On the topic of piercing sounds and thunder: As you know there are high pitched sounds and low pitched sounds and any sound in any range can have a high volume or a low volume.

Thunder is very loud, and pretty low. Even if you can't hear it you would still feel it vibrating your stomach in a kind of rumble. That's the same feeling you get when you hear it except the fact that its loud can be startling/downright scary.

High pitched sounds feel like someone is drilling with a tiny drill into your head. Most of the time its not pleasant, and its actually painful to hear a loud high pitched sound.

A piercing sound would be in the high-pitched, high volume area.

Also: Chat is what you do on msn/google talk/irc with your friends, and not the type of conversation you're trying to have when you're writing an email applying for a job.

Edit: Animal sounds - People speak not just by pushing air through their vocal chords and making a sound but by changing the shape of their mouth to greatly extend the range of noise one can produce. When you put your lips sort of around your teeth and close your mouth and hum (at a medium pitch) you get the 'mmmmmmm' sound. If you pucker your lips and make a low sound you get an "ooooooo" sound. Combining these gives you a sound that resembles what cows make, so they say a cow goes "moo". A dog's bark is named in a smiliar way.