(where is the reference level, the value of which at the moment escapes me, but we don't need a value for it anyway.)
For the second sound
So the "loudness" will be:
I have corrected the above calculation (thanks again to CaptainBlack). The result is still practically the same as my original result in that it would be VERY difficult to hear the 94 dB sound as it barely contributes compared to the 128 dB sound.