The crest contains the animal's nasal cavity-a tube that loops around twice, creating a chamber two and a half meters long.
头冠包含有这种动物的鼻腔——一个双循环的管道形成了一个2.5米长的腔体。
Calls, vibrations originating in the voice box, travel along these tubes.
来自喉部的声音和振动在这条管道中穿行。
Like the chambers of a trombone, those tubes amplify and lower that sound.
就像长号的套管一样，这些管道将声音扩大并降低频率。
The result-an extremely low-frequency hum, even deeper than a foghorn.
使之变成频率极低的嗡嗡声，比船上雾角的声音还要低。
Each species has its own distinct shape. Each species would have its own distinct sound.
每个物种都有其独特的外形。也具有独特的声音。
The arrangement of the chambers inside each animal is unique.
各个物种的音室都是与众不同的。
And the sound they create like a fingerprint.
因此发出的声音就像指纹一样独一无二。
These calls are Parasaurolophus' primary form of defense.
这些声音就是副栉龙最主要的防御手段。
They are communicative, social beings that live in herds.
它们是善于沟通的群居动物。
Parasaurolophus have learned there's safety in numbers.
它们知道只有群居才更安全。
An isolated Parasaurolophus would be a dinosaur in trouble.
一旦落单，副栉龙就很可能有危险。
It's gonna have to look out for predators on its own.
就需要独自面对捕食者的威胁。
And therefore, a lone individual might do its call to say, "I'm alone,"
因此落单的副栉龙就会发出"我落单了"的声音，
and wait to hear for other members of its herd to make the corresponding call.
等候族群的其它成员回复的信号。
This tactic is still used today on the plains of Africa.
这种策略仍被今天非洲草原上的动物沿用。

If you look at various species of plant eaters, they live together in groups,
如果你去观察各种食草动物会发现它们都是群居的，
and if one of them spots a predator, they can whinny or hoot and let the rest of the herd know,
如果它们中的一个发现了捕食者，它们会发出不同声响警示其它成员，
so that they can keep on alert, or if the predators are right there,
所以它们可以保持警惕，就算捕食者已经很靠近，
they can all break out into a run and run away from the attacker.
它们也可以迅速逃离躲避捕食者的进攻。
Parasaurolophus' ability to communicate complex messages is a tremendous defensive advantage.
副栉龙这种传递复杂信息的能力是很了不起的防御手段。
Using its sensitive hearing, these creatures can detect a predator far off in the distance.
利用敏感的听觉，它们可以在很远以外就感知到捕食者的踪迹。
Then send out an alarm call to warn the herd.
然后发出信号警示族群。
Even more effective, low-frequency sounds,
更有效的是，低频声音波长较长，
with their long wavelengths, travel much further than high frequencies.
比高频声音传播得更远。
These are kinds of sounds that can be transmitted over very long distances.
它们发出的声音可以传到非常非常远的地方。
This extremely low-frequency sound is called infrasound and can travel for miles.
这种极低频率的声音称为次声波，能传播几英里。
You can produce a noise so low and so deep not only it goes through the air,
极低频的声音不仅能在空气中传播，
it goes through the rocks and through the soil, and you pick it up in your feet.
而且能在岩石和土壤中传播，用脚就能感知到。
Elephants do that. Rhinos do that. Hippos do that. Crocodiles do that. Alligators do it. They produce infrasound.
大象就会用次声交流，犀牛也会。还有河马，鳄鱼，短吻鳄。它们都能发出次声波。
But for a Parasaurolophus, these calls can be used for more than just communication.
但对副栉龙来说，这种声音不仅用来交流。
Low-frequency infrasound can put up an aggressive form of defense. lnfrasound is a weapon.
低频次声波也是一种进攻性防御措施。次声波也是一种武器。
You can scramble the brains of your enemy with a blast of infrasound.
强烈的次声波能给敌人的大脑造成混乱。
If you have 100 duckbills, 1,000 duckbills, facing the same direction, producing high-decibel sounds,
比如一百只甚至一千只鸭嘴科恐龙面对同一方向发出高分贝声音，
that's a wave of energy that could knock over a predator or at least discombobulate it, scramble its brains.
这种声波的能量能击倒一个捕食者，至少让它神志不清，思维错乱。
Despite packing a deafening secret weapon, a Parasaurolophus, like other plant eaters,
尽管有这种振聋发聩的秘密武器，副栉龙和其它食草动物一样，
knows that the best way to stay alive is to keep predators at a distance.
明白真正的生存之道在于与捕食者保持距离。