It usually means that the flow is too fast for the baby and the noise is them protecting their airway. The baby usually ends up swallowing a lot of air as they are gulping and trying to keep up with the flow.
If you are breastfeeding, after about the first 5 min of feeding, stop and burp them. They may need more burping during the feeding session. It may be that you have a lot of milk and\or you have heavy let down.
If you are bottle feeding, you can try a side lying feeding position so the baby can control the flow better versus laying straight back and gulping. You can also find a slower flow nipple, newborn versus level 1.
Either way you are feeding, if they are making the noise, they are gulping air and need to be burped more frequently. You run the risk of them getting irritated and wanting to suck and then pulling away, as they are full of air and have a tummy ache. You also run the risk of your baby spitting up more as they are working to get the air out but have the milk sitting on top of the air bubble.
Usually after the first 5 min of feeding and then burping, their suck may be a little less aggressive as they now have milk in their tummies. Burping more will decrease the chances of your baby being gassy, fussy and spitting up. They will usually eat more and be content after the feeding as they are not uncomfortable.
As babies get bigger, they can handle the faster flow but when they are a small baby or a newborn they will tend to make this noise.