My Seasonic PSU is making some unexpected noise
Any PSU will generate some kind of noise either due to the fan or the coils (due to electric current passing through it), and this is completely harmless and normal. Some units produce more noise depending on the quality of the electrical system in your location or house. This can manifest itself when high-drain, high-Ampere appliances are in use (like a vacuum cleaner, blender, airconditioning unit, water heater, etc). See if you can remove these variables and determine if the power supply is still producing an unexpected noise.
We have confirmed reports that high drain units, like instantaneous water heaters (those attached to showers) cause the power supply to make a noise, almost like a buzzing sound even when it is powered off. Depending on how your electrical system is designed, even servo type AVRs will cause this noise under the same conditions. However, it really depends on the type of water heater is being used as well.
Steps that might help identify the issue:
1. Remove any high-drain, high-ampere appliances are in use (like a vacuum cleaner, blender, airconditioning unit, water heater, etc).
2. Use a servo-type AVR, or alternately, no AVR/UPS (direct to mains)
3. Remove high drain peripherals (i.e. Video cards).
4. If possible, try the unit on a different electrical system (i.e. on a friend's house, office, etc)
Once you identify the source, then we can say that the power supply is not defective, as the noise is caused by an external stimulus.
However, if the noise is accompanied by unexpected shutdowns, intermittent power or otherwise abnormal behavior that causes the unit to shut down, it is best to open a ticket.