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A number of personal attributes allow others to guess someone's age — the lines on a face, the erectness of carriage, the color of hair.

The voice also signals how old a speaker is. Your voice's sound quality and vocal strength change and weaken as the years add up.

Peter Watson, a University of Minnesota professor in the department of speech, language and hearing sciences, has become a popular speaker to groups of older Minnesotans, offering advice on how, as he puts it, to not sound old.

Watson himself speaks in the plummy tones of a broadcast announcer or audiobook narrator. He was still a boy when his appreciation of a resonant voice began; his mother regularly tuned in the Metropolitan Opera on the kitchen radio in their Iowa farmhouse.

A talented singer, Watson was inspired to study opera, earning a master's degree in voice performance. But allergies and overuse fogged his instrument, and that got him interested in the mechanics of vocalizing, which sent him back to college for additional advanced degrees and inspired the study of voice disruptions as his specialty and area of academic scholarship.

In addition to his teaching, Watson works at the university's Lions Voice Clinic, seeing patients with Parkinson's disease and other disorders that effect speech quality.

Watson follows the advice he sets out in this interview. His own baritone is rich and supple, and by listening to it, you would not guess that he's 69.

Q: Is it true that listeners can tell how old someone is by their voice?

A: It is. There have been numerous studies that play audio recordings to participants who are blinded. We see that respondents are remarkably good at scaling [a speaker] within a decade of their age.

Q: Can you provide a simple explanation of what happens in our bodies that shifts the sound of the voice?

A: Subtle changes occur in the throat, mouth and nose as we age. As we become a little older and stiffer, our breathing mechanism is not as flexible. The breath is the power source of the voice, coming up from the lungs through the trachea to the vocal cords or vocal folds. There's five different types of tissue in the vocal folds. One layer is gelatinous; it has to be pliable when the air comes up from the trachea to make them vibrate. As we age, we lose some bulk and mass there. The vocal folds shrink and are not as efficient at vibrating to produce sound; they don't come together as they did and that adds to that rough, breathier sound.

Q: Are there other physical factors that contribute to vocal quality?

A: Yes. There are two major joints that open and close the vocal folds. Arthritis can affect them; if you're prone to arthritis, I would imagine you could find it in these joints too.

Q: Are these changes inevitable?

A: It's always going to occur; it's a matter of to what degree. A study done several years ago and published in a professional journal looked at people who test as biologically younger than their chronological age, looking at their resting heart rate, blood pressure, BMI. Turns out they had the voice characteristics of younger adults, too. The conclusion is, when everything else is functioning at that level, so will the voice.

Q: Can you damage your voice?

A: You want to avoid a lot of yelling, shouting. If you live with someone with a hearing problem and you raise your volume all day every day, that can be problematic. We see more teachers than from any other profession. They strain the voice because they use it all day in the classroom. Back in the '80s we saw lots of aerobics teachers in the clinic; now they wear wireless mics for amplification.

Some of my favorite singers have apparently taken good care of their voices and are still performing. I think of Carole King and James Taylor — he still has that "Sweet Baby James" quality to his voice even though he is up in years.

Q: What helps to preserve the voice?

A: To maintain good vocal fold health and keep the tissue from drying out, have a relative humidity of 40% or greater. Smoking, even several cigarettes a day, is hard on that tissue. Eat right, exercise, get good sleep — it all contributes.

Staying hydrated is important. I always have a carafe of water sitting on my desk. I'm careful with coffee. It's a diuretic and relaxes the sphincter from the stomach to the esophagus. When acid in the stomach comes up and pools in the larynx, it leaves that tissue swollen and irritated. Reflux is associated with voice problems. And people with a persistent postnasal drip experience a flow of mucous that rides on top of the vocal folds. There's a sticky viscosity that makes you feel like you need to clear your throat. Lots of water helps with that, too.

Q: What else do you do to keep your own voice tuned up?

A: Certain exercises help. One called a pitch glide stretches and shortens the vocal folds. Basically hold a note and slowly move your voice from high to low, up and down, and then back again, making the sound you get from a slide whistle. I do a sequence of four of them, three times a day. I also push my palms together while saying "ah, ah." This exercise causes the vocal folds to be pushed closer together.

Q: What about singing?

A: Yes! Singing is great for the voice; you stretch your vocal cords by singing high and low, loud and soft. Sing in the shower, sing in the car, join a choir. There are choirs all over the Twin Cities. My wife and I are in an all-ages choir and we really enjoy it. It's also good for cognitive health, because you're learning something new.

Q: Are there medical interventions for an aging voice?

A: A surgeon can inject a substance to fatten up the tissue in the vocal folds so there's no gap. That's referred to as a "voice lift." People who use their voices professionally sometimes seek out that procedure. It's elective. I suppose someone who doesn't want to sound old may want to have it done, like Botox or plastic surgery.

Q: Can vocal issues be a symptom of other problems?

A: Anyone who notices significant changes in their voice or has persistent problems that last longer than two weeks should consult their doctor or an ENT [ear, noise and throat doctor]. It's rare, but it could be cancer or the human papillomavirus that can attack the mucosa of the mouth and throat. Or it could be a breathing problem. We use the same airway to ventilate ourselves that we use to produce the voice.

Kevyn Burger is a Minneapolis-based writer and broadcaster.