Especially when either is detached and looks at these as a surface movement, we say that the mind or vital is quiet.Sri Aurobindo
Letters of Sri Aurobindo
04. The Foundation of Sadhana
Fragment ID: 1131
Quietness is when the mind or vital is not troubled, restless, drawn about by or crowded with thoughts and feelings. Especially when either is detached and looks at these as a surface movement, we say that the mind or vital is quiet.
Calmness is a more positive condition, not merely an absence of restlessness, over-activity or trouble. When there is a clear or great or strong tranquillity which nothing troubles or can trouble, then we say that calm is established.