ABSTRACT
This error may also be expressed in terms of difference between the pressure-residual intensity index b plO (formerly termed the 'residual pressureintensity index') and the observed pressure-intensity index bpI at the field point (eqn (6.3)). (Note: the observed pressure-intensity index is biased if the intensity estimate is biased.) By definition
Hence the term D may be written D = ± Ie 10-(6plO-6PI)/10
(7.10) The quantity b plO - bpi has been termed the phase error index and denoted by L", in Section 6.3.1. Since the signs (directions) ofintensity are suppressed in the definition of the pressure-intensity indices, the positive sign is chosen if both Ie and Ires have the same sign (i.e. direction by reference to the calibration data). The ratio of estimated to true intensity is given by
(7.11a) where the negative sign is chosen if Ie and Ires have the same sign. The normalised bias error is given by
where the positive sign is used when Ie and I,es have the same sign. These equations are valid provided that the bias error is not so great as to
make IelI negative. The same equations give the phase mismatch bias error in an estimate of the spectral density I(w) of the active intensity of a timestationary aperiodic field by replacing the mean square pressure by its auto-spectral density and the pressure-intensity indices by their spectral equivalents.
