Standards Respecting Noise Control and Hearing Protection in Canadian Towboats Over 15 Tons, Gross Tonnage is available in PDF format (file size 28.5 KB) which will download in approximately 8 seconds on a 28.8 connection and may be viewed using Acrobat Reader (version 3.0 or higher). This reader is available free of charge. Please visit the Adobe’s web site where you can download the Acrobat Reader.