Acoustic Glossary

Joule the derived SI unit for work • energy • sound energy.

Equivalents : N·m = Kg·m²/s² = W·s = Pa·m³ = 10⁷ ergs
where kg is the kilogram, m is the metre, s is the second, N is the newton, Pa is the pascal, W is the watt.

J/kg : joule per kilogram = specific energy

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J/m³ : joule per metre-cubed = energy density = sound energy density

J·s/m² (joule second per metre-squared) the derived SI unit of flux density
Equivalent : W/m² = sound intensity

J/s : joule per second = W (watt) = sound power

Jerk a vector quantity that specifies time rate of change of acceleration - units m/s³

Judged Perceived Noise Level (IEC 801-29-10) sound pressure level, in decibels, of a frontally presented octave band of pink noise centred on 1 kHz and lasting for two seconds, that is subjectively judged equally noisy as a given sound.

See also aircraft noise • effective perceived noise level • maximum perceived noise level • noise and number index • noise exposure forecast • perceived noise level • T10 • tone-corrected perceived noise level