It is true that all forms of electronics emit some form of high pitched noise (along with an electro-magnetic field). Whilst the hearing range of adults deteriorates (for very high and low pitched noises), as mentioned before, all children and some young adults (depending on the environment they live in - loud noises/music can deteriorate the ears) can hear it. Old TVs, chargers, Broadband Routers, and generally anything involving some kind of resister, diode, transformer or capacitor (all of which contain filaments - or so I recall) create a slightly less high pitched noise that children and some young adults find easier to hear than the low-frequency radio waves that they are also capable of hearing (when there are no other noises around - usually associated with tinitus).
However, to stop those with unfortunately sensitive hearing go crazy, and to stop adults from being able to hear their whiney children (excuse the generalisation), all ears produce a sound frequency known as "white noise", which cancels out sounds of the same wavelength. In addition to this, the brain also blocks out all sounds except the ones it is paying attention to, for example, the person you're talking to. An interesting side-effect of this is known as "coctail syndrome", where if you're in a social gathering and talking to someone in front of you, and someone suddenly calls your name, you will suddenly focus on the source of the person calling your name, and essentially hear it above the people who are talking in front of you.
There is also a condition that some people suffer from where they are unable to produce enough white noise to block out most sounds. The effect of which (from experience) is that if you're in a crowded room of people talking, you are forced to hear just about every conversation at the same time. Without a certain level of brain control, it'd drive you insane. Likewise, certain types of autism prevents the brain from blocking out sounds, and make them able to take in more information than usual, at the expense of being unable to focus or concentrate on a single sound.
But this is going beyond the scope of the topic. A PSP/charger is making a noise while charging. This likely means it is old and may need replacing. As I said before though, it'd be advisable to determine if it's from the PSP itself, the battery, or the charger. PSPs are harder to replace.