Acoustics — the typical ambient noise level in a quiet private business office is approximately how many decibels (dB)?

Introduction:
Noise exposure guidelines classify interior environments by typical sound levels. The question asks for the approximate decibel level for a quiet private office, an everyday acoustic reference for building services and environmental engineering.

Given Data / Assumptions:

• Context: steady background noise in a quiet office, not a call center.
• Metric: A-weighted decibels (dB(A)) commonly used for environmental noise.
• Comparison options: 25, 50, 70, 85 dB.

Concept / Approach:
Indoors, very quiet spaces such as recording studios or libraries may be near 30–40 dB. Comfortable private offices commonly sit around 45–55 dB. Higher levels (70 dB and above) suggest busy traffic or machinery, not a quiet office.

Step-by-Step Solution:

Verification / Alternative check:
HVAC and building acoustics references target office background levels around mid-40s to low-50s dB(A), aligning with 50 dB among the discrete options.

Why Other Options Are Wrong:

• 25 dB: unusually quiet, closer to studio-grade spaces; impractical for normal offices.
• 70 dB: resembles loud conversation or busy street; too high for a quiet office.
• 85 dB: occupational noise exposure threshold for hearing conservation; far too high for offices.

Common Pitfalls:
Confusing peak event noise with steady background levels; the question concerns typical ambient conditions.

Final Answer:
About 50 dB is typical for a quiet private business office.