Journal of the Acoustical Society of America
1520-8524
0001-4966
Mỹ
Cơ quản chủ quản: ACOUSTICAL SOC AMER AMER INST PHYSICS , Acoustical Society of America
Lĩnh vực:
Acoustics and UltrasonicsArts and Humanities (miscellaneous)
Các bài báo tiêu biểu
Computer-Controlled PCM System for Investigation of Dichotic Speech Perception To facilitate study of dichotic speech perception, a computer-controlled PCM system has been devised for preparation of dichotic tests from natural speech. A test is a series of paired utterances, presented one at each ear, simultaneously or with interaural delay. In compiling a test, each of several tape-recorded utterances is digitized at a 8-kHz rate (10 bits/sample) and read into computer memory. The stored utterance is played back, and its waveform simultaneously displayed on a storage oscilloscope. The experimenter defines the exact beginning and end of the utterance and adjusts its intensity. The edited utterance is saved with others on a disk file. According to the experimenter's test order, the two utterances of each pair are retrieved, converted with a specified relative delay, and recorded each on a separate audio tape track. The system is a useful tool for investigation of lateralization and fusion in speech perception. [Support from the Office of Naval Research and the National Institute of Health (NICHD) is acknowledged.]
Tập 46 Số 1A_Supplement - Trang 115-115 - 1969
Lower Limits of Auditory Periodicity Analysis Tests utilizing an iterated, uninterrupted section of random noise disclose that periodicity (iteration) is easily detectable to about 1 cps and detectable with especial difficulty below 0.5 cps. Frequencies bounding regions of perception of pitch, motorboating, and whooshing are specified as 19, 4, and 1 cps, respectively.
Tập 35 Số 4 - Trang 610-610 - 1963
Experiments on the Four-Eared Man Subjects were required to listen to messages consisting of 1, 2, 3, or 4 letters of the alphabet over each of 1, 2, 3, or 4 channels. It was found that increasing the number of channels above 2 had a markedly deleterious effect upon recall of the messages, 2 letters over each of four channels being less well recalled than 4 letters over each of two channels. In a second experiment, it was found that, providing only one channel was required in recall, and this one was indicated by a light immediately after the stimuli had been presented, then the decrement could be largely offset and the total number of signals stored held constant at about 8 regardless of how many channels were used. However, if the letters had to be recalled in exactly the correct order in which they arrived, performance dropped to almost zero. The results are discussed in terms of the channel capacity of the nervous system and in relation to corresponding findings in other sense modalities.
Tập 38 Số 2 - Trang 196-201 - 1965
Electromechanical properties of (Pb, Ln) (Ti, Mn) O3 ceramics (Ln = rare earths) Electromechanical properties of PbTiO3 ceramics modified by the partial substitution of rare earths for Pb, particularly, (Pb, Ln) (Ti, Mn) O3 (Ln = La, Pr, Nd, Sm, or Gd) ceramics, are examined. It is found that the Sm substitution for Pb dramatically increases the ratio of electromechanical coupling factor of the thickness dilatational mode to that of the planar extensional mode. Extensive studies of the resonant properties of rectangular strip resonators make it clear that the Sm-substituted PbTiO3 ceramics are very useful for high-frequency array transducer applications. It is also shown that the pulse responses of array transducers can be improved using Sm substituted PbTiO3 ceramics instead of the other PbTiO3 ceramics studied here.
Tập 72 Số 4 - Trang 1114-1120 - 1982
Electromechanical Properties of PbTiO3 Ceramics Containing La and Mn 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 ε11T/ε0 230, ε33T/ε0 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 high potential for use in electromechanical devices at high frequency and high temperature.
Tập 50 Số 4A - Trang 1060-1066 - 1971
Speech Privacy in Buildings Obtaining adequate speech privacy in modern buildings is one of the important goals of the architect and consultant. This paper deals with the development of a rating method which takes into account the several factors influencing speech privacy. Our work in this area began with a brief laboratory study. The results indicated that speech privacy is related to speech intelligibility rather than to level. The initial experiments were supplemented with an analysis of about 40 case histories representing about 400 pairs of spaces in different kinds of buildings. There appears to be good correlation between the articulation index of intruding speech sound and the reactions of building occupants.
Tập 34 Số 4 - Trang 475-492 - 1962
New Wall Design for High Transmission Loss or High Damping A typical single wall is characterized by a free flexural wave speed, cB, which increases with ω12. When cB approaches c0 (the speed of sound waves in the surrounding medium) the impedance of the wall to incident sound wave ceases to be mass-like because of the coincidence effect and the transmission loss will be less than that given by mass law. Since cB = (B/M)12(ω)12 for homogeneous walls, the deleterious effects of the coincidence of the flexural wave speed with the phase velocity of sound in the medium can be avoided for homogeneous walls by reducing the ratio of B/M. (B is the dynamic bending stiffness of the wall; M is the mass per unit area of the wall.) Thus the problem of good acoustical performance in homogeneous walls is seen to be in essential conflict with the need for structural rigidity.
A new wall design has been found in which the ratio of the static to the dynamic stiffness can be in excess of 1000:1 and where the stiffness changes from the static to the dynamic value in such a way that the acoustical behavior is nearly that of a perfectly limp wall. If desired, the loss tangent of the wall can be made large and nearly constant over a wide range of frequencies.
Tập 31 Số 6 - Trang 739-748 - 1959
A model for active elements in cochlear biomechanics A linear, mathematical model of cochlear biomechanics is presented in this paper. In this model, active elements are essential for simulating the high sensitivity and sharp tuning characteristic of the mammalian cochlea. The active elements are intended to represent the motile action of outer hair cells; they are postulated to be mechanical force generators that are powered by electrochemical energy of the cochlear endolymph, controlled by the bending of outer hair cell stereocilia, and bidirectionally coupled to cochlear partition mechanics. The active elements are spatially distributed and function collectively as a cochlear amplifier. Excessive gain in the cochlear amplifier causes spontaneous oscillations and thereby generates spontaneous otoacoustic emissions.
Tập 79 Số 5 - Trang 1472-1480 - 1986
Acoustic ray tracing in moving inhomogeneous fluids Null geodesics of the metric tensor formed from the coefficients of the second-order terms in the partial differential equation for sound are interpreted as the space-time path histories of sound pulses in a geometric ray trace theory for sound propagation in moving inhomogeneous inviscid fluids.
Tập 53 Số 6 - Trang 1700-1704 - 1973
Modified impulse method for the measurement of the frequency response of acoustic filters to weakly nonlinear transient excitations In this paper, a modified impulse method is proposed which allows the determination of the influence of the excitation characteristics on acoustic filter performance. Issues related to nonlinear propagation, namely wave steepening and wave interactions, have been addressed in an approximate way, validated against one-dimensional unsteady nonlinear flow calculations. The results obtained for expansion chambers and extended duct resonators indicate that the amplitude threshold for the onset of nonlinear phenomena is related to the geometry considered.
Tập 107 Số 2 - Trang 731-738 - 2000