Carbonated drinks are noisy.
While they're not going to damage anyone's hearing they are loud enough to be disturbing if you open it in the middle of a class, library or somewhere else where silence is required.
Cans make two types of noise:
To open a can quietly you need to find a way of muting both the noise of the tab opening and the gas escaping.
There are a few ways you can achieve this:
To open your can quietly simply pull the tab up very slowly.
Ensure that the pressure against the can opening is applied gently to avoid a large popping noise.
Carefully wiggle the tab until the seal is slightly broken, this will allow a small of gas to quietly hiss out.
Once the can stops hissing continue pulling the can ring up slowly to avoid any metal noise.
Reducing the temperature of a pressurized can will significantly reduce the air pressure inside the can.
This means you can open it with minimal hissing sounds.
You don't need to completely freeze the contents of the can, 10-15 minutes in a freezer should be long enough to bring the air pressure down without solidifying the liquid inside it.
Once the can has been inside the freezer for long enough remove it and carefully and slowly lift up the tab so that it doesn't make a big noise when the seal breaks, due to the low temperature there should be almost no hissing sound.
Instead of pulling the tab to open the can slowly pushing the opening of the can is a far quieter way to open your can.
Put the can down on a firm stable surface and slowly apply pressure on the can opening with the base of your thumb.
Keep applying pressure until the seal breaks a little bit, this will allow some of the pressurized gas to escape without making the loud 'pop' that is caused by lots of gas escaping quickly.
Allow the gas to continue to escape until it stops hissing, once it has stopped then push the opening until the can is fully open.
Be careful with this method as it can be dangerous!
You will need something sharp that is capable of piercing the can such as a knife or protractor.
Use your chosen tool to pierce a small hole in the top of the can which will allow the air to slowly escape.
Once the air has stopped coming out of the hole you can either slowly open the can or you can make the hole a bit bigger and pour the liquid out of there.
Alternatively, you could pierce the can towards the bottom however be aware this can be very messy (you may get sprayed) so make sure you have containers ready to catch the liquid in.
This method will completely prevent any hissing noise as the air is trapped at the top of the can and by the time the can is empty enough for the air to escape the pressure has completely dropped.