Opera seems to be making a comeback. The Metropolitan Opera’s simulcast of productions to movie theatres around North America has been selling out.
If you see an opera in the movie theatre or on television, you probably take it for granted that you can hear the singers over the orchestra, because everything on television is miked to make sure that you can. But if you see an opera in an actual opera house, you may well have wondered how those singers can make themselves heard over all those noisy orchestra instruments, each of which, on its own, is likely louder than most voices.
You’re not the first person to wonder. John Smith, a physicist at the University of New South Wales in Sydney, Australia, recently took a crack at answering the question for Scientific American.
First, some background. Speech and singing involve four major functions: breathing, phonation, resonance and articulation. Breathing is important because sounds are generated by expelling air. Phonation is what happens next: as that air is forced between two folds of mucous membrane, called the vocal folds, the folds vibrate like guitar strings, producing sound.
The sound resonates–and picks up power–in the throat, the mouth, the nose, the nasal sinuses and the chest cavity. Differences in these help account for the very different voices different people have.
Finally, there’s articulation, the complex maneuvering of the lips, tongue, soft palate and facial muscles to shape the sound into words.
Anyone who can talk can do all of these things. Anyone who can sing can do all of these things, and keep the sound going at a specific pitch for a specific period of time. But not all of us who can sing can project our voices over a symphony orchestra. So how do opera singers do it?
According to Smith, everyone’s vocal folds vibrate at a fundamental frequency, which determines the pitch, Smith explains. Normal speech typically falls between 100 and 220 hertz (Hz), or vibrations per second.
Speech and singing also contain harmonic frequencies, multiples of the fundamental frequency: two times the fundamental frequency, three times, four times and so on.
The fundamental frequency has the greatest acoustic power, but the very high harmonics have an advantage in an opera: even though less powerful, they reside in the range over 3,000 Hz, where there is little competition from the orchestra, which is strongest around 500 Hz.
Sopranos have an even greater advantage, because their fundamental frequency when singing is when singing ranges up to 1,500 Hz–which places much of their range above that 500 Hz orchestra. Those of us with lower voices therefore have a harder time making ourselves heard.
Trained singers also boost their power through resonance tuning: they shape their vocal tract so that its resonance frequencies match up with the their voice’s harmonics. You can see this: sopranos tune one of the resonance frequencies, called R1, by adjusting the configuration of their mouth, which makes them look like they’re smiling or yawning when they hit the high notes. (Of course, changing the mouth like that can also effect intelligibility, which is why it can be hard to understand what sopranos are singing in the high passages, but that’s what surtitles are for, isn’t it?)
All this resonance tuning helps, it’s not the only reason you can hear opera singers above the orchestra. Classically trained singers often have more vibrato in their voice than non-classically trained singers. Vibrato is a slow, cyclic “wobble” in pitch. Some musical instruments have vibrato, too, but it’s usually much more pronounced in singers, and that vibrato helps the voice stand out in our ears apart from the instrumentation.
Finally, it seems likely that human beings are simply hard-wired by evolution to pay attention to loud sounds produced by other people. After all, they might be warning us of the approach of a sabre-toothed tiger!
The fact that they’re really singing at the top of their lungs about their impending depth from consumption doesn’t change our programming.
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