# Acoustical Separation

**URL:** <https://community.blackspectacles.com/t/acoustical-separation/7093>\
**Category:** Project Development & Documentation\
**Created:** [June 22, 2025, 10:54pm UTC](https://community.blackspectacles.com/t/acoustical-separation/7093 "2025-06-22T22:54:57Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![jdziama](https://blackspectacles.com/uploads/images/23.png) [@jdziama](https://community.blackspectacles.com/u/jdziama)\
**Post date:** [June 22, 2025, 10:54pm UTC](https://community.blackspectacles.com/t/acoustical-separation/7093/1 "2025-06-22T22:54:57Z")

</div>

I’ve encountered a question in my study materials (Ballast 5.0 Practice Exam) that asks about the noise reduction in a room (a) that is separated from another room (B) by a sound partition. There is a noise producing source in room B.

The answer explanation states that “The thickness of a partition or other acoustical separation is irrelevant to the total noise reduction within a space.”

My question is, how is it possible that the thickness of a partition has nothing to do with noise reduction in adjacent space

@coachmarissayee @coachmikeparaszczak

---

<div class="post-metadata">

**Author:** ![coachmikeparaszczak](https://blackspectacles.com/uploads/images/9.png) [@coachmikeparaszczak](https://community.blackspectacles.com/u/coachmikeparaszczak)\
**Post date:** [June 23, 2025, 4:24pm UTC](https://community.blackspectacles.com/t/acoustical-separation/7093/2 "2025-06-23T16:24:48Z")

</div>

Hi!

It sounds like the question is really about the difference between **noise reduction (NRC)** and **sound transmission (STC)**.

- **NRC** measures how well surfaces inside a room absorb sound (reducing echo and reverberation). Think of acoustic treatments in a recording studio - these are porous, absorptive materials applied to the surfaces.
- **STC** , on the other hand, measures how well sound is blocked from traveling **between** rooms, which is where mass, air gaps, and thickness of assemblies come into play.

Since the question specifically asks about **noise reduction** , it’s focused on **internal room acoustics** , where adding wall thickness doesn’t help much. That kind of change would affect STC, not NRC.

On a real project, you’d likely consider both. But for the AREs, understanding what the question is really asking makes a big difference in getting to the right answer.

Hope that helps!

Thanks,  
Mike

---

<div class="post-metadata">

**Author:** ![jdziama](https://blackspectacles.com/uploads/images/23.png) [@jdziama](https://community.blackspectacles.com/u/jdziama)\
**Post date:** [June 25, 2025, 1:22am UTC](https://community.blackspectacles.com/t/acoustical-separation/7093/3 "2025-06-25T01:22:54Z")

</div>

Thank you for the explanation. NRC being focused on sound within a room vs. STC dealing with sound between rooms is a really helpful distinction to be mindful of.