dB (decibels) is simply a measurement of how loud a noise is. 50dB is quiet while 140 dB is so loud that is can immediately injure your ears. Think of dB as the volume knob on your receiver.

STC (sound transmission class) is a measurement of the dB (volume) difference on either side of a wall. Let’s say we have a 100dB tone on one side of a wall. Pretty loud. We measure this same tone on the other side of the wall and find we have 75 dB. So we would say that at this tone or pitch, we have 25 dB Transmission Loss. 25 dB less sound energy made it through the wall to the other side.

For new construction, the International Building Code (IBC) requires lab-tested STC 50 for walls, floors, and ceilings. Note that this is a minimal amount of isolation and you will likely be disturbed by neighbors. Better to look at STC 55 to STC 60 for best satisfaction.


STC Examples
STCTrack Application
25 Normal speech can be easily heard and understood
30 Loud speech can be easily heard and understood
35 Loud speech heard, but not understood
40 Loud speech now only a murmur
45 Loud speech not heard, music systems / heavy traffic noise still a potential problem
50 Very loud sounds such as musical instruments or a stereo can be faintly heard
60+ Excellent soundproofing

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