Before-and-after

Before

• hiss: broadband noise floor elevated across high frequencies
• hum: low-frequency tonal component at mains frequency with harmonics
• crowd noise: non-stationary background speech and transient claps masking dialogue

After

• hiss: reduced noise floor while preserving sibilants and fricatives
• hum: attenuated tonal peaks and harmonics without removing voice fundamentals
• crowd noise: reduced between-word masking; dialogue remains dominant in the speech band