This study investigates the characteristics of the sound field during the 2013 and 2014 Southern California Behavioral Response Study. Acoustic data were collected before, during, and after simulated mid-frequency active sonar (MFAS) playbacks. A numerical approach, incremental computation method, is developed to quantify the inter-ping sound field during the simulated MFAS playback. Comparisons are made between inter-ping sound field and natural background in three distinctive frequency bands: low-frequency ( 4.5 kHz) bands. The results show significantly elevated sound pressure levels (SPLs) in the inter-ping interval of the MFAS-frequency band when compared to natural background levels before and after playbacks. No difference is observed between inter-ping SPLs and natural background levels in the low- and high-frequency bands. In addition, the duration of elevated inter-ping sound field depends on the MFAS source distance. The prolonged eleva...