Steady State Noise is defined as:

• A. A periodic or random variation in atmospheric pressure at audible frequencies.
• B. A short burst of acoustical energy with rapid rise to maximum intensity followed by slower decay.
• C. A continuous tone at a fixed frequency.
• D. A single impulse from a machine.

Answer: (A)

Steady-state noise refers to continuous fluctuations in air pressure that persist over time within the audible frequency range, forming a background level rather than a single event. This captures the ongoing, random or patterned variations you hear as background sound, as opposed to a one-time burst or a single pure tone.

That’s why the best choice is the description of a continuous variation in atmospheric pressure at audible frequencies. It emphasizes the ongoing, background nature of the sound, which distinguishes steady-state noise from transient events or a single tone. The other descriptions point to a short, impulsive burst, a single pure tone, or a one-off impulse—none of which match the idea of a continual noise present over time.