Paper Summary
In the follow-up to the previous newsletter, I begin by considering new source designs wherein the sources are towed with larger lateral source separation. This leads to each source naturally comprising one sub-array of air guns. If we want to achieve the ambition of dispersed sources wherein the streamer spread is surrounded by a flotilla of small sources we must also develop cost-effective and operationally-robust source vessel conceptsono easy task. I then compare various compact source concepts in terms of their three-dimensional pSPL and SEL. Some surprising results suggest that one sub-array may not be much different to several sub-arrays in terms of received sound levels. New Zealand now has one of the strictest regulatory regimes for air gun operations, and I use that as a template to suggest how compact sources could be defined in an environmental context. I also share another surprising result wherein substantial amplitudes may be recorded in the 1-2 Hz frequency range when single air guns are continuously activated and recorded in a particular manner. Collectively, the notion of compact sources suggests that point sources, whether impulsive or electromechanical in nature, provide several intriguing opportunities.