We actively determine if new information enters our working memory or is ignored based on how much signal it has: how much it's related and useful to our current goals or not.
In this way, we are active in that process of signal detection.
David Green and John Sweet developed this as a "signal detection theory"
We adjust our threshold for which information to let in: if we're more receptive, it comes with a cost of dealing with more noise. If we're less receptive, it comes with a cost of missing out on good signals.
In the attention economy, it's crucial to be "sending good signals". Attention has a monetary value and is not to be traded away freely (Davenport & Beck, 2002)
Ideally, people should be given the opportunity to reduce the amount of noise coming at them (e.g. adjust ads preferences).