Noise-induced deafness
Noise trauma is a primary preventable cause of sensorineural hearing loss, which occurs due to damage to the hair cells in the inner ear. It can result from various sources:
- Occupational Noise: Prolonged industrial exposure or sudden loud sounds.
- Recreational Noise: Exposure to loud music or other recreational activities.
- Accidental Noise: Such as blast injuries or gunfire.
Types of Occupational Noise Damage
- Occupational Acoustic Trauma:
- Definition: A sudden change in hearing due to a single exposure to a loud sound (e.g., explosion).
- Occupational Noise-Induced Hearing Loss (NIHL):
- Definition: Gradual hearing loss developed over a long period due to continuous or intermittent loud sound exposure.
Characteristics of Occupational Noise-Induced Hearing Loss
- Nature: Always sensorineural.
- Accompanied by: Often high-pitched tinnitus.
- Affected Area: Hair cells of the inner ear.
- Laterality: Typically bilateral, but may be unilateral.
- Frequency: High frequencies are affected first.
- Audiogram Signs: “Notching” at 3000, 4000, or 6000 Hz, with recovery at 8000 Hz.
- Factors Affecting Notch Location:
- Frequency of damaging noise.
- Length of the ear canal.
- Rate of Hearing Loss:
- Highest during the first 10-15 years of exposure.
- Rate reduces as hearing threshold increases but accelerates with age-related loss.
- Irreversibility: Hearing loss is not reversible.
Diagnosis
- Clinical Basis: Based on history of noise exposure.
- Early Sign: A 10 dB threshold shift from baseline in pure tone average at 2000, 3000, and 4000 Hz.
Treatment
- Irreversibility: Damaged hair cells do not recover; the condition cannot be treated.
- Importance of Early Detection: Crucial for improving prevention efforts.
Prevention
- Noise Protection: Aggressive use of noise protection devices.
- Foam-insert earplugs: Can decrease noise exposure by 30 dB.
- Regulation: Industry exposure limit of 90 dB for an 8-hour shift.