As the title states, if sound is audible, light is visible, what is a smell? And what is an object when you touch it?
Things capable of being seen are visible, things capable of being heard are audible, things capable of being touched are tangible or palpable, things capable of being smelled are odorous, things capable of being tasted are gustable.
Gustable is rarely used and primarily in technical settings. The concept is most often expressed as "tastable" when we reach for the concept in common usage. Because of the "-ible" "-able" endings of the other sensate adjectives, "odorous" is an unexpected form but a perfectly correct expression of the concept (though today most of us are more likely to use "malodorous" to describe a bad smell than to use the word "odorous" itself).
Some prefer "palpable" to "tangible" for things capable of being touched because tangible has slipped into being a synonym for the more general and inclusive "sensible", particularly in the use of the word in the practice of law.
'Smellable' is a legitimate, though perhaps not a very euphonious adjective. Other alternatives are 'aromatic' and 'odoriferous'.
'Palpable' is the most germane one for touch.
Remember that some things are tastable or edible.
I would also think that some poorly-defined proprioceptive feelings, like earthquake phenomena, are sensible (in the generic)
See - Visible/(Seeable*)
Hear - Audible/(Hearable*)
Smell - Olfactible (used very rare)/Smellable
Taste - Edible (for food)/Potable (for water)/(Tastable*)
Touch - Tangible/Palpable/Tactile/(Touchable*)
*Note: They can be used but word on the first column (except for olfactible) are commonly used, but smellable is rather used than olfactible