He stood there, motionless, until a subtle vibration warned him that visitors were approaching his door.

A moment later, feeling the subtle vibrations running clearly into him through his toes, he gave a grim nod.

Drizzt pressed his hands against the stone, feeling the subtle, rhythmical vibrations.

Or to some subtle vibration that affected the brain?

He placed his hand on the ground, feeling for subtle vibrations, anything that might offer a hint.

An instant later, he felt a subtle vibration through the deck of his ship.

For a moment it seemed to tingle in his fingers with a kind of subtle vibration.

The rest of the house was fairly quiet, only subtle vibrations coming down to him.

It now carried a subtle vibration suggesting the great spider at the heart of the web had begun to stir.

The subtle vibrations of the ship changed, as it powered up and began to move into open space.