^ Vodanovich, Stephen J. (November 2003) "Psychometric Measures of Boredom: A Review of the Literature" The Journal of Psychology. 137:6 p. 569 "Indeed, a shortcoming of the boredom literature is the absence of a coherent, universally accepted definition. The lack of an agreed-upon definition of boredom has limited the measurement of the construct and partly accounts for the existence of diverse approaches to assessing various subsets of boredom."

Boredom is a condition characterized by perception of one's environment as dull, tedious, and lacking in stimulation. This can result from leisure and a lack of aesthetic interests. Labor and art may be alienated and passive, or immersed in tedium. There is an inherent anxiety in boredom; people will expend considerable effort to prevent or remedy it, yet in many circumstances, it is accepted as suffering to be endured. Common passive ways to escape boredom are to sleep or to think creative thoughts (daydream). Typical active solutions consist in an intentional activity of some sort, often something new, as familiarity and repetition lead to the tedious.
Boredom is similar to mental fatigue and is caused by repetition and lack of interest in the details of our tasks (such as tasks that require continuous attention, waiting at the airport, prisoners locked in cells). Any experience that is predictable and repetitive becomes boring. In general, too much of the same thing and too little stimulation can cause in its victim an absence of desire and a feeling of entrapment (Toohey, 2012).    
The people who heard the barely noticeable TV rated themselves as more bored than either the ones who heard the loud TV or heard no soundtrack. The idea is that both the loud TV and the soft TV were distracting, but for those who heard the loud TV it was clear why they were distracted from the article. Thus, they may have been frustrated with the noise, but they were not bored. Those who heard the soft soundtrack had difficulty concentrating, but they were not sure why, and so they attributed the difficulty concentrating to boredom.
The most common way to define boredom in Western culture is having nothing to do. Boredom is generally viewed as an unpleasant emotional state in which the individual feels a pervasive lack of interest in and difficulty concentrating on the current activity. The condition corresponds more precisely to the French ennui, an existential perception of life’s futility. Ennui is a consequence of unfulfilled aspirations (Goodstein, 2005).