Research appearing in The Journal of the Acoustical Society of America shows the effects of sustained wakefulness on speech and describes a novel method to acoustically analyze the effects of fatigue on the central nervous system as revealed through speech.

The Australian study involved 18 young adults who provided speech samples (sustained vowels, counting, and reading tasks) every 2 hours. Australia acoustician Adam Vogel and his colleagues looked at components of speech such as length of pauses and total time to complete a spoken task.

Their results showed that as fatigue progresses, speech slows and variations in pitch increase and tone diminishes.

Their conclusion is that we have less control over the muscles that produce speech as we become more and more tired.

Measuring fatigue by analyzing a person’s speech and quantifying any changes from their normal, rested speech may enable doctors to make objective decisions about a person’s ability to function in a work environment. It may also be a useful tool for monitoring fatigue in clinical trials where alertness is a key measured outcome.