- People talking
- A running fan
- Clothes rubbing against each other
- Hands rubbing together
- or other omni-directional sound sources.
These sounds can however be used to make broad observations such as the size of a room or proximity to a flat wall. Other estimations may be possible depending on the actual content, level and clarity of the sound and any other distracting sounds that also exist, noticeable or unnoticeable.