The term 'deep hollow sound' can be summarized by the word 'BOOM', which is a four-letter word. A BOOM is a loud, low, and resonant sound that is often associated with explosions or thunder. It is also used to describe the sound of a large drum or bass instrument. The term 'deep hollow sound' is often used to describe the reverberating sound of an explosion or thunder, as well as the sound of a large drum or bass instrument.