Sometimes when assessing situations for students who use hearing, a vehicle's detection-to-arrival time is considerably less than that of other vehicles because when the student first heard it, there was extraneous masking noise (perhaps unnoticed by the student). In that case, you can't use the detection-to-arrival time of that vehicle to conclude it is a Situation of Uncertainty. However, you can take the opportunity to make students aware of the presence of a masking sound and how it can reduce their ability to hear the vehicles (this will be covered in Section 4). |