Download Amplification systems: Hearing aids

Noise induced hearing loss

Predisposing factors:
 Drug
use (aspirin)
 Gender

Cause: Exposure to noise

Acoustic trauma: Damage due to loud impulsive
noise

Two forms of NIHL

Temporary threshold shift (TTS)

Permanent threshold shift (PTS)

Relationship between noise level and duration of exposure (OSHA,
1983)

85 dB A: 8 hours
90 dB A: 4 hours
95 dB A: 2 hours
105 dB A: 30 minutes



Audiometric findings

Sensorineural hearing loss

Usually progressive with continued noise
exposure

Characteristic notch around 4000 Hz

Tinnitus matched to frequencies around 3-6 kHz
Measures to prevent NIHL

Avoid noise exposure, especially if on certain
types of medication

Hearing protection

Monitor hearing loss periodically
Presbycusis

Age-related hearing loss

Progressive, sensorineural

Effects first seen in high frequencies

Age-related changes occur not only in cochlea

Often: Speech-understanding difficulties
Progression of hearing loss with age in
females and males
500
Males
Frequency (Hz)
Frequency (Hz)
1000
2000
4000
6000
8000
250
0
0
10
10
20
20
30
40
60-64
50
65-69
70-74
60
75-79
70
80-84
80
85-89
dB HL (ANSI, 1969)
dB HL (ANSI, 1969)
250
Females
500
1000
2000
4000
6000
8000
30
60-64
40
50
65-69
70-74
60
75-79
70
80-84
80
90
90
100
100
85-89
Méniére disease

Disease that originates in the labyrinth

Classic symptoms: Hearing loss, tinnitus, and vertigo

Symptoms can be paroxysmal, and are usually
progressive.

Probable causes: Endolymphatic hydrops, others

Treatment: Diuretics to limit fluid retention, diet control,
sedatives, vestibular suppressants, surgery.