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Now, ruling out the clearly audible ones, what would be the perception check difficulty for the 100 dB (wolf howls, metal on metal clashes) and lower levels?

a few pointer: 70 dB ambient is like a loud TV yelling at you, or a lively mess hall at lunch time. 100 dB at 1 meter from the origin is what you hear when standing next to a guy using a jackhammer - or a dog barking in your face. 120 dB is a vuzuzela in your face - a wolf howls louder than that. A gun can go to 170 dB.

Now, ruling out the clearly audible ones, what would be the perception check difficulty for the 100 dB (wolf howls, metal on metal clashes) and lower levels?

Now, ruling out the clearly audible ones, what would be the perception check difficulty for the 100 dB (wolf howls, metal on metal clashes) and lower levels?

• In the next room, hearing 68 dB in a 70 db loud ambience (a lively mess hall, a loud TV) clearly should be medium test, over a 60 dB TV-ambience would be easy and thus automatic with passive perception.
• Hearing 58 dB over a 60 dB ambient noise again is probably medium, and hard over a loud 70 dB room.
• Hearing 48 dB in a 60 dB ambient should be hard, while in a 70 dB ambience it should be impossible. Against the only conversation in the room (50 dB) it would be medium.
• Hearing 38 dB against a the 60 dB ambience is close to impossible (the room is 10 times as loud as the noise), against the only conversation (50 dB) hard, against whispered 40 dB conversations medium and against a quiet room of people staring at each other (20-30 dB) automatic.

To make it easier: a table of equivalent noise levels based on the one provided by Wikipedia, using this to calculate the dB to pressure and vice versa. This assumes each step having the previous as a new step and ignores the unknown properties of the door and hallway - it basically assumesopen space. $$\begin{array}{r|lll} \text{noise level} & \text{Pressure} & \text{At the door} & \text{At the curtain} & \text{In the room} & \text{equivalent noise level} & \text{This is...} \\ \text{in the Room} & \text{in the room} & \text{in 2m distance} & \text{down the hallway} & \text{10 feet in} \\ \hline 120\text{ dB} & 20 Pa &10 Pa & 1,64 Pa & 0,538 Pa & 88,6\text{ dB or a busy roadway} & \text{...clearly audible!} \\ 110\text{ dB} & 6,32 Pa &3,16 Pa & 0,518 Pa & 0,170 Pa & 78,6\text{ dB or a loud car passing by} & \text{...clearly audible!} \\ 100 \text{ dB} & 2\text{ Pa} &1\text{ Pa} & 0,164\text{ Pa} & 0,0538\text{ Pa} & 68,6\text{ dB or a loud TV} & \text{...audible over a normal conservation when the moment is not too noisy} \\ 90\text{ dB} & 0,63\text{ Pa} &0,315 Pa & 0,0516 Pa & 0,016 \text{ Pa} & 58,6 \text{ dB or a normal TV} & \text{ ...audible against a normal conservation when the moment is somewhat lively} \\ 80\text{ dB} & 0,2\text{ Pa} &0,1\text{ Pa} & 0,0164\text{ Pa} & 0,00538\text{ Pa} & 48,6\text{ dB or a normal conversation} & \text{ ...maybe audible if the conversation is more quetly and the ambient sounds are dimmed} \\ 70\text{ dB} & 0,063\text{ Pa} &0,0315\text{ Pa} & 0,00516\text{ Pa} & 0,00169\text{ Pa} & 38,6\text{ dB or a not too calm room} & \text{ ...barely audible against a normal conversation} \\ \end{array}$$

(Second instance of table, for formatting/testing purposes)

$$\begin{array}{r|lll} \text{noise level} & \text{Pressure in the room/} & \text{equivalent noise level} & \text{This is...} \\ \text{in the Room} & \text{at the door/at the curtain/} & (dB)\\ & \text{10 ft. in next room (Pa)} \\ \hline 120\text{ dB} & 20/10/1,64/0,538 & 88,6\text{ (busy roadway)} & \text{...clearly audible!} \\ 110\text{ dB} & 6,32/3,16/0,518/0,170 & 78,6\text{ (loud car passing by)} & \text{...clearly audible!} \\ 100 \text{ dB} & 2/1/0,164/0,0538 & 68,6\text{ (loud TV)} & \text{...audible over a normal conservation when the moment is not too noisy} \\ 90\text{ dB} & 0,63/0,315/0,0516/0,016 & 58,6 \text{ (normal TV)} & \text{ ...audible against a normal conservation when the moment is somewhat lively} \\ 80\text{ dB} & 0,2/0,1/0,0164/0,00538 & 48,6\text{ (normal conversation)} & \text{ ...maybe audible if the conversation is more quietly and the ambient sounds are dimmed} \\ 70\text{ dB} & 0,063/0,0315/0,00516/0,00169 & 38,6\text{ (a not too calm room)} & \text{ ...barely audible against a normal conversation} \\ \end{array}$$

To make it easier: a table of equivalent noise levels based on the one provided by Wikipedia, using this to convert the dB to pressure and vice versa and \$p_2=p_1\frac{1m}{distance}\$ between each point of reference. This ignores the unknown properties of the door, curtain and hallway - it basically assumes open space, so the result should be treated as an order of magnitude.

$$\begin{array}{r|lll} \text{noise level} & \text{Pressure in the room/} & \text{equivalent noise level} & \text{This is...} \\ \text{in the Room} & \text{at the door/at the curtain/} & \text{in the next room}\\ & \text{10 ft. in next room [Pa]} \\ \hline 120\text{ dB} & 20/10/1,64/0,538 & 88,6\text{ dB or a busy roadway} & \text{...clearly audible!} \\ 110\text{ dB} & 6,32/3,16/0,518/0,170 & 78,6\text{ dB or a loud car passing by} & \text{...clearly audible!} \\ 100 \text{ dB} & 2/1/0,164/0,0538 & 68,6\text{ dB or a loud TV} & \text{...audible over a normal conservation when the moment is not too noisy} \\ 90\text{ dB} & 0,63/0,315/0,0516/0,016 & 58,6 \text{ dB or a normal TV} & \text{ ...audible against a normal conservation when the moment is somewhat lively} \\ 80\text{ dB} & 0,2/0,1/0,0164/0,00538 & 48,6\text{ dB or a normal conversation} & \text{ ...maybe audible if the conversation is more quetly and the ambient sounds are dimmed} \\ 70\text{ dB} & 0,063/0,0315/0,00516/0,00169 & 38,6\text{ dB or a not too calm room} & \text{ ...barely audible against a normal conversation} \\ \end{array}$$