Page 48 - Fall 2006

The newsletter of
The Acoustical Society of America
EXCERPTS FROM ECHOES
Scanning the Journals
Thomas D. Rossing
􏰀 Two papers presented at the 2005 Australian Acoustical Society conference are reprinted in the December issue of Acoustics Australia. A paper entitled “Learning Acoustics through the Boundary Element Method: An Inexpensive Graphical Interface and Associated Tutorials” was awarded the President’s Prize for the best technical paper. The Boundary Element Method (BEM), the paper points out, is particularly useful for analyzing sound radiation and acoustic scattering problems. The other paper “Acoustic Systems in Biology: From Insects to Elephants” discusses the physical principles in the sound production and hearing of a variety of creatures. The dominant frequencies used for communication by a large range of air-breathing animals is nearly proportional to the body mass raised to the -0.4 power.
􏰀 Tunable nanoresonators constructed from telescoping multiwalled carbon nanotubes (MWNTs) are described in the 2 June issue of Physical Review Letters. Such res- onators, with their low masses, low force constants, and high resonant frequencies, are capable of weighing single bacteria, detecting single spins in magnetic resonance sys- tems, and even probing quantum mechanics in macroscop- ic systems. In the device, a specially prepared MWNT is suspended between a stationary contact and a mobile piezo- controlled electrode. Varying the length of the nanotube beam through the controlled telescoping of the inner nanobtube core from the outer nanotube shell tunes its res- onant frequency.
􏰀 Higher sound clarity is obtained in classrooms when sound diffusers are applied to rear walls and ceilings rather than side walls, according to a paper in the Proceedings of WESPAC IX. However, absorbers increase sound clarity
even more effectively with smaller area in comparison with diffusers.
􏰀 A protein associated with a disorder that causes deaf- ness and blindness may hold a key to one of the foremost mysteries of hearing, according to a paper in the June 28 issue of Journal of Neuroscience. Scientists have identi- fied protocadherin-15 as a likely player in the conversion of sound into electrical signals. The findings will not only provide insight into how hearing takes place at the molec- ular level, but may also help us explain why some people temporarily lose their hearing after exposure to loud noise but regain it a day or two later. The protein is referred to as the “tip-link antigen” (TLA) because it induces the pro- duction of special antibodies which bind to the protein at the stereocilia tips in the cochlea. Using mass spectrome- try, the researchers analyzed the makeup of the TLA and found two peptide sequences that match up to key seg- ments of the protein protocadherin-15 in humans, mice and chickens.
􏰀 For any touch, sound, or image to be perceived, our senses have to activate neurons at the center of the brain, in the thalamus. According to a paper in the 16 June issue of Science, the weak neurons along the thalamocortical path- way may find strength through amplification within corti- cal layer 4. Researchers were able to measure excitatory electrical activity generated in a single cortical neuron in a mouse cortex by a single thalamic neuron.
􏰀 Several interesting effects are reported when cavitation bubbles are generated inside water drops in microgravity, according to a paper in the 1 September issue of Physical Review Letters (97, 094502). Toroidally collapsing bubbles generate two liquid jets escaping from the drop, and the
46 Acoustics Today, October 2006