Hypersonic Effect

The hypersonic effect is a phenomenon reported in a controversial study by the Japanese researcher Tsutomu Oohashi and colleagues, which claims that although people cannot consciously hear ultrasound, meaning sound above roughly 20 kilohertz, the presence or absence of those inaudible frequencies still produces a measurable effect on a listener's physiological and psychological responses. A number of later studies have contradicted the part of the claim concerning subjective reaction to high frequency audio, finding that listeners with especially sensitive hearing, using high fidelity equipment capable of reproducing sound up to 30 kilohertz, could not reliably tell the difference between high resolution audio recordings and ordinary compact disc quality audio.