I've googled a bit and it seems a good number of people had this problem (search for ticking, chirping, scratching, clicking), even when I limit the search to only Seasonic. Some switched to another brand, others went the RMA route, others yet were experiencing chirping for years without other problems. No one has reported (that I've seen) that their Seasonic PSU has died after experiencing this.
Since I'm planning to buy a new PSU for myself and was considering Seasonic, I put a little more effort into this and the most interesting stories I've found are:
This guy was experiencing chirping on college but not at home, on the same machine, even while using a UPS both times. That's just X-files territory, unless an EE would like to elaborate on it... I'm all ears.
This guy (post #6) and this answer mention that it could be capacitors. In the first link, the guy explains that the chirping is actually gas being rapidly released and than re-sealed somewhere on a failing cap. A chemical reaction from a possible short supposedly produces the gas. The OP there went for a replacement and "this one is making the same chirping noises now too, even when i turn the computer off"...
Now, that could be a bad series or a crappy model, but I've heard stories of branded PSU's deteriorating rapidly due to a bad electrical grid. A thing you can try first is take your PC to a friends house and try it there to see if the electrical grid is screwing up your PSU somehow. Do the same gaming there, maybe you'll end up with the same result as the guy from the first link (the ex-college guy).
If you know anyone who has a UPS, ask if you can borrow it just for a test.
Lastly, (and I don't recommend this, especially if it's under warranty) you could open the PSU and take a peek. Other than that, if you have an electrical repair shop nearby, you could take it there.