Sound & Acoustics Calculators — Decibels, Doppler & Speed of Sound
Calculate decibel levels, Doppler effect frequency shifts, and speed of sound at different temperatures and through various media.
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Understanding Sound & Acoustics
Sound is a mechanical wave that travels through matter by compressing and expanding the medium. In air at 20°C, sound moves at 343 m/s — about 1,235 km/h. The speed increases with temperature (roughly 0.6 m/s per °C) and varies dramatically between media: 1,480 m/s in water and 5,960 m/s in steel. The decibel scale measures sound intensity logarithmically, compressing the enormous range of human hearing (from 10¹² W/m² at the threshold of hearing to 1 W/m² at the threshold of pain) into a manageable 0-120 dB range.
The Doppler effect explains the familiar pitch change of a passing siren: as the source approaches, wave crests arrive more frequently (higher pitch), and as it recedes, they spread apart (lower pitch). This same principle lets astronomers measure the speed of distant galaxies via redshift and allows radar guns to clock vehicle speeds. Sound intensity follows an inverse-square law — doubling your distance from a source reduces the intensity to one-quarter.
Sound and acoustics are a branch of waves & oscillations, sharing the same mathematical framework of frequency, wavelength, amplitude, and superposition. Sound also travels through fluids, and the speed of sound in a gas depends on temperature, pressure, and molecular mass — connecting acoustics to thermodynamic properties.