"In Batman Begins, Batman manages to silently 'summon' a whole lot of bats to his rescue - can you really whistle for a bat?"
Batman has to be my favorite superhero- he doesn't rely on some amazing and unbelievable superpowe,r but instead spent years training his body and mind to become the ultimate crime fighter. As he says in one comic "I've got to know science thoroughly to become a scientific detective". And he meant it too - all of his high-tech gadgets and weapons are based on real scientific principles, even if they are a bit beyond us at the moment. So in the recent Batman Begins film when he calls bats to attack the bad guys, its not completely wrong, just not completely right either.
You probably know that bats use sound rather than sight to find their way around (this comes in pretty handy when you only venture out of your bat cave to hunt at night). The bats emit sound waves that bounce off anything in their path, with the echoes being detected by Mr Bat; allowing him to work out the distance, direction and speed of his insect snack.
So how come humans can't hear a bat's calls? Well, bats use much higher frequencies than the human ear can detect. Typical bat calls are in the range of 125KHz to 20kHz, sometimes of constant frequency and sometimes sweeping over a range of frequencies in a split second. Humans would have difficulty detecting even the lowest frequency calls (our speech peaks at around 3KHz).
The reason that bats use such high frequencies is that these sound waves have a much shorter wavelength and this makes it easier to detect tiny insects for their dinner. It also makes it easier for the bat to tell the difference between its call and all the background noise that is at a much lower frequency. Obviously a person would also be unable to make a high enough sound to talk to the bats using human vocal cords, they would need some sort of whistle device.
So what is the problem with Batman's bat whistle? Firstly, for a sound wave to reach a target it has to have a clear path. If there are walls, lampposts, people or anything else in its way, it will be bounced off. So Batman would need direct line of sight to wherever the bats are living. Then there is the problem of how far sound travels. You don't try and shout to your friends across an entire city, that would just be dumb and hard on your vocal cords, so why would it work for Batman? Unless the bats are hiding just outside the window, he would have a problem calling them.
Even if we forget the problem of the bats not being able to hear him, Batman would need to know Bat-ish to be able to talk to the little flying rodents to persuade them to come to his aid. I don't know whether bats use ultrasonic waves to communicate with each other in this way, perhaps there really is a Bat word for "please come here and attack these nasty people". I would have thought that his whistle would be more likely to repel the bats rather than attract them (in fact some slightly dodgy companies sell high frequency sound emitters to keep insects and bats out of your house, but these are frowned upon by animal lovers).
I've been thinking how Batman's method could be adjusted to work
in the real world. In my version of the story, Batman has hidden
tiny speakers around the city and in the bat cave. During a fight
somewhere in the city, he requires the help of the bats. So he
activates his bat whistle via a button concealed in his bat uniform.
A satellite tracking system is used to pinpoint his location and
chooses the best route for the bats from the bat cave. The tiny
speakers around the city are then activated to emit ultrasonic
sound waves that either repel the bats or trick them into believing
a tasty snack is flying about somewhere close by. The bats then
move from speaker to speaker until they reach their destination.
Someone let me know if they get it to work....
