bluuebunny/crossref_metadata_2025 huggingface dataset:
Electroacoustic Reproduction of “Perceived Reverberation” for Comparisons in Architectural Acoustic Investigations
Authors: Plenge G. , Romahn G.
Published: October 2005

The correct reproduction of “perceived reverberation” serves as quality criterion about electroacoustic transmission systems. By the use of such transmission systems, quality judgments in architectural acoustics may be made without differences between sound sources influencing these judgments.
Microphone Thermal Agitation Noise
Authors: Olson Harry F.
Published: October 2005

In electrodynamic microphones there are two major sources of thermal agitation noise, namely, the electromotive force due to the thermal agitation of the electrons in the conductor and the electromotive force produced by the motion of the diaphragm due to the thermal agitation of the molecules impinging upon the diaphragm. In commercial microphones, the thermal acoustic noise is far below the thermal electric noise. Therefore, in order to detect the thermal-acoustic noise, a special high-sensitivity ribbon velocity microphone was designed and built. The presence of the thermal acoustic noise was detected and measured in the microphone. The theoretical and experimental data correspond for both the thermal electric noise and the thermal acoustic noise.
Cochlear Resonance and Phase-Reversed Signals
Authors: Hiesey Ralph W. , Schubert Earl D.
Published: October 2005

An old psychophysical test for degree of mechanical resonance in the cochlea was repeated, taking advantage of modern methods for controlling and reproducing audio signals. Unfortunately, the perception of a time separation pitch enters into the judgments and makes this particular method useless.
Monaural and Binaural Masking Patterns for a Low-Frequency Tone
Authors: McFadden Dennis , Russell William E. , Pulliam Kenneth A.
Published: October 2005

A tonal masking experiment of the sort pioneered by Wegel and Lane was conducted with both monotic and dichotic stimulation. The forms of the masking patterns under these two conditions of listening were markedly different. The monotic data were similar to the classical data—there was a local minimum in masking at the masker frequency, gradually more masking at adjacent frequencies, and then a gradual, and asymmetric, decline in masking at frequencies more distant from the masker. For the dichotic condition, however, masking was greatest at the masker frequency, and it showed two local minima at about ±10 Hz from the masker before declining gradually for more distant frequencies. These two minima are interpreted as reflecting a kind of time constant in the binaural system, an interpretation that receives support from research on binaural beats. Across signal frequencies, the masking-level differences (MLDs) ranged from about 1 to 11 dB. Masker: 400 Hz, 70 dB SPL, continuously present. Signal: 100-msec duration, 10-msec rise-decay time. Method: Two-interval forced choice with feedback. Listening conditions: Nm-Sm and N0-Sπ.
Functional Changes in the Ear Produced by High-Intensity Sound. II. 500-Hz Stimulation
Authors: Price G. Richard
Published: October 2005

Experiments were performed in which one ear of each of 36 cats was exposed to a 500-Hz pure tone for periods totaling 80 min at one of four intensities while cochlear microphonic (CM) measurements were made. Exposure intensities were those necessary to produce a maximum in CM at 500 Hz, or 10 dB, 20 dB, or 30 dB higher than that. CM sensitivity before and after exposure was measured for frequencies from 100 Hz to 20 kHz. Losses were widespread and, at the highest intensity, were maximal at 500 Hz. Losses grew gradually with increasing intensity until somewhere between the two highest intensities the rate of loss became very rapid. The results of the present experiment were similar to those of a previous experiment in which a 5.0-kHz exposure tone was used [G. R. Price, J. Acoust. Soc. Amer. 44, 1541–1545 (1968)]. The implications of the data with respect to damage-risk criteria were discussed.
Sound-Induced Electrical Impedance Changes in the Guinea Pig Cochlea
Authors: Strelioff David , Haas Gustav , Honrubia Vicente
Published: October 2005

To test the “variable-resistance” theory of production of cochlear microphonics, the impedance variation between scala media and the neck of guinea pigs was measured during low-frequency sound stimulation. Results show an impedance variation at the sound frequency that can be as large as 100 Ω (1% of the dc impedance) occurring in the walls of the endolymphatic space. This supports the concept that the cochlear microphonic potentials are produced because of resistance change at the reticular lamina.
Suprathreshold Binaural Unmasking
Authors: Townsend Thomas H. , Goldstein David P.
Published: October 2005

Binaural unmasking behavior was investigated at suprathreshold levels using 250- and 500-Hz sinusoids. First, the traditional detection masking-level difference (MLD) was measured; then a loudness balance was made between the masked S0 and Sπ signals at four sensation levels to infer the superthreshold binaural advantage. The results showed that the antiphasic advantage decreased with the increasing sensation level of the signals and implied that the loudness of the masked antiphasic signals grew more slowly than that of the masked homophasic signals. The influence of this loudness effect on other data in the literature is discussed.
Temporal Resolution of Tonal Pulses
Authors: Williams Kendrick N. , Perrott David R.
Published: October 2005

Temporal resolution, as defined by the minimum detectable gap between successive tonal pulses, was observed to decrease as a direct function of both the frequency disparity between successive pulses and the duration of the pulses. An interaction between frequency disparity and pulse duration was also observed.
The First Twenty Years of Acoustic Signal Processing
Authors: Anderson Victor C.
Published: October 2005

The decade of the 1950s marks the beginning of acoustic signal processing as a subfield of underwater acoustics. The forerunner, signal recognition, gradually evolved into a unified class of spatial and temporal processing techniques and theory which came to stand on its own. The doctrines that emerged in that decade, such as spectrum analysis, correlation, and multiple beamforming, have continued to grow in sophistication, until we now find methods such as the fast Fourier transform, sequential detection, and adaptive beamforming handed down to us from the 1960s. The milestones of signal processing over the past 20 years present a striking record of progress in that field.
Characteristics of Line and Disk Underwater Sound Transducers in the Near- to Farfield Transition Region
Authors: McKinney C. M. , Harvel K. W. , Ellis G. E.
Published: October 2005

The history of the study of radiation characteristics from certain simple apertures, which extends at least from Lommel (1884) to the recent work of Zemanek (1971), is summarized. Theoretical and experimental data concerning resolution, minor lobe behavior, and axial pressure level as a function of range in the near- to farfield transition region are presented and compared for a circular disk and a strip line transducer. The use of near- to farfield information in transducer calibration, range determination, and sonar design, is discussed.
Helmholtz-Kirchhoff Theory for Sound Transmission through a Statistically Rough Plane Interface between Dissimilar Fluids
Authors: Medwin H. , Hagy J. D.
Published: October 2005

The dependence of sound transmission on the statistics of a randomly rough interface between two dissimilar fluids is studied by use of the Kirchhoff-Helmholtz integral. Both plane waves and waves from a point source are considered. The analysis is very similar to that of scatter from a randomly rough surface; for example, for low roughness, the transmitted mean-square pressure is coherent and e−R times the smooth surface value, whereas for large roughness the transmitted sound is incoherent and depends also on the surface correlation length. The critical roughness parameter for transmission is R = k22σ2[(c2/c1) cosθ1 − cosθ2]2 where k, c, and θ are the propagation constant, speed of propagation, and angle with the normal, respectively; subscript 1 refers to the incident medium; σ is the rms height of the surface.
Sound Propagation in Shadow Zones
Authors: Sachs David A.
Published: October 2005

By admitting complex-valued solutions to the equations of ray acoustics (complex rays), ray theory is extended to yield nontrivial sound-pressure levels in the shadow zone adjoining a caustic. For a steady-state source, the sound field in the shadow is found to decay exponentially with frequency and with distance from the caustic. In the transient case, the theory appears to be in general qualitative agreement with results from experiments involving explosive sources.
The Use of High-Power Ultrasonics (Macrosonics) in Studying Fatigue in Metals
Authors: Mason Warren P. , MacDonald Douglas E.
Published: October 2005

High-power ultrasonics has been a useful tool in studying fatigue in metals, since a large number of cycles can be obtained in a small time. In the case of brass and iron the mechanisms appear to differ with frequency, since at the high frequencies fatigue occurs in isolated regions whereas at the low frequencies the slip is generally spread over the grains. The same mechanism can be produced at high frequencies by going to higher temperatures. In iron the stress required for fatigue at higher frequencies is considerably less than for low frequencies. Recent measurements in titanium have shown that the required stress is about the same for high and low frequencies. The crack propagation velocity, however, is much faster at the ultrasonic frequencies. This was proved by striation measurements with a scanning electron microscope. Thus, the high-frequency fracture is not only localized, it is virtually catastropic in the localized area.
Radiation Resistance of a Rectangular Panel
Authors: Wallace C. E.
Published: October 2005

The radiation resistance corresponding to the natural modes of a finite rectangular panel is theoretically determined from the total energy radiated to the farfield. The panel is assumed to be simply supported in an infinite baffle. Asymptotic solutions for the low-frequency region are derived, and curves covering the entire frequency range for various mode shapes and aspect ratios are obtained through numerical integration. When the ratio of the acoustic wavenumber to the panel wavenumber is a constant much less than unity, the radiation resistance for all modes is a minimum if the intranodal area (the area between adjacent node lines) is square, and increases with the aspect ratio of the intranodal area.
Driven Nonlinear Oscillations of a String
Authors: Eller Anthony I.
Published: October 2005

Nonlinear vibrations of a string may become unstable when the string is driven with sufficient amplitude near resonance. This paper describes the experimental conditions under which transverse oscillations of a horizontal string, driven in the vertical plane, become unstable. It is found that the planar oscillations become unstable in two different ways. One instability involves a spontaneous growth or decrease in the amplitude of the driven vertical motion. The other instability involves the spontaneous appearance of a transverse horizontal component of vibration perpendicular to the driving force, thus leading to a whirling or nonplanar motion of the string. The paper also describes the response of the nonplanar mode of oscillation, and it is found, for example, that for certain conditions the driven vertical component of oscillation decreases in amplitude when the driving level is increased. The experimental results agree qualitatively with theoretical predictions based in part on the work of Anand [J. Acoust. Soc. Amer. 46, 667–677 (1969)].
The Response of a Plate Bonded to a Randomly Vibrating Viscoelastic Half-Space
Authors: Remington Paul J.
Published: October 2005

The response of an infinite Bernoulli-Euler plate placed on the surface of a randomly vibrating viscoelastic half-space is calculated, allowing for the presence of shear stresses between the plate and the half-space. The shear stresses arise from the condition that the relative motion between the plate and the half-space vanishes at the interface. The three components of displacement of the free surface of the half-space before the plate is added are assumed to be stationary homogeneous random functions of position and time. From the wavenumber-frequency spectra of these displacements the frequency spectra of the three components of displacement of the plate half-space interface are calculated. As an example, the frequency spectrum of the vertical interface displacement is calculated for two assumed forms of the wavenumber spectra of the free-surface displacements.
Acoustical Design of the John F. Kennedy Center for the Performing Arts
Authors: Harris Cyril M.
Published: October 2005

The John F. Kennedy Center for the Performing Arts opened in Washington, D.C., on 8 September 1971. This institution was originally established by Act of Congress in 1958 as the National Cultural Center, but, following the death of President Kennedy, a law was passed in 1964 renaming it as his sole official memorial in the nation's capital. This paper describes some of the special problems related to noise control that required solution, the basic features of the acoustical design of the halls—a 2759 seat concert hall, a 2319 seat opera house, and a 1142 seat theater—and some of the physical characteristics and acoustical properties of the halls.
Measurement of Sound Transmission Loss by Combining Correlation and Fourier Techniques
Authors: Schomer P. D.
Published: October 2005

The feasibility of performing transmission loss and diffraction measurements using correlation techniques is demonstrated. In contrast to standard measurements which make use of reverberant sound fields, the correlation techniques developed herein directly yield the responses due to signals transmitted through and around the acoustic barriers. The technique consists of first cross-correlating noise signals, then finding the Fourier transform of the resulting impulse response, and finally correcting for source imperfections in the frequency domain. Comparative measurements of the transmission loss of some common materials are presented along with transmission loss measurements made as functions of angle and distance, and also presented are measurements of sound diffraction around panels. The results of these measurements (where comparison is possible) are shown to be as good or better than measurements resulting from standard techniques, and these results are shown to be in excellent agreement with existing theory.
Self-Consistent Theory of Interdigital Transducers
Authors: Emtage P. R.
Published: October 2005

The generation and absorption of surface waves by an interdigital transducer with uniform finger spacing are calculated with the aid of a surface dielectric constant related to the TM-wave impedance. It is found that the response of an infinite transducer can be calculated with complete consistency, i.e., the field due to the distortion of the piezoelectric medium is correctly included in the determination of the distortion. For a finite transducer, the solutions given are in error only at lines on the surface at either end of the transducer, and are therefore accurate when the transducer is long. It is found that the parallel equivalent circuit derived in the weak coupling approximation is a reasonably accurate representation of the transducer when the coupling is strong and the transducer long, but that the central resonance is then distorted.
Analysis of the Difference Between Log Mean and Mean Log Averaging
Authors: Hershey Robert L.
Published: October 2005

The acoustic data analysis procedures at various installations differ in the intervals at which readings are converted from volts squared to decibels. There has been much speculation as to what would be the decibel difference between the results obtained for the same data, i.e., the difference between the log of the average and the average of the logs. In this analysis, the difference is treated as a random variable. By making the practical assumption that the distribution of the samples is Gaussian with mean μ and standard deviation σ, the expected value of the difference is found, as well as its appropriate confidence limits, for the special case of small σ/μ. These results are found to depend on the ratio σ/μ and on n, the number of samples averaged. It is found that the expected value of the difference is approximately equal to 2.17[(n − 1)/n] (σ/μ)2 and that the standard deviation of the difference is equal to [2/(n − 1)]12 times this expected value. For practical values of σ/μ the expected value of the difference is found to be less than 0.2 dB and the Chebyshev 95% upper confidence limit of the difference is found to be less than 0.5 dB.
The Influence of Rise Time on Loudness
Authors: Gjaevenes Kjell , Rimstad Erling R.
Published: October 2005

The influence of the rise time on the loudness of sound pulses and the meaning of the sound spectrum on this influence were examined. A “paired comparison” method was used. The sound pulses had a duration of 0.7 to 1.0 sec and the rise time was varied between 0.03 and 1.0 sec. For most of the measurements, a signal level of 95 dB re 2×10−5 N/m2 was used. The signals with the fastest onset showed the highest loudness. The influence of the rise time on the loudness was significantly dependent on the signal spectrum. The possibility of explaining the observed effects on the basis of changed synchronism of the neural activity and on the basis of a rapid adaptation in the nervous system is discussed.
Temporary Hearing Loss Induced by Noise and Vibration
Authors: Okada Akira , Miyake Hirotsugu , Yamamura Kǒtaro , Minami Masayasu
Published: October 2005

Five male students (19 20 years old) with normal ears were given exposures to (1) steady-state noise, (2) vibration, and (3) noise and vibration at the same time. In a control experiment the subject sat beside the moving vibrator with ear plugs and earmuffs. Temporary threshold shift (TTS) occurred after both 20 and 60 min of exposure to the vibration of acceleration 500 cm/sec2 and frequency 5 Hz, which is regarded as a resonance frequency of human body. The TTS by a steady-state noise [101-dB sound-pressure level (SPL) broad band] was increased by simultaneous vibration (500 cm/sec2 and 5 Hz).
Temporary Threshold Shift and Recovery Patterns from Two Types of Rock and Roll Music Presentation
Authors: Rintelmann William F. , Lindberg Robert F. , Smitley Ellen K.
Published: October 2005

The purpose of this experiment was to clarify the effects of exposure to intermittent and continuous rock and roll music on hearing threshold level. Twenty normal-hearing females were exposed to recorded rock and roll music on two occasions in a sound field at 110-dB sound-pressure level. One taped recording consisted of music played continuously for 60 min; the other recording was the same music, but with 1 min of discotheque ambient noise (“break times”) spliced between each 3-min musical selection. Pure-tone air-conduction threshold levels were measured monaurally via Békésy audiometry at 1000, 2000, 3000, 4000, 6000, and 8000 Hz prior to, and four times following, each exposure. Temporary threshold shift (TTS) and recovery patterns from the continuous and intermittent conditions were compared. Statistical analysis revealed that TTS2 in the intermittent condition was significantly less than in the continuous condition at 2000, 3000, 4000, and 8000 Hz. Recovery time, however, was similar under both conditions.
Electrophysiological Studies on the Spatial Distribution of the Crossed Olivocochlear Bundle along the Guinea Pig Cochlea
Authors: Teas D. C. , Konishi T. , Nielsen D. W.
Published: October 2005

The effectiveness of electrical stimulation of the crossed olivocochlear bundle (COCB) was measured at different locations along the cochlear partition. Differential electrodes were used to sample the cochlear microphonic (CM) at turns I, II, and III. A pipette inserted into scala media in turns I, II, and III was used to measure the slow negative potential associated with electrical stimulation of the COCB. The responses of auditory nerve fibers were sampled within the modiolus and included a wide range of best frequencies. The magnitude of the slow negative potential was maximum in turn I and decreased in turns II and III. The increment in CM, produced by COCB stimulation, depended not only upon the location along the cochlear partition from which it was recorded, but also upon acoustic frequency. For low-frequency acoustic signals (below 700 Hz), the increment in CM was greatest at turn I and decreased toward the apex. At 5 kHz, COCB stimulation produced no detectable increment in CM at turn I. The reduction in discharges of auditory nerve fibers produced by COCB stimulation was greatest (16–20 dB in titration) when best frequency lay between 7 and 10 kHz. As best frequency decreased, the reduction in discharge rate with COCB stimulation decreased. Nerve fibers with very high best frequencies also showed minimal COCB effects. These data are discussed in relation to other recent information.
Intensity Discrimination of Pulsed Sinusoids: The Effects of Filtered Noise
Authors: Viemeister Neal F.
Published: October 2005

It has been shown repeatedly that Weber's law does not hold for intensity discrimination of pulsed tones. The masking function for such waveforms (10 logΔI vs 10 logI, for constant performance) typically is linear with a slope of 0.9 over a range in I of at least 60 dB. The present experiment indicates that the slope of the masking function increases from 0.9 to 1.0 as regions above the signal frequency are masked by filtered noise. A sufficient condition for a slope of 1.0 is a high-pass noise which masks regions at and above the second harmonic of the signal. This suggests that the “near miss” to Weber's law reflects the observer's use of information at aural harmonics. A model based upon this notion gives a good quantitative account of the data. The amount of distortion assumed in the model is in reasonable agreement with other data.
Extensional Wave-Propagation Characteristics in Striated Muscle
Authors: Truong Xuan T.
Published: October 2005

The real part of the complex dynamic modulus for frequencies 50–10 000 Hz was derived from viscoelastic wave-propagation constants in whole frog skeletal muscle, in order to provide a material function characteristic of the dynamic longitudinal viscoelastic behavior of resting skeletal muscle in the higher-frequency range. The method of measuring the phase velocity and attenuation coefficient of longitudinal waves propagated along the longitudinal axis of thin muscles is described. The results showed that there were significant viscoelastic effects between 50 and 5000 Hz with some leveling off above 5000 Hz, as indicated by the frequency dependence of the wave propagation constants. The relaxation time spectrum derived from the dynamic modulus-frequency function showed that about half of the relaxation times were less than 1 msec. The results were generally consistent with other studies based on the time course of stress relaxation and on the relationship between sinusoidal stress and strain.
Construction of a Dummy Head after New Measurements of Thresholds of Hearing
Authors: Mellert V.
Published: October 2005

A dummy head was constructed after new measurements of thresholds of hearing. Correlated structures were found in the thresholds of hearing for all subjects. It was possible to average the identifiable structures and to adjust the frequency responses of the dummy-head to the average threshold of hearing.
MLDs in Forward and Backward Masking
Authors: Small A. M. , Boggess J. , Klich R. , Kuehn D. , Thelin J. , Wiley T.
Published: October 2005

Masking-level differences (MLDs) of substantial magnitudes were found in forward and backward masking situations. Their magnitude diminishes exponentially as the silent interval between signal and masker increases. Implications of the data for current models relating to the MLD are suggested.
Cochlear-Microphonic and Middle-Ear Pressure Changes during Nitrous Oxide Anesthesia in Cats
Authors: Starr A. , Schwartzkroin P.
Published: October 2005

The amplitude of cochlear-microphonic responses in cats was attenuated up to 18 dB during both induction and recovery from nitrous oxide anesthesia, with smaller changes (up to 3 dB) occurring during the periods of maintained anesthesia. This response variability was clearly related to alterations of middle-ear pressure and could not be attributed to changes in middle-ear muscle or efferent olivocochlear bundle activities. Middle-ear pressure rose during inhalation of nitrous oxide with periodic abrupt returns to baseline levels during the period of maintained anesthesia; pressure became negative after withdrawal of nitrous oxide.
Rank Ordering Procedure for Auditory Stimuli
Authors: Nakatani Lloyd H.
Published: October 2005

Sorting is a quick and reliable procedure for rank ordering stimuli along a subjective continuum. However, sorting auditory stimuli is difficult because they cannot be physically handled. This difficulty was overcome with a computer by assigning numbers to stimuli stored digitally on a random-access disk. Subjects ordered the stimuli by rearranging the order of the numbers in a displayed list. Only a few subjects were necessary to obtain reliable results with the ordering procedure in several speech evaluation experiments.
Sources of Noise in Axial Flow Fans
Authors: Mugridge B. D. , Morfey C. L.
Published: October 2005

Experiments and theory relating to fan noise sources are reviewed with emphasis on axial flow machines. At supersonic rotor speeds, the steady shock pattern attached to a rotor is an efficient radiator of sound. In most practical cases of subsonic rotor operation, however, direct radiation from the rotor-locked pressure field is negligible compared with the indirect radiation, or scattering, caused by circumferential distortions in the steady flow field surrounding the rotor. Random timewise modulation of the distortion changes the scattered spectrum from discrete to continuous with a gradual progression from narrow-band tones to broad-band noise as the modulation bandwidth is increased. Similar scattering occurs when a nonuniform unsteady flow impinges on stator vanes, but here the radiated frequency is that of the impinging flow. Finally, for blades operating in flows free from circumferential distortions, self-generated turbulence becomes an important source of noise. The paper describes the physical mechanisms involved in each of these processes, including the generation of unsteady lift by turbulence. Order-of-magnitude sound-power estimates are compared where possible with experiment.
Analysis, Testing, and Design of Lined Ducts
Authors: Wirt L. S.
Published: October 2005

Lined ducts containing flow and intense sound have been extensively studied in recent years. Parametric studies have revealed so many variables that design procedures are obscured. Analysis by solution of the convected wave equation has been complicated by uncertainties about the actual modal distribution and by uncertainties about the actual boundary impedance. As a result, when discrepancies occur between experimental and analytical results it is difficult to interpret whether the wave-equation solution, the modal assumption, the impedance value, or the test procedure is deficient. The simultaneous refinement of all four factors has resulted in a very satisfactory correlation between theory and duct test results and provides a basis for lucid duct design procedures and the evolution of new liner materials. A duct test facility has been built which appears to provide equipartition of energy. The impedance of nonlinear materials has been redefined and measurement methods modified. Contours of equal duct attenuation in the impedance plane have been generated and prove to be simple in shape. From these, a design methodology is deduced which may be applied to any liner material and which eliminates many redundant parameters. The new methodology has led directly to the creation of new liner materials.
Blade Interaction Noise from Lift Fans
Authors: Krishnappa G.
Published: October 2005

The discrete-frequency noise radiation from a single-stage lifting fan is analytically estimated from measured steady and unsteady aerodynamic data on the fan and compared with the measured noise levels. Unsteady forces acting on the stator blades are calculated from measurements of the rotor blades' wake, using a hot-wire anemometer. The viscous interaction noise estimated is compared with the potential interaction noise from the rotor blades. Rotor potential-flow interaction and stator viscous interaction noise both seem to be important in the case of close rotor-stator spacing. The estimated results show a reasonable agreement with the measured results.
In-Duct Investigation of Subsonic Fan “Rotor Alone” Noise
Authors: Moore C. J.
Published: October 2005

The production of tones by an isolated rotor interacting with fluctuating and steady flow distortions is first discussed and a method of separating the steady components is explained. Circumferential, radial, and axial microphone traverses have been made in the duct of a 1-m-diam four-bladed subsonic ventilation fan with no stators. The steady components of the rotor tones were measured and phase related to the shaft rotation. The results show that the acoustic field close to the rotor is dominated by its steady force field: at any multiple of rotational frequency, the basic mode is present, having a number of lobes equal to the rotational frequency harmonic order. At greater axial distances from the rotor, the basic mode decays, leaving only modes of low circumferential order at the intake. The estimated power in these modes is in agreement with the acoustic power measured from farfield traverses. The loading spectrum of the fan is determined from the acoustic modes in the intake and compared with the spectrum used in helicopter noise theory.
Attenuation of Sound in Suspensions and Emulsions: Theory and Experiments
Authors: Allegra J. R. , Hawley S. A.
Published: October 2005

The absorption of sound in emulsions and suspensions is due to viscous and thermal transport processes occurring at the interface of the nonhomogeneities, as well as to the intrinsic absorption in the materials comprising the system. A complete description of these processes for systems of fluid particles suspended in fluid media was given by Epstein and Carhart [J. Acoust. Soc. Amer. 25, 553 (1953)]. However, subsequent investigators of liquid systems have generally neglected the thermal transport process. We show in this work that the Epstein-Carhart results provide a good description of our experimental attenuation data in emulsions, and that the thermal transport process can be the major factor in the attenuation. We have here also extended the theory further to include the attenuation in suspensions of solid particles, and good agreement is found between our theory and experimental results for aqueous suspensions of polystyrene spheres.
Atmospheric Absorption of Sound: Theoretical Predictions
Authors: Evans L. B. , Bass H. E. , Sutherland L. C.
Published: October 2005

By assuming that air is composed of four gases (i.e., nitrogen, oxygen, water vapor, and carbon dioxide) and applying energy transfer rates for the binary collisions inherent in such a system, absorption of sound in the atmosphere has been predicted. The calculated curves based upon 24 energy transfer mechanisms are compared with experimental data over the humidity range of 0–100% relative humidity. Agreement between theory and experiment is very good. By including classical absorption and rotational relaxation effects, the total atmospheric absorption is also predicted at 20°C. Calculations made for various concentrations of CO2 indicate that low CO2 levels (less than 0.1%) do not significantly affect absorption of audible sound at high humidities. At very low humidities, however, CO2 is an important factor.
Determination of Third- and Fourth-Order Longitudinal Elastic Constants by Shock Compression Techniques — Application to Sapphire and Fused Quartz
Authors: Graham R. A.
Published: October 2005

A number of solids sustain large elastic compressions under shock-wave loading. In these solids, measurements of the stress and compression in the direction of shock propagation can be used to calculate both third- and fourth-order longitudinal elastic constants if measurements are carried out over a wide range of compressions. Only limited measurements of fourth-order constants have been previously determined by other techniques. Determinations of third-order constants under these large elastic compressions afford the opportunity to test the applicability of the finite-strain formulation of constitutive relations. A general method for calculating these third- and fourth-order constants is presented and applied to shock compression data for sapphire and fused quartz. For sapphire, it is found that C111 ≈ C333 = − (3.3±0.3) × 104 kbar and C1111 ≈ C3333 = + (5.0±1.5) × 105 kbar. For fused quartz, it is found that C111 = + (5.5±0.1) × 103 kbar and C1111 = + (110±10) × 103 kbar. The technique and method of analysis seem generally applicable to solids that exhibit elastic limits of a few percent of their longitudinal elastic constants.
Use of Bragg-Diffraction Imaging for Acoustic Velocity Measurement
Authors: Powers John P. , Wang Keith Y. , Wade Glen
Published: October 2005

Acoustic velocities in platelike elastic materials satisfying certain conditions can be measured by irradiating the materials with ultrasound and processing the ultrasonic transmission patterns with laser light to obtain Bragg diffraction of the light. Simple observation or measurement of the diffracted optical image as the acoustic frequency is varied gives both compressional and shear-wave velocities through the materials. A real-time visualization of the acoustic transmission pattern can also be obtained. This method provides a simple means of detecting inhomogeneities in platelike material and obtaining a quantitative comparison of the velocity characteristics with reasonable precision in localized regions.
Temperature Dependence of the Hypersonic Attenuation and the Nonlinearity Constant “D” for Copper
Authors: Tripathi R. C. , Aggarwal V. C. , Joshi M. M.
Published: October 2005

Values of the nonlinearity constant “D,” which are instrumental in conversion of the acoustic phonons to thermal phonons, are determined in this paper for copper in the temperature range from 300° to 80°K, using experimental data of third-order elastic constants of this material. The previously predicted temperature-dependent behavior of this constant D, which found experimental support partially at room and liquid-nitrogen temperatures only in Ge, has been thus tested for the first time on experimental basis even for a metallic crystal. The results are found to be in agreement with the previous prediction. Moreover, the temperature-dependent curve for phonon viscosity component of hypersonic attenuation can be recalculated by using our values of D. When this is done, a better agreement is obtained than that obtained previously between the theoretical and corresponding experimental curves of hypersonic attenuation as a function of temperature for longitudinal wave propagation in the (100) direction.
Visualizing and Calculating the Response due to a Pressure Impulse over an Arbitrary Surface
Authors: Schomer Paul D.
Published: October 2005

Most radiation problems are normally solved in the frequency domain, and quite often transform techniques are employed. This paper points to a large class of problems for which the solutions are much more readily found directly in the time domain. Furthermore, in many cases these solutions are expressible in terms of elementary generalized functions and hence are easily transformed, so the steady-state frequency domain solutions follow immediately. More specifically, a simple method is presented to visualize and calculate the response at any point P in space to a pressure impulse occurring at time t0 in an area of space defined by an arbitrary hypothetical surface or curve.
Dynamic Response of Suspended Underwater Systems
Authors: Iwan Wilfred D.
Published: October 2005

A method is presented for analyzing the steady-state or stationary random heave response of suspended underwater systems. The nonlinear continuous system is replaced by a discretized pseudolinear system by means of an equation difference minimization technique. The resulting pseudolinear system is solved by an iterative scheme. An example of the application of the proposed method of analysis to a suspended hydrophone system is given. The example shows that the nonlinear pressure drag forces have a very significant effect on the over-all response of the system. The nature of the response is discussed and some practical conclusions are given.
Vibration of a Kettledrum
Authors: De Sasadhar
Published: October 2005

In this paper, the vibration of a kettledrum, i.e., a circular membrane stretched over one end of an air-tight vessel, is described.
Transverse Vibrations of Double-Tapered Cantilever Beams
Authors: Mabie H. H. , Rogers C. B.
Published: October 2005

The differential equation is developed from the Bernoulli-Euler equation for the free vibrations of a double-tapered cantilever beam. The beam tapers linearly in the horizontal and in the vertical planes simultaneously. From a computer solution of this equation, a table has been developed from which the fundamental frequency, second, third, fourth, and fifth harmonic can easily be obtained for various taper ratios. Charts are plotted for selected taper ratios in the vertical plane to show the effect of taper ratios on frequency.
Comments on “Sound Pressure in Water from a Source in Air” [R. W. Young, J. Acoust. Soc. Amer. 50, 1392–1393(L) (1971]
Authors: Russell G. A.
Published: October 2005

The present letter points out some typographical errors and suggests a slightly different interpretation of the reported test results.
Theory of Steady-State Urban Noise for an Ideal Homogeneous City
Authors: Shaw E. A. G. , Olson N.
Published: October 2005

The city is treated as a plane surface with many identical sound sources (motor vehicles) randomly distributed over its area. The mean energy density at any point in the plane is expressed in terms of the individual source strength, the average number of sources per unit area N, the atmospheric absorption constant α, and a shielding factor F associated primarily with obstacles in the transmission path. To obtain the steady-state (median) energy density, a central cell containing a single discrete “local” vehicle is identified and treated separately from the rest of the distribution. Graphs and tables of steady-state level and energy density as functions of N and α are given for the homogeneous infinite city, the city of finite size, and the traffic-free zone within a city. The theory indicates that the spreading of urban noise is determined by a characteristic distance with a typical value of 0.25 km. The observed octave-band sound-pressure levels from 31.5 to 4000 Hz at one location in Ottawa are compared with calculated levels based on statistical data for vehicle source strength, estimates of vehicle density, and known atmospheric absorption constants. The differences are consistent with a shielding factor of 15 dB which is in good agreement with measurements of sound transmission in urban areas reported by others. The shielding factor has an effective value substantially independent of frequency.
Acoustic Surface-Reflection Channel Characterization through Impulse Response Measurements
Authors: Spindel R. C. , Schultheiss P. M.
Published: October 2005

An underwater acoustic surface-reflection channel is treated as a linear random time-varying filter. Thus complete characterization of the channel reduces to a statistical description of its stochastic system functions. This paper presents the results of measurements made in a model tank with a wind-driven surface in terms of the channel impulse response, transfer function, bifrequency function, and their ensemble averages. The impulse response is taken as the primitive because it permits evaluation of the transfer and bifrequency functions without need to resort to multiple measurements at different frequencies. Both the time- and frequency-spreading characteristics of the channel are clearly evident in the system function data. It is shown that, given a single set of impulse response measurements for each geometrical configuration of interest, it is an easy matter to study the frequency response and frequency-spreading behavior of the channel over the bandwidth of the acoustic pulse. The impulse response itself, of course, yields the time-spreading behavior of the channel directly. Furthermore, favorable comparisons are made between impulse response derived data, and data obtained by single-frequency measurement techniques.
A Hybrid-Computer Model of the Cochlear Partition
Authors: Hubbard Allyn E. , Geisler C. Daniel
Published: October 2005

A hybrid-computer simulation of the Peterson-Bogert model of the cochlea is reported. The present simulation is shown to be a good representation of the original model except near 10 kHz. The output of the model at one point has many similarities to recent experimental data. In particular, the low-frequency slope of the amplitude function is +6 dB/oct and the high-frequency slope is steeply negative. The phase function shows a break from linearity near the resonance frequency and approaches +90° at low frequencies. Quantitative discrepancies between model and experimental data exist, but they could be appreciably reduced by changes in parameter values. Incorporating nonlinear membrane damping in the simulation produces nonlinear effects similar to those observed in the cochlea. With increasing intensity, the displacement peak becomes relatively reduced and occurs at a somewhat lower frequency.
Tympanic Membrane Vibrations in Cats Studied by Time-Averaged Holography
Authors: Khanna Shyam M. , Tonndorf Juergen
Published: October 2005

The vibratory characteristics of the cat's tympanic membrane (TM) were studied in fresh cadavers and living animals with the aid of time-averaged holography. Initially, technical difficulties were presented by the TM's small size, low stiffness, and its transparency. Time-averaged holograms of the TM were obtained for various sound-pressure levels at a number of frequencies between 600 and 6000 Hz. Reconstructions of such holograms show an image of the TM superimposed by isoamplitude contour lines giving the absolute displacement amplitude at any point on the TM. Vibratory patterns remain essentially unchanged in their first mode up to a frequency of 2000 Hz, with higher modes occurring above that value. At all frequencies, the TM vibrates maximally in the posterior-superior quadrant and less in the anterior and inferior ones. These results show that, even in its first mode of operation, i.e., below 2000 Hz, the TM does not vibrate like a stiff plate as observed by von Békésy in human cadavers. Rather, the present findings support the curved-membrane concept of Helmholtz. Contributions to the total transformer action of the middle ear by the area ratio: TM/stapes footplate, the ossicular lever ratio, and that due to the curved membrane action are reevaluated.
Masking with Continuous and Gated Sinusoids
Authors: Leshowitz Barry , Cudahy Edward
Published: October 2005

The detection of a 5-msec tonal signal presented at various delays after the onset of a 500-msec tonal masker was investigated in several transient-masking experiments. Changes in the amount of masking were measured as a function of the delay between onset of the signal and the onset of the longer-duration masker. In agreement with previous investigations of transient masking there was a large decrease in masked threshold, 26 dB in some conditions, with an increase in signal delay. A “transient overshoot” at masker termination was also noted. These data are consistent with a short-time energy-sensing model of detection. In a second transient-masking study, the masking produced by a gated sinusoid in the presence of a continuous tonal pedestal was investigated. The pedestal results indicate that a simple, linear, time-invariant, energy-detection scheme cannot account for the results of two-tone masking experiments.
Equal Loudness Contours Derived from Sensory Magnitude Judgments
Authors: Schneider Bruce , Wright Anthony A. , Edelheit William , Hock Peggy , Humphrey Christopher
Published: October 2005

Magnitude estimates were obtained for the loudness of 77 pure tones varying in frequency (11 values) and intensity (seven values) when (1) all 77 tones were presented intermixed within a session, and (2) all tones of one frequency were presented before presenting tones of another frequency. A power function described the growth of loudness for each frequency for both conditions 1 and 2, and the exponent of the power function varied with frequency. Equal loudness contours were derived from the power functions of Condition 1 and were compared to those obtained from other experiments using different procedures.
Measuring the Resonances of Treble Viol Plates by Hologram Interferometry and Designing an Improved Instrument
Authors: Ågren Carl-Hugo , Stetson Karl A.
Published: October 2005

This paper is a presentation of the first application of the techniques of vibration analysis by hologram interferometry to the study of stringed instrument resonances. The instrument studied was the treble viol, which was a convenient size for a hologram system and allowed approximate simulation of the actual instrument by the clamped top plate. After study of an instrument of classical proportions by hologram interferometry, a new instrument was designed that was longer, wider, and flatter. Holographic study of the top plate of this new instrument verified that it should function well on a finished instrument since its resonance frequencies suited the instrument range. The rest of the instrument was built and tested holographically after assembly to confirm the previous simulation. The instrument was completed and played with very good results, i.e., more volume, easier playing, and more agreeable tone than the classically designed treble viol. The primary experimental difficulty encountered was the swelling of the wooden plates with humidity which adversely affected real-time interferometry, and the steps taken to overcome this were only partially successful.
New Electronic Tuning Device for Pianos
Authors: van der Woerd A. C.
Published: October 2005

In the tuning device being described a reference oscillator generates 84 crystal-controlled frequencies, which follow a stretched scale whose deviations are programmed in an interchangeable diode matrix. Three different diode matrices have been realized, intended for tuning small, medium-size, and grand piano's, respectively. A bandpass filter is used, the transmission range of which automatically follows the reference frequency. An electromagnetic device is used as a sound transducer. In consequence of this, tuning of all strings on their fundamentals becomes fully feasible. With one medium-size piano, the achieved accuracy was measured. The accuracy of the tuning with respect to the reference frequency was <10−4 in all cases. The total accuracy (including the inaccuracy of the reference oscillator) varies from 10−4 for the lowest note to 5×10−4 for the highest note.