While it's true that Android 4.0 Ice Cream Sandwich has been announced , other than the SDK it hasn't been released yet. That means you can't buy a phone running ICS and you can't flash a stock or custom ICS ROM onto your current phone.
Earlier today I told you how you could make your phone look like it was running Android 4.0 with a custom theme (but only if it was running a ROM that supports themes), now you can make your phone SOUND like it's running ICS — no custom ROM needed!
All you need to do is download the audio files from the source below, then extract them to the root of your sdcard! It's super-easy, and can freshen-up those stale Gingerbread or Froyo sounds that you've been using so far in minutes.
Just to be clear, you'll want to have an audio folder on the root of your sdcard with subfolders for alarms , notifications , ringtones , and ui .
Once the files are on your phone, reboot it and head to Settings then Sounds. From there simply pick the event you want to change the sound for set it to your preferred sound!
Bonus Tip: If you want to add your own sounds, simply create the folder structure mentioned above on your sdcard, then add your own audio files in the appropriate place. .OGG files work best, but .MP3 files will work, too.
Source: My Droid World