The consonants of the Japanese 'ta' row often become aspirated at the beginning of a word.
Please explain the difference between aspirated and unaspirated consonants.
無気音 is the opposite: an unaspirated consonant, produced without a strong burst of breath.
Compound of 帯 (carry, bear) + 気 (air, breath) + 音 (sound), literally 'breath-carrying sound'. A modern technical term in linguistics.