Chest Voice
A term used within vocal music, especially in classical singing. However, the use of this term varies widely within vocal pedagogical circles and there is currently no one consistent opinion among vocal music professionals in regard to this term. It is not acoustically measurable. The term can be used in relation to the following:
• A particular part of the vocal range or type of vocal register
• A vocal resonance area
• A specific vocal timbre
[Source: Wikipedia].