Why does watching TV make you fall asleep? Here's how different sounds can affect focus, learning and sleep

The sound of raindrops gently tapping against the window may be audio salve for some individuals. For others, it could be the lo-fi playlist on Spotify that helps them to block out distractions. Yet others may enjoy the ASMR tingles from triggers such as ear brushing, whispering and gentle tapping.

Suffice it to say, different people find different sounds pleasurable – and sometimes, the very same noises may elicit different responses from you in different situations. For instance, one man’s chewing could be another’s misophonia (that is, you get triggered by certain sounds). You could be glaring at the person making smacking noises next to you in the food court; but at home, you find it entertaining – relaxing even – to watch mukbang videos in all their biting, chomping and slurping glory.

It begs the question: What makes certain sounds an audio spa to your ears and not nails on a chalkboard? More intriguingly, can you harness the power of sounds to help you focus better, fall asleep faster or learn better? Here’s a look.

FIRST, THE BRAIN

According to Dr John Shepherd Lim, the chief wellbeing officer of Singapore Counselling Centre, a few areas of the brain are activated when we engage in mental tasks such as reading, writing and analysing data. For instance, “the prefrontal cortex is heavily involved, particularly for decision making and attention”, he said.

Meanwhile, “the parietal lobes process sensory information, and handle numerical and mathematical processing”, said Dr Annabelle Chow, the principal clinical psychologist at Annabelle Psychology. The hippocampus is another important part as it provides “essential memory formation and retrieval”, she said.

What’s the point in knowing these various parts of your brain? “Sound can impact these areas by either enhancing or distracting focus, depending on its nature,” said Dr Lim. Think about the times when soothing music helped you to concentrate on a report versus loud and unpredictable sounds disrupting your focus.

And it’s not because Mozart or Enya wields certain sorcery over us. The hippocampus, one of the first regions of the brain to be ravaged by Alzheimer’s disease, is found to benefit from music, which “may increase neurogenesis in the hippocampus, allowing production of new neurons and improving memory”.

Studies also suggest that noise-induced stress may decrease dopamine availability in the prefrontal cortex. This results in decreased higher brain function and impaired learning and memory.

YOUR BUILT-IN NOISE CANCELLATION FUNCTION

If you’re wondering why you can ignore certain sounds in your office (the photocopier printing, general chatter, keyboards clacking etc) but not someone erratically tapping his pen next to you, that’s because the type of sound you hear can shift your brain’s focus, said Dr Chow.

Most of the time, your brain is in “selective attention” mode, which helps it to filter out unimportant sounds and lets you continue with your task, she said. “When we receive sound signals that are not relevant to our current focus, our brain detects them because they might be important or unexpected.

“If our brain decides the sound is important, our prefrontal cortex and parietal lobe shift our attention to the sound involuntarily,” said Dr Chow. In a way, it’s like deactivating your brain’s built-in noise cancellation function.

“However, this process of hearing, deciding and filtering adds to the brain’s cognitive load, reducing our working memory capacity and impairing task performance,” said Dr Chow. Sound can also make it harder to focus as it competes for your attention, she said.

How you’re feeling that day plays a part as well. “Our emotions toward sounds can be influenced by factors such as our control of attention — how we manage and inhibit impulses — and our emotional states,” said Dr Chow. “For instance, we might feel more irritated by laughter and talking when we are angry, and desire peace and quiet.”

Generally, volume, pitch and rhythm play a role in how your brain reacts, said Dr Lim. “For instance, high-pitched or loud noises might be irritating to some, while rhythmic or predictable sounds can help others concentrate by providing a steady auditory background.” Still, the reactions can vary from person to person “due to individual differences in auditory processing and personal preferences”, he said.

There are also those who require complete silence to work or study. “This need for silence may be due to heightened sensitivity to auditory stimuli, or a brain that is less adept at filtering out background noise,” said Dr Lim.

WHY YOU WORK BETTER OR FALL ASLEEP IN FRONT OF THE TV

White noise refers to any sound (it can be static or forest sounds) that “contains all frequencies across the spectrum of audible sound in equal measure”. Some people like white noise because it can minimise the disturbance caused by unexpected noises for them.

But does white noise really work? “Our current understanding of the impact of white noise, nature sounds and similar auditory stimuli on the brain is incomplete,” said Dr Chow. “Research suggests that white noise is likely to have little general effect on cognitive functions in neurotypical individuals, while nature sounds are associated with reduced stress levels and improved cognitive performance at certain tasks.”

And it doesn’t have to be a specific white noise playlist either. Ever found yourself falling asleep or working better with the TV on? The background noise provided by the TV can be relaxing or sleep-inducing, said Dr Vikas Jain, a clinical assistant professor of sleep medicine at the Stanford University School of Medicine, especially when it’s your favourite movie or TV show that may reduce the anxiety keeping you awake at night, he said.

If you’re working from home, background TV can “serve multiple purposes”, according to Dr Lim. “They can distract you from unpleasant thoughts, provide a comforting auditory presence, and enhance learning through auditory cues.

“These effects are grounded in how the brain processes sensory input and regulates emotions,” he added. “The brain’s limbic system, which governs emotions, can be influenced by auditory stimuli; pleasant sounds can help regulate mood by reducing cortisol levels and increasing serotonin.”

On the flip side, there is also research that suggests having the TV on while you work may not be a good idea. In a study on 90 college students tasked to read the newspaper, those who did so with the TV on in the background recalled less than the ones who read in silence. The moral of the story? You do what works for you.

Before you go download White Noise 10 Hours from Spotify, figure out what sounds calm you first. “We know that individuals have differences in sensory processing and varying sensitivity levels to different sounds,” said Dr Chow. “Some people might find the pitter-patter of rain soothing due to its stable and consistent nature, while others with sensitivity to repetition may find it overwhelming.

“An individual might associate forest sounds with peace and comfort, helping them feel calm and focused,” continued Dr Chow, “while that same individual might associate the sound of the ocean with a near-death experience, making it unsettling and fear inducing. These positive and negative associations stem from our lived experiences.”

WHAT WORKS BEST FOR WORK, LEARNING AND SLEEP THEN?

On the whole, sounds that provide a good soundscape for work and sleep are “typically consistent, low in volume, and free from sudden changes, like soft instrumental music”, said Dr Lim. “Elements such as language, beats per minute, volume and recording quality can all influence the brain’s response. Lo-fi music, for example, often includes ambient sounds like raindrops or soft taps, which can create a comforting and familiar auditory environment conducive to both work and relaxation.”

Sounds that have “low variability in tone and articulation”, and can be played on loop or are predictable are “generally the least arousing and perhaps more appropriate as background music”, said Dr Chow. “It might help us feel secure because we can subconsciously predict what sound comes next.”

If you’re reading or writing, it might be best to avoid music with lyrics, said Dr Chow. “Listening to music with lyrics activates the parts of the brain that deals with auditory information. If we’re attempting to concentrate on a task that involves words, it can be taxing for our brains to do both flawlessly.” For that matter, you might not be able to concentrate on reading a report if you have a K-drama on TV.

Sometimes, learning may yield better results if the material is presented in an audio format, said Dr Chow. “Some individuals may have better developed auditory processing skills and are thus, better able to comprehend and retain information presented in an auditory format.”

For example, if you’re able to focus and retain the information better by listening to an audio recording than reading the book, you are better able to comprehend the material and learn, she said. “Some materials are better taught with auditory cues. For example, it may be easier to understand the tone and emphasis of words when learning a new language through audio than text.”

For sleep and relaxation, Dr Chow suggested slower music based on what studies have found. “Slower music synchronises with our parasympathetic nervous system through a process called entrainment, where the body aligns with the environment's rhythm.

“Essentially, the brain recognises that it does not need to be in fight-or-flight mode because the sounds remain consistent. Focusing on these sounds helps distract us from anxious thoughts or other noises that might keep us awake. These sounds help decrease stress by regulating stress hormones like cortisol,” she said.