Harmonic? Anharmonic? Inharmonic?

In molecular spectroscopy, an anharmonic oscillator has a nonparabolic potential which results in a nonharmonic absorptionspectrum, but the same oscillator treated classically has a precisely harmonic vibrational spectrum. To avoid confusion, it is suggested that such an oscillator should simply be called nonlinear. The term “inharmonic” is suggested as an appropriate descriptor for classical oscillators, such as metal bars, that have nonharmonic vibrational spectra even in the linear limit of small vibrations

Hyperhelices: a classical analog for strings and hidden dimensions

A hyperhelix is a structure consisting of a rod coiled into a helix, coiled into a helix,…, through a finite or even infinite number of orders. An examination of the transverse vibrations of such a structure shows that the macroscopic behavior is accounted for by waves on the rod that are confined to an extremely small range of wave numbers centered about a value equal to the reciprocal of the smallest helical radius involved. All other dynamical aspects of the behavior and their associated physical dimensions are completely hidden at the level of the final helix. It is suggested that the study of the dynamics of such a structure might provide a fruitful analogy for understanding the string theory

The Variety of Information Transfer in Animal Sonic Communication: Review from a Physics Perspective

For many anatomical and physical reasons animals of different genera use widely different communication strategies. While some are chemical or visual, the most common involve sound or vibration and these signals can carry a large amount of information over long distances. The acoustic signal varies greatly from one genus to another depending upon animal size, anatomy, physiology, and habitat, as also does the way in which information is encoded in the signal, but some general principles can be elucidated showing the possibilities and limitations for information transfer. Cases discussed range from insects through song birds to humans

The Cochlear Amplifier as a Standing Wave: Squirting Waves Between Rows of Outer Hair Cells?

This paper draws attention to symmetric Lloyd-Redwood (SLR) waves-known in ultrasonics as "squirting" waves-and points out that their distinctive properties make them well-suited for carrying positive feedback between rows of outer hair cells. This coul

Nonlinear frequency shifts in quasispherical‐cap shells: Pitch glide in Chinese gongs

The large‐amplitude vibrational behavior of a shallow spherical‐cap shell is investigated theoretically using simple arguments. The results of this approximate analysis are expressed in the form of appealingly simple nondimensional quantities. It is shown that the frequency of the fundamental mode of such a shell falls by as much as 50% as the vibration amplitude is increased to approximately the shell depth. For even larger amplitudes the frequency rises, and it exceeds the small‐amplitude frequency when the amplitude is more than about twice the shell depth. The influence of shell thickness is considered and increasing thickness is shown to decrease the frequency shift. This analysis is shown to account for the pitch glide behavior of certain Chinese opera gongs.The author was affiliated with CSIRO when the paper was publishe

Tuning a pentangle—A new musical vibrating element

As part of a program in musical acoustics, it was required to design a non-regular but reflection-symmetric pentagonal gong, made from steel rod, of such geometry that the first 5 or 6 of its planar normal modes provide partial tones in nearly harmonic relationship, in order to achieve a musically satisfactory bell-like sound. Techniques are described for exploring the accessible configuration space to reach this objective, using a combination of analytic solution and finite-element analysis. The results and methods, which may be of wider applicability and interest, are described in detail, as also are two independent solutions reached to the design problem. The final gong has markedly different tone quality depending upon whether it is struck so as to excite the harmonic in-plane modes or the inharmonic out-of-plane modes

Nucleation by Crystalline Particles

Classical nucleation theory is applied to the production of particles of a crystalline phase by growth upon small foreign particles. Various possible particle shapes are considered and general curves are derived which can be simply applied to a large variety of physical situations