marine seismic operations today. Te computed source level depends
on the frequency range over which the acoustic pulse is measured. Seismic arrays are frequently measured over 0–125 Hz or 0–250 Hz. Tere may be a slight underestimation of total energy by these bandwidths, but the error is small because output above 250 Hz is limited. It is known, however, that the output from airguns extends well into the kHz band but with much-reduced pressure level (see Section 3.4). For a longer discussion on decibels, see Section 3.7.
Figure 3.11: Source signature and amplitude spectrum for the 3,397-in3
