Making a noise/speed curve to determine vessel noise
The performance of the CS90 will always be limited by different noise sources. The weather and sea conditions for the noise measurements will be those at the time of the test.
Prerequisites
The CS90 is turned on, and it is working normally. The vessel is at sea. Recommended minimum depth is 100 metres.
If the CS90 is operated from any other compartment than the bridge, an open two-way oral communication channel with the bridge is required.
You need the following equipment:
•  Personal computer
•  Spreadsheet program
For the best possible conditions to complete the test, the ship must be "silent".
•  There must be no other vessels in the vicinity.
•  As much machinery as possible must be switched off. It is particularly important to switch off electrical motors, as well as cooling systems and hydraulic pumps that may cause electric noise.
•  To prevent interference, all other hydroacoustic instruments must be switched off.
Context
In order to measure the noise, you must record the noise value using the functionality in the BITE dialog box. Since the noise will vary with each ping, you must make five measurements for each vessel speed, and then calculate the average noise.
Tip
If you record all the raw data during the noise test, you can repeat the test later using the replay file. You may then use more than five noise samples for each vessel speed to make a more accurate curve.
It is always best to do make the noise/speed curve under realistic conditions. This means that all relevant vessels systems should be in use as under normal operations. However, if you experience abnormally high noise levels, you may want to repeat the test with "silent ship" settings. To isolate noise sources, turn individual vessel systems on or off to monitor any changes in the noise level.
Procedure
1 Make sure that you have sufficient water depth below the keel before you lower the transducer.
2 Lower the transducer to its bottom position.
3 If necessary, establish a separate communication line with the bridge to verify the vessel speed during the test.
4 Make the following preparations.
a At the bottom of the CS90 presentation, select a suitable presentation mode, and activate the Horizontal view.
b Open the Operation menu.
•  Set Operation to Normal.
•  Set TX Power to Off.
c Open the Active menu.
•  Select No TVG.
•  Set Ping-Ping Filter to Off.
•  Set AGC (Automatic Gain Control) to Off.
•  Set RCG (Reverberation Controlled Gain) to 0 (zero).
d Open the Setup menu.
e Select BITE to open the BITE (Built-In Test Equipment) dialog box.
f Select Noise to open the page.
5 Repeat the following cycle for each vessel speed:
a Ask the bridge to set the speed.
b Once the bridge reports that the speed has been obtained, select Start Noise Measurements.
c If possible, verify the vessel speed on the top bar.
d Record the values in the result table.
e Calculate the average noise , and record it in the table.
f Ask the bridge to set the next speed.
6 When all the measurements have been made, type the data (speed and noise) into a spreadsheet to create the curve.
7 Hoist the transducer to its upper position.
Result
Speed/Noise
Speed Noise level Average
0  

 
2  

 
4  

 
6  

 
8  

 
10  

 
12  

 
14  

 
16  

 
18  

 
20  

 
Sea state:  

Water depth:  

Use this table to record the noise values, or write them straight into a spreadsheet.
Use the following plot to record the noise values for 0° bearing. Make additional copies if required, or use the functionality of the spreadsheet program.
Image
Requirements Results
A noise/speed curve is created.  
Date and signature: