May Pik Yu Chan –

University of Pennsylvania, 3401-C Walnut Street, Suite 300, C Wing, Philadelphia, PA, 19104, United States

Jianjing Kuang

Popular version of 4aMU6 – Ultrasound tongue imaging of vowel spaces across pitches in singing
Presented at the 186 ASA Meeting
Read the abstract at

–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–

Singing isn’t just for the stage – everyone enjoys finding their voices in songs, regardless of whether they are performing in an auditorium or merely humming in the shower. Singing well is more than just hitting the right notes, it’s also about using your voice as an instrument effectively. One technique that professional opera singers master is to change how they pronounce their vowels based on the pitch they are singing. But why do singers change their vowels? Is it only to sound more beautiful, or is it necessary to hit these higher notes?

We explore this question by studying what non-professional singers do – if it is necessary to change the vowels to reach higher notes, then non-professional singers will also do the same at higher notes. The participants were asked to sing various English vowels across their pitch range, much like a vocal warm-up exercise. These vowels included [i] (like “beat”), [ɛ] (like “bet”), [æ] (like “bat”), [ɑ] (like “bot”), and [u] (like “boot”). Since vowels are made by different tongue gestures, we used ultrasound imaging to capture images of the participants’ tongue positions as they sang. This allowed us to see how the tongue moved across different pitches and vowels.

We found that participants who managed to sing more pitches did indeed adjust their tongue shapes when reaching high notes. Even when isolating the participants who said they have never sung in choir or acapella group contexts, the trend still stands. Those who are able to sing at higher pitches try to adjust their vowels at higher pitches. In contrast, participants who cannot sing a wide pitch range generally do not change their vowels based on pitch.

We then compared this to pilot data from an operatic soprano, who showed gradual adjustments in tongue positions across her whole pitch range, effectively neutralising the differences between vowels at her highest pitches. In other words, all the vowels at her highest pitches sounded very similar to each other.

Overall, these findings suggest that maybe changing our mouth shape and tongue position is necessary when singing high pitches. The way singers modify their vowels could be an essential part of achieving a well-balanced, efficient voice, especially for hitting high notes. By better understanding how vowels and pitch interact with each other, this research opens the door to further studies on how singers use their vocal instruments and what are the keys to effective voice production. Together, this research offers insights into not only our appreciation for the art of singing, but also into the complex mechanisms of human vocal production.


Video 1: Example of sung vowels at relatively lower pitches.
Video 2: Example of sung vowels at relatively higher pitches.
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