Have you ever found yourself so completely engrossed in something on your smartphone that you tune out the rest of the world?

You can blame your brain. Intense concentration on a visual task causes our brains to temporarily reduce our sensitivity to the environmental sounds around us, according to EurekaAlert.

“In order to hear, we don’t just need our ears to be operating; we need our brain to respond to the sound,” study author Nilli Lavie, professor of psychology and brain sciences at the University College London (UCL), told ABC News. “If our brain doesn’t respond because our attention is fully taken by another task, then we experience deafness."

To confirm what so many of us have experienced first-hand, researchers at UCL measured the real-time brain activity of 13 people using a process called MEG (magnetoencephalography). They then took the participants through an increasingly difficult series of visual tasks while sounds were played in the background. For those moments that required the greatest concentration, the brain almost completely blocked out the clearly audible background sounds.

“We have confirmed an experience that people commonly report, that they may fail to notice a sound when they are concentrating," added Lavie. "It’s because the brain signal related to hearing is significantly reduced during more demanding visual tasks.”

The findings should come as a warning to any of us who like to visually focus on something (i.e.: an email on a smartphone or a good book) while the rest of the world carries on around us. And if you happen to run into a friend doing exactly that, don't take offense if they don't hear you calling their name right away.

"You may think that the person is ignoring you," Lavie told "Today." "But their brain just can't respond to your voice. So you shouldn't take it personally."

The research appeared in the Journal of Neuroscience, and the abstract can be found here.