Some people turn on closed captions because they like how it helps them understand the plotlines of shows and movies, and multitask in front of the tube. Others turn them on because they can’t hear what actors are saying. That doesn’t always mean they are hard of hearing.

Muddled audio is the top reason why more people are watching video with on-screen text, according to a May survey commissioned by language-teaching app Preply. As more video-production studios embrace advanced audio formats for at-home content, not every device can keep up. Plenty of viewers can’t keep up, either. 

“If you have people talking or shouting during the adventure scenes, the explode-y sounds are way higher than the dialogue,” said Melanie Brooks, a 43-year-old professional musician in Boston. Catching some of the lines in her favorite fantasy and adventure TV series is hard without captions, she added. 

People tend to blame their flat-screen TVs for bad sound. The tube TVs of decades past had front-facing speakers that sent audio toward you, while new, super-thin models have speakers that are behind the screen or point downward, bouncing sound away from you. But your TV is just one of the culprits.

The rest of the problem lies within virtually every other step of the audio process, from a studio’s production choices to the device used to watch the content, said Richard Nevens, senior director of audio-hardware product management at Avid Technology, which specializes in audio- and video-editing tools.

Sound mixers combine all the sound in the video, including dialogue, music and background noises, into the audio we hear when we watch movies and shows. The professionals have advanced audio capabilities at their disposal, but they might not translate clearly on devices that aren’t built to support state-of-the-art audio, Mr. Nevens said. For this reason, a movie designed to sound great in a giant theater might not sound the same on your smartphone—or your TV.

Sound Mixing for Theaters

In recent years, directors have gravitated toward making their films and TV shows look and sound as though the events are larger than life, even if that means viewers might struggle to make out the dialogue, said David Bondelevitch, who teaches recording arts at the University of Colorado Denver and works as a sound designer on documentaries and other projects.

Director Christopher Nolan ‘s films, such as “Tenet” and “Interstellar,” are known for their realistic imagery, but the dialogue can be hard to discern. When his new movies hit theaters, viewers often complain they can’t tell what actors are saying. But Mr. Nolan has defended his sound mixing, saying it allows him to be creative. His films have racked up numerous Academy Award sound nominations and wins, including best sound-editing and sound-mixing Oscars for “Dunkirk” in 2018. 

When dialogue is muddled, actors frequently rerecord their lines in a postproduction studio, but those tracks might not sound like they were recorded in the original scene, Mr. Bondelevitch said. There is only so much sound engineers can do to improve audio, he said.

Rather than mixing for mono (one-speaker) and stereo (two-speaker) audio—which makes audio sound clearer on basic TVs—sound engineers today often design for a higher number of speakers and then scale audio down for less-capable systems. Other higher-end setups include surround sound, which tends to have five speakers plus a subwoofer, and Dolby Atmos, which can work with even more speakers to match the action on screen. For example, the placement of the speakers can make it feel like a helicopter is buzzing around you.

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Dolby’s immersive technology has become popular with studios that want to make at-home viewing more like going to a theater. That is great if you have a high-end sound setup, but not ideal if you have a basic TV or often watch video on your older phone or tablet. 

“The creators are pushing the boundaries of the creative experience,” as well as the limits of people’s TVs and home speakers, said John Couling, senior vice president of entertainment at Dolby.

If you don’t have high-end TV speakers or an external-sound system, more immersive audio will be compressed into your existing speakers, said

Mark Lanza, president of Motion Picture Sound Editors, an honorary society of sound-editing professionals. “That’s never going to sound good,” he added.
How to Fix Your Audio

It can be hard to pinpoint whether sound issues are a result of production choices, poorly converted mixes or your own ears. Experimenting with speaker placement, your surroundings, new audio equipment and your device’s settings can help.

For all her knowledge of sound, Mrs. Brooks, the Boston musician, still relies on her Samsung TV’s built-in speakers. “It’s not great,” she said, noting that she might invest in new equipment.

Placing a soundbar on a stand below a TV helps better direct audio to your ears.

Photo Illustration: THE WALL STREET JOURNAL, SHUTTERSTOCK

That flat-screen TV with downward-facing speakers? Place it on a bare table or stand to give the sound something to bounce off, rather than hanging it on a wall. In a large room, try carpeted floors and thick curtains to absorb noise and contain the sound, Mr. Lanza said.

If you are planning to buy a soundbar, make sure it has at least three channels, or speakers, Mr. Bondelevitch said. The center channel will help dialogue sound clearer. 

Some TVs come equipped with features that reduce loud noises or boost dialogue. Samsung TVs have an Amplify feature, LG TVs have Clear Voice II, and some  Roku TVs have Dialogue Enhancement or Speech Clarity, depending on your setup. You can find these in the settings menu of your TV. 

Playing around with settings could help you find one that works. Still, Mr. Lanza warns that there is no guarantee the tweaks will make “Tenet” sound crisp.

If you are watching TV with others and need an audio boost, you can pair certain earbuds to your TV to pipe sound straight to your ears. You can link two pairs of AirPods to Apple TVs if you are watching alone or with one other person. Google and Apple offer accessibility features that let you use your phone as a speaker. Place it by your TV and pop in earbuds to hear the audio through them.

When watching video alone on your mobile device, certain earbuds such as AirPods offer surround-sound level quality that can improve audio. 

If dialogue still sounds muffled, you might want to explore hearing aids. They are now available over the counter. 

And if all those options don’t work, you still have captions to make sure you don’t miss a thing.

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Write to Cordilia James at cordilia.james@wsj.com