Hypersonic effect Hypersonic effect The hypersonic effect is a term coined to describe a phenomenon reported in a controversial scientific study by Tsutomu Oohashi et al., which claims that, although humans cannot consciously hear ultrasound (sounds at frequencies above approximately 20 kHz), the presence or absence of those frequencies has a measurable effect on their physiological and psychological reactions. Numerous other studies have contradicted the portion of the results relating to the subjective reaction to high-frequency audio, finding that people who have "good ears" listening to Super Audio CDs and high resolution DVD-Audio recordings on high fidelity systems capable of reproducing sounds
500 kHz 1 MHz). International standards for the use of 500 kHz were expanded by the Third International Radiotelegraphic Convention, which was held after the sinking of the RMS "Titanic". This Convention, meeting in London, produced an agreement which was signed on July 5, 1912, and became effective July 1, 1913. The Service Regulations, affixed to the 1912 Convention, established 500 kHz as the primary frequency for seagoing communication, and the standard ship frequency was changed from 1,000 kHz to 500 kHz, to match the coastal station standard. Communication was generally conducted in Morse code, initially using spark-gap transmitters. Most two-way radio