[The 2f1-f2 DPOAE amplitudes and latencies in the groups of older people with presbyacusis and young people with normal hearing].

Otoacoustic emissions have been shown to be useful as indicators of the cochlear function. One of the most valuable techniques is distortion product otoacoustic emission recording (DPOAE), mostly 2f1-f2 distortion, which is described as being present regularly and indicating the strongest connection with hearing level. DPOAE amplitudes are analysed as relating to the frequency (DP-gram) or to the signal levels (input-output function). Another feature of DPOAE providing many details with regard to cochlear mechanics seems to be the assessment of 2f1-f2 DPOAE latencies. In the present study 2f1-f2 DPOAE amplitudes and latencies were analysed and compared in two groups: the elderly with presbyacousis and the young with normal hearing level. All measurements were taken using Otodynamics ILO 92 system. DPOAE latencies were recorded by phase gradient method with fixed-f1 and swept-f2 signal. The following signal parameters were used: f2 ranging from 732 to 6396 Hz, signal levels L1 = L2 = 70 dB SPL, f2/f1 ratio ranging from 1.18 to 1.25. According to the mathematical formula y = 1.412 + exp(7.685-0.7698ln(f2)) 2f1-f2 DPOAE latencies were calculated in the group of young people at f2 = 1.0 kHz; 2.0 kHz; 3.0 kHz; 4.0 kHz; 5.0 kHz; 6.0 kHz as follows: 12.08 ms; 7.67 ms; 5.99 ms; 5.08 ms; 4.50 ms; 4.10 ms. The analogous analysis revealed the following results in the group of the elderly: y = 2.402 + exp(9.293-1.019ln(f2)) and calculated latencies--11.9 ms; 7.09 ms; 5.50 ms; 4.71 ms; 4.24 ms; 3.93 ms. The greater differentiation of the latencies measured in low frequency band was observed in the elderly while in the young subjects in mid and high frequency bands. The 2f1-f2 DPOAE amplitudes recorded for the whole frequency band were significantly higher in the young people than in the elderly. No correlation was observed between latencies and amplitudes in both investigated groups.