Method:

• Ten Otolarngologically normal subjects were selected for the tests.
  The subject was seated in a chair in an anechoic chamber with his head positioned on the chin rest.
• The sound source was located in front at a distance of 30cms from each ear.
• The subject’s open ears hold (without any ear defender) and closed threshold (while wearing an ear defender) were then determined using the ear defender the under test. he following pure tone frequencies were tested: 250Hz, 500Hz, 1000Hz, 2000Hz, 3000Hz, 4000Hz, 6000Hz, 8000Hz, each subject was given their test in intervals of ‘One Minute’.

Results:

• The hearing thresholds shifts caused by wearing of the ear defenders, which corresponds to the attenuation values for the frequencies of 250Hz, 500Hz, as the ‘closed thresholds’ could not be determined due to audio- matric limitation of maximum tone intensity at these frequencies.
• The attenuation for the 250Hz and 500Hz exceeded 10dB and 15dB respectively. It is seen that the maximum attenuation is provided at the important frequencies of 2000Hz, 3000Hz, 4000Hz to ranging from 30 to 47dBs with a mean of about 35dBs.
• The new design earmuffs have shown better attenuation at frequencies of 1000Hz, 2000Hz, 3000Hz & 4000Hz. The improvement is satisfactory has regards fitting, adjustability and comfort. None of the subjects reported any discomforts.