Musical marine mammals

If one thing has set humans apart from animals, it has been our appreciation for—and ability to make—music.

Music, at least for most of us, is distinguished from noise by certain characteristics. For one, it consists primarily of tones, as opposed to noise. Noises are sounds identified not by characteristics so much as their source—the barking of a dog, the crash of a tipped-over garbage can. Tones, on the other hand, exist apart from any specific source: possessing controlled pitch, loudness, timbre and duration, they can be created by any one of a number of different instruments and still be recognizable.

Obviously, it is easier to organize a series of tones into something we recognize as music than it is to organize a series of crashes, thuds and dog barks (certain avant-garde musical experiments notwithstanding).

Pitch is dependent on the frequency of the sound waves: high pitches have a higher frequency than low pitches. (Middle C–the key directly under the first letter of the brand name on most pianos–has a wavelength of about 1.3 metres.)

Loudness is determined by the amplitude, or height, of the sound wave.

Timbre is not what lumberjacks yell as they finish cutting down a tree. It’s the total “feel” of the sound, arising not only from the main vibration that determines pitch, but from all the secondary vibrations set up in the instrument producing the sound.

“Pure” tones, without secondary vibrations, are very rare. Among traditional musical instruments, the flute, with its simple tube construction, comes closest. Violins, on the other hand, with their complex curves and wooden bodies, produce sounds particularly rich in complementary vibrations, called overtones.

The timbre of the tone may also change depending on the environment. As sound bounces off objects in its path, it changes character, especially at high frequencies (low frequencies are less easily affected, which is why the hip-hop CD the guy in the apartment upstairs is playing sounds like it consists entirely of bass drum beats).

As well, the speaker cabinets and sometimes even the room itself resonate. (This is why singing in the bathroom sounds good. Small rooms have a resonant frequency that can be matched by the human voice. Match the resonant frequency and you get a big, booming sound. In large rooms the resonant frequency is generally too low to be matched vocally.)

Duration is how long the tone last. By varying the durations of a series of tones, we produce another important part of music: rhythm.

Our ability to recognize rhythms embedded in sounds has long been thought unique to humans, because scientists believed it was closely related to our linguistic ability.

Now, however, bottlenose dolphins have taken us down a peg or two, in two studies led by Heidi Harley, associate professor of social sciences at the New College of Florida in Sarasota, and involving dolphins at The Living Seas exhibit at the Disney World Resort’s Epcot Center in Lake Buena Vista, Florida.

In one study, an adult male dolphin positioned itself in front of a hydrophone (an underwater sound projector), to listen to six different four-second rhythms. Each rhythm had an action associated with it (i.e., wave a fin, toss a ball), and if the dolphin performed the appropriate action, it was rewarded. The dolphin’s ability to learn the appropriate actions demonstrated it could distinguish among different rhythms.

In the second study, another adult male dolphin was trained to produce rhythms using a pneumatic switch. When the switch (essentially an air-filled ball) was pressed, a computer generated sound. The dolphin was taught to associate certain objects with certain rhythms: i.e., when shown a Batman doll, he received a fish if he produced a short sound and then a long sound (like the “Batmaaaaan” part of the old Batman theme song).

The dolphin began spontaneously vocalizing to the rhythms, so the researchers rewarded him whenever his vocalizations matched the rhythm he was supposed to be producing. By the end of the studies, if shown the Batman doll, the dolphin would both press the switch in the correct rhythm and sing the rhythm himself.

These studies are the first to show a non-human mammal has the ability to recognized rhythmic patterns. They demonstrate that in this, as in many other things, we aren’t as unique as we think we are.

But not to worry. After all, it was only a very short version of Batman.

I, for one, refuse to be impressed until a dolphin sings the complete theme to Gilligan’s Island.

Or better yet, Flipper.

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