Why do I hear myself in a big cave?

What BBN said about it

1. 

   Dr. Nina Byte · Tech & Science CorrespondentChip asked me why he hears himself in a big cave. Apparently, this is what my advanced degree prepared me for.

2. 

   Chip Darnell · U.S. News AnchorBecause the cave is a really good listener, Nina. Like a bartender, but made of rock.

3. 

   Dr. Nina Byte · Tech & Science CorrespondentNo. Step one. When you shout, sound waves fly away from you.

4. 

   Chip Darnell · U.S. News AnchorSo the shout leaves, like a guest who overstayed their welcome at a dinner party.

5. 

   Dr. Nina Byte · Tech & Science CorrespondentStep two. When the waves hit a hard wall, they bounce back.

6. 

   Chip Darnell · U.S. News AnchorThe wall is the returns counter, and it says no refunds, so my shout gets handed right back.

7. 

   Dr. Nina Byte · Tech & Science CorrespondentStep three. If the wall is far away, the bounced sound arrives a bit later.

8. 

   Chip Darnell · U.S. News AnchorSlow clerk. Long line. Everybody's holding a mattress.

9. 

   Dr. Nina Byte · Tech & Science CorrespondentStep four. You hear your shout again.

10. 

    Dr. Nina Byte · Tech & Science CorrespondentThat is an echo, and per Wikipedia, it is a reflection of sound that arrives after a delay.

11. 

    Chip Darnell · U.S. News AnchorHow fast does sound travel?

12. 

    Dr. Nina Byte · Tech & Science CorrespondentThat is actually a great question. In dry air at twenty degrees Celsius, about three hundred forty-three metres every second.

13. 

    Dr. Nina Byte · Tech & Science CorrespondentLight is almost a million times faster.

14. 

    Chip Darnell · U.S. News AnchorSo my shout gets back before the clerk even finds the receipt. I want that receipt.