Oh geez!
Sadly 1st edition has been dead for about 30 years, and I haven't seen my 1e rulebook in over a decade
IF I recall right, that was covered by the perception skill.
And, as always it was a SKILL + ATTRIBUTE + DP for your total thrown dice VS whatever target number the GM assigns. (usually between 3 and 9. 3 for something noticeable, 9 for something incredibly hard).