Arphi Electronics Private Limited

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IMPROVED VARIETY OF INDIGENOUS MUFF TYPE EAR DEFENDER :

TEST PURPOSE : Performance Evaluation

TEST SPECIFICATION :IS: 6000-1971-method of measurement of Real Ear Attenuation of Ear Protectors at threshold.

Arphi is the exclusive distributor for Electone 100% Digital Hearing Aids. Electone Hearing Aids are available in BTE , ITC and CIC range.

• Audio frequency generator
• Audio amplifier
• Calibrated audio frequency attenuator
• Loudspeaker

METHOD

Ten Otolarngologically normal subject 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.

The 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- matriclimitation 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.

CONCLUSIONS

The attenuation characteristics of the new design ear muff type ear defender are superior to those of ear muffs which are used currently specially in frequencies 1000Hz to 4000Hz although not fully to the specification. 

THE TEST RESULTS

The ear protectors were evaluated for their sound attenuation properties according to IS : 6229 -1971 by measuring the threshold shifts due to the ear protectors determined by 22 persons in an anechoic room using a pure tone signal incident from the front. The ambient noise in the anechoic room at the position of the subjects ear was then that given in cause 3.1.1