Hearing Conservation & Noise Awareness

1. Hearing Conservation & Noise Awareness TDI-Brooks International Revision June 2016

2. What we’ll talk about: • Definitions • Parts of the ear • How the ear works • Occupational hearing loss • Hearing loss risk factors • Hearing conservation

3. Definitions • Sound is any pressure variation that the ear can hear. The number of pressure variations over time is frequency (Hz). • Noise -unwanted sound. • Decibels (dB) is how sound is measured • Loudness depends upon sound pressure and impacted by frequency (pitch).

4. Ear Anatomy • There are many parts of the ear, but they are divided into 3 main sections

5. Outer Ear • Outer Ear- the open part up to the drum

6. Middle Ear • Middle Ear- (air filled) drum, bones & Eustachian tube

7. Inner Ear • Inner Ear- (liquid filled) cochlea, organ of corti and semi-circular canals

8. Organ of Corti • This is a tiny layer in the tubes of the cochlea.

9. Organ of Corti • If you unroll the cochlear tube and look inside, you will see three smaller tubes.

10. Organ of Corti • The organ of corti is in the middle tube. It is made of a membrane laid over hair cells (stereocilia), which are connected to a nerve.

11. Organ of Corti • The liquid in the cochlea is constantly moving in response to sound. The liquid moves the basilar membrane against the hair cells, sending signals to the nerve.

12. Organ of Corti • Then the nerve sends signals to the brain, which are interpreted as sounds.

13. How The Ear Works • Basically, outer ear collects sound waves from the air and funnels them into the ear canal where they are transported to the ear drum. The collected sound waves cause the eardrum to move back and forth in a vibrating mechanical motion that is passed on to the bones of the middle ear.

14. How The Ear Works • As the stirrup rocks back and forth it passes vibrations on to the inner ear through the oval window and into the fluid of the inner ear (cochlea). The movement of the fluid interacts with the hair cells in the cochlea which are connected to nerves that transmit the sound signals to the brain.

15. Organ of Corti • The hair cells can recover from some damage, but once permanently damaged, do not grow back…

16. How Damage Occurs • Think of the hair cells like grass on a summer day. If you walk on it, your footprints press the grass down. If the grass is healthy, it will eventually spring back up.

17. How Damage Occurs • But if people continue to walk in the same place, the grass will eventually die and become a path.

18. Occupational Hearing Loss • Occupational hearing loss is defined as a hearing impairment of one or both ears, partial or complete that results from noise exposure at work. • Two categories of hearing loss • Noise-induced hearing loss • Acoustic trauma

19. Noise Induced Hearing Loss Noise induced hearing loss happens over months or years of repeated noise exposure and is permanent .

20. Noise Induced Hearing Loss • Just like the path in the grass, frequent exposure prevents the hair cells from repairing themselves, leaving “paths” of damage in the cochlea.

21. Acoustic Trauma Acoustic trauma is the injury to the sensorineural elements of the inner ear. Acoustic trauma is produced by one or a few exposures to sudden, intense noise from blasts, explosions or by direct trauma to the ear. • Examples: small arms fire, explosions, fireworks

22. Acoustic Trauma • Examples: small arms fire, explosions, fireworks Blasted area in grass- will not repair on its own Blasted area in row of cochlear hair cells- unlikely to repair on its own

23. Average Noise Levels

24. Average Noise Levels

25. Hearing Loss • Examples: • 20% of the population between 50 and 59 experience a hearing loss of 20% without any industrial noise exposure. • However, this increases to 27% if exposed to steady state noise at 90 dB, and is 36% if exposed to 95 dB

26. Hearing Loss Risk Factors • Noise Exposure Factors • Intensity of the noise (sound pressure level) • Type of noise (frequency) • Period of daily exposure (dose) • Total duration of exposure • Other Factors • Individual susceptibility • Age • Coexisting hearing loss and ear damage

27. Hearing Conservation • Current beliefs are that exposure of the unprotected ear to sound levels about 115 dB is hazardous. • Exposure to sound levels below 70 dB is safe and does not produce any permanent hearing loss. • The majority of industrial noise exposure fall within this range.

28. Hearing Conservation • Frequency also factors into hearing loss. Noise about 500 Hz has a greater potential for causing hearing loss. • The incidence of noise-induced hearing loss is directly related to total exposure time. Intermittent exposures are less damaging to the ear.

29. Permissible Noise Exposure (OSHA)

30. How to Prevent Hearing Loss • Controls • Engineering- add sound controls • Administrative- alter work schedules to reduce worker exposure, alter machine operation times to expose fewer workers. • PPE- hearing protection devices-acoustic barriers that reduce the amount of sound energy transmitted through the ear canal to the inner ear.

31. When do you need hearing protection? • OHSA recommends hearing protection when workers are exposed to more than 85 dB over a continual exposure of 8 hours.

32. Smart Phone Apps Areas of the vessel that require hearing protection are clearly marked with signage. But if you want to double check… There’s an app for that…

33. Protective Equipment (PPE) • Ear canal caps - seal external openings of the ear canal but do not go into it. (good for short periods and light protection) Soft material held in place by a light weight headband. Good

34. Protective Equipment (PPE) • Ear plugs – soft plastic or foam plugs that are inserted in the ear canal. Better

35. Protective Equipment (PPE) Better Ear plugs – only effective if properly inserted into ear canal.

36. Protective Equipment (PPE) • Ear muffs – two cup shaped devices that fit over the entire external ear held in place by headband. Better (Please adjust for proper fit)

37. Protective Equipment (PPE) • Ear muffs AND ear plugs Best

38. Audio sample of hearing loss Hear the World Foundation assists children with hearing loss around the world.