# Speed of sound confuses me

Just a random question out of interest.

When you hear an explosion, e.g. a firework, firecrackers etc, from far awa how does the sound reach our ears so quickly?

The speed of sound in air is like 300m per second, and if a firework 2 km diagonally away from me in the sky explodes, then mathematically it should take 2000m/300mps ~ 6-7 seconds to travel to our ears..... But in reality we all hear it right away. Whats going on?

Do all sounds I hear from afar, like planes, are sounds created seconds ago in 'the past' or do I hear it closely to when it was formed

• You don't hear it right away. You just have no direct experience with fireworks so are completely unable to judge their size or distance when they are up in the sky. Have someone hit a shovel on concrete from even just 1km away. You will clearly experience the delay. I noticed this when I was ten years old outside playing during the winter and people were trying to break through ice on their driveways. And personally, I do hear a delay. You have to listen and watch carefully because if all you ever see and hear are fireworks from far away your brain tunes it out as the way fireworks should be. Jan 2 at 5:01
• for reference, fireworks are usually sent less than 100m in the sky. But they definitely obey the speed of sound Jan 2 at 6:14
• It's possible that the sound from a firework reached you around the same time another firework went off. Also, you can tell that the sound from a plane flying high overhead appears to come from far behind it.
– Puk
Jan 2 at 6:26
• if I had to choose personal experience or physics (done right), I'd always rely on physics first. Never watched fireworks from long distance and short distance? Time delay is proportional to distance as $L/a$: you could easily make mistakes in your estimation of distance $L$, while you can take $a=300 \, m/s$ as a good estimate of speed of sound in air within 20% error Jan 2 at 9:25