Believe it not, that sound is a registered trade mark!
Can I really register a sound…?
Yes! A trade mark must be capable of being represented
graphically so you may think that a sound cannot be registered.
However, as long as the sound can be written down in a clear,
precise and objective way, it can be registered as a trade
mark.
How should I represent the sound?
Simply listing the notes is not enough, as this tells you
nothing about timing. Spelling out the sound using an onomatopoeia
is not enough either, as it will be interpreted differently in
different languages. However, using a musical stave is
satisfactory; as this is an accurate representation of the
melody.
Doesn't copyright protect me?
Yes, but remember a trade mark is useful because your mark is
listed on a public register. This means that if somebody infringes
your sound trade mark, there is less of an evidential burden on you
to prove your rights as they are all there for anybody to see!
Is it worthwhile?
Direct Line and Intel seem to think so. Direct Line's famous
jingle and Intel's chord sequence are both registered as trade
marks as well as many other famous sounds.