What Determines What Your Voice Sounds Like?

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As a marker of singularity, our voices are as effective as our fingerprints. Though people may share a similar pitch or certain vocal characteristics, under close examination, no two voices are alike.
Height, weight, hormones, provenance, allergies, structural anomalies, emotions, and environmental factors all play a role in determining how your voice ultimately emerges, which means not only is your voice yours alone, but that you'll have a few variations on that voice throughout your life.