Why Can People Sing Over an Orchestra?

If you’ve ever been to a major opera house, you may have noticed that the singers are able to make their voices carry over an orchestra without amplification. Why is this? Do opera singers sing with so much breath power that their voices produce more volume than all the instruments in the orchestra put together? Well, no. Opera singers might use their breath efficiently, but they can’t overpower an orchestra in sheer decibels. The acoustical phenomenon has more to do with why dogs are jarred by high-pitched whistles.

What are Overtones

Let’s first talk about what overtones are. When a string vibrates, it vibrates along the length of the whole string, our fundamental frequency, or what we usually call the pitch. But the halves of the string are vibrating as well, as are the thirds of the string, and so on. These form what we call overtones, and they greatly influence how our ear perceives that note. Since it’s easier to see in action, check out this video by Two Minute Music Theory.

A similar phenomenon happens when we sing, except that our resonating chamber is much more complex. Instead of a simple string, we have all this pharyngeal space we can manipulate to alter our overtones: a soft palate that can be lifted, a tongue that can move around, a larynx that can be high or low, and so many other possibilities. Every manipulation we make changes the overtones and, thereby, the way a pitch is perceived by listeners.

So What Does This Have to Do With Singing Over an Orchestra?

There’s a particular arrangement of overtones that can occur whose frequencies (between 2000 and 4000 Hz) will vibrate sympathetically with the human eardrum. This means that we’ll perceive those sounds as particularly loud and piercing, cutting through other sound. These sounds need not be more powerful for us to perceive them as such, similar to how a dog whistle isn’t a particularly powerful sound but is piercing and disconcerting to a dog.

How do our Voices Do That?

It’s still being studied exactly what opera singers are doing anatomically (and it may be different for different voice types), but one thing we do know is that narrowing our aryepiglottic sphincter (AES) a certain amount will produce those bright spots between 2 and 4000 Hz. That term may sound intimidating, but your AES is just the top of your larynx, and narrowing it is something you’re all very familiar with. The piercingness of a witch’s cackle and the taunt of a bratty kid are both produced with this mechanism.

In Evolution

A baby’s cry, so heartrending to mothers, so grating to passengers on an airplane, shares that piercing quality, partially because the baby’s larynx is so small (and doesn’t need a whole lot of narrowing). Our eardrums are literally programmed to hear a baby’s cry cut through other sounds.

Isn’t it fascinating that we replicate this quirk of evolution by narrowing our own larynx to make it more like a baby’s?