High frequency noises can often be annoying and can be emitted from a plethora of possible sources, such as a TV switched on in the room next door.
Appliances in use in other rooms can emit these sounds through the walls, despite the device being turned on mute. Because noises towards the top end of the spectrum can very often be difficult to hear, they can leave you with an unwanted ringing sound, especially for those with sensitive ears. The good news is, we can often take steps to reduce these othersome sounds or even eliminate the problem.
Many headsets these days are specifically designed to block out any annoying background noise for a purer sound while listening to music. Even wearing them without can muffle high frequency sounds around the home.
Musicians earplugs are specifically designed for the individual ear, and can reduce sounds and can even out frequencies. They are often used to protect your inner ear from damage while at the same time allowing you to hear normal sounds. You'll still be able to hear people talking, or listen to music and other normal sounds, but the unwanted frequencies sound will be muffled.
Both of the above solutions are temporary fixes, which is why the only real way to reduce or eliminate the transmission of high frequency sounds between rooms is by soundproofing.
In its most basic sense, soundproofing simply muffles noise via the placement of items in a room in order to stop sounds traveling beyond it, and is particularly effective with high frequency noise. In fact, soundproofing only becomes more of an issue the lower the frequency.
It should also be noted at this point that all levels of sound can not be transmitted from one room to another without there being a continuous transmission medium. In most cases, the transmitting medium is not air (unless you have a hole in your wall), but most likely wood or drywall. These materials make very good sound conductors.
You can start soundproofing by simply putting down objects such as heavy rubber mats and carpet, anything with a greater mass, which will prevent high frequency sounds from traveling downward. For doors, you can add soundproofing runners; another effective soundproofing method.
Since high frequency sounds are difficult for us to perceive, taking a few simple soundproofing steps can greatly reduce or even eliminate these annoying high-pitched sounds.