Discuss NCARB Project-Planning-Design Exam Topic 1 Question 12

Which of the following is the most effective way to reduce noise in mechanical air delivery systems?

AIncrease the size of the ductwork

BProvide exterior duct insulation

CReduce the free area of the supply air grille

Suggested Answer: A

Comprehensive and Detailed Explanation From Exact Extract:

Noise in mechanical air delivery systems is often caused by high air velocity and turbulence within ducts, which generate sound that can be transmitted to occupied spaces.

Increasing the size of the ductwork (A) lowers the air velocity for a given volume of air flow, which reduces turbulence and noise generation inside the duct. Larger ducts allow air to move more quietly and efficiently.

Exterior duct insulation (B) can reduce noise transmission through the duct walls but is less effective at controlling the noise generated by airflow itself inside the duct.

Reducing the free area of the supply air grille (C) increases velocity at the grille, potentially increasing noise at the outlet and causing discomfort.

Therefore, the most effective strategy is increasing duct size to reduce air velocity and noise.

ARE 5.0 PPD -- Building Systems and Assemblies, HVAC and Acoustics

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12 comments · newest first

Jaime 3 months ago

C might actually increase noise. Grilles need to stay open for airflow.

Samira 3 months ago

I disagree, A could work too. Bigger ducts mean less turbulence.

Patria 3 months ago

I think B is the best choice. Insulation really helps with noise.

Larae 3 months ago

Really? I doubt that insulation is the most effective method.

Carolynn 3 months ago

Wow, I didn't know duct insulation could make such a difference!

Arleen 4 months ago

I thought reducing the grille size would help too, but not sure.

Wendell 5 months ago

I disagree, A might be better for airflow.

Isadora 5 months ago

B is definitely the way to go! Insulation works wonders.

Ellen 6 months ago

I practiced a similar question where insulation was the right answer, so I’m leaning towards option B here.

Abraham 6 months ago

Reducing the free area of the grille sounds familiar, but I can't recall if that would actually help with noise or just restrict airflow.

Tenesha 6 months ago

I feel like we discussed duct insulation in class, and it seemed like a good option for noise reduction.

Tegan 6 months ago

I think I remember that increasing duct size can help with airflow, but I'm not sure if it actually reduces noise.

NCARB Project-Planning-Design Exam - Topic 1 Question 12 Discussion