Changes

Recently, ''sleeve guns'', which are designed to be more efficient and reliable than conventional air guns, have been introduced. A disadvantage of the sleeve gun is that it is currently offered in only a few discrete sizes, which handicaps the air gun array designer. ''Clustered guns'' are another recent advancement. When two or three air guns are fired in close vicinity of one another, it is possible to get a strong initial pulse and a weak bubble sequence because the composite bubble formed is not spherical and thus does not tend to support oscillations.

Recently, ''sleeve guns'', which are designed to be more efficient and reliable than conventional air guns, have been introduced. A disadvantage of the sleeve gun is that it is currently offered in only a few discrete sizes, which handicaps the air gun array designer. ''Clustered guns'' are another recent advancement. When two or three air guns are fired in close vicinity of one another, it is possible to get a strong initial pulse and a weak bubble sequence because the composite bubble formed is not spherical and thus does not tend to support oscillations.

[[file:marine-seismic-data-acquisition_fig2.png|thumb|{{figure number|2}}Air gun array strength.]]

[[file:marine-seismic-data-acquisition_fig2.png|300px|thumb|{{figure number|2}}Air gun array strength.]]

The output of an air gun array is typically illustrated by a normalized pressure time sequence called a ''signature''. The signature of a 1000-in.³ air gun subarray is shown in [[:file:marine-seismic-data-acquisition_fig1.png|Figure 1]]. One measure of the strength of the source is the ''peak-to-peak pressure'', which is often quoted in pressure units of bars at [[length::1 m]] (bar meters). Another measure of the performance of the array is the ''peak-to-bubble ratio'', which is the peak-to-peak magnitude of the initial pulses divided by the magnitude of the residual bubble oscillations. These simplistic measures of performance can be used to compare different sources provided the signatures have been recorded using the same techniques, especially the same field filters<ref name=pt07r24>Johnston, R. C., Reed, D. H., Desler, J. F., 1988, SEG standards for specifying marine seismic energy sources: Geophysics, v. 53, p. 566–575., 10., 1190/1., 1442492</ref>.

The output of an air gun array is typically illustrated by a normalized pressure time sequence called a ''signature''. The signature of a 1000-in.³ air gun subarray is shown in [[:file:marine-seismic-data-acquisition_fig1.png|Figure 1]]. One measure of the strength of the source is the ''peak-to-peak pressure'', which is often quoted in pressure units of bars at [[length::1 m]] (bar meters). Another measure of the performance of the array is the ''peak-to-bubble ratio'', which is the peak-to-peak magnitude of the initial pulses divided by the magnitude of the residual bubble oscillations. These simplistic measures of performance can be used to compare different sources provided the signatures have been recorded using the same techniques, especially the same field filters<ref name=pt07r24>Johnston, R. C., Reed, D. H., Desler, J. F., 1988, SEG standards for specifying marine seismic energy sources: Geophysics, v. 53, p. 566–575., 10., 1190/1., 1442492</ref>.