You’re Gonna Hear Me Roar

Tiger, Tiger, burning bright / In the forests of the night….

Few things can spark primal fear like the sight of a tiger on the prowl. Or, as it turns out, the sound of a tiger on the prowl.

And while tiger roars are loud (they usually just make it into the top 10 list of loudest roars), that’s not the secret behind that sudden burst of fear that a tiger’s roar inspires. After all, lions, whales, elephants and even rhinos produce much louder sounds than tigers. What’s different about tigers according to bioacousticians (those who study sounds made by animals) is the frequency. There’s the part that humans hear, which is relatively pitiful compared to us felines, and an infrasound level – a very low frequency that can’t be detected by the human ear but can travel great distances to reach those who can hear it.

More importantly, infrasound can als be felt, whether or not you can hear it. The infrasound frequency used by tigers is around 18 Hz and or even lower. This is the magic range that often triggers that sense of fear and a fight or flight response in anyone who “feels” this sensation. It also creates a sudden paralysis. It’s not long-term – that giant boar isn’t going to simply stand there for two minutes and wait for the tiger to show up – but it’s just enough to give the tiger that extra second or two that might mean the difference between dinner that night or going hungry.

So we’re mighty proud of our big cousins.

Of course, there are doubters out there. It even made it onto an episode of Myth Busters, which declared that the infrasound frequency was not what triggered the fear response. (We’re assuming they’re dog lovers.) But other tests have found support for the notion that infrasound can create sudden feelings of fear, anxiety and even extreme sorrow or chills. Scientists in England have found that adding infrasound to music can create these same sensations, for example.

There’s also the work of Vic Tandy, who found that infrasound was responsible for the appearance of a “ghost” at his office and at a nearby pub. Turns out that infrasound at 19 Hz resonates with the human eye so objects in your periphery appear much larger than the really are. Amorphous grey shapes that disappear when you try to look at them straight on are really just dust and other detritus in the air that you would not normally notice resonating at 19 Hz.

Infrasound also travels much more quickly than higher frequencies and scientists believe they can turn this to their advantage. Major events like earthquakes and volcanic explosions are often preceded by infrasound. With the proper equipment, scientists are hoping they can warn people of impending danger.

Certain weather phenomena also produce infrasound, such as seasonal winds and certain storm patterns. Meteorologists have used infrasound to improve alert systems as well as weather forecasts. The hope is that one day infrasound can be used to better predict not just the path of major storm events like hurricanes but also their creation.

And all of this made possible by the study of a tiger’s roar.

Maybe Blake should have written about the tiger’s roar instead.

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