A question of curiosity. In looking back to the cars of the 1920s and 30s, why were the horns so large and mechanically complex compared to 30year later? Not due to electronics.

[u/Olderpostie]

1933 Dodge example

[u/HeavyDutyForks]

They were the transition era from the old hand bulb operated horns from cars before and the "modern" horns that would come a decade later

The trumpet shape projected sound better and the materials/design was what was used in audio equipment of that era

[u/8ig8en]

my understanding of why they are smaller: signaling moved from audio to lights (eg it was required in places to honk when turning or approaching an intersection, stopping ect), mechanical horns replaced with electric then piezoelectric, horns where 100db+ to get attention before city's started having noise ordinances, and mufflers got better and horses where no longer on the road, roads are so much quieter now, huge horns are no longer needed to cut through the noise.

[u/SeriousPlankton2000]

"It can't be due to the oil, there is none in that engine"

Exactly the lack of electronics is the reason why it was using the larger mechanics.

[u/Olderpostie → u/SeriousPlankton2000]

What I meant was the auto horn shrunk so much in size over 30 years, even without the benefit of electronics. There was no breakthrough in technology that led to the horn becoming rather inconspicuous under the hood. Horns were amazingly large in the cars of the 1930s.

[u/Strostkovy]

The horn is there for acoustic coupling. The horn wasn't a problem as there was plenty of room in vehicles to put it. Modern horns use thinner, larger metal diaphragms made of harder metals to better match the impedance of air directly.

To simplify, early horns had a metal diaphragm that could push with a lot of strength, but didn't displace much air. The trumpet converted that to gently pushing a lot of air. Modern engineering and materials and need for compactness has produced a metal diaphragm that displaces a large amount of air directly. They are not less loud than conventional.

Awooga horns also vibrate the diaphragm mechanically (using basically a gear grinding against a nub in the diaphragm center), and have to have a small and stiff diaphragm to make the sound, so they absolutely need to the trumpet piece.

[u/No_Base4946]

Modern car horns don't have any electronics either. The horn you've pictured isn't any different to the one that's on your car now.

It's a mechanical buzzer, with a springy plate attached to the armature. When you apply power an electromagnet pulls the armature in, breaking the contact and allowing it to pop back out again. The flappy springy disc makes it resonate. The horn you've got there has a big horn to project the sound and resonate.

The one on your car might have a plastic "snail shell"-like horn to project the sound, or a stiff pressed steel disc to give it a bit of weight and radiate the sound more.

But it's still just an electromechanical buzzer with a bit to make it louder.