A level change is not selective cleanup
If an owned recording contains both speech and room noise, increasing their shared gain increases both. A louder result can therefore make the noise more noticeable without changing their underlying relationship. Normalisation and noise reduction serve different tasks.
Begin with a representative speech passage and the original source. Identify whether the problem is overall level, inconsistent delivery, competing music, recording noise or missing intelligibility. Avoid choosing a heavy processing chain from the word quiet alone.
A hypothetical gain adjustment applied equally to every sample cannot know which sound the listener wants. This is simple processing reasoning, not a claim about one recording or a recommendation for a universal cleanup setting.
Choose a bounded candidate
Keep the original and prepare one candidate serving the actual delivery need. If unwanted noise is processed, use a documented tool and review speech consonants, pauses and transitions. Aggressive cleanup can create its own audible defects, so more reduction is not automatically better.
Measure loudness and peaks according to the recipient's requirement after the chosen processing. EBU R128 provides a framework in its broadcast context; it does not decide which background sounds are editorially wanted in an interview.
Listen at an appropriate consistent monitoring level and compare the same passage. Record whether the result improves understanding without distracting processing artefacts. If essential speech was never captured clearly enough, state that limitation rather than promising that gain or one filter can recover it.
Questions answered
Does normalising a recording remove room noise?
No. A shared gain change raises wanted and unwanted sound together.
Is the strongest noise reduction always the best candidate?
No. Review intelligibility and processing artefacts in the actual speech.
Sources & further reading
Official references for the subjects discussed. Service terms and device software can change.