A Quiet Place: the science behind how filmmakers made aliens hear using distractions and deviant sounds

By now, you may have heard about highly rated film A Quiet Place. This excellent thriller is set in the near future, a time when almost all humans are dead, and those left alive are hiding from alien reptilian creatures who have poor eyesight but incredibly sensitive hearing. “If they hear you, they hunt you,” we are told.

The film follows the Abbott family as they scavenge ghost-like towns for supplies, all the while making as little sound as possible to avoid alerting their presence to their new co-inhabitants.

The use of sound – or rather lack of it, to be more precise – is pivotal to the success of this film, so much so that requests have been made for patrons not to attend viewings with noisy refreshments, not to engage in conversations, or use their mobile phones. But it’s not just the idea of silence that has audiences hooked. As a cognitive psychologist, I find it very interesting how the filmmakers have tapped into the phenomenon of auditory distraction.

Deviant sounds

It has recently been suggested that there are two types of auditory distraction, where tasks are impaired by background sound. The most commonly researched of these is the irrelevant sound effect, where the processes that underpin task performance (for example, trying to remember things in order, or understanding the meaning of information while reading) can be interfered with by the similar processing of information from background sound, for example, from certain types of music.

The second route is called the deviant effect. It is an evolutionarily adaptive function that we share with many other animals – and, in the Quiet Place universe, with alien creatures. It alerts us to potential changes in the environment that might indicate, for example, a threat to survival or a possible food source.

The explanation of the deviance effect is conceptually quite intuitive. It is when an unexpected or unpredictable sound captures one’s attention. More specifically, any auditory item that deviates from an expected sequence of sounds is able to capture attention via a physical orienting response. Consider the example of a baby lying on the floor, looking up to the left at its parent. If the baby hears a sound on their right-hand side, they will turn their head towards it, and so are no longer attending to their parent.
Laboratory research has shown this very same effect in different ways. Compared to the rest of the sound sequence, a deviant sound can be temporally different (presented at the rate of half a second compared to one second), have a different pitch (male voice compared to female voice, for example), or be semantically different (such as hearing one’s own name). In each of these cases, performance on a short-term memory task is significantly impaired compared to when there is background noise with no deviant sounds.

The aliens in A Quiet Place rely on deviant sounds to alert them to their prey: when one of the children switches a toy space shuttle on it suddenly emanates a lot of noise (see the trailer above). The trees rustle, as the aliens have presumably been alerted by the sound, and the father rushes towards his child. The noise was clearly a change from the aliens’ usual environmental sounds.

Masking sounds

A second auditory distraction phenomenon shown in the film has also been observed in the real world. In the film, the dad demonstrates to his frightened son how, in certain environments, making a noise will not alert the creatures. Specifically he does this by shouting under a gushing waterfall. The sound of the waterfall masks the shout so that it is not heard by the creatures.

In the laboratory, we find that a masking sound (such as through white noise, speech, or music) masks target sounds so that differences between sound items are less well perceived. This results in a reduced irrelevant sound effect, because it decreases the acoustical variation in the sound – a key determinant of the impairment. This process is common in the treatment of tinnitus where music, for example, is used to mask the internal tones that are responsible for tinnitus.

Although the effect of masking the deviant sound has not been explored by researchers, we would predict that a masking procedure would produce a reduced deviant effect. This is because it would not be able to capture attention so easily. An additional example from the film occurs when the dad says that if one accidentally alerts the creatures by making a noise, producing a louder noise somewhere else will capture their attention, making them search for the source of that new sound. Although this has not been shown in deviance research yet, it is a very interesting idea that could be easily explored.

Though the film is very much a work of science fiction, the auditory science behind it is sound. Whether it works to save the Abbott family, however, is something only viewers will find out.