Testing the Underwater Ear

World War II fueled technologies for underwater listening, such as hydrophones, and Cold War antisubmarine strategies further rendered the oceans audible, noisy even. This novel ability to hear marine sounds radically transformed not only the discipline of oceanography but also the oceans themselves and the people listening. An examination of U.S. Navy ear-training manuals and sound recordings reveals continuities of testing protocols and ontologies between military oceanographers and marine biologists. Underwater listeners were additionally informed by musical training and technologies such as graphic representation and image processing software. In the oceanic soundscape, marine life was defined relative to Soviet vessels and was approached through an epistemology of error: plankton stood in the way of sound waves, shrimp distorted hydrophone receptions, and whales emitted enigmatically unclassifiable sounds that questioned existing sound signature catalogs. As technologies and data were disclosed to the biologists, this knowledge about error became scientific knowledge.

A New Timbre Visualization Technique Based on Semantic Descriptors

This article introduces the concept of Sound Signature audio visualization, a new form of amplitude waveform that also visualizes perceptually salient spectral features and their evolution over time. A brief review of existing research into timbre description and visualization is given. This is followed by an in-depth description of the algorithm. Rationale is given for the various visual mappings with reference to existing literature. The results of an online subjective evaluation survey are reported and discussed. The survey examined user preferences for the visual mappings used in Sound Signature visualizations. Results show a preference for inverse mapping of spectral centroid to the first component of the hue, saturation, value (HSV) color space.

Investigation of Acoustic Signals During W1 Tool Steel Quenching

Quenching is an important part of the heat treatment process for strengthening medium and high carbon steels. In the heat treatment cycle, the metal is heated to a desired temperature (above the eutectoid temperature) in the furnace and then cooled in a fluid medium such as water, brine, oil or air. Depending on the cooling rate, the mechanical and metallurgical properties of the metal can be altered in order to achieve the specific design parameters that are required by the part. The process in which the metal is cooled rapidly is termed the quenching process. Due to rapid cooling in a medium, such as water, brine, or oil, the quenching process produces an audible sound signature, as well as, acoustic emissions. In this paper, W1 tool steel is investigated through the use of a beam former that is equipped with 32 microphones. Using this device, it is demonstrated that the audible sounds that are produced when quenching depend on the heat treatment temperature and the size of the specimen.