Physical exertion affects the pitch, intensity, and temporal characteristics of speech, making speech recognition difficult for systems used by emergency response personnel and wearable devices.

PHILADELPHIA, May 14, 2026 — The “talk test” is often used as a low-tech way to measure exercise intensity: If you can easily talk or even sing, your workout is fairly light, but if conversation is difficult, you are exercising vigorously.

Physical task stress affects the coordination between breathing and speaking. Zahra Omidi from the University of Texas at Dallas studies this relationship and will present her work Thursday, May 14, at 11:15 a.m. ET as part of the 190th Meeting of the Acoustical Society of America, running May 11-15.

Vocal pitch, intensity, and pause structure are the vocal characteristics most impacted by changes in breathing and exercise. Credit: Zahra Omidi and Presidio of Monterey (CC0)

“Physical exertion directly alters respiration and phonation, and because speech shares the same respiratory system, these changes propagate into pitch, timing, and voice quality,” Omidi said.

Vocal pitch, intensity, and pause structure are the vocal characteristics most sensitive to changes in breathing and effort. Pitch and intensity both increase, while intensity also becomes less stable. Because speakers need to allocate more time to breathing, their speech rate slows down and becomes more segmented with longer and more frequent pauses.

Some of these changes might not be so noticeable to a listener, but the measurements clearly indicate a physiological difference.
“Features like pitch, intensity, and timing show clear and consistent changes, even when those differences are not immediately obvious by listening,” Omidi said. “This suggests that physical stress may operate below the threshold of perceptual salience in some cases but still induces measurable changes in the production mechanism.”

Understanding exactly how physical stress causes changes to vocal patterns can help train speech recognition systems, which often struggle with speech that differs from the average.

“Examples include emergency response, military operations, aviation under workload, and wearable voice interfaces, where people are speaking while physically active,” Omidi said. “In all these cases, speech deviates from neutral conditions due to respiratory and vocal effort constraints, leading to reduced intelligibility and system performance.”

In order to better represent real-world speech behavior, Omidi hopes researchers will adapt a more holistic view of speech variation as a reflection of a speaker’s characteristics rather than focusing solely on linguistics. Task stress is just one of the many physiological variables that can affect these variations.

“Human speech is inherently shaped by the body, and physical task stress provides a clear example of how physiological factors influence speech production,” Omidi said.

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