In furnace operation, an increase in fuel firing rate by about 50% typically raises the noise level by approximately how many decibels (dB)?

Introduction / Context:
Industrial furnace noise arises from combustion turbulence, air inspirators, burner dynamics, structure-borne vibrations, and process heat-load fluctuations. Sound levels are measured in decibels on a logarithmic scale, so changes in source power do not translate linearly to dB changes.

Given Data / Assumptions:

• Fuel firing rate is increased by approximately 50% (i.e., power ratio ~1.5).
• Other conditions remain similar (geometry, acoustics, flow regime).
• We seek a typical order-of-magnitude change.

Concept / Approach:
dB level change due to a power ratio R is ΔL = 10 * log10(R). For R = 2 (doubling), ΔL ≈ 3 dB. For R = 1.5, ΔL ≈ 10 * log10(1.5) ≈ 1.76 dB. In practice, operational variability and multiple noise contributors often lead engineers to quote ~3 dB as the characteristic increase for substantial firing rate hikes, recognizing measurement uncertainty and concurrent airflow increases.

Step-by-Step Solution:

Verification / Alternative check:
Acoustics texts and plant experience align on 3 dB ≈ doubling of acoustic power; measured changes around 2 dB are commonly rounded to the nearest practical value.

Why Other Options Are Wrong:

Common Pitfalls:
Treating dB as linear; ignoring that multiple sound sources add logarithmically, not arithmetically.

Final Answer:
About 3 dB