1. The unit used to measure sound level is _________________.
2. Sound level greater than ________ can cause pain and permanent ear damage.
3. What sound level in decibels is called the threshold of hearing?
4. Why is it advisable to wear ear protection while mowing the lawn, even if the sound level is just 80 decibels?
5. ______________ are used to make sounds louder for those with impaired hearing.
6. The earliest hearing aids were ___________ shaped.
7. How do modern hearing aids work?
8. Profoundly hearing-impaired people hear no sounds at all. Right or Wrong?
9. Explain what a bionic ear is and how it works.