Based on the constraints provided by the planning stage, formulae and/or guidelines will be provided for deriving the following characteristics of towed system hardware:
(1) Required frequency bandwidth, noise floor, calibration, sensitivity, and flow noise compensation characteristics of hydrophones and flow-through electronics;
(2) Required hydrophone positions relative to towing vessel and other sources of noise interference (e.g., range behind towing vessel and towing depth, as derived from knowledge of vessel source levels);
(3) If localization capability is required, required and/or recommended minimum numbers of and separations between hydrophone elements.
(4) Minimum standards on towed cable mechanical and electrical performance, along with winch capabilities.
(5) Standards for the recording system, analog/digital conversion for monitoring software, and signal pathways. As one possible example, the standard might require that data pass through the recording system before entering monitoring software, so that if problems with the recording system occur the situation will be immediately noted.
(6) Minimum capabilities of computers or laptops that process real-time data for monitoring or mitigation purposes.
(7) Standards for the recording of array supporting data that may be available, including water temperature, array depth, array droop, time stamps from either internal or external clocks, fathometer data, ship radar data (to help with ambient noise analyses), etc.
The working group will also need to decide whether absolute requirements or recommendations should be set for certain hardware specifications, in addition to the derived requirements provided by the planning stage. To provide a couple of illustrative examples, should the standard always require that at least 16-bit A/D conversion be required, regardless of the species, location, and noise sources involved? Should a towed cable always have at least twisted single pairs jacketed by a ground shield? Should a PAM survey always record all raw data, or are there circumstances where only subsets of data (e.g. event detection) are permissible?