What is the primary characteristic of a noise described as 'unpleasant'?

The primary characteristic of noise that is described as 'unpleasant' typically relates to its loudness, among other factors. 'Unpleasant' noise usually disrupts the listener’s comfort and can be characterized by being harsh or jarring. While something that is extremely loud can often be unpleasant, it doesn't always have to be loud to evoke a negative reaction; rather, it often relates to the dissonance or the type of sound itself.

In this context, identifying loudness as a defining characteristic aligns with common perceptions and studies related to how sound is perceived in our environment. Unpleasant noise is frequently characterized by being intrusive or disruptive, which is often enhanced by high decibel levels.

Other options such as being enjoyable or musical do not align with the general understanding of what makes noise unpleasant, as they imply positive associations, while going unnoticed contradicts the concept of 'unpleasant' because a significant feature is that it captures attention due to its distasteful nature.