2. HEARING LOSS

3. Hearing Loss Children and Adults who are deaf are those who cannot hear or understand conversational speech under normal circumstances. Their hearing loss exceeds 75 db, and in many cases, the loss may be greater than 90 db.

4. THE HUMAN EAR The ear of an average, healthy, young adult can respond to frequencies in the range of 20 Hz to 20,000 Hz. The human ear is most sensitive to sounds of 1000 to 4000 Hz.

5. Anatomy of the EAR

6. Anatomy of the Ear (Outer Ear) The Outer Ear (pinna), captures sound waves and funnels to the middle ear. The tympanic membrane is commonly called the eardrum.

7. Anatomy of the EAR (Middle Ear) The middle ear is that part of the ear between the external and the inner ear. Its outer border is the thin membrane known as the ear drum, or tympanic membrane.

8. Anatomy of the Ear (Inner Ear) The inner ear is the delicate structure which transforms the sound vibrations from the stapes into nerve signals that are transmitted to he brain. It also plays an important role in maintaining our balance.

9. Sounds Several animals can hear sounds of much higher frequency, which is why humans do not hear special whistles that may be heard by dogs. Sounds vary not only in frequency, but also in intensity.

10. Levels of Sounds For example, the intensity of normal conversational speech varies between 50 and 70 db. Very intense sounds, such as those of a lawn mower, may be as high as 100 db SPL.

11. Levels of Sounds The intensity of live rock concerts may reach 115 to 120 dB SPL. A sound of 140 dB induces pain.

12. Intensity Is related to amplitude, which is the extent of displacement of the molecules in their to-and-fro motion. The greater range of displacement, the greater the amplitude of sound. The greater the amplitude of sound, the higher the intensity of sound.

13. Decibel The decibel is a relative measure; it helps compare the intensity of one sound against the other, a standard. The decibel also is a measure of sound pressure.

14. PERMISSIBLE NOISE EXPOSURE

16. Hearing Protection Noise Reduction Rating - 29 dB

17. Hearing Protection Noise Reduction Rating - 31 dB

18. Hearing Protection Noise Reduction Rating - 22 dB

19. Hearing Protection Noise Reduction Rating - 23 dB

20. A SELF HEARING EVALUATION Can you usually hear and understand what a person says, without seeing his face, if that person whispers to you from across a quiet room? Can you usually hear and understand what a person says without seeing his face, if that person talks in a normal voice to you from across a quiet room? Can you usually hear and understand what a person says without seeing his face, if that person shouts to you from across a quiet room? Can you usually hear and understand a person, if that person speaks loudly into your better ear? Can you distinguish the sound of speech from other sounds and noises? Can you usually tell one kind of noise from another? Can you only hear loud noises? How difficult do you find it to follow conversations if there is surrounding noise (for instance, while several people are talking at the same time as in a restaurant?