Search

The Reflections series takes a look back on historical articles from The Journal of the Acoustical Society of America that have had a significant impact on the science and practice of acoustics.

A substantial fraction of the membership of the Acoustical Society of America are faculty at various types of educational institutions and are actively engaged in educational activities. However, papers focusing on aspects of teaching, pedagogy, demonstrations, student learning, and other education topics are not often published in JASA, even though the Education in Acoustics Committee regularly offers special sessions on these topics at every ASA meeting. This special issue of JASA dedicated to Education in Acoustics includes 41 papers from authors all over the world. This introduction to the special issue briefly describes each of the papers, which have been organized into several broad categories: teaching methods and exercises; project-based learning; use of experiments, demos, and experiential learning; adapting to teaching during COVID-19; circuit models and impedance concepts; software apps and online resources; teaching musical acoustics; and descriptions of acoustics programs at a variety of institutions. [ABSTRACT FROM AUTHOR]

In many paper handling machines, the sound radiated from impacts on paper is a major noise source. It is shown that in typical impact line printers both nonresonant and resonant paper vibration are significant mechanisms of sound generation. Both can probably be controlled by increasing the backing bar stiffness of the printer while keeping the printing force constant. The paper-hammer impact on the backing bar dominates paper impact noise below 1250 Hz. Above 2500 Hz the hammer impact on the paper is the dominant source. From 1250-2500 Hz the two impacts contribute equally to the sound generation. Finally, consideration of the design of a ''quiet'' paper leads to the suggestion of a paper with high density and low bending rigidity. This might be accomplished through microcreping of the paper. [ABSTRACT FROM AUTHOR]

Prescoring based upon the material contained in abstracts was used to allocate presentation times for the papers in Speech Communication submitted for presentation at the 80th Meeting of the Acoustical Society. After the papers were actually presented, their technical content, presentation quality, and discussion quality were judged. No casual relationships could be established between the prescoring and postjudging of the paper, although the papers allocated 15 min were judged statistically better in technical content than the papers allocated 5 or 10 min. It is hoped that this letter might entice others to conduct further experimentation and subjective assessment of different methods for improving professional meetings. [ABSTRACT FROM AUTHOR]

Sonoluminescence is the production of electromagnetic radiation, much of it in the form of visible light, that is emitted from a gas-filled cavity that has grown and collapsed under the influence of a varying pressure field. This resource paper provides a guide to the literature of sonoluminescence, from its early history to the present.

Experiments with laser generation and detection of ultrasound in copy paper indicate that earliest arrivals of ultrasound are antisymmetric. A likely explanation is that the out-of-plane interferometer is relatively insensitive to the symmetric compressional pulse because of the low Poisson ratio of copy paper, but rather sensitive to its antisymmetric flexural wake associated with the random heterogeneities and gradients present in copy paper. © 1997 Acoustical Society of America. [ABSTRACT FROM AUTHOR]

A through-transmission, dry-contact ultrasonic technique aimed at investigating sound propagation in the thickness direction of paper materials is presented. The method uses piezoelectric ceramic transducers immersed in fluid-filled rubber wheels. Thickness and longitudinal velocity are determined from time domain measurements for several commercial paper specimens between 40 and 1750 μm. Dispersion and attenuation are reported at frequencies up to 1.5 MHz. Dispersion is less than 10% between 0.25 and 1.25 MHz. Amplitude calculations are used to evaluate the attenuation coefficient versus the frequency. Using a nearly local form of the Kramers-Kronig relationships, the attenuation coefficient is also obtained from the phase information. By comparing the amplitude- and phase-determined attenuation coefficients, an apparent reflection coefficient is predicted. It is shown that the Kramers-Kronig relationships can be applied to papers thicker than 200 μm under dry coupling conditions. The attenuation coefficient is inversely related to the elastic stiffness for homogeneous specimens. A linear relationship is observed between the attenuation loss and the thickness. The apparent reflection coefficient correlates to the apparent surface roughness of paper. [ABSTRACT FROM AUTHOR]

The A0 Lamb mode in copy paper is generated and detected by using laser ultrasonics. The frequency dependence of the group velocity of the A0 mode is found from the wavelet transform of the measured signal. A best fit of the dispersion curve against predictions based on orthotropic plate theory yields an estimate of the bending stiffness of the sample. The sample is enclosed in an environmental chamber so that the effects of temperature and humidity can be controlled. Results indicate that the bending stiffness decreases with increasing temperature at an approximate rate of 4×10-6 N m/°C, and that it decreases with increasing percent moisture content (PMC) at an approximate rate of 2×10-5 (N m)/PMC. © 2002 Acoustical Society of America. [ABSTRACT FROM AUTHOR]

It has been previously determined that precompressed onionskin paper may be used as an acoustic decoupler. In our evaluation, compressional-wave measurements were made on various types of paper, and in particular onionskin typing paper, at 32 and 1000 kHz. At the lower frequency, a composite material technique was used to allow pressurization of the samples. The velocity of sound and attenuation were found to vary nonlinearly with pressure over the range from 0 to 2000 psi. This nonlinearity introduces a nonlinear acoustic loading of the transducer elements and is the main disadvantage of onionskin paper. However, it was confirmed that the onionskin paper should be more stable with pressure than the other papers, provided that it has been properly precompressed. Most of the insertion loss provided by onionskin paper is caused by the mismatch in acoustic impedance. Thus, a fairly wide variety of materials should provide equivalent acoustical properties. [ABSTRACT FROM AUTHOR]

In the present editorial, the Editor-in-Chief of the Journal explains the processes by which manuscripts are handled when they are submitted for publication. Various categories of problem papers are described, and it is emphasized that the outcome of the review process is not always predictable. Metrics for measuring paper quality and journal quality are reviewed and discussed. Arguments are given to the effect that the quality of a paper and its chances of being selected for publication will be considerably improved if the authors adopt a philosophy of literate writing and collegial citing. The detailed meaning of these phrases is discussed with accompanying examples, including the case of a paper by J. J. Waterston, the publication of which was delayed for 47 years until the paper was rediscovered by Rayleigh. © 2000 Acoustical Society of America. [ABSTRACT FROM AUTHOR]