Side question -- do submarines really have the ability to ping, like in Hunt for Red October, do they ever use it, and does it actually use the frequency range of human hearing like that? Do torpedoes? Or are they ultrasonic (given that depth gauges I know are ultrasonic). I assume that subs once did use such pings historically given how common that sound effect is associated with them. Maybe not any more I guess?
The thing about the ping is that everyone that can hear it gets the benefit of that ping. So you are 100% giving away your position with a ping. Nowadays, you want to stay silent, so you use passive sonar. A very long tail is trailed behind the sub with lots of microphones listening. They've done it so long, they know what all sorts of things sound like. Man made objects likes subs and surface ships, airplanes flying above the water, rocks sliding, crabs crawling, etc.
My (admittedly very armchair) understanding is the ping is a lot worse for the hunter than the target - the distance you can hear the ping is roughly 2x the distance* you'll get a useful return from it, so if the target is beyond that range you'll effectively lose all stealth and confer a huge advantage to the enemy.
* this is complicated by thermal layers, geography, etc. but very approximately 2x is the figure I've heard.
Yes, I understand, though my question was more whether subs actually have the ability to issue an audible ping like in that movie -- and why they would ever do it.
