Sounds produced when space between vocal folds is closed completely (very briefly) and then released?

The sound produced when space between vocal folds is completely closed and then released is called glottal stop.

Explanation:

When the airflow in the glottis or the vocal tract is completely obstructed and then released, we have a consonantal sound called glottal stop or glottal plosive. Due to the obstruction, glottal vibration either becomes irregular or stops.

This sound is more common in certain languages than others. When it comes to the English language, it tends to happen more often in certain regional accents. For American speakers, it is usual to use the glottal stop in words such as curtain or mountain, when the /t/ phoneme is followed by a /n/ phoneme. Americans tend to interrupt the flow of air in the glottis as a means to connect both sounds. To better understand a glottal stop, think of the pause you make between the two syllables of the interjection "uh-oh". That pause is caused by the interruption of airflow in the glottis and is, thus, a glottal stop.

the character has felt many emotions that are mainly focusing on negative emotions.

the answer is fantasy