Acoustic Characteristics of Small Research Vessels

Round 1

Reviewer 1 Report

Errata

line 147 "the effective of"?????

       163 "appear to be logistic"?????

        291 "and lead resulting"

Line 192: perhaps the observation relates to higher noise from the suction side cavitation on approach while lower when shielded on departure.

Fig 7 would be better presented as 1 plot per vessel; each containing curves for the 4 speeds.  As presently plotted the speed variation needs to be assessed over 4 plots.

in the "discussion" there is not one re-reference to the tables and figures, so it becomes a bit of a slog reading dense prose interspersed with MSL etc numbers.  More difficult when reading from a PC screen where only 1 page is visible.

Tip vortex cavitation is a major element in propeller noise.

Photographs of the size and extent of the vortices in the slipstream could have provided another key parameter.

Lines 379-383 might also benefit from consideration that no measurements were made of the power absorbed at each speed and hull inclination angle.  No photos were taken from a support  boat at the attitude obtained on the steady-speed track. 

An interesting paper which should provide guidance for future studies, perhaps in deeper water.

Author Response

The authors would like to thank the reviewers for taking the time to consider the manuscript and for their valuable suggestions.

Reviewer 2 Report

The authors report measurements of sound radiated by small research vessels (of less than 6 m length) in a very shallow water environment (~10 m depth). The authors do a good job of stating the importance of the problem to the near coastal sound scape and the current deficiencies in existing data to sufficient address noise management and mitigation from small watercraft. The reported measurements are thus a valuable contribution in helping to address these issues. The vessel used in the experiment seem to be representative of small watercraft that might be used for recreational fishing or other pleasure activities.

The authors use the metrics radiated noise level (RNL) and environmentally affected source level (ASL) to quantify the radiated sound. ISO criteria are specified for measuring these quantities in deeper water, but do not specify them for shallow water as encountered in the near shore environment relevant to the small vessels described here.

RNL is defined as taking the received level (RL) at a given hydrophone and back-propagating it to 1 m using spherical spreading loss. Normally, monopole source level (MSL) would be estimated by propagating the RL back to 1 m using a more accurate propagation model. Instead of doing this calculation which the authors state would require more accurate knowledge of the environment, they estimate the propagation loss empirical from the RL data at various ranges and use that empirically estimated loss to back propagate the RL to 1 m, calling it the ASL. The approach seems reasonable, and the authors do provide some comparison between their results and other measurements of vessels of comparable size.

I have no major comments or revisions. Please address the minor revisions listed below:

-Authors use kmph to abbreviate kilometers per hour. Should use km/h instead throughout the paper.

-Incorrect usage of italics in equations: for example “log” should not be italicized. Also abbreviations like “SL” or “ref” are not usually italicized. Should only be for variables like v or C.

-Figure6. Black dotted lines are extremely difficult to see. These should be made more visible.

Author Response

The authors would like to thank the reviewers for taking the time to consider the manuscript and for their valuable suggestions.