Disclosed are seismic sources that may utilize an external driver to energize the air in the seismic source for generation of acoustic energy. An apparatus for generating acoustic energy may comprise a seismic source comprising an internal cavity configured to contain a fluid. The apparatus may further comprise a piston external to the seismic source and in fluid communication with the internal cavity, wherein the piston operable to energize the fluid in the internal cavity of the seismic source. The apparatus may further comprise a linear motor coupled to the piston.