| If your 303 fan has… | You will perceive it as… | Best for… | |----------------------|--------------------------|------------| | < 1.0 sone | Barely audible | Bedrooms, home theaters | | 1.0 – 1.5 sones | Quiet background | Living rooms, offices | | 1.5 – 3.0 sones | Noticeable hum | Bathrooms, utility rooms | | > 3.0 sones | Intrusive | Garages, industrial areas |
| Sones | Perceived Loudness | Real-World Example | |-------|--------------------|---------------------| | 0.5 | Very quiet | Rustling leaves | | 1.0 | Quiet library | Refrigerator hum | | 2.0 | Moderate | Normal conversation (soft) | | 3.0 | Noticeable | Office background noise | | 4.0+ | Intrusive | Vacuum cleaner (far away) | sone+303