Can sounds and smells be considered marks too?

As long as it is the sound or the smell which makes the mark distinctive, the sound or smell could be registered as a mark. However, there is no international obligation to provide for the possibility of registering sound and smell marks and it would depend on the particular national law in question as to whether it is in fact impossible to register such marks. Many countries that allow also the protection of signs which are not as such visually perceptible confine registrability for practical reasons to those signs that can be represented graphically without major difficulties which is usually the case for sounds.