When walking into a busy restaurant or café, our sense of hearing is bombarded with different sounds that our brain has to sort through to make sense of our surroundings. Our brain has to balance the desire to focus our attention on sounds we choose to listen to (such as the friend we are having a conversation with) and sounds that attract our attention (such as the sound of someone else’s phone ringing). Without the ability to be distracted, we might miss a noise that may or may not be crucial to our survival, like the engine roar of an approaching vehicle or a ping notifying us of an incoming email. However, it remains unclear what happens in our brains that enables us to shift our attention to background sounds.
To investigate this further, Huang and Elhilali asked 81 participants to focus their attention on a repeating sound while being exposed to background noises from everyday life, such as sounds from a busy café. The experiment showed that when a more noticeable sound happened in the background, such as a loud voice, the participants were more likely to lose attention on their task and miss changes in the tone of the repeating sound.
Huang and Elhilali then measured the brain activity of 12 participants as they counted the number of altered tones in a sequence of sounds, again with noise in the background. This revealed that brain waves synchronized with tones that the participants were concentrating on. However, once there was a noticeable event in the background, this tone synchronization was reduced and the brain waves aligned with the background noise. Huang and Elhilali found that distracting noises in the background activate the same region of the brain as sounds we choose to listen to. This demonstrates how background sounds are able to re-direct our attention.
These results are consistent with the idea that we have a limited capacity for attention, and that new sensory information can divert brain activity. Having a better understanding of how these processes work could help develop better communication aids for people with impaired hearing, and improve software for interpreting sounds with a noisy background.