You've not told us how the soundbar is connected to the TV. To the best of my knowledge, all soundbars have a 3.5mm jack socket (for taking a signal from a TV's headphone socket) and some offer additional inputs, such as for optical cables or for HDMI.
If you use something other than the 3.5mm jack socket for the input you should get an audio signal from the TV which is at the right level for the sound bar to be able to use easily. However if you use the 3.5mm jack socket (connected to the TV's headphone socket) it's important to adjust the headphone volume to a suitable level. In particular, if it's set too high it will overload the sound bar's input circuit, resulting in distortion and generally poor quality audio.
So (if you're using the TV's headphone socket to provide the audio output), I suspect that you need to decrease the headphone volume. With some TV sets that simply means reducing the normal volume level on the set, whereas on others you need to go into the TV's menu settings to make the necessary adjustment. (Check the set's manual or post the exact model number, here, from the back of the set, so that we can try to assist you further).