Journal of the Acoustical Society of America
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Plate-Edge Admittances The response of a semi-infinite plate bounded by a straight edge and excited harmonically by a stud attached to its edge is presented in terms of an admittance matrix that relates the two in-plane rotatory velocities and the transverse velocity of the stud to the respective forces. The problem is solved by means of the classical theory of thin plates and by assuming a simple stress distribution along the plate edge. Numerical results for stud widths smaller than one-third of the flexural wavelengths and for a value of Poisson's ratio σ=0.3 are given. They are found to relate well to known results for the full infinite plate.
Journal of the Acoustical Society of America - Tập 36 Số 2 - Trang 344-348 - 1964
Most Comfortable Loudness for Pure Tones, Noise, and Speech Most comfortable loudness (MCL) levels for pure tones, broad- and narrow-band noise, and connected speech were studied in three independent experiments using Békésy audiometers and young normal-hearing males and females. Differences in MCL were explored as a function of attenuation rate, sex, frequency of the pure-tone and narrow-band stimuli, interrupted versus continuous pure-tone stimuli, instructional set, session, and a modified Békésy operation which allowed the subject to hold intensity constant over time versus standard Békésy operation. There were no significant sex, set, session, or operation differences. In all three experiments, a 2.5-dB/sec attenuation rate produced higher MCLs than a 1.25-dB/sec rate. In general, a 500-Hz tone or narrow-band noise centered at 500 Hz was tracked at the highest sound-pressure levels (SPLs), while broad-band noise was consistently tracked at the lowest levels. Regardless of frequency or attenuation rate, continuous pure tones were tracked at higher SPLs than interrupted pure-tone stimuli. Although intersubject variability was relatively high, the majority of test-retest differences in each experiment was 10 dB or less. Over-all MCLs in decibels SPL re 0.0002 μbar were 49.3 for speech, 49.4 for noise, and 51.7 for pure tones.
Journal of the Acoustical Society of America - Tập 49 Số 6B - Trang 1805-1813 - 1971
Equivalent Peak Level: A Threshold-Independent Speech-Level Measure Previous research showed that the logarithm of the absolute voltage of a speech waveform is nearly uniformly distributed between same arbitrary threshold and a peak. In the present study, the equivalent peak level (epl) of a speech sample is defined as that peak of a log-uniformly distributed random variable that would have produced the same rms above threshold as was measured from the speech sample. Measurements on 116 speech samples show that if threshold is varied over a range of at least 35 dB on repeated measurements of the same speech sample, the epl varies ±1 dB. Equivalently, if the measuring threshold is held constant, the epl will follow known speech level changes on a decibel-for-decibel basis to within ±1 dB over a 35-dB range. The epl may be measured with any facility having means of obtaining rms-above-threshold.
Journal of the Acoustical Society of America - Tập 44 Số 3 - Trang 695-699 - 1968
Thermoacoustic engines Thermoacoustic engines, or acoustic heat engines, are energy-conversion devices that achieve simplicity and concomitant reliability by use of acoustic technology. Their efficiency can be a substantial fraction of Carnot’s efficiency. In thermoacoustic prime movers, heat flow from a high-temperature source to a low-temperature sink generates acoustic power (which may be converted to electric power using a transducer). In thermoacoustic heat pumps and refrigerators, acoustic power is used to pump heat from a low-temperature source to a high-temperature sink. This review teaches the fundamentals of thermoacoustic engines, by analysis, intuition, and example.
Journal of the Acoustical Society of America - Tập 84 Số 4 - Trang 1145-1180 - 1988
Higher-order finite-element analysis of topographic guides supporting elastic surface waves A method of computing the eigenmodes of acoustic waveguides of arbitrary cross section is described. It is a finite-element technique, based on a variational formulation of the guided-wave problem. The accuracy of the method is assessed by comparing numerical and experimental results for a few specific structures. In particular we describe an acoustic surface ridge waveguide with low dispersion over a broad band.
Journal of the Acoustical Society of America - Tập 53 Số 4 - Trang 1116-1122 - 1973
Steady-State Wave Propagation in Infinite Bars of Noncircular Cross Section An approximate solution to the equations of elasticity is obtained for the problems of steady-state longitudinal, flexural, and torsional wave propagation in isotropic bars of infinite length and rectangular cross section. Results were obtained for sections with various ratios of width to depth. These results indicate that, in a phase-velocity versus wavenumber plot, the higher branches exhibit a certain minimum feature; i.e., these branches approach their limiting value at bγ = ∞ from below. This feature has not been reported in the case of bars with a circular cross section.
Journal of the Acoustical Society of America - Tập 40 Số 6 - Trang 1501-1508 - 1966
Phonetic tone signals phonological quantity and word structure Many languages exploit suprasegmental devices in signaling word meaning. Tone languages exploit fundamental frequency whereas quantity languages rely on segmental durations to distinguish otherwise similar words. Traditionally, duration and tone have been taken as mutually exclusive. However, some evidence suggests that, in addition to durational cues, phonological quantity is associated with and co-signaled by changes in fundamental frequency in quantity languages such as Finnish, Estonian, and Serbo-Croat. The results from the present experiment show that the structure of disyllabic word stems in Finnish are indeed signaled tonally and that the phonological length of the stressed syllable is further tonally distinguished within the disyllabic sequence. The results further indicate that the observed association of tone and duration in perception is systematically exploited in speech production in Finnish.
Journal of the Acoustical Society of America - Tập 128 Số 3 - Trang 1313-1321 - 2010
Analytical expressions for the tonotopic sensory scale Accuracy and simplicity of analytical expressions for the relations between frequency and critical bandwidth as well as critical-band rate (in Bark) are assessed for the purpose of applications in speech perception research and in speech technology. The equivalent rectangular bandwidth (ERB) is seen as a measure of frequency resolution, while the classical critical-band rate is considered a measure of tonotopic position. For the conversion of frequency to critical-band rate, and vice versa, the inversible formula z=[26.81/(1+1960/f )]−0.53 is proposed. Within the frequency range of the perceptually essential vowel formants (0.2–6.7 kHz), it agrees to within ±0.05 Bark with the Bark scale, originally published in the form of a table.
Journal of the Acoustical Society of America - Tập 88 Số 1 - Trang 97-100 - 1990
k -space propagation models for acoustically heterogeneous media: Application to biomedical photoacoustics Biomedical applications of photoacoustics, in particular photoacoustic tomography, require efficient models of photoacoustic propagation that can incorporate realistic properties of soft tissue, such as acoustic inhomogeneities both for purposes of simulation and for use in model-based image reconstruction methods. k-space methods are well suited to modeling high-frequency acoustics applications as they require fewer mesh points per wavelength than conventional finite element and finite difference models, and larger time steps can be taken without a loss of stability or accuracy. They are also straighforward to encode numerically, making them appealing as a general tool. The rationale behind k-space methods and the k-space approach to the numerical modeling of photoacoustic waves in fluids are covered in this paper. Three existing k-space models are applied to photoacoustics and demonstrated with examples: an exact model for homogeneous media, a second-order model that can take into account heterogeneous media, and a first-order model that can incorporate absorbing boundary conditions.
Journal of the Acoustical Society of America - Tập 121 Số 6 - Trang 3453-3464 - 2007
The <i>k</i>-space formulation of the scattering problem in the time domain: An improved single propagator formulation The storage allocation requirement and solution speed of the k-space formulation of the scattering problem in the time domain developed by this author [N. Bojarski, J. Acoust. Soc. Am. 72, 570–584 (1982)] were improved by a factor of 2 and 4, respectively, by the replacement of the earlier two temporal propagators by a single more accurate propagator and the utilization of the special case real to complex FFT algorithm. It is shown that for problems of the size of about one million spatially discretized cells this method is about five times slower than an ideal solution, and requires about five times as much in core storage allocation as an ideal solution. It is shown that for a modern array processor this solution is I/O bound. It is pointed out that this method is ideally suited for parallel array processor implementation, resulting in even greater speed.
Journal of the Acoustical Society of America - Tập 77 Số 3 - Trang 826-831 - 1985
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