i am worried and i am a newbie with an attic furnace. banging noises (knock)

[HVACbasicapprentice]

i am worried and i am a newbie with an attic furnace. banging noises ( sounds like knock at door) .  i get about 3 knocks which resonate like a knock at my door but from the attic. they seem to be at regular intervals. the flue / exhaust seems to be sputtering and struggling with water and or moisture. i just got home at 4 am. i live in a shitty neighbourhood and have 3 other units below mine ( my furnace is just for me) . im assuming that i am being over cautious and or frightened but bad stuff happens around here all the time. is it normal or possible for a furnace to make steady and somewhat regular bangs. it legitimately sounds like a neighbours door is being knocked on, but again, in somewhat regular intervals.  im sorry to bug you guys about this but i am relatively concerned. i am a g3 studying and working on my g2. i am nowhere near a pro or an average tech as of now.

any help or input would be greatly appreciated. i have already armed myself just incase.  thanks in advance.

[HVACbasicapprentice]

i yelled at my attic in a pathetic scared voice a few times. my deterrents are to no avail .  i have been theorising that excess moisture from a bad flue exhaust ( with a negative / backwards flow) is allowing mositure to drip back into the system and get to the flame to make the "knocking/ puff" sound

i feel like such a jackass but this neighbourhood is pretty messed up to start with .

[Hgye]

You (or someone else qualified) needs to go into the attic to troubleshoot and figure out what is making the noise.  It is very difficult to diagnose from the floor below.

[HVACbasicapprentice]

thanks for the reply, i will contact the landlord this coming morning. it seems like an issue regardless of me being scared of someone being in the attic or something silly like that.