Right your problem either stems from the menu settings that are incorrect/ silent mode, or your speakers are damaged, the other option is that no sound output is being achieved through any speakers you fit (this is a more serious problem).
Now depending on your type of fault cause, will depend on how technically and electronically minded you will have to be, and also on cost factor (whether it is a finacial interest to spend repairing the unit, or replacing it).
Now firstly, i would check your sound settings in the menu and also turn your volume dial, button/ switch on to full. Although this is plainly obious, it is surprising how many times a simple issue like this is overlooked in favour of a more serious fault, and for no reason at all.
Next up, i would remove the speakers and test the unit on another set of speakers of the same output, if the test speakers work, then the original speakers from your unit MUST BE discarded or overhauled. now discarding them is the easier option because of cost, but you can take them to a place that will recycle them, or post them to the centre in question.
Lastly, if you have a circuit board issue, then this is potentially critical, and the cost and time to repair the unit may often be outweighed by the cost and ease of just condemning the unit and replacing it, now if you do condemn the product, you can always make some money back towards the cost of a new product by putting the faulty device on an online auction.
Now if you do decide to repair this yourself, start by checking wwww.google.com and seeing what others have to say about the product, and also look for the service/ repair manuals for this manufactured product.
I wish you best of luck in whatever of these decisions you decide to take, and if you need further advice or assistance, then please do not hesitate to contact me,