bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparison between the growths of loudness of vibrotactile pulse and sinusoidal stimuli
Authors: Collins Amy A. , Cholewiak Roger W.
Published: October 2005

The growths of loudness of pulsatile and sinusoidal stimuli were examined by the method of absolute magnitude estimation. Fourteen observers judged 32-pps pulse and 250-Hz sine stimuli on two sites on the palm: the thenar and hypothenar eminences. Estimates revealed that pulse stimuli were perceived as being louder than the sine stimuli on both sites. Power functions fit to the sine data had exponents of 0.84, while those fit to the upper limbs of the pulse data had slopes of 0.82. Cross-quality matches between the two types of stimuli were made by nine of these observers. The group matches were not found to be internally consistent. That is, those made when the sine was the standard were not equivalent to matches made when the pulse was the standard. Such consistency was apparent, however, in some individual observer's data. In addition, slopes of matching functions were often well predicted by magnitude estimates using a procedure based upon the absolute scaling hypothesis. Intercepts were also predicted in some individual cases. [Work supported by NANCDS.]
Wood for piano soundboards
Authors: Haines Daniel W.
Published: October 2005

The wood soundboard of the piano is among the most important components of the instrument. It is essential for projecting the desired volume of sound, and the soundboard material strongly influences the quality of the sound. As it is for the sound radiating elements of many string instruments, spruce is the unanimous choice of wood for piano soundboards. The reasons for the use of spruce and selection criteria for superior performance will be discussed.
The mathematics of piano tuning
Authors: Sanderson Albert E.
Published: October 2005

It is a well-known fact that piano strings vibrate inharmonically—the partials actually run sharp by amounts that vary from piano to piano and from note to note on any one piano. This affects the tuning significantly, and it is correct to say that no two pianos should be tuned exactly alike. This paper presents a mathematical solution to the problem of tuning such instruments for typical classes of inharmonicity versus note-number curves, the most important case being a straight-line logarithmic increase of about 3:1 per octave. Equal temperament is literally impossible in this case, and if one forces it with an electronic tuning, the instrument sounds very unmusical. The octave is no longer exactly 2:1, and must be redefined to allow for different types of octave partial matching. More general definitions of equal temperature and octaves lead to a tuning solution in the form of a difference equation. Although no two octaves or even semitones are exactly the same width, they are consistently wide by an amount that grows wider as the inharmonicity rises. Comparison with pianos tuned aurally shows that fine piano tuners have been solving this equation subconsciously for centuries.
Timing in skilled piano performance
Authors: Palmer Caroline
Published: October 2005

Skilled music performance is characterized by expressive variations that communicate the performer's interpretations of structural content to a listener. Four experiments are described that address the procedures that pianists use to govern the assignment of structural interpretation to timing variations. Six piano performances of the same music were recorded on a computer-monitored acoustic piano. Three timing methods were measured in each performance; chord asynchronies, rubato patterns, and overlaps (legato/staccato patterns). Each pattern corresponded to the pianists' notated interpretations of musical structure. Experiment 2 investigated the development of the timing methods during learning. Each pianist's successive performances of an unfamiliar musical excerpt demonstrated the methods: Students' performances showed an increase in each method, while experts' performances stayed constant (with more of each method). In experiment 3, each pianist performed different interpretations of the same music. The same methods (applied in different amounts) were used in each performance, and increased in exaggerated performances of the same structural interpretation. These results support a mapping of musical intentions to performance timing through a set of procedures shared by many pianists. [Supported by NSF, MIT Media Laboratory and Psychology Department, Cornell University.]
On ear canal measurement techniques applied to hearing development
Authors: Keefe Douglas H. , Ling Robert
Published: October 2005

Few data exist on the functional development of the human external and middle ear, yet constraints imposed by these structures limit the sound power transmitted to the cochlea. One measure of hearing development is the middle ear reflectance, the fraction of incident sound power reflected at the eardrum. Single and double microphone techniques measure the impedance at the tip of an assembly snugly inserted into the ear canal. This impedance is of limited usefulness, since it depends not only upon the middle ear reflectance, but also upon insertion depth, variations in cross-sectional ear canal area, and ear canal curvature. A method has been constructed to assess the joint influence of the ear canal area function and curvature with a spatial resolution along the ear canal of 4 mm (cT/2, for phase velocity c and sample period T). The reflectance at the assembly tip is transformed to that at an ear canal location just outside the eardrum. The method is also relevant for constructing the output impedance of the ear, as seen by a source on the eardrum. This technique makes no use of invasive probe microphones, has a frequency resolution of 40 Hz, and is well suited for use with infants. Preliminary data on tubes of known geometry will be discussed. [Work supported by NIH.]
Directional dependence of free-field-to-eardum transformations in cats
Authors: Rice J. Jeremy , May Brad , Spirou George A. , Young Eric D.
Published: October 2005

The directional dependence of the transfer function from free-field plane waves to a point near the tympanic membrane was measured in anesthetized domestic cats. A probe tube microphone was placed from a ventral approach, which minimally affects the head and pinae. Acoustic measurements were taken using a quasianechoic method in which an impulsive stimulus was presented and room reflections were rejected using a Kaiser window. The transfer functions are similar to those reported earlier [A.D. Musicant et al., 12th ICA, Toronto (July 1986)]. They can be broken into three distinct frequency ranges: A low-frequency range (< 5 kHz), where interaural level differences vary smoothly with azimuth; a midfrequency range (5–18 kHz), where a prominent spectral notch is observed; and a high-frequency range (> 18 kHz), where the spectrum varies greatly with source location. The frequency of the midfrequency notch is a robust cue for sound source direction; it varies with both azimuth and elevation in a monotonic fashion in the frontal field. Source direction is uniquely determined by combining the midfrequency notch cue from both ears. These results suggest that simple consideration of interaural level differences may not be sufficient for the study of sound localization at high frequencies. [Work supported by Grant No. NS12524 from NINCDS/NIDCD.]
Stimulus frequency otoacoustic emissions: Evidence for multiple sources in the cochlea
Authors: Prieve Beth A. , Abbas Paul J.
Published: October 2005

Stimulus frequency otoacoustic emissions (SFE) were measured in humans by recording the total sound-pressure level in the ear canal upon stimulation with continuous pure-tone stimuli across a wide frequency range. SFE are typically not equal in magnitude as a function of frequency. There are frequencies at which large magnitude emissions exist bounded by frequencies at which smaller magnitude emissions exist. SFE can be masked by simultaneous presentation of a second pure tone and the masking functions demonstrate strong frequency dependence. These tuning properties were measured with probes at frequencies evoking large magnitude and those evoking the surrounding smaller magnitude emissions. For each tuning curve, the trip is higher in frequency than that of the probe. As probe frequency is increased, the tip frequency also increases, although not always proportionally. Assuming that the tip of the tuning curve is indicative of a place on the basilar membrane, the data are consistent with a model in which otoacoustic emissions are generated at more than one place in the cochlea.
Effect of contralateral acoustic stimulation on 2f1−f2 acoustic distortion in human ears
Authors: Tough Kenneth R. , Kunov H.
Published: October 2005

The normal human cochlea is known to exhibit acoustic nonlinearity, observed most easily as a 2f1−f2 distortion product tone in response to two tonal stimuli. This distortion product is physiologically vulnerable, and can be influenced in animals by electrical stimulation of the cochlear efferent nerves. The function of the efferent cochlear innervation is poorly understood but currently revived theory suggests a feedback system may exist between the opposite cochlea, influencing cochlear micromechanics through the outer hair cells [D. O. Kim, Hear. Res. 22, 105–114 (1986)]. The influence of a contralateral acoustic stimulus on cochlear nonlinearity was studied in human subjects through the changes observed in the 2f1−f2 distortion product. The influence of interaural acoustic transmission of the stimulus was controlled by using constant SPL stimuli on subjects with varying degrees of sensorineural hearing loss in the stimulated (contralateral) ear. Results indicate a slight suppression in distortion product with no significant frequency tuning. Strong correlation with middle ear reflex threholds and lack of correlation with sensation level indicate the suppression is not caused by a cochlea-to-cochlea neural mechanism, and is likely caused by the middle ear reflex.
Detection of modulation in pulse trains by patients and cochlear implants
Authors: Shannon Robert V.
Published: October 2005

Detection of amplitude and pulse-width modulation was measured in patients with the Symbion and Nucleus cochlear implants as a function of modulation frequency. The resulting temporal modulation transfer functions (TMTFs) are similar to those of normally hearing listeners [N. F. Viemeister, J. Acoust. Soc. Am. 66, 1364–1380 (1979)]. Modulation detection functions are basically low pass, with best sensitivity to modulation frequencies of 20–100 Hz and decreasing sensitivity for modulation frequencies above 100 Hz. Modulation detection performance is similar whether the carrier is an analog sinusoidal stimulus or a biphasic pulse train. These results suggest that envelope detection mechanisms are intact in these implanted patients, even though their cochleae are not functioning and the pattern of activation in their auditory nerves are quite different from any normal acoustic pattern of activity. [Work supported by NIH NS24754.]
A negative correlation between endocochlear potential and endolymph potassium concentration
Authors: Salt Alec N. , Thalmann Ruediger , DeMott John
Published: October 2005

It is widely accepted that the endocochlear potential (EP) arises from a secretion of K+ into endolymph by stria vascularis, although, as yet, there is no consensus concerning that cellular basis of this process. Studies in which changes in EP and endolymph potassium (Ke) were recorded during anoxia or treatment with transport inhibitors (e.g., ouabain) have shown that a decline of Ke is associated with the suppression of EP. On the basis of such experiments, it would be presumed that Ke would tend to be positively correlated with the magnitude of EP. On the contrary, a number of procedures have been found in which a decrease of Ke is associated with an increase of EP. Perilymphatic perfusion of solution containing 20 mM K+ caused a transient increase of EP (by up to 10 mV) followed by a decline. During this period, Ke recorded by ion-selective microelectrodes typically showed a decrease, followed by an increase. Similarly, iontophoretic injection of Ca++ into endolymph produced an EP decrease that was mirrored by a Ke increase. These findings cannot be explained by changes in K+ transport and/or K+ permeability alone, but are more likely accounted for by changes in anion permeability. [Work supported by NIH Program Grant No. P01 NS24372.]
Global brain asymmetries in regional cerebral blood flow (rCBF) observed during resting conditions with positron emission tomography (PET): Establishing a baseline for experiments on brain asymmetries and complex sounds in the CNS Project
Authors: Lauter Judith L. , Plante Elena
Published: October 2005

During 1981–1985, the first author and colleagues at the Mallinckrodt Institute of Radiology at Washington University in St. Louis collected a series of 29 PET-scan studies of the brains of 16 normal young adult subjects using the PETT VI and intravenous oxygen-15 to test each subject in multiple 40-s scans, comparing rCBF topography during session-initial and session-final control scans, and under a variety of auditory stimulation conditions. Global hemispheric rCBF in all control scans are currently being measured in this library. Results will be presented for work to date, detailing between- and within-subject comparisons, including patterns to within- and between-session replications. These measurements will provide a baseline for the Coordinated Noninvasive Studies (CNS) Project, in which subjects first examined behaviorally for processing asymmetries (e.g., ear advantages), are then tested with PET to determine the degree of correlation between behavioral and physiological asymmetries. [Work supported by AFOSR.]
Efficient computation of ideal starting fields for parabolic equation models
Authors: Robinson E. Richard , Wood David H.
Published: October 2005

When the Helmholtz equation is replaced by the related parabolic equation, the resulting gain is the relative numerical ease of solving the parabolic equation using a marching type algorithm. However. there is still the problem of providing the initial data—or the starting field for the PE model. Although it is well known that the normal mode starter is the correct initial data, it is not widely used because of the expense involved in the computation. In the present approach, however, the idea is exploited that it is not necessary to compute the normal modes individually to obtain the correct starting field. If the function represented by a weighted sum of the normal modes is considered, then it is found that the correct starting field can be obtained by computing the −1/4 power of the matrix generated from the FFT of the index of refraction. This result is derived and some example starting fields are presented compared to starters computed or approximated in other ways. Further, the effects on PE model outputs using the various starters are demonstrated.
The use of acoustical levitation to study the coalescence of oil drops in water
Authors: Gardner Edward , Apfel Robert
Published: October 2005

The behavior of emulsions composed of immiscible liquids has been the object of many theoretical and experimental studies [for review, see Chen et al., AIChE J. 30, 622–630 (1984)]. The coalescence of a drop separated by a film from its homophase has been studied to explain the stability of emulsions; there have not been experiments, however, on free drops contacting other free drops over long periods of time due to the difficulty encountered in containing the drops. Acoustical radiation pressure provides a means of controlling free fluid drops and was considered for application to the study of coalescence. Hexane drops were trapped by a 45-kHz standing wave in a resonant water column. The time two drops remained in contact before coalescing was measured for both pure and surfactant stabilized systems. This time was then compared to theoretical predictions and nonacoustical coalescence experiments. [Work supported by the Heyl Foundation.]
Applications of higher-order parabolic equations
Authors: Collins Michael D.
Published: October 2005

The parabolic equation (PE) model is very useful for many range-dependent acoustic calculations. However, the PE solution breaks down for propagation at large angles, out to long ranges, and in domains in which sound-speed variations are relatively large. This problem was reduced with the introduction of the wide-angle PE of Claerbout, which is based on a rational linear Padé approximation. Generalizing this approach to a sum of rational linear terms [Bamberger et al., SIAM J. Appl. Math. 48, 129–154 (1988)] leads to a higher-order PE that is easy to solve numerically. Calculations will be presented to demonstrate that this higher-order PE accurately handles problems involving very wide angles of propagation and large differences in sound speed including elastic wave propagation involving a superposition of both shear and compresisonal waves.
Spectral decomposition of parabolic equation fields
Authors: Gilbert Kenneth E. , Di Xiao , Huang Dehua
Published: October 2005

The parabolic equation (PE) method has an advantage over normal-mode and fast-field program methods because it can easily handle a broad class of range-dependent problems. Normal-mode and fast field program methods, however, do provide useful information on the horizontal wavenumber spectrum, while the PE method gives only the total field. In some situations, such as upslope propagation, a spectral decomposition of the PE field into horizontal wavenumber components is a valuable tool for analyzing the acoustic field. This paper shows that for a PE field p(r,z), the spectral decomposition φ(κ,r,z) can be obtained by solving a one-dimensional elliptic equation. The derivation of the decomposition equation is given along with a numerical method for solving it. Numerical examples are given for several typical PE fields.
A self-consistent theory of wave propagation and scattering through weakly inhomogeneous media
Authors: Tang Dajun , Frisk George V.
Published: October 2005

A unified perturbation approach to wave propagation and scattering in weakly inhomogeneous media is presented. By separating the total wave field into an averaged coherent propagation part and a random scattering part, a set of coupled wave equations is found. The problem of a wave propagating in a random medium is changed to a problem of a pair of coupled waves propagating in a deterministic medium with randomly distributed sources. This method not only improves upon the conventional Born approximation for the scattered field, but also gives the attenuation behavior of the coherent propagating field related to the statistics of the random media. Examples of underwater acoustic waves in an inhomogeneous water column and an inhomogeneous bottom are given.
The use of multipath time-delay estimation for source localization with passive broadband sonar systems
Authors: Bilazarian Peter , Pistacchio David J.
Published: October 2005

The employment of multipath time-delay estimation for acoustic source localization with passive autocorrelation and cross-correlation systems is examined. Important differences in multipath time-delay estimation with wideband and narrower band systems are delineated. Several algorithms are presented that convert multipath time-delay estimates into localization quantities, such as source depth or range. Some algorithms presume an isospeed medium, while another employs a procedure using the generic sonar model (GSM) and is applicable to a nonisospeed medium. Examples from a variety of multipath environments are provided that demonstrate consistent improvement in localization performance with the nonisospeed technique over the isospeed algorithms. Also, dramatic improvements are reported at ranges that exhibit a fairly complicated multipath structure. A theoretical comparison of the performance differences as a function of signal-to-noise ratio between a wavefront curvature ranging system and a multipath ranging system is provided. Finally, advantages of combining localization information obtained from wavefront curvature systems and systems which employ multipath time-delay estimation are discussed.
Optimization of placement of piezoelectric elements for the active control of plate vibrations
Authors: Bayer Janice I. , Varadan Vasundara V. , Varadan Vijay K.
Published: October 2005

Active vibration control of structures using piezoelectric sensors and actuators is explored. Finite element analysis providing theoretical predictions of the amplitudes of vibration of each of a mesh of nodes distributed over a plate is described. Statistical analysis of the predicted nodal amplitudes furnishes an optimized scheme for the placement of piezoelectric sensors and actuators. Said scheme provides for the minimum number of sensors and actuators needed to control the important vibration. Generalization of this algorithm to the control of other types of structures is discussed.
Experiments on optimization of active control on a three-dimensional acoustic source
Authors: Giordano Jeffrey A. , Cunefare Kenneth A. , Koopmann Gary
Published: October 2005

In this experiment, a box-shaped, acoustic radiator has top and bottom plates that are arbitrarily driven at their structural modes. The sides of the box consist of six loudspeakers that are used as active sources. An acoustic boundary element program is used as the basis for the active control strategy. The program, which allows active sources to be modeled at any position on the acoustic radiator, provides the magnitude and phase at which to drive the active sources to minimize the radiated power for a prescribed frequency and normal velocity distribution on the plates. The plate velocity profiles were determined via experimental modal analysis. The radiated power measurements, which were performed in a calibrated reverberation chamber, compared favorably to the theoretical predictions.
SH waves in an inhomogeneous elastic solid
Authors: Kim Hyun S. , Ginsberg J. H.
Published: October 2005

This paper concerns the propagation of SH waves in an inhomogeneous elastic half-space subject to a distributed shear excitation on the free-surface. The density and second-order elastic coefficient are assumed to deviate by small amounts from the average values, where such variations are periodic functions of the coordinate normal to the surface. Integral transform methods are used to solve the first- and second-order equations of motion, which are obtained from striaghtforward perturbation expansion of the displacement. Two cases of spatial distribution of shear excitation on the surface are considered; sinusoidal and Gaussian distribution. When the shear excitation is temporally periodic, it is shown that the periodic inhomogeneity can cause secular solutions. In the sinusoidal distribution case, either the first- or second-order displacement becomes secular if the wavelength of the signal and the periodicity of inhomogeneity and of the spatial distribution satisfy certain relations. In the case of a Gaussian distribution, it is shown that the second-order displacement becomes secular when the wavelength is twice the periodicity of inhomogeneity. [Work supported by NSF.]
Amplification of noise from liquid jets by entrained gas bubbles
Authors: Ribner H. S.
Published: October 2005

This study reexamines turbulence-driven pulsations of gas bubbles in submerged liquid jets. The expectation of large amplifications—as much as 106—of the jet noise under restricted conditions is confirmed. A macroscopic view via the dilatation theory of jet noise and a microscopic view examining individual bubble pulsations both predict sound power amplification equals (liquid sound speed/mixture sound speed). This follows also from the classical treatment of Crighton and Ffowcs Williams (1969). They related bubble monopole pulsations to Lighthill's jet noise quadrupoles in terms of scaling laws. Herein the bubble pulsations are related to those of local liquid monopoles by a direct amplification factor. This factor is quantitative rather than order-of-magnitude: It provides further insight into the properties of the bubbly jet noise. Strong inward refraction is expected when the bubbles are confined to the jet, leading to a focused axial lobe of enhanced emission. Both studies postulate a stable bubble population, but, in real flows, bubble breakup and the violent collapse of cavitation are prevalent and even noisier. Criteria for their occurrence are discussed.
Characterization of viscoelastic materials used to control underwater sound
Authors: Reader Wayne T.
Published: October 2005

The control of sound fields within confined regions such as water-filled tanks may require the use of a combination of three types of materials: one designed to absorb waterborne sound, one designed to block the passage of waterborne sound, and one that damps structural vibrations. The most frequently used materials consist of viscoelastic polymers containing voids or gas filled inclusions in volume fractions that are essentially zero for damping materials, are of the order 10% for absorbers, and that may approach 90% for blocking materials. The empirical characterization of these very different materials during their development or prior to their installation is achieved with a variety of apparatus and techniques. Typical forms of these apparatus, the associated principles of operation, the physical properties that are measured, and limitations of the techniques will be reviewed. Described will be procedures for obtaining the most fundamental property of underwater acoustical materials, viz., the complex modulus, the use of water-filled waveguides to determine the reflectivity and transmissivity of small samples at normal incidence, and measurement of the same properties on finite sized panels at oblique angles. Finally, contrary to common wisdom, a procedure is proposed for “scaling” acoustical materials.
Characterization of piezoelectric ceramics for high-power transducers
Authors: Gonnard Paul , Eyraud Lucien
Published: October 2005

The choice of piezoelectric materials for a high-power electromechanical conversion must take into account various factors such as the figure of merit of the material (FOM), the stability of the electromechanical parameters, and the dielectric and mechanical losses. Materials suitable for impact-type igniters must present both a high FOM and a good stability under repetitive shocks. For high-power electromechanical conversion, the FOM of a single piezoelectric bar and of a Langevin-type transducer depends on the ratio of the piezoelectric coefficient d33 over the elastic compliance s33I of the material. Without losses, the limiting factor would be the maximum dynamic stress at a vibration mode. Methods for characterizing the dielectric and mechanical losses under high driving level are given. The electromechanical characteristics and losses of some new compositions are compared with those of standard “hard” materials. An interpretation of the high-level behavior is given taking into account a compensation of the oxidation state of manganese during cooling by a change in the valency of the substitution ions. [Work supported by DCAN.]
Evaluation of the property coefficients of piezoelectric polymers
Authors: Ricketts Donald
Published: October 2005

Analytical models are presented for evaluating the property coefficients of thick-film piezoelectric polymers. In particular, these models facilitate the evaluation of the complex elastic compliance coefficients ŝ1′1′D, ŝ12D, ŝ22D, ŝ33D, and ŝ66D from the measured set of quantities {fm,fl,fn,Al,An}, where fm is the resonance frequency of the test specimen fl<fm<fn and Al and An are the relative amplitudes at the selected frequencies fl and fn. Impact excitation of the test samples, a vibration sensor, and a FFT-based spectrum analyzer are used to measure these quantities. In addition, a model is presented for evaluating the complex electromechanical coupling factor k̂31 from the measured value of the transfer function of the length expander polymer bar with divided electrodes. Experimental results were obtained on PVF2 samples made by Raytheon Research Division, and the analytical models were used to evaluate the property coefficients of these samples. The results of these evaluations for ŝ11D, ŝ1′1′D, ŝ12D, ŝ22D, ŝ33D, ŝ66D, and k̂31 are presented.
Ambient noise in open plan offices
Authors: Moreland J. B.
Published: October 2005

This paper summarizes ambient noise data that were collected in open plan offices over the past 2 years. The approach centered on monitoring the noise level in empty workstations to establish some statistics of the noise that would be auditioned by a person sitting in that workstation during a normal work day. Offices both with and without electronic sound masking were investigated, as were offices with either acoustically hard or acoustically soft screens. It was found that the noise level in an individual workstation increases with the number of people in this office. For the 25 workstations considered in this investigation, the average daily noise level in a workstation ranged from 42.2–58.6 dBA. The noisier workstations usually had both (i) electronic sound masking and (ii) acoustically hard screens, whereas the opposite was usually found for the quieter workstations.
Computer graphics for acoustic simulation and visualization
Authors: Stettner Adam
Published: October 2005

Computer simulation can be used to generate the spatial and temporal data describing acoustical behavior. By using computer graphics to display the multidimensional data, substantially greater amounts of information than conveyed by standard techniques can be communicated to the designer. A methodology is presented for evaluating an acoustical environment using a two phase approach. The first phase entails simulating the time varying spatial distribution of sound energy, using techniques similar to those used in computer graphics to model illumination. These techniques, specifically probabilistic geometric ray tracing and reflection modeling, have been highly refined. By modifying these methods to account for a few basic differences between light and sound, they can be well suited to the simulation of sound propagation. The second phase entails an investigation of techniques of displaying multidimensional data that are useful to the user. These techniques, which include the use of three-dimensional color image generation, animation, and icon representation, are used to visualize acoustical measurements derived from the simulation data. Using these criteria, three variations in the design of a performance hall are evaluated and compared. [Work supported by NSF.]
Standard measurement of sound transmission through suspended ceilings
Authors: Quirt J. D. , Halliwell R. E.
Published: October 2005

Sound transmission through the space above the suspended ceiling commonly limits insulation between offices where interoffice partitions do not extend above the suspended ceiling. This paper presents a detailed comparison of standard test methods for evaluating suspended ceiling performance. A laboratory has been constructed that can readily be converted to satisfy requirements of ISO Standard 140 Part 9, or a corresponding ASTM draft standard, or the Acoustical Manufacturers' Association standard (AMA I-II) from which these descended. Characteristics of the test environment have been studied, and a series of suspended ceiling systems have been tested using all three standard methods. Significant differences and their causes will be discussed.
Transfer function method for measuring characteristic impedance and propagation constant of porous material
Authors: Utsuno Hideo , Tanaka Toshimitsu , Fujikawa Takeshi , Seybert Andrew F.
Published: October 2005

A method for measuring the characteristic impedance and propagation constant of porous materials is described. Measurements were performed based on a surface impedance method that required a set of distinct acoustic impedances derived at the material surface. This requirement is satisfied by arbitrarily changing the air space depth behind the material, and then a new formulation is derived so that a recently developed method of determination, called the transfer function method, can be applied. An appropriate set of air space depths is also discussed. Glasswool and porous aluminum were used to assess the usefulness of the present method. The normal acoustic impedance and normal absorption coefficient of the test materials with arbitrary thicknesses or with an arbitrary air space depth were calculated from the obtained characteristic impedance and propagation constant, then they were compared with the measured values that were obtained directly using the transfer function method. The good agreement achieved suggests that the present method is reliable and effective enough to measure the characteristic impedance and propagation constant over a broadband frequency range.
Efficient real-time musical spectrum analyzer using DSP chip
Authors: McGee William F.
Published: October 2005

A 72-note transcriber for polyphonic music has been realized. A Texas Instruments TMS320C25 digital signal processor operating with a 40-MHz clock (100-ns instruction times) has been programmed to provide a musical spectrum analyzer. The analyzer is a bank of 72 filters, tuned to the frequencies of western music. Each filter has a transfer function of unity at its center frequency and a zero at the 71 other frequencies. Due to the design, only 14 instructions per filter per sample are needed. Logarithmic response of each filter is computed at a slower rate, once every 72 samples. Response times appear adequate to permit transcription of polyphonic music. Postprocessing to remove weaker notes a semitone away is found to improve the transcription capabilities, whereas removing partials does not appear to offer as much improvement. The transcriber is tested by passing the output to a MIDI synthesizer. Synthetic music is reasonably accurate, other music is usually recognizable; further postprocessing will improve performance. [Work supported by BNR and NSERC.]
Computer simulation of the guitar, work in progress
Authors: Zintel Harold A.
Published: October 2005

The guitar without strings is modeled by the displacement response of the bridge and the pressure response at an observer location due to an impulse forcing function at the bridge. The model thus entails nine unique impulse response functions, six for combinations of impulse directions and displacement responses and three for the observer location pressure due to each direction of the impulse direction. These nine impulse responses are obtained experimentally. A finite difference approach is used to model a string and its interaction with the instrument. The observer pressure levels predicted by the program are plotted as a waterfall spectrum and also sent to headphones by way of a D/A conversion. By conducting modal analysis of the guitar, the effect of modifications to the structure of the instrument can be estimated. Further, analyzing the new modal parameters using an acoustic boundary element method (CHI), the impulse pressure response can be estimated. The final result, when the project is complete, is a tool that can be used to predict the sound of a particular instrument after structural modifications.
Statistical data modeling approach for determining the acoustic impedance of musical instruments
Authors: Lemay Gerald J.
Published: October 2005

Recent theoretical models [M. E. McIntyre et al., J. Acoust. Soc. Am. 74, 1325–1345 (1983)] for the oscillation mechanism of musical instruments have utilized an analytic closed-form relationship between the Green's function g(t), the reflection function r(t), and the acoustic impedance Z0 (which may also be time varying). Given two of the three quantities {g(t), r(t), Z0}, the method used to find the third function usually involves the discrete Fourier transform. This paper presents an alternate approach to the problem of estimating Z0 from measurements of g(t) and r(t). Statistical data modeling in the context of digital filter design provides a solution that does not require the computation of a discrete Fourier transform. It is shown that the acoustic impedance is the impulse response of the cascade of two digital filters whose coefficients minimize the fitting error between an (M,N)th order model and the observed sequences.
Electroelastic interactions, biasing states, and precision crystal resonators
Authors: Tiersten H. F.
Published: October 2005

In the interaction of the quasistatic electric field with deformable insulators, the condition of rotational invariance causes a combination of the electric field and the deformation gradients to occur in the constitutive equations along with the finite strain. Since the resulting system is intrinsically nonlinear, the linear dynamic equations are more general than those of linear piezoelectricity when a bias is present and reduce to them only in the absence of a bias. Even in the simplest case of stress-free thermal deformation, which is just about always present, the more general equations arise when the fixed reference coordinates at the reference temperature are employed. The advantage of the use of reference coordinates, which cannot be employed within the usual linear theory, in the accurate calculation of the temperature sensitivity of high precision contoured quartz resonators is shown. In the treatment, the equation for the perturbation in eigenfrequency of the piezoelectric solution due to a bias, which is obtained from the more general linear equations, is employed. However, both the biasing state and the vibrational solution are obtained by solving systems of unbiased linear equations. The change in frequency resulting from any bias may readily be calculated from the perturbation equation when the linear piezoelectric solution and biasing state are known. The importance of the phenomenon of energy trapping in crystal resonators is discussed and means of controlling it are noted.
Noise control in microelectronics clean rooms
Authors: Gordon Colin G. , Yazdanniyaz Amir M.
Published: October 2005

Modern clean rooms of the sort used by the microelectronics industry may entail 600 air changes per hour. They pose, therefore, unique noise control problems. These problems are exacerbated by the fact that conventional acoustically absorbent materials cannot be used within the clean room. In this paper, some typical sound data that have been measured in clean rooms are presented. Also discussed are the noise criteria that are desirable for personnel working within the space and for sound-sensitive equipment that may occupy the space. Some practical ideas for noise control are suggested.
Physiologic effects of environmental noise and talking in coronary care patients
Authors: Baker Carol F.
Published: October 2005

The purpose of the study was to describe changes in heart rate and blood pressure in patients with acute myocardial disease when exposed to noise and talking in the environment. A convenience sample of ten adult patients admitted to an 18-bed university hospital CCU were selected as subjects. Private rooms separated patients from an open nurses' station. Sound-pressure level and content of sounds were measured with a Bruel & Kjaer type 2230 sound level meter; the microphone was placed above the head of the bed. Heart rate and ECG from the bedside monitor were recorded simultaneously with dBA and sound on a TEAC R-61 physiologic tape recorder and later printed onto a 2600S Gould chart recorder. Blood pressure was measured every 5 min with a Dinamap. Data collection occurred during four 45-min periods on two consecutive days. Mean sound-pressure level of noise sources were: toilet flush-76 dBA, alarms-66 dBA, talking inside the room-65 dBA, and ambient-49 dBA. Repeated measures ANOVAs compared noise sources, content of conversation, and roles of people with changes in decibel, heart rate, and blood pressure. Short bursts of noise showed the greatest mean change in maximum dBA, followed by talking of nurses or doctors inside the room. Heart rate changes were greater when family talked. Mean arterial pressure was higher during talking and background noise. [Work supported by a University Seed Grant.]
Efficiency of absorbent layers on barrier
Authors: L'Espérance André
Published: October 2005

This paper presents a method for calculating the insertion loss of barriers having the source side, the receiver side, or both sides covered with an absorbent material. In this method, the approximate solutions for diffraction over an absorbent wedge proposed by Koers is combined with a classical model of sound propagation over an impedance ground. Theoretical and experimental results are compared for various geometrical configurations and barrier surface conditions and confirm the accuracy of the method proposed. This study has enabled one to discover that it is more efficient to place the absorbent covering on the surface of the barrier associated with the most important angles of diffraction (source top edge and/or receiver top edges). When these angles are about the same on both sides of the barrier, an absorbent covering will reduce the diffracted field, no matter if it is placed on the source side or on the receiver side. These results explained various conclusions found in literature about the usefulness of absorbent barriers compared to hard barriers.
Acoustic absorption in high-temperature gas mixtures of atmospheric constituents
Authors: George Wallace
Published: October 2005

Experimental data on acoustic absorption at high temperatures (up to 1000 K) due to vibrational molecular relaxation are presented for gas mixtures of O2, N2, CO2, and H2O. These absorption tests represent some of the first acoustical measurements in gas mixtures at these elevated temperatures. These data are compared with the predicted results of the matrix formalism for sound absorption in multicomponent gas mixtures, due to molecular relaxation. This formalism, which is based on irreversible thermodynamics, was utilized by Bauer, Bass, and others. The literature was examined to determine the temperature dependence of the various empirically derived energy transfer rates required by this model. Some of the rates were adjusted to correspond with the current data. This means that the empirical rate constants are adjusted based on high-temperature acoustical tests, rather than on less reliable shock tube data.
Extended Huygens-Kirchhoff method for predicting transient sound propagation through inhomogeneous moving media
Authors: Kouzoupis Spiro , Pierce Allan D.
Published: October 2005

The linear acoustics equations for when the ambient medium has inhomogeneous flow yield an integral corollary analogous to that originally derived by Helmholtz for the reduced wave equation and by Kirchhoff for the wave equation. Such a corollary involves a Green's function for the ambient medium that is here approximated using the eikonal approximation following the technique of Sommerfeld and Runge. The corollary enables one to predict transient waveforms at distant points from information prescribed over a surface and improves upon ordinary geometrical acoustics in that it can account for the presence of caustics in the intervening space. Huygens' principle is realized by this corollary and geometrical acoustics and parabolic equation approximations arise as limiting cases. Numerical examples are given for some simple cases of flows and the use of the overall technique to explore sonic boom propagation in the turbulent atmosphere is outlined. Although the Green's function is approximate, the relation is a good approximate technique for advancing the overall field over moderate distances, without having to explicitly consider the field at intermediate points. [Work supported by NASA-LRC and by the William E. Leonhard endowment to Pennsylvania State University.]
Laser-Doppler vibrometry measurements of acoustic-to-seismic coupling and geophone-ground coupling ratios
Authors: Arnott W. Pat , Sabatier James M.
Published: October 2005

The surface of the ground is an air-filled porous material because of weathering and vegetation. Typically, soils are porous to a depth of several feet. An airborne sound wave can couple into the ground as a pore fluid wave. The pore fluid wave is attenuated through viscous drag at the pore walls; hence, energy can be coupled into the soil matrix as seismic motion [J. M. Sabatier et al., J. Acoust. Soc. Am. 79, 1345–1352 (1986)]. This mechanism gives a coupling ten times that which would be expected for momentum transfer from the fluid air to the solid soil. In the past, ground velocity was measured using geophones. A modified off-the-shelf laser-Doppler vibrometer (LDV) is presently being used for ground velocity measurements. The measurements are difficult because high atmospheric sound-pressure levels (80–90 dB) are necessary for good signal-to-noise in the acoustic-to-seismic coupling ratio measurements; the LDV also couples with the sound field. Good agreement has been reported among geophone and LDV measurements of vertical ground velocity for an impulsive atmospheric sound source and adequate agreement for a cw sound source in the frequency range 100–500 Hz. Use of the LDV for ground-geophone coupling measurements, also pertinent in seismology, will be discussed. [Work supported by ONR.]
Surface waves above porous ground surfaces
Authors: Daigle G. A.
Published: October 2005

In atmospheric acoustics, the subject of surface waves has been an area of discussion for many years. Theory for spherical wave propagation above an impedance plane describes the reflected field as a branch line integral (ground wave) with the possibility of a contribution from a pole. The contribution from the pole possesses the standard properties for a surface wave. Ground waves exist because curved wave fronts strike different parts of the surface at different angles of incidence and because the reflection coefficient is also a function of angle of incidence. Surface waves exist when the surface is sufficiently porous, relative to its acoustical resistance, that it can influence the airborne particle velocity near the surface and reduce the phase velocity of sound waves in air at the surface. This traps some of the sound energy in the air, regardless of the shape of the incident sound field, to remain near the surface as it propagates. Above porous grounds, the existence of surface waves has eluded direct experimental confirmation and indirect evidence for its existence has appeared contradictory. Experiments made here several years ago, but unreported, will be described and discussed in the light of some recent theoretical work. Further experiments are also planned.
The effect of number of components and component spacing on the ability to detect a delayed component embedded in a diotic complex
Authors: Stellmack M. A. , Dye R. H. , Jakubczak S. V.
Published: October 2005

The purpose of this study was to understand the processes that produce interference when observers attempt to lateralize a target component in the presence of other components. To this end, threshold interaural differences of time (ΔIDTs) were measured for 753-Hz tones presented against a diotic background consisting of 2, 4, 6, or 8 additional components. The frequency spacing (Δf) of the components was 10, 25, 50, 100, or 200 Hz. A modified same-different task was employed in which a diotic 753-Hz tone was presented followed by either a diotic n-component complex or a complex containing a delayed (to the right channel) 753-Hz component. Stimuli were 200 ms in duration with 10-ms rise/decay times, with each component presented at 55 dB SPL. The largest thresholds were obtained when Δf's were 25 or 50 Hz and the number of components in the background was large. Interestingly, thresholds fell as the frequency spacing was narrowed from 50 or 25 Hz to 10 Hz. In all cases, the obtained thresholds are larger than those obtained with a 753-Hz tone presented in isolation. The results are explained in terms of binaural processing that is spectrally synthetic for moderate to wide frequency separations and spectrally analytic at small frequency separations.