Exam Questions And Correct Answers

CA D77 Soundproofing Contractor Exam Questions And Correct Answers (Verified Answers) Plus Rationale2026 Q&A| Instant Download Pdf

• What is the primary purpose of soundproofing in a building?
• Increase air circulation
• Reduce structural load
• Minimize sound transmission
• Improve lighting

Rationale: The main goal of soundproofing is to reduce the

transmission of sound between spaces.

• Which material is commonly used as a sound absorber?
• Concrete
• Steel
• Mineral wool
• Glass

Rationale: Mineral wool is porous and effectively absorbs sound

waves, reducing echo and noise.

• Which type of sound is most effectively blocked by mass-loaded

barriers?

• High-frequency sound
• Low-frequency sound
• Mid-frequency sound
• Ambient noise only

Rationale: Mass-loaded barriers are heavy and dense, which makes

them effective at blocking low-frequency sound.

• What does STC stand for in soundproofing?
• Sound Transmission Control 1 / 3

• Sound Transmission Class
• Standard Transmission Coefficient
• Structural Thermal Coefficient

Rationale: STC measures how well a building partition attenuates

airborne sound.

• Which construction assembly provides the best airborne sound

isolation?

• Hollow metal door
• Glass window
• Double-layer drywall with insulation
• Concrete floor without ceiling

Rationale: Double drywall with insulation significantly reduces

airborne sound transmission.

• Which of the following is a common decoupling technique in walls?
• Adding mass
• Using a thicker concrete block
• Resilient channels
• Painting the wall

Rationale: Resilient channels create a gap between the drywall and

studs, decoupling vibrations.

• What is the main difference between sound absorption and

soundproofing?

• Absorption increases sound volume
• Soundproofing is decorative
• Absorption reduces echo, soundproofing blocks transmission
• There is no difference

Rationale: Absorption improves room acoustics by reducing echo,

while soundproofing prevents noise from passing through barriers.

• Which material is most effective for vibration isolation?
• Glass
• Concrete
• Rubber
• Aluminum

Rationale: Rubber and similar resilient materials absorb vibrations,

preventing transmission through structures.

• In acoustic design, what is “flanking”?
• Adding decorative panels 2 / 3

• Painting walls for sound absorption
• Sound traveling through paths other than the main partition
• Installing acoustic tiles

Rationale: Flanking refers to noise bypassing a soundproof barrier

via alternate paths like floors, ceilings, or ducts.

• What is the typical STC rating required for a bedroom wall in

residential construction?

A. 20–25

B. 25–30

C. 40–50

D. 60–70

Rationale: Residential building codes recommend STC 40–50 for

interior walls to ensure privacy and comfort.

• Which of the following reduces impact noise between floors?
• Drywall
• Carpet with padding
• Paint
• Glass

Rationale: Soft materials like carpet and padding absorb impact

noise, preventing sound from transmitting to lower floors.

• What does NRC stand for in acoustics?
• Noise Reduction Coefficient
• Noise Reduction Coefficient
• Neutral Resonance Capacity
• Natural Resonance Coefficient

Rationale: NRC measures a material’s ability to absorb sound across

frequencies.

• Which factor has the greatest effect on low-frequency sound

transmission through a wall?

• Wall color
• Wall texture
• Mass of the wall
• Window placement

Rationale: Heavier walls with more mass are better at blocking low-

frequency sounds.

• When installing soundproofing in a ceiling, what is the most

effective technique?

• / 3