Time and frequency analysis of seismic airgun calibration data from an environmental acoustic recording system (EARS) buoy

• Published in: The Journal of the Acoustical Society of America 2005-09, Vol.118 (3_Supplement), p.2002-2002
• Main Authors: Ioup, George E., Ioup, Juliette W., Chapin, Sean R., Tashmukhambetov, Arslan M., Newcomb, Joal J., Sanders, William M., Walker, Christopher D., Brack, Benjamin, Rayborn, Grayson H., Stephens, James M., Sidorovskaia, Natalia A.
• Format: Article
• Language: English
• Subjects: Marine
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.4785671

In the summer of 2003 two Environmental Acoustic Recording System (EARS) buoys were deployed in the northern Gulf of Mexico by the Littoral Acoustic Demonstration Center. The buoys were collocated and recorded ambient noise and seismic airgun array shots up to approximately 25 kHz. The gains and hydrophone sensitivities were set such that one EARS buoy could record the seismic shots without clipping and the other could record ambient noise. The M/V Kondor towed an airgun array on parallel linear tracks with horizontal closest points of approach to the buoy of 0, 500, 1000, 2000, and 5000 m, giving experimental data for a wide range of horizontal distances (up to 7 km) and arrival angles. The raw data were calibrated using the EARS system parameters to produce calibrated pressure time series for each shot. These data are analyzed in both the time and frequency domains. Maximum pressures for each shot as well as sound exposure levels (pressure squared integrated over time for 200 ms in this case) are presented. Also presented is a spectrogram analysis. The maximum time-domain peak pressure recorded is 200 dB re: 1 μPa. The maximum sound exposure level is 177 dB re: 1 μPa2 s. [Research supported by Industry Research Funding Coalition.]