The following are audio test files, all in MP3 format.
25Hz to 29Hz
30Hz to 34Hz
35Hz to 39Hz
40Hz to 44Hz
45Hz to 49Hz
50Hz to 54Hz
55Hz to 59Hz
60Hz to 64Hz
65Hz to 69Hz
70Hz to 74Hz
75Hz to 79Hz
1kHz Test Tone 1 min
Pink Noise 1 min