1. The repetition of sound which is reflected from an object is referred to as _______.   the amplitude   an echo   the pitch   Hint Half-n-half Clue   2. The sound of thunder is heard 8 s after the flash of lightning. If the speed of sound in air is 330 m/s, then the cloud is at a distance of _______.   41.2 m   82.5 m   1320 m   2640 m   Half-n-half Clue   3. The part of the inner ear shaped like a snail is called the _______.   cochlea   eardrum   hammer   Half-n-half Clue   4. Echoes are caused by _______ of sound.   rarefaction   reflection   refraction   Half-n-half Clue   5. The number of sound vibrations per second is called _______.   time period   frequency   amplitude   Half-n-half Clue   6. The lower limit of frequency that can be heard by the average human is about   2 Hz   20 Hz   200 Hz   2000 Hz   Half-n-half Clue   7. If a flash of lightning is observed in a cloud 2640 m away and the speed of sound in air is 330 m/s, then the sound of thunder will be heard _______ s after the flash of lightning.   3   8   16   24   Half-n-half Clue