1. The part of the inner ear shaped like a snail is called the _______.   hammer   cochlea   eardrum   Hint Half-n-half Clue   2. Echoes are caused by _______ of sound.   reflection   rarefaction   refraction   Half-n-half Clue   3. The apparatus used in a ship to find out the depth of the sea underneath is called _______.   tuning fork   sonar   bell jar   Half-n-half Clue   4. When sounds reach the _______ or tympanic membrane, they make it vibrate.   hammer   eardrum   cochlea   Half-n-half Clue   5. 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   6. The _______ keeps the pressure in the middle ear the same as the outside air pressure.   Eustachian tube   eardrum   semicircular canal   Half-n-half Clue   7. The approximate speed of sound in air is _______ m/s.   330   3 × 108   1600   5000   Half-n-half Clue