The concept of acoustic impedance was known in the ear of 1910 and its clinical application was developed after Metz's report in 1946. Many studies in the field of hearing test and screening test by impedance audiometry was reported. Author measured acoustic reflex sensation level according to each age group on 176 normal male(352 ears) and 152 normal female(304 ears). Results were as follows ; 1) Average acoustic reflex sensation level was 79.3 dB at contralateral side, 77.3dB at ipsilateral side. 2) Acoustic reflex sensation level at contralateral side was higher than at ipsilateral side in 1 KHz and 2 KHz. 3) There was no difference significantly of acoustic reflex sensation level in male and female. 4) Acoustic reflex sensation level in above 65 years old was lower than other age group at contralateral and ipsilateral side. 5) Acoustic reflex sensation level in 4 KHz and 8 KHz at contralateral side in above 40 years old group was lower than other age group. 6) Incidence of non-acoustic reflex in above 60 years old was higher than other age group. 7) Incidence of non-acoustic reflex in 8 KHz was higher than other age group.