Each basic emotion produces recognizable vocal changes:

• Happiness — higher pitch, wider pitch variation, faster pace, and upward inflections
• Sadness — lower pitch, narrow pitch range, slower pace, and a monotone quality
• Anger — louder volume, faster pace, and tight, clipped articulation
• Fear — higher pitch, irregular pace, breathiness, and a slight vocal tremor

These signatures are produced involuntarily as emotion acts on the nervous system and vocal muscles. They are consistent enough that most people can recognize basic emotions from clips in unfamiliar languages at well above chance.