Showing papers in "Journal of the Acoustical Society of America in 1971"

Transformed Up‐Down Methods in Psychoacoustics

Abstract: During the past decade a number of variations in the simple up‐down procedure have been used in psychoacoustic testing. A broad class of these methods is described with due emphasis on the related problems of parameter estimation and the efficient placing of observations. The advantages of up‐down methods are many, including simplicity, high efficiency, robustness, small‐sample reliability, and relative freedom from restrictive assumptions. Several applications of these procedures in psychoacoustics are described, including examples where conventional techniques are inapplicable.

Observations of the Vibration of the Basilar Membrane in Squirrel Monkeys using the Mössbauer Technique

Abstract: The amplitude and the phase of vibration of the basilar membrane and the bony limbus of the cochlea were measured in living squirrel monkeys using the Mossbauer technique. In the middle ear, the vibration of the malleus (and occasionally the incus) was measured. The Mossbauer technique makes possible the measurement of very small velocities, e.g., 0.2 mm/sec. This sensitivity permits measurement of the motion of the malleus at sound‐pressure levels (SPLs) of 90 to 110 dB and measurement of the motion of the basilar membrane at 70 to 120 dB SPL, depending on the frequency. The basilar membrane vibrates nonlinearly for frequencies which produce the largest deflections at the spot on the basilar membrane under observation. The ratio of the displacement of the basilar membrane to that of the malleus was observed to have the following characteristics: (1) As the frequency is increased from a low value, its amplitude increases at 6 dB/oct until just below the maximum ratio where the slope increases to about 24 dB/oct; (2) the maximum ratio was about 24 dB for the SPLs used; (3) for frequencies above that producing the maximum ratio, the drop‐off rate was approximately 100 dB/oct; (4) the amplitude ratio did not drop off indefinitely but tended to level off; (5) the motion of the basilar membrane differs from the motion of the malleus by 90° at very low frequencies; (6) for frequencies below that producing the maximum ratio, the phase differences between the motion of the basilar membrane and that of the malleus is a linear function of frequency; (7) near the frequency corresponding to the maximum ratio, the phase difference decreases at a faster rate; and (8) the phase difference approaches a constant value (7π 8π or 9π) for high frequencies. Anatomical constraints allowed only a small portion of the basal turn to be studied (6.5–7.5 kHz produced maximum deflection of the basilar membrane in this region).

Simulation of Multivariate and Multidimensional Random Processes

Abstract: Efficient and practical methods of simulating multivariate and multidimensional processes with specified cross‐spectral density are presented. When the cross‐spectral density matrix of an n‐variate process is specified, its component processes can be simulated as the sum of cosine functions with random frequencies and random phase angles. Typical examples of this type are the simulation, for the purpose of shaker test, of a multivariate process representing six components of the acceleration (due to, for example, a booster engine cutoff) measured at the base of a spacecraft and the simulation of horizontal and vertical components of earthquake acceleration. A homogeneous multidimensional process can also be simulated in terms of the sum of cosine functions with random frequencies and random phase angles. Examples of multidimensional processes considered here include the horizontal component f0(t,x) of the wind velocity perpendicular to the axis (x axis) of a slender structure, the vertical gust velocity field f0(x,y) frozen in space, and the boundary‐layer pressure field f0(x,y,t). Also, a convenient use of the present method of simulation in a class of nonlinear structural vibration analysis is described with a numerical example.

Classification of Russian Vowels Spoken by Different Speakers

Abstract: The problem of speaker normalization is investigated for classifying the Russian vowels. The known methods of normalization of formants F1 and F2 which make their normalized values F1N and F2N invariant to compression or expansion and to parallel shift are mentioned. A new statistical method of normalization is then suggested. All of these methods are compared using an index of normalization quality (η). The result of the comparison shows that the normalization suggested in this letter has the largest index, not only on the average but also for each individual vowel pair. The procedure of classification of the Russian vowels using a self‐normalized formant plot is shown at the end of the letter.

Contour, Interval, and Pitch Recognition in Memory for Melodies

Abstract: Melodic contour (the sequence of ups and downs in a melody, regardless of interval size) expresses those aspects of a melody that are most essential to manipulation of that melody in various musical structures, e.g., folktunes and fugues. This is demonstrated by brief analyses of actual music. Two experiments demonstrate the role of melodic contour recognition in memory for melodies. Experiment 1 (2×3 factorial design) involved short‐term memory with comparison melodies either transposed or not transposed from the key of the standard. Separate groups had the tasks of distinguishing (a) between same and different melodies; (b) between same melodies and ones with only the same contour; and (c) between melodies with the same contour and different ones. The effects of transposition and task and their interaction were significant (p<0.001). Untransposed melodies were recognized by their exact pitches, so that tasks (a) and (b) were equally easy. Contour recognition was more important with transposed melodies, so that task (b) was very difficult, and tasks (a) and (c) were easier. Task (c) was about equally difficult under both conditions. Experiment 2 involved recognition of distorted versions of familiar folktunes having the same length and rhythmic structure. In ascending order of recognizability, these distortions preserved merely the harmonic basis of the melody, the melodic contour, and the contour plus the relative sizes of successive intervals between notes (chi‐square = 50.4, p<0.001).

Cube‐Resonance Method to Determine the Elastic Constants of Solids

Abstract: The Rayleigh‐Ritz method of eigenvalue approximation is used to obtain a solution for the free vibrations of an elastic solid. The resonant frequencies of an isotropic cube, calculated by this method, agree with the frequencies of the Lame modes, for which an exact solution is possible, up to eight significant digits. Experimental measurements of the 13 lowest‐frequency modes of a cube of fused quartz are all within 0.5% of the results computed by using the elastic constants determined by another method. These constants differ from the elastic constants determined directly from the experimental frequencies by less than 0.2% for the shear modulus and by less than 0.003 for the value of Poisson's ratio. The cube‐resonance method of elastic constant determination is also applicable to substances of more general crystallographic symmetry.

Temporal Position of Discharges in Single Auditory Nerve Fibers within the Cycle of a Sine‐Wave Stimulus: Frequency and Intensity Effects

Abstract: Period histograms, which display the distribution of spikes throughout the period of a periodic stimulus, were computed for discharges recorded from single auditory nerve fibers of the squirrel monkey when low‐frequency tones were employed. For frequencies up to about 4 kHz, where phase locking is observed, the average phase angle of the discharges was tracked as frequency was varied in small steps from low to high. To a first approximation, the cumulative shift in average phase angle is a linear function of frequency as would be observed for an ideal delay line. The slopes of these phase‐versus‐frequency lines were found to be related through a power law to the best frequencies of the fibers. Thus, it seems possible to estimate the travel time of a mechanical disturbance between the oval window and any point on the cochlear partition. A more detailed examination revealed that average phase angle is also sensitive to intensity, depending upon the relation of the stimulating frequency to the best frequency. For stimulating frequencies below best frequency, discharges tend to occur progressively later in the cycle as intensity increases. Above best frequency, an opposite tendency often prevails if a change in phase angle occurs. At or near best frequency, little change in average phase angle is noted as intensity varies.

Stimulus Features in Signal Detection

Abstract: Short bursts of computer‐generated Gaussian noise were rated by observers for the presence or absence of a 500‐Hz signal tone burst. A multiple regression analysis found for each observer the linear combination of the energies in narrow bands around the tone frequency that best predicts his total ratings. The estimates of the regression coefficients provide graphs of the “frequency responses” of the observers. Most of the reliable variance in the total ratings was accounted for by the regression analysis in terms of energy in narrow bands. Differences among observers are explained in terms of differential weighting by observers of features labeled “tone presence,” “pitch,” and “loudness.”

Beam Behavior within the Nearfield of a Vibrating Piston

Abstract: A numerical investigation of the nearfield region of a vibrating piston was conducted. While existing literature is not exactly clear about how close to a transducer a regular beam pattern is formed, the results of this investigation show the limits of operation one can expect. From one interpretation of literature, a −3‐dB beam with a minimum spot size equal to the transducer diameter would be expected to form beyond an axial distance z = 3.89 a2/λ. This investigation shows that such a beam forms at z = 0.75 a2/λ and has a minimum spot size equal to one‐quarter the transducer radius. These results are verified for transducers with a/λ's ranging from 1 to 20 and can be extended with confidence to higher a/λ's. Similar results are also obtained for −1.5‐, −4.5‐, −6.0‐, −7.5‐, −9.0‐, −10.5‐, and −12‐dB beams.

Dorsal‐Aspect Target Strength of an Individual Fish

Abstract: Experiments are described in which the dorsal‐aspect target strengths of a number of individual teleostean fishes of eight species were measured at various frequencies. The results of these experiments indicate that the variations of target strength with frequency are different for fishes in two major teleostean groups, the malacopterygians and the acanthopterygians. These results are combined with results from eight other sources and an empirical equation approximating the dorsal‐aspect target strength of an individual fish determined for 0.7⩽L/λ⩽90, where L is the fish length and λ is the incident acoustic wavelength. The combined results are compared to similar results for the maximum side‐aspect target strength of an individual fish, and curves showing the trend of dorsal‐aspect and maximum side‐aspect acoustic cross sections of an individual swimbladder‐bearing fish are presented for all L/λ⩽90.

Airflow and Turbulence Noise for Fricative and Stop Consonants: Static Considerations

Abstract: A number of speech sounds are generated by creating turbulent airflow in the vicinity of a constriction in the vocal tract. The equations relating the airflow through such a constriction, the pressure drop across the constriction, and the dimensions of the constriction are reviewed and are summarized in graphical form. Previous theoretical and experimental data on turbulence noise generation at a constriction or obstruction in a tube are described. These data are consistent with a model that represents a turbulence noise source in the vocal tract as an equivalent sound‐pressure source whose magnitude is proportional to the pressure drop across the constriction or obstruction. The characteristics of the sound radiated from the mouth opening are determined by the source location and radiation characteristics, as well as by the properties of the source. The airflow and acoustic characteristics for various classes of speech sounds produced with turbulence noise at the glottis or at a supraglottal constriction are discussed in the light of these findings.

Factor analysis of tongue shapes.

Abstract: Tracings from x rays were made of the shape of the tongue in nine vowels as spoken by five speakers of General American. The midline of the tongue on each tracing was specified in terms of twelve numbers (two orthogonal measurements for each of six defined points). The resulting 9×5×12 matrix was analyzed by the PARAFAC procedure (Harshman, this meeting). The data indicate the extent to which the midline of the tongue can be described in terms of a small number of factors. The paper will discuss the relation between these factors and the following physiological parameters: (1) jaw opening; (2) forward pull of the posterior genioglossus muscle on the tongue root (and hence raising of the body of the tongue) as opposed to backward pull of the glossopharyngeus muscle; (3) upward and backward pull of the styloglossus muscle; (4) downward pull of the hyoglossus muscle; and (5) actions of the intrinsic muslces that control the bunching of the tongue.

Sweep‐Tone Measurements of Vocal‐Tract Characteristics

Abstract: The vocal tract was excited transcutaneously at a point just above the glottis by an external sweep‐tone signal, in order to measure its transfer characteristics acoustically as continuous frequency functions. An analysis‐by‐synthesis procedure derived reliable data of vowels, in particular of the formant bandwidths, for three male and three female normal subjects. It has been shown for the closed glottis condition that the first formant bandwidths are higher for close vowels (typically 70 Hz for male subjects) than for semi‐open vowels (typically 35 Hz for male subjects). Stationary consonantal articulations including stops, nasals, and nasalized vowels also have been studied, as well as the effect of opening the glottis on the vocal‐tract transfer characteristics. The stop articulations give rise to a first‐formant frequency slightly below 200 Hz. This fact and the high dissipation of the first formant is explained by assuming nonrigidness of the surrounding wall. Characteristics of nasalized vowels and nasal murmurs are also discussed based on the data obtained in this experiment.

Electromechanical Properties of PbTiO3 Ceramics Containing La and Mn

Abstract: A piezoelectric ceramic material having low dielectric constant, high thickness coupling factor, high mechanical quality factor, high stability, and high operating temperature, has been prepared from PbTiO3 incorporated with 2.5 mol% of LaO12 and 1.0 mol% of MnO2. Typical electromechanical constants of this material are as follows: dielectric constant e11T/e0 230, e33T/e0 170; coupling factor k33 0.46, kt 0.46, k15 0.28, kp 0.07, k31 0.04; mechanical quality factor Q 1100, Poisson's ratio σE 0.20. Frequency constants Nt and N3t of the fundamental and third‐harmonic thickness vibrations have temperature coefficients of −1.1 × 10−4°C−1 and −2 × 10−5°C−1, respectively. Aging rates of Nt and N3t, are +0.02% and −0.02%/time decade at 30°C, respectively. The Curie point of this material exists at 470°C, and k33 and kt increase gradually with temperature up to 400°C. This material has grain size of 2–3 μ and bending strength of 2 × 107 kg/m2, and can be polished into very thin plate. The PbTiO3 ceramics have a h...

Behavioral Measurements of Absolute and Frequency‐Difference Thresholds in Guinea Pig

Abstract: Absolute and frequency‐difference thresholds were determined by the conditioned‐suppression technique. The results show that the average frequency range of audibility at +50 dB sound‐pressure level extends from 86 Hz to 46.5 kHz, with a best frequency near 8 kHz. Individual differences in sensitivity are related to body weight and, probably, age. The average frequency‐difference limen is 3.5% from 125 Hz to 42 kHz. Compared to other mammals, the auditory capacities of guinea pig are within one standard deviation of the mammalian mean on each of six dimensions: high‐frequency and low‐frequency cutoff, lowest intensity, best frequency, area of the audible field, and frequency discrimination.

The Time‐Dependent Force and Radiation Impedance on a Piston in a Rigid Infinite Planar Baffle

Abstract: An approach is presented to compute the time‐dependent force acting on a piston in a rigid infinite planar baffle as a result of the specified velocity of the piston. The approach to computing the force is applicable to both sinusoidal and nonsinusoidal velocity pulses and is valid for all piston shapes. The approach, which is based on a Green's‐function solution to the time‐dependent boundary value problem, utilizes a transformation of coordinates to simplify the evaluation of the double surface integrals. An impulse response function is defined such that the time‐dependent force can be obtained by differentiating the convolution of the impulse response and piston velocity time functions. A closed‐form expression for the impulse response of a circular piston is derived and discussed. Numerical results for the impulse response and the forces on large square pistons resulting from sinusoidal piston velocities are then presented and discussed to compare the transient and steady‐state behavior of the forces. Finally, an approach is presented to compute the radiation impedance as a function of normalized frequency from the impulse response data, and the approach is used to obtain the normalized radiation resistance and reactance for square pistons.

Underwater Sounds from the Blue Whale, Balaenoptera musculus

Abstract: Powerful low‐frequency sounds were recorded from blue whales, Balaenoptera musculus, off the Chilean coast. These three‐part sounds lasted about 36.5 sec, and ranged in frequency from 12.5 to 200 Hz. The sounds occurred in a repetitive pattern that was interrupted as the whale came to the surface to breathe. We estimated that these moanings, in a 14‐ to 222‐Hz band, were 188 dB re 1 μN/m2 (= 88 dB re 1 μbar) at 1 m. They are the most powerful sustained utterances known from whales or any other living source. This finding is especially noteworthy because it is doubtful if these animals, the largest ever to inhabit the earth, will survive man's overharvest.

Determination of vocal-tract shape from impulse response at the lips.

Abstract: A method is described for determining the shape of the vocal tract from a measurement of the acoustic impulse response at the lips. Under the assumptions that the wave motion is planar and that the losses are negligible, the method gives the area function uniquely. It is further shown that a one‐point measurement cannot provide any information about losses. A preliminary experiment is described which verifies the feasibility of the method.

Investigation of the Timing of Velar Movements during Speech

Abstract: High‐speed cinefluorographic films were taken of four normal subjects speaking English sentences containing various combinations of nasal consonants (N), consonants (C), and vowels (V) at normal speaking levels and rates of production. Word and syllable boundaries were designed to fall across the sequences in various ways. From frame‐by‐frame tracings, measures of velar movement and velopharyngeal opening were made. Results indicate extensive anticipatory coarticulation of velar movement toward velopharyngeal opening in CVN and CVVN sequences such that velar movement toward opening began during the approach to the initial vowel in all cases and some velopharyngeal opening was observed on all vowels. For NC and NCN sequences, velar movement toward closure for the consonant usually began during the preceding nasal such that some velar closure was observed during all plosive and fricative consonants used. These results directly contradict the hypothesis that a CV‐type syllable is the minimal unit of coarticulation and production. The data are consistent with the predictions of a model which assumes phone‐sized input unit and which incorporates a “look ahead” mechanism whereby an articulatory feature can be systematically anticipated prior to the occurrence of the phone with which that feature is associated.

Voice Spectrograms as a Function of Age, Voice Disguise, and Voice Imitation

Abstract: In order to determine if speech spectrograms can be used to identify human beings, two questions must be studied: (1) does the formant structure of phonemes uttered by a certain speaker change over a long interval of time, and (2) can the formant structure be changed by disguise, or is it even possible to imitate the formant structure of another speaker? Spectrograms of utterances produced by seven speakers and recorded over periods of up to 29 years showed that the frequency position of formants and pitch of voiced sounds shift to lower frequencies with increasing age of test persons. Speech spectrograms of texts spoken in a normal and a disguised voice revealed strong variations in formant structure. Speech spectrograms of utterances of well‐known people have been compared with those of imitators. The imitators succeeded in varying the formant structure and fundamental frequency of their voices, but they were not able to adapt these parameters to match or even be similar to those of imitated persons.

Sonic‐Boom Minimization

Abstract: There have been many attempts to reduce or eliminate the sonic boom For supersonic aircrafts such attempts fall into two categories: (1) aerodynamic minimums and (2) exotic configurations In the first category, changes in entropy and the Bernoulli constant are neglected, and equivalent body shapes required to minimize the overpressure, the shock pressure rise, and the impulse are deduced These results include the beneficial effects of atmospheric stratification In the second category, the effective length of the aircraft is increased by modifying the Bernoulli constant a significant fraction of the flow past the aircraft A figure of merit is introduced which makes it possible to judge the effectiveness of such schemes Finally, the sonic boom reductions that can be achieved by hypersonic flight at high altitudes are summarized

Mechanism of Absorption of Ultrasound in Liver Tissue

Abstract: The dominant part of the acoustic absorption of liver tissue and its components results from macromolecular relaxation processes. The absorption has been investigated over the frequency range 1–10 MHz and the following results have been obtained: (1) About two‐thirds of the total absorption arises at the macromolecular level, with the remainder caused by macroscopic structure. (2) The specific absorption of tissue macromolecules, as expressed in absorption per weight percent, varies considerably from one biopolymer to another. (3) The absorption is related to the structure of the biological macromolecule or its hydration and changes with heat denaturation and pH. (4) A similar frequency dependence results for all materials investigated. This dependence is to be expected if one assumes that the molecular processes of absorption are characterized by a broad spectrum of relaxational time constants and activation energies extending over a range of at least 1:7.

Enhancement of Heat Pulses in Crystals due to Elastic Anisotropy

Abstract: The generation of thermal acoustic waves by a heated metallic film on the surface of a dielectric crystal at low temperatures is discussed. It is shown that even if the waves produced correspond to a uniform distribution of directions of wave vector, there may be a large enhancement of energy flow in some crystallographic directions compared to the average. This effect arises because of elastic anisotropy. Explicit expressions are given for the enhancement expected in the principal directions of cubic crystals.

Residual Potential and Approximate Methods for Three‐Dimensional Fluid‐Structure Interaction Problems

Abstract: A method developed previously for an analysis of the two‐dimensional excitation of an elastic cylindrical shell by a transverse, transient acoustic wave is extended to three‐dimensional applicability. In addition, some fluid‐structure interaction approximations are presented that follow naturally from the rigorous development. Application to finite element analysis of the transient response of submerged structures is discussed.

Discrimination of Temporal Gaps

Abstract: This research investigates the human observer's ability to judge differences in duration without the benefit of such cues as differences in energy and energy spectrum. Three observers compared two silent durations, T and T+ΔT, in a two‐alternative forced‐choice procedure. The value of T ranged from 0.63 to 640 msec. For each T, seven values of ΔT were chosen to cover the range of the psychometric function. The duration and amplitude of noise markers bounding the temporal gaps were varied across three experimental conditions. For silent durations less than 160 msec, the results showed that discrimination depended on the parameters of the marker. For each marker condition, the function relating the Weber fraction and T was non‐monotonic, reaching a local minimum at about 2.5 msec and a local maximum at 10 msec. These results were used to evaluate current theories about the central processing of duration.

Ultrasonic Exposure Thresholds for Changes in Cells and Tissues

Abstract: Biological change consequent on ultrasonic exposure may arise through three distinct modes: thermal, cavitational (including stable bubble), and “other.” The thermal mechanism is quite well defined and predictable. Wide divergencies occur between different authors on values of cavitation thresholds, but these may be due, in part, to differences in criteria used. Our results are reported for dependence of “stable cavitation” on intensity, frequency, pulsing parameters, ambient pressure, and nature of the medium (liquid, gel, or organized tissue). Evidence is reviewed for the existence of, and relevant thresholds for, other mechanisms that are effective in living cells and tissues irradiated by ultrasonic beams.

Helicopter Noise due to Blade‐Vortex Interaction

Abstract: The generation of impulsive sound, commonly called blade slap, due to blade‐vortex interaction for helicopter rotors is discussed. The unsteady lift on the blades is calculated using linear unsteady aerodynamic theory for an oblique gust model of the blade‐vortex interaction. A theoretical model for the radiated sound due to the transient lift fluctuations is presented. Expressions for the directivity, frequency spectrum, transient signal, and total power of the acoustic signal are derived. Typical results are presented and discussed. Calculations of the transient signal are presented in comparison with recent experimental results. The agreement is very good.

Acoustic Force on a Liquid Droplet in an Acoustic Stationary Wave

Abstract: This paper considers the time‐averaged acoustic force exerted on a spherical liquid droplet in an acoustic stationary wave. Experimental and theoretical values are presented for the minimum acoustic pressure amplitudes required to trap small individual droplets of various liquids near the pressure antinodes of a stationary sound field in a cylinder filled with water. The liquids used were paraldehyde, hexane, benzene, toluene, chlorobenzene, and carbon tetrachloride. Droplet radii ranged from 400 to 800 μ, and acoustic‐pressure amplitudes required to trap the droplets ranged from 1 to 15 bars. Calculated and observed values for the acoustic force are in substantial agreement, provided the compressibility of the liquid droplets is considered.

Aural combination tones and auditory masking.

Abstract: In experiments mapping pure‐tone masked audiograms at low to moderate masker intensities, in which the signal is either a pure tone or a narrow band of noise, a notch appears on the high‐frequency side of the masker with a low point at a frequency one critical bandwidth from the masker frequency. The evidence indicates that this notch is caused by the detection, on the lower‐frequency side of the masker, of the cubic combination tones that are produced by the addition of masker and signal. At higher masker intensities, the difference tone may also be involved in accordance with the conclusions of Wegel and Lane [Phys. Rev. 23, 266–285 (1924)]. Similar results are obtained when a very narrow band of noise masks a pure‐tone signal. The implication that the same process that creates combination tones creates combination bands further supports other evidence as to the mechanical nature of combination tones. The immediate further implications that combination bands or tones arising from complex maskers should ...

Head‐Related Two‐Channel Stereophony with Loudspeaker Reproduction

Abstract: Reproducing stereophonic signal pairs with two loudspeakers on the front left and right of a listener yields acoustical crosstalk resulting from sound diffraction at the head. Stereophonic phantom sound sources are therefore heard only between the two loudspeakers. However, signal pairs can be constructed from the original signals generating extremely lateral phantom sources. A filter for this purpose is constructed using concentrated elements (“90° filter”). The complex frequency response of the 90° filter is determined in a listening experiment with narrow‐band noise. Two 90° filters are combined for a two‐channel reproduction system. Signals received by a dummy head with a microphone in each ear are fed to the inputs of the 90° filters. This transmission system was tested for its directional fidelity with many test persons. Localization is nearly ideal for the entire horizontal plane including front‐back discrimination and is partly correct even for the median plane.