Two cases of impulsive discharge, balloon burst and engine exhaust, are experimentally investigated to find scaling laws for the discharge time τ and the pressure amplitudeAof the acoustic pulse. Observations show that the flow may be modeled as a pressure reservoir of dimensionDand overpressure Δpsuddenly discharging through an aperture growing with time. IfWis a characteristic aperture velocity, the aperture area varies as (Wτ)2for the balloon burst and asWτ for the engine exhaust. The flow is driven by a complex, unsymmetric wave field within the volume. It is shown thatD/τ∝ (CiW2)1/3andA/Δp∝ (Ci/W)4/3for the balloon burst, whereCiis the sound speed in the reservoir. The corresponding quantities for the engine exhaust pulses are (CiW)1/2andCi/W.