Question 6 of 7: Hearing Loss, Noise/Vibration Controls, and Instruments

Question 6: Hearing Loss, Noise/Vibration Controls, and Instruments (20 marks: 6/6/8)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

(i) Types of Hearing Loss

• Conductive — outer/middle-ear problem (wax, damaged eardrum/ossicles); often treatable.
• Sensorineural — inner-ear/nerve damage, including noise-induced; usually permanent.
• Mixed — both. Noise first causes a temporary threshold shift, then (with repeated exposure) a permanent sensorineural loss (notch near 4000 Hz).

(ii) Engineering Controls for Noise and Vibration

• At source (quieter/low-vibration equipment, maintenance, balancing); enclosures and barriers (acoustic enclosures, absorptive materials, mufflers/silencers); isolation and damping (vibration mounts, resilient couplings); and path treatment (distance, absorption).

(iii) Measurement Instruments

• (a) Sound level meter — measures instantaneous sound-pressure level (dBA); area/noise surveys.
• (b) Impulse meter — captures short-duration impulsive/impact noise peaks.
• (c) Frequency (octave-band) analyzer — separates noise into frequency bands to identify dominant frequencies for control and protector selection.
• (d) Dosimeter — worker-worn; integrates exposure over the shift to give the personal noise dose/TWA.