PARAM, PREFDB

Bulk Data Entry Used to activate dB and dB(A) output in H3D and PUNCH file formats for Fluid-Structure Coupled Frequency Response Analysis.

Parameter	Values	Description
`PREFDB`	Real > 0.0 No default	This parameter specifies the reference pressure value used to calculate the pressure level in decibels (dB) and A-weighted decibels (dB(A)). The pressure level in decibels (dB) can be calculated using the following equation:(1) $P L_{d B} = 20 \log_{10} (\frac{\|P L\|}{P R E F D B})$ $P L_{d B} = 20 \log_{10} (\frac{\|P L\|}{P R E F D B})$ Where, $P L_{d B}$ $P L_{d B}$ Pressure level in decibels (dB) $\|P L\|$ $\|P L\|$ Magnitude of the pressure from Coupled Fluid-Structure Frequency Response Analysis $P R E F D B$ $P R E F D B$ Reference sound pressure value specified using this parameter Note: The pressure level in decibels (dB or dB(A)) is not output unless PARAM,PREFDB,<value> is specified. If this parameter is specified without a value, then an error is issued. In the PUNCH file, within the PRESSURE (dB, dBA) section, the first two values printed for each frequency are the pressure level output in dB and dB(A) formats. The remaining values of each frequency are set to 0.0 for formatting purposes. Figure 1.