The process of analysing the frequency components of a complex sound into octave or third octave bands when all of the band levels are obtained at the same time. This is sometimes referred to as simultaneous frequency analysis and is a feature usually found on the more sophisticated models in a manufacturer’s range of instruments due to the complexity of the signal processing involved. This type of analysis is required for the correct determination of transient sounds such as aircraft flyovers or impulsive signals from blasts. Since all of the bands are calculated simultaneously no energy is lost or missed when performing this type of analysis.