Patzer

In the lab experiment involving the rats, David Baker is told the frequency was 100,000 (Herz). A frequency that high is not detectable by human ears, so there was no reason for anyone to be wearing hearing protection. Human hearing range is only 20 Hz to 20,000 Hz, so a frequency of 100,000 Hz would not have been audible, even though the machine was making an audible sound.