The Effect of Single Harmonic Tuning on Vocal Loudness.
Ingo R Titze
PMID 32245662WHAT IT FOUND
Tuning a single vocal harmonic increases perceived loudness less efficiently than adjusting the overall spectral slope.
While single-harmonic tuning can boost loudness, it requires large sound pressure level changes and risks producing a whistle-like timbre, unlike the more natural dynamic control achieved by varying spectral slope.
Key findings
01Changing the spectral slope produces a greater increase in perceived loudness per decibel of sound pressure level than tuning a single harmonic.
02Single harmonic tuning at low fundamental frequencies (125 Hz) yields less than two doublings of loudness for a 40 dB increase in sound pressure level.
03Achieving high loudness gains through single harmonic tuning often results in a whistle-like timbre and is less effective for natural vocal dynamics than spectral slope variation.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study is purely computational and does not include human listeners or voice production data. The model assumes specific vocal tract configurations and spectral slopes that may not reflect all natural speech or singing variations. The authors note that the high dB gains simulated for single harmonic tuning (up to 40 dB) are unlikely to be achieved in typical vocal tract resonances without extreme skill.
The easy way to misread this
Do not assume that higher sound pressure level (SPL) always equals higher perceived loudness. The study shows that spectral slope changes are more efficient for loudness regulation than single harmonic tuning, meaning SPL alone is a poor predictor of how loud a voice sounds to a listener.