Physics Puzzler: Sound Reasons

Those who spend time outdoors have likely noticed that sounds can be heard at greater distances downwind from their source. And “shouting into the wind” is an idiom for futile attempts to communicate. Why does the wind affect how far away one can hear sounds?

Under some weather conditions distant sounds, even on a windless day, seem to be heard at greater distances. When I was a child I remember standing waiting for the school bus at the end of a long country lane in Iowa. On a cold, sunny morning after a fresh winter snow, distant sounds of dogs barking, and other farm animal sounds, could be clearly heard that wouldn’t be heard as well on a summer day. You may have had a similar experience in a city, where the sound of passing traffic is louder early in the morning than in the evening (even if the number of cars remains the same). Why is this?

These days one can find answers to such questions on the Internet. But I hope you wouldn’t think of looking there before you puzzle them out yourself. In this case, many of the answers on the Internet are simply wrong, but correct treatments can be found with a bit of effort.

Ready for the answers? See “Sound Reasons: The Answer ”.