Table 3 Comparison of DP amplitudes at different intensities and frequencies between control and study groups

500 Hz

35/25 dB

3

26.0

6

35.0

 − 2.00

0.046*

45/35 dB

3

24.7

6

36.3

 − 2.57

0.010*

55/45 dB

5

25.7

11

35.3

 − 2.12

0.034*

65/55 dB

5

25.2

10

35.8

 − 2.34

0.019*

75/65 dB

10

28.5

11

32.5

 − 0.906

0.365

1000 Hz

35/25 dB

 − 3

19.9

1

41.1

 − 4.75

 < 0.001*

45/35 dB

2

23.3

4

37.7

 − 3.19

0.001*

55/45 dB

2

23.7

9

37.3

 − 3.01

0.003*

65/55 dB

10

27.8

13

33.2

 − 1.21

0.228

75/65 dB

11

24.8

15

38.2

 − 2.53

0.012*

2000 Hz

35/25 dB

 − 8

19.6

0

41.4

 − 4.93

 < 0.001*

45/35 dB

 − 7

23.2

0

37.8

 − 3.33

0.001*

55/45 dB

 − 2

20.1

3

40.9

 − 4.64

 < 0.001*

65/55 dB

6

25.8

11

35.2

 − 2.08

0.038*

75/65 dB

7

26.3

8

34.7

 − 1.89

0.059

4000 Hz

35/25 dB

 − 7

20.4

0

40.6

 − 4.75

 < 0.001*

45/35 dB

 − 8

21.4

0

39.6

 − 4.23

 < 0.001*

55/45 dB

 − 5

25.1

0

35.9

 − 2.51

0.012*

65/55 dB

 − 2

24.3

0

36.8

 − 2.81

0.005*

75/65 dB

12

37.7

7

23.3

 − 3.21

0.001*