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
60-meter band bandplan strongly recommends that the WRC-15 frequencies should only be used if other 5 MHz frequencies, allocated under Article 4.4, are not available. It does not require stations to adopt the USB dial frequencies of 5354, 5357, 5360 and 5363 kHz but these frequencies provide a good fit with the American channel on 5357 kHz, and UK stations which can use 5354 and 5363 kHz (but not the middle two). Also, it is only by using these exact frequencies that there will be enough room for four simultaneous SSB conversations without mutual interference, assuming the 2.8 kHz "de facto" standard