Author Topic: STC - What is it?  (Read 5471 times)


  • Guest
STC - What is it?
« on: September 03, 2006, 02:14:13 PM »
Per the following website:

The actual behavior of two partitions with the same STC rating can be dramatically different, as the STC is weighted in favor of the part of the sound spectrum that represents the human voice. In practice, one of the most annoying transmitted sounds between dwelling units tends to be the bass in music, a part of the sound spectrum far removed from the voice range. So, an eight inch concrete block wall rated at STC 50, that can block 20 dB more sound in some bass frequencies would be a better choice than an STC 50 drywall partition for an application where music or mechanical noise will be a problem.

Due to the definition of the rating, STC is only applicable to air-borne sound, and is a poor guideline for construction to contain HVAC or other mechanical equipment noise, music, transportation noise, or any other noise source which is more heavily weighted in the low frequencies than speech. The standard thus only considers frequencies above 125 Hz. Composite partitions composed of elements such as doors and windows as well as walls will tend to have an STC close to the value of the lowest STC of any component.

STC -Lab   Field STC   Subjective description of effectiveness
26-30        20-22  Most sentences clearly understood  
30-35        25-27  Many phrases and some sentences understood without straining to hear  
35-40        30-32  Individual words and occasional phrases clearly heard and understood
42-45        35-37   Medium loud speech clearly audible, occasional words understood
47-50        40-42   Loud speech audible, music easily heard  
52-55        45-47   Loud speech audible by straining to hear; music normally can be heard and may be disturbing
57-60        50-52   Loud speech essentially inaudible; music can be heard faintly but bass notes disturbing
62-65        55   Music heard faintly, bass notes "thump"; power woodworking equipment clearly audible
70             60   Music still heard very faintly if played loud.  
75+           65+   Effectively blocks most air-borne noise sources  


  • Guest
Re: STC - What is it?
« Reply #1 on: February 27, 2009, 05:28:40 PM »
Outstanding, straight-up information.... Thank you.


  • Guest
Re: STC - What is it?
« Reply #2 on: June 01, 2009, 04:05:24 AM »
Imake sure you know STC deeply.I willcantct you later.