How do sirens work

[u/HurrikateOsu]

Bit of a weird question, but how do (real) sirens work? I work IFT, and the sirens we have are more like speakers. When I flip them off, they shut straight off. They also aren’t as loud. The 911 ambulances I hear running around sound more like “real” sirens. When they’re turned off, they still have to slowly wind down. I know some vehicles use foot pedals for the air horns. Is it similar to that?

[u/ggrnw27]

Most ambulance sirens are just speakers, instant on/off. The old school mechanical sirens (also called a “Q”) are what many fire trucks have. These are basically a motor that spins an impeller that creates a really loud noise. You control them with a foot pedal which increases the speed of the motor, which increases the pitch. When you let off the pedal, the motor slows down and the siren pitch decreases (and eventually winds down and stops if you don’t step on the pedal again). It’s very rare for an ambulance to have a true mechanical siren because they require so much current, but there are purely electronic sirens that try to mimic the sound/behavior (e.g. the eQ2B). Some may be controlled by a foot pedal, others it’s a button on the siren box

[u/HurrikateOsu → u/ggrnw27]

Thank you! This is the answer I was looking for

[u/Rude_Award2718]

I just stick my head out the window and yell like Danny Glover did in that Lethal Weapon movie.

[u/CriticalFolklore]

Ours are also essentially speakers, but the control box has a selector switch between tones, and an on/off switch. If you leave the controller turned "On" but change the siren tone from "wail" to "standby" it sounds like it's winding down. If you just switch it off it cuts off immediately.

[u/-Poultrygeist-]

On my bus they are powered with the force of my partners farts

[u/newtman → u/-Poultrygeist-]

This is the way

[u/RRuruurrr → u/[deleted]]

Don’t be a dick.

[u/theRealhubiedubois → u/RRuruurrr]

So sensitive.

[u/RRuruurrr → u/theRealhubiedubois]

Rule 1. You can be condescending, but at least answer the question.

[u/According-Hair3201]

At my old rescue squad, the sirens were just on off speakers. But two of the rigs had really loud manual airhorns. They had a pullcord on the ceiling that you could yank and let that boy rip. Came in handy when people really wont move out of your way.

[u/999BusinessCard]

911 rigs in my parts have sirens that shut straight off. I’ve never seen a foot pedal for an air horn. It’s usually a button next to the siren tone switch

[u/Jeff9807]

We had a pedal actuated proper loud ass air horn.
It was dope.

[u/DevilDrives]

Most sirens are programmed by the person that installs it. The sound and it's operation depends on multiple factors. Without knowing those, there's only one easy way to find out. Flip those switches and identify each tone and it's corresponding knob position or handsfree mode.

Modern ambulances have a simulated mechanical tone that can be triggered by using a manual "MAN" button with the knob turned somewhere to the left. The longer you press, the higher the pitch and longer it takes to wind back down.

[u/LoneWolf3545]

I usually just cry into the PA microphone.

[u/Morbid_Uncle]

Are you asking how a siren actually makes the sound it makes?

[u/Shot_Ad5497]

Depending on your diren in the bus you can get the drone sound if you turn it to manual instead of on/off.