Co-Relation between Pure Tone Threshold and Acoustic Reflex Threshold in Normal Hearing Population

Introduction The main components of routine audiological test battery are pure tone audiometry as well as immittance audiometry. The purpose of the present study was to find the correlation between acoustic reflex threshold (ART) and pure tone threshold (PTA) in normal adults. Method Thirty subjects in the age range of 20 to 25 years with normal hearing sensitivity were selected with equal number of both the genders. All the participants underwent otoscopic examination, Weber test and tympanometry which revealed to be normal. All the subjects with otological symptoms, hearing loss and neurological symptoms were excluded from the study. Modified Hughson Westlake (1959) procedure was followed using pure tone stimulus in calibrated GSI-61 Audiometer. Ipsilateral ART was taken in calibrated GSI Tympstar middle ear analyzer, using a probe stimulus to monitor admittance changes elicited by a reflex- activating stimulus. Subjects were asked to be seated in a well illuminated sound treated audiometric room.  Calibrated headphone TDH-49 was used and pure tone average was calculated using the modified Hughson Westlake procedure. Frequencies measured were 250HZ, 500Hz, 1 KHz, 2 KHz, 4 KHz and 8 KHz. All the subjects' tympanograms revealed to be type 'A'.  ART was measured in frequencies 500Hz, 1 KHz, 2 KHz, and 4 KHz.  Results The statistical evaluation revealed that the lower limit is 68.62 in right ear and 71.60 in left ear. The upper limit is 90.11 in right ear and 87.52 in left ear, i.e. approximately 70-90 dB HL in both the ear. There is a slight difference between the thresholds of right and left ear. Discussion PTA and ART findings are correlating according to the theoretical norms. Conclusion Co-relation between acoustic reflex thresholds and pure tone thresholds for tones in subjects with normal hearing and normal middle ear function are 70-90 dB HL.