All downed power lines pose a shock hazard.
Downed lines can shock you even if they do not hum or spark. They can also energize the ground nearby and create a step potential zone. And, even dead lines can become re-energized at any time due to automatic re-closers.
If you know or even suspect that a power line is down, contact the local electric utility immediately, and take precautions to protect yourself and the public.