(HealthDayNews) -- If you think that's the sound of the ocean you hear when you put a seashell to your ear, listen up.
It's the echo of the blood moving in your ear, says the book, Amazing Facts About Your Body, published by Doubleday and Co.
Among other "eary" tidbits from the book:
- The easiest sounds for humans to hear are vowel sounds -- ah, aw, eh, ee and oo.
- Humans can distinguish the direction of two sounds if they originate from points at least 45 degrees apart, while dogs, with their movable ears, can distinguish sounds only 11 degrees apart.
- A baby can hear sounds up to 30,000 cycles per second; a teenager cannot hear sounds above 20,000 cycles per second; a man age 50 cannot hear above 8,000 cycles; and a man age 80 cannot hear above 4,000 cycles.
