If a sound of 75 dB is reduced to 36 dB after passing through a wall, what is the Sound Transmission Loss (TL) rating of the wall?

To determine the Sound Transmission Loss (TL) rating of the wall, one must calculate the difference in sound levels before and after passing through the wall. The TL can be found by subtracting the final sound level from the initial sound level.

In this case, the initial sound level is 75 dB and the reduced sound level after passing through the wall is 36 dB. The calculation would be:

TL = Initial Sound Level - Final Sound Level

TL = 75 dB - 36 dB

TL = 39 dB

This TL value of 39 dB represents the effectiveness of the wall in reducing sound. It's a key measurement in assessing the sound isolation performance of walls. The higher the TL rating, the better the wall is at blocking sound, and thus a TL of 39 dB indicates significant sound reduction capabilities.

The other options do not reflect this correct calculation, focusing on the differences between the dB levels and their implications in sound transmission properties of building materials.