Mediocre would be the best terminology. There are plenty worse units than what Sirtec puts out, but also plenty better. For your power needs with that i5 and 1060, it's fine.
As to a buzzing noise, that's coming from the psu fan, more than likely, but could be coming from an internal component. With the fan it's 1 of 3 things, dirt on the fan blade causing an imbalance (like a car tire that only bounces at certain speeds), the bearings on the fan are worn out, or lackadaisical quality control is allowing a wire/paper to touch the fan blade when it warps due to centrifugal force. Could start with giving the psu a good blowout with a can of compressed air, hopefully cleaning any dirt off the blades. Any other fix requires pulling the psu...