Modeling, First Institute of Oceanography, SOA, Qingdao, 266061, China Article History: Registration Date: 04/01/2004

We discuss the simulation of a system consisting of a rectangular box that contains two identical hard disk gases with the same number of particles, separated by an internal movable piston. The piston exhibits a random oscillatory motion with a frequency that depends on the mass of the piston, the mass of the disks, the temperature, and the length of the box. The measurement of this frequency allows us to deduce the speed of sound in the gas. The result is compared with the speed of sound from the usual expression in terms of the isothermal compressibility.

The potential application of this work is the detection and imaging of buried objects using acoustic methodology. To image buried artifacts, it is vital to know speed and attenuation of sound in the particular soil being examined because they vary in different soil types and at different moisture contents. To that end, our research involved six soils representing a range of properties expected to influence acoustic response. Clay ranged from 2 to 38%, silt from 1 to 82%, sand from 2 to 97%, and organic matter from 0.1 to 11.7%. Signals from an acoustic source were passed through soil samples and detected by an acoustically coupled hydrophone. From a total of 231 evaluations, we determined the acoustic attenuation coefficient and the propagation speed of sound in the soil samples as a function of four levels of soil moisture and two levels of compaction. Attenuation coefficients determined over frequencies of 2 to 6 kHz ranged from 0.12 to 0.96 dB [cm.sup.-1] [kHz.sup.-1]. Lower attenuation tended to be in loose dry samples. Correlation coefficients were 0.35 (P = 0.01) and 0.31 (P = 0.03) between attenuation and soil water content and soil bulk density, respectively. Propagation speeds ranged from 86 to 260 m [s.sup.-1]. The correlation coefficient with speed was -0.28 (P = 0.05) for soil water content and -0.42 (P = 0.002) for total porosity. Given the acoustic properties, it is theoretically possible to detect an object down to ~40 cm below the soil surface.

A physics exercise is described where students determine what the speed and intensity of sound would be in the atmospheres of other planets. Students use planetary atmospheric data obtained from Planetary Data Systems to calculate how the acoustic waves would act differently from the acoustic waves on earth.

Byline: W. M. Drake (1), J. P. Brown (2), C. Banville (2), D. L. Kendler (1) Keywords: Key words:Monitoring -- Osteoporosis -- Phalangeal BMD -- Speed of sound -- Therapy Abstract: In women with postmenopausal osteoporosis (PMO), response to therapy with bisphosphonates is conventionally monitored using central-site (hip and spine) bone mineral density (BMD), but more convenient alternatives are desirable. During a randomized parallel-group study of the efficacy of once-weekly (80 mg vs 160 mg) oral alendronate in the treatment of PMO, 81 women (mean age 70.2 years +- 4.6 SD) had BMD measurements of total hip (TH) and lumbar spine (LS) (L1--L4, Hologic) and of the middle phalanx of the middle digit of the non-dominant hand (accuDXA) at baseline and after 6 and 12 months of therapy with alendronate. At the same timepoints, subjects also had measurements of speed of sound (SOS) through bone at four sites (distal 1/3 radius, proximal phalanx of the third finger, midshaft of the tibia and fifth metatarsal) using the Sunlight Omnisense Ultrasound Bone Sonometer. Data from both patient groups were pooled for this analysis. Mean TH BMD at baseline was 0.705 g/cm.sup.2+- 0.093 (SD) and increased by 1.7%+- 2.3% and 2.5%+- 2.3% at 6 and 12 months respectively (p= 0.09 and p&lt 0.0001). Mean LS BMD at baseline was 0.718 +- 0.076 g/cm.sup.2 and increased by 3.9%+- 3.6% and 6.1%+- 3.5 % at 6 and 12 months respectively (both p&lt 0.0001). There was no statistically significant change from baseline in mean BMD by accuDXA at either 6 or 12 months. The only statistically significant changes in SOS were at the radius (decrease in SOS at 12 months, p=0.04) and tibia (increase at 6 months, p&lt 0.01, but no change between baseline and 12 months). Baseline correlation coefficients between accuDXA and LS and TH DXA were 0.22 (p= 0.05) and 0.27 (p= 0.02) respectively. Correlation coefficients between SOS and LS DXA ranged from 0.05 to 0.22 and between SOS and TH DXA ranged from --0.08 to 0.10 (all p= NS). These data suggest that the response to alendronate therapy over this time period cannot be measured by accuDXA or Sunlight SOS at the sites studied. Author Affiliation: (1) Osteoporosis Research Center, University of British Columbia, Vancouver , CA (2) Centre de recherche du CHUL, UniversiteA' Laval, Ste-Foy, QueA'bec, Canada, CA Article note: Received: 26 June 2001 / Accepted: 27 September 2001

Byline: A. S. Starkov (1) Abstract: The problem of the wave field of a source moving in an inhomogeneous medium is considered. It is assumed that the velocity of the source is less than the velocity of sound for t &lt 0 and is greater than this velocity for t &gt 0 (subsonicasupersonic transition). An asymptotic expansion for the wave field in a neighborhood of the source is constructed on the basis of the well-known Hadamard ansatz. The expansion derived is uniform with respect to the velocity of the source and contains new special functions. These functions are generalizations of the Hankel and Bessel functions and possess some remarkable properties. Bibliography: 7 titles. Author Affiliation: (1) St.Petersburg State University, Russia Article History: Registration Date: 12/10/2004

Byline: J. P. W. van den Bergh (1), C. Noordam (2), J. M. Thijssen (3), B. J. Otten (2), A. G. H. Smals (1), A. R. M. M. Hermus (1) Keywords: Key words:Broadband ultrasound attenuation (BUA) -- Quantitative ultrasound (QUS) -- Precision errors -- Speed of sound (SOS) -- Trend assessment interval Abstract: We measured the quantitative ultrasound (QUS) parameters broadband ultrasound attenuation (BUA) and speed of sound (SOS) at the calcaneus using an ultrasound imaging device (UBIS 3000) in 698 healthy Caucasian male and female subjects (110 prepubertal, 356 pubertal/adolescent and 210 adult) between 6 and 77 years of age. The influence of different region of interest (ROI) diameters (6--20 mm) and software techniques (automatic (ROIaut), copied (ROIcop) and fixed coordinate (ROIfix) measurements) on annual rate of change, trend assessment interval (TAI an estimate of the follow-up time required for measuring a true change), percentage of positioning errors (positioning of the ROI partly at the cortical edge or even partly beyond the calcaneus) and short-term precision error was studied. When using ROI diameters increasing from 8 to 20 mm, the annual rate of change of BUA and SOS did not change in adults, but was higher in prepubertal subjects (when subjects with positioning errors were excluded) as well as in pubertal/adolescent subjects. TAIs for BUA were shortest when using ROIaut with ROI diameters between 8 and 14 mm (TAI between 1.2 and 1.5 years for prepubertal boys and pubertal/adolescent subjects, 2.4 years for prepubertal girls, 2.7 years for postmenopausal women, and 9 years in men and premenopausal women). TAIs for SOS were 4 years or more, except for postmenopausal women (2.1 years) and prepubertal boys (3.2 years). Measurements with large ROI diameters, especially with fixed region coordinates, resulted in a high percentage of positioning errors and mostly in longer TAIs. Analysis of the short-term precision errors did not reveal these important differences between the various ROI diameters. Our results indicate that calcaneal ultrasound imaging may be useful for measuring skeletal changes in healthy children, especially with BUA, and in postmenopausal women with BUA and SOS using an automatic measurement in the region of lowest attenuation. ROI diameters of 12 mm should be used in prepubertal subjects and of 14 mm in pubertal/adolescent and adult subjects. Author Affiliation: (1) Department of Endocrinology, NL (2) Department of Paediatric Endocrinology, NL (3) Department of Clinical Physics Laboratory, University Hospital Nijmegen, Nijmegen, The Netherlands, NL Article note: Received: 30 October 2000 / Accepted: 13 June 2001

Research describing an ultrasonic resonant technique for characterizing liquids is presented. An important aspect of this method is that it requires only small liquid samples.

Research is presented describing the use of particle image velocimetry to measure micromachined flexural plate wave devices for acoustic streaming.

Culvert whistlers created from acoustic waves in air confined by large cylinders are analyzed with both wave and geometrical ray models. Two distinct types of whistlers, on-axis and off-axis, are shown to have compatible explanations from both models that completely account for their time-dependent and frequency characteristics. The work of previous authors is revised and extended.

The speed of sound is affected by air temperature. Experiments can yield this result in either a small office or in more extreme environments such as a walk-in freezer. Sound waves generated by a speaker connected to a function generator can be detected by a microphone, boosted by an amplifier and recorded by an oscilloscope. Experimental results agree with theory within 1%.

A study was conducted to analyze the influence of acoustic forcing on velocity fields during the absence of chemical reactions. The temperature field was determined using fluorescence from an inert seed while thermocouple measurements were taken from the combustor's line of symmetry. Results indicated the importance of coupling efficiency between the control actuator for a dump combustor and its reactive flow.

An effective medium theory of the nonlinear elasticity of a random sphere pack based upon the underlying Hertz-Mindlin theory of grain-grain contacts was developed. Results showed that the second-order elastic moduli and sound speeds can be calculated as unique path-independent functions of an arbitrary strain environment. However, the elements of the stress tensor were not unique functions of the strain environment and their values depended on the strain path. Consequently, the sound speeds, which are considered as functions of the applied stresses, were path dependent.

The measurement of sound velocity and attenuation in thin specimens and films using the transmission acoustic method is discussed. The method measures the output signal A as a function of the distance z between radiating the receiving lenses of a two-lens focusing systems in a transmission microscope. Local values of sound velocities and attenuation could be determined.

Historical details describing how twentieth-century engineers used theoretical calculations to prove that aircrafts could break the speed of sound are rare. It is unclear how the phrase 'sound barrier' came about although it was first used by newspapers in 1935 after aerodynamicist W.F.Hilton was interviewed. The Bell XS-1 airplane broke the sound barrier before any other aircraft in 1947.

There are five mutually dependent variables relevant to Brillouin lidar measurements of temperature and sound speed in the ocean; they are (1) the Brillouin shift, (2) the sound speed, (3) the index of refraction, (4) the temperature, and (5) the salinity. We use three well-known relations to analyze rigorously the interdependence of these five variables. Clearly, a Brillouin shift measurement does not provide a stand-alone determination of temperature or sound speed; one more variable or one more relation must be known. The use of mean values of salinity that have been obtained by an analysis of a large set of historical in situ data is considered for this additional relation. Key words: Brillouin, lidar, temperature, sound speed, salinity, refractive index.

Ultrasonic relaxation spectroscopy in the frequency range of 0.2-2000 MHz was used to examine the molecular relaxation properties of carbohydrates in aqueous solutions. The observed structural conformations among the monosaccharides studied indicated that ultrasonic relaxation in these compounds occurring within the time range of 10(super -10) and 10(super -6) seconds proceeds due to the rotation of the exocyclic -CH2OH group.

Sound speeds, at pressure, and the overdriven Hugoniot were measured for the plastic-bonded explosive PBX-9501. The two curves intersected at the Chapman-Jouguet (CJ) state due to the sonic condition D = c + u. This allowed a unique derivation of the thermodynamic CJ pressure. A value of 34.8+/-0.3 GPa was derived. The data enabled a direct experimental determination of the isentropic gamma and the Gruneisen parameter in the overdriven pressure range.

Sound velocity measurements in spermaceti oil from a male sperm whale change as a function of pressure and temperature. At stable temperatures between 22 to 38 degree centigrade, and with pressure range between zero to 90 atm, the sound velocities range from 1390 ms(super -1) to 1540 ms(super -1). There is a linear relationship between velocity and pressure, and a non-linear relationship between velocity and temperature. There is a lack of transition in sound velocity as the oil changes from liquid to solid states.

A simple, direct, and inexpensive determination of the speed of sound in air, suitable for an undergraduate laboratory exercise, is presented. The same apparatus is used to demonstrate acoustic pulse reflections from closed and open ended tubes of circular cross section.

Analysis of longitudinal and transverse acoustic velocities in nine single-crystal diamonds by ultrasonic pulse-echo experiments indicates a decrease in the velocities with enhancement of 13C content for (100) samples. In the (111)-oriented samples, the phase velocities are directly proportional to the isotope content. Cubic elastic moduli for (100) phase, c11 and c44 and off-axis alignments effect enable calculation of the elastic modulus c12.

A picosecond pump-probe method helps determine longitudinal sound velocity and thermal conductivity of diamondlike carbon (DLC) and amorphous diamond (a-D) thin films at room temperature. Thermal conductivity and sound velocity decreased with the hydrogen levels in the films. The a-D films have conductivities ranging from 5 to 10 x 10 to the power of minus 2 W per cm per K, which is the higher than the corresponding values for all other amorphous insulators except HID. The velocity values lie between 14 and 10 x 10 raised to the 5th power cm per second for a-D films and 6 and 9 x 10 raised to the 5th power cm per second for DLC films.

Ultrasonic velocimetry technique facilitates structural and chemical analyses of the acidic molten globule form of alpha-lactalbumin, A-state. A-state sound-velocity in the conventional alpha-lactalbumin is greatly enhanced at zero pH and 2-megahertz sound frequency in comparison with that observed in the A-state of alpha-lactalbumin at pH2, the percentage difference in the sound velocities being 11% which is reduced by additional quantities of calcium. This effect is ascribed to enhanced time scale of conformational relaxation in native state of alpha-lactalbumin. Sound-velocity enhancement in the disturbed apo-state of alpha-lactalbumin at neutral pH declines by 4% from that of the conventional form of alpha-lactalbumin.

The details of an experiment that students can do at home to determine the speed of sound in air are discussed.

Issues concerning the measurement of the speed of sound in gases and in air under temperature variations is examined. Topics include the use the speed of sound in air as a constant factor and comparisons between speed of sound in air and in carbon dioxide.

The propagation speed c of an infinitesimal pressure step is obtained as a compatibility condition on the system of equations derived from the thermal equation of state and balances of mass, momentum, and total energy. Because the entropy is not introduced during the derivation, c is given initially in terms of the pressure, volume v per unit mass, and derivatives of the internal energy. An identity using only the first law of thermodynamics is then used to show that c = [square root of [gamma]]v[K.sub.T], where [gamma] is the specific heat ratio, and [K.sub.T] is the isothermal bulk modulus. This derivation differs from existing ones as the entropy is not used to obtain the result for c, but only to interpret it. [DOI: 10.1119/1.1456070] (Received 24 July 2001; accepted 9 January 2002)

Directions for assembling and using a device that measures the speed of sound in various gases using resonance is presented.

Direct experimental measurements of hard transition shift (HTS) were obtained for a set of different velocities of the magnetic medium. Results showed that HTS increases at higher medium velocity. Numerical simulation of the writing zone dynamics indicated a time delay in the writing of the hard transition compared with the easy one. The dependence of HTS on medium velocity explained the degradation of overwrite at high recording data rates.

An experiment was conducted to measure the speed of sound on an aluminum rod which was stimulated in its fundamental mode wherein only one length was utilized. The experiment was based on the theory regarding traveling waves which form standing waves and focused on the production of a continuous singing rod whose driver's frequency was controlled. The results of the experiment, which showed differences in calculated velocities, suggested that further study should be conducted to analyze the discrepancy in sound velocities.

X-ray scattering measurements of sound wave propagation in ice and water indicate that sound waves having wavelength between 0.5-3 nanometer propagate at the same velocity in both media. At low Q-values, longitudinal acoustic phonon modes dominate the spectra of polycrystalline ice, whereas quasielastic central peak dominate the spectra in liquid medium.

Derivations of several velocity squares in model superlattices with graded profile are linearly proportional to the squares of the elastic constant modulation amplitude for a small amplitude regime. This square-wave modulation profile reveals alternating homogeneous layers of two or more different materials in superlattices. Numerical methods mediate simple dependencies by model superlattices on elastic constant modulation amplitudes.

The speed of sound in a gas can be measured with sufficiently high precision to observe real gas properties at one atmosphere and 300 K through the use of an easy-to-make cylindrical resonator. Heat capacity is shown to be able to be obtainable from speed of sound measurements.