When is an Octave Band (OB) Filter used, and how should the Sound Level Meter be setup for use with the OB filter?
When a measurement is made with a SLM without the OB filter, the SLM is measuring sound levels over a range of frequencies and combining them into one overall (broad-band) sound level. An OB filter is used to find the sound level just at one specific frequency. When used with an OB filter, the SLM should be set to Fast Response (for quicker settlings after changing frequency selection on the OB filter), and Linear Weighting. The Linear weighting setting will not attenuate, or lessen, the sound level at any frequency.