2006-09-22 07:50:27 · 7 answers · asked by Anonymous in Science & Mathematics ➔ Other - Science
Typically this is what happens.
When the sun goes down the earth's surface starts to cool quite rapidly. The air close to the surface cools by conduction. This results in a temperature inversion.
A temperature inversion can result in a layer of cold air at ground level with a layer of warm air above. Air is a poor conductor of heat and so it is not uncommon for a distinct boundary to form between the lower layer of cool air and the higher layer of warmer air. The boundary between the layers can act as a reflector (think total internal reflection) such that sound will travel much further and with less attenuation.
The different levels of humidity in the two layers will also have an effect.
2006-09-22 08:52:57 · answer #1 · answered by Stewart H 4 · 1⤊ 0⤋
It is because the air is more dense at night. Sound needs a medium to travel through and typically the denser it is the more efficient it travels. That is why sound travels farther when it is foggy when the air is saturated with water vapor. Next time you go swimming go under water and have someone gently tap two rocks together underwater at the other end of the pool. You can hear it really well compared to when you do it in the air. An example of the converse is space. Space is almost a vacuum so there is no matter there to transmit sound and it can't be heard in space.
2006-09-22 15:42:14 · answer #2 · answered by wishiwerewest 2 · 0⤊ 0⤋
I'm going to have to disagree with p l gray. At night the air is cooler and therefore denser. The increased density allows for greater distance. But at the same time I would have to say that the difference in temperature is so minor that the effect would be barely measurable. The most probable answer (again given by other people) is that there is less ambient sound enabling a person to hear better.
2006-09-22 15:01:43 · answer #3 · answered by BobbyD 4 · 1⤊ 0⤋
It doesn't. The level of background noise is lower so the sounds that ARE made can be picked out more easily from a greater distance. Sort of like how can see the moon during the day but rarely notice it because the rest of the sky is so bright.
2006-09-22 14:54:18 · answer #4 · answered by AmigaJoe 3 · 1⤊ 0⤋
The air is cooler and less dense at night allowing sound waves to travel farther.
Added:
You're right, my physics is backwards, cooler air is more dense. My bad.
But the increased density does increase the ability of sound to travel. Sound needs a medium to travel.
2006-09-22 14:53:37 · answer #5 · answered by Anonymous · 0⤊ 1⤋
i think its just more noticable at nite, because there is not as much ambient noise to cancel or overpower it. so you can hear that train whistle or stuff from a long ways away more easily.
2006-09-22 14:54:35 · answer #6 · answered by Big hands Big feet 7 · 1⤊ 0⤋
This is untrue. I believe what you are referring to is AM radio waves.
2006-09-22 15:25:42 · answer #7 · answered by wjsst22 2 · 0⤊ 0⤋