I'm sure I could easily Google the answer, but this is always more fun.

Does sound travel more easily in colder temperatures? I ask this question because I live in a condo complex, whenever i ride the bike early in the morning or late at night, I set off car alarms. In the afternoon, nothing, ever.

The other morning I was riding to work, leaving the complex, 4 alarms went off just idling through the lot. It was freezing cold (California-wise, in the 50's) so I'm wondering if that had anything to do with it.

Any ideas/experiences?

 

I'll take a shot.

Theoretically sound (since it is really waves of energy moving through the air think waves on a pond) would travel farther through cold air than hot air but the speed of travel wouldn't be affected appreciably. The denser the medium (liquid is denser than air, and cold air is denser than hot air) the more coherent the wave energy would be. I.E. the less likely to dissipate. The force would be affected though I think. Sound waves through denser medium, would retain more force thus more like to set off motion sensitive alarms. there might be enough of a difference in the force of the waves produced by your exhaust, between cold and hot air to make a difference.

Of course I am relying on a lay person's understanding of physics.

USMAMule

 

Yes. Colder air is more dense so sound travels faster. Just as water is more dense than air and sound travels approx 4 times faster in water than air. The closer the molecules are together, the faster and easier sound travels through them

 

I asked my wife, who`s a Harley rider and a physics teacher (brains and beauty, believe me) and she says, "USMAMule has his physics right, but it seems that those changes in wave speed and dissipation -- loosing less oomph -- wouldn't be significant over such a short range. (You can definitely hear far-away things better when it's very cold. There are also fewer competing noises outside on a cold night.) I wonder if it isn't in the car's sensors. Most are designed to detect vibrations, and in the cold, whatever spring is in the sensor would be more rigid and might trigger more easily. Awesome question! I'm going to toss it out to my students on Monday."

 

Glad I can help the young minds out there! It's funny, when you Google it you get two viewpoints. One being yes, sound travels better in cold temps due to more densely packed molecules. Others say warm air because hot molecules are moving faster than slow-moving cold molecules, which makes the sound travel more easily. Basically an object in motion tends to stay in motion, so trying to move more densely packed cold molecules is more work.

But you're probably right, car alarms are more motion based than sound so the cold molecules would make more movement.

 

Those of us old timers will remember the days that you could receive more radio stations at night than you could during the day. Probably for the same reasons. Only radio waves instead of sound waves.

 

emerican19. Cool thread, I know for sure sound is louder at very low temps. I have O'hare jets (every 5 mins. or less) taking off near my house in the deep cold of January.

No matter what technology they use too silence the engines, at though Temps. ie. -9 to 10*f. Damn loud!

 

maybe the cars with alarms arent in the lot in the afternoons?or there not on... people off to work etc etc...

 

so what your saying is: if i call in pizza when its cold out I will get it to my house faster than if i ordered and it is hot out. due to sound traveling faster and all?

 

as fast as sound travels!