# Spectral acceleration density

**Spectral acceleration density** ( english *Acceleration Spectral Density* (ASD), and *Power Spectral Density* (PSD)) is a term used in vibration - Measurement .

The spectral acceleration density is the root mean square value (over the frequency range ) of an acceleration signal that has passed a narrow- band filter of a certain frequency range, divided by the bandwidth of the filter. This normalizes the signal. The spectral acceleration density is the value for the borderline case in which the bandwidth approaches zero and the averaging duration approaches infinity.

It is defined somewhat differently in DIN EN 60068-2-64: 2009-04 than in DIN EN ISO 2041. MIL-STD-810H defines the ASD as a function using a Gaussian curve .

Applications are e.g. B. Vibration tests of mechanical systems that are exposed to random shocks .

The units used are:

- with for the unit Hertz or

- the common, but not SI-compliant unit

- with the standard acceleration of fall , often rounded up.

A structurally similar defined variable is the spectral power density .