Who's There? Exploring the Use of Knocking Sound Effects in Cinema

Knock Knock. Who’s there?

Knocking sounds are a universal symbol of anticipation. They trigger a range of different emotions depending on the situation. For example, a knock at the door might come from a friendly visitor or mark the beginning of an investigation.

In this article, we’ll share a detailed overview of how these sounds have been used in films. Below you’ll find a collection of 20 royalty-free knocking sound effects that you can download and use in your own projects. Just click on the “free download” link below to get started.

For a bigger collection of sounds, check out our Household sound pack within Audio Design Desk! Here you’ll find over 500 royalty-free recordings from the around the house and home office.

Knocking sound effects in classic films

The pace and pattern of a knocking sound effect is as important as the timbre of the sound itself. A fast and furious effect implies that the visitor is rushing to connect with whoever’s inside. A shy and slow tap might suggest a nervous visitor who fears the moment of contact. In some cases, the rhythm of a knock acts as a secret code. Let’s explore further in the sections below.

The Shining, The Matrix – Door knocking sound effects

Stanley Kubrick’s classic movie The Shining features an iconic and intense knock-knock moment from horror film history. Jack Nicholson’s arhythmic knocking is paired with maniacal facial expressions to build tension and add a layer of fear to the sequence. Like the big bad wolf, his innocent knock is followed by a burst of violence as he chops through the door with an axe.

An equally important moment takes place near the beginning of The Matrix, when Keanu Reeves’ character Neo receives a series of cryptic messages from an unknown sender on his computer. After a few exchanges, they send the words Knock, Knock, Neo, and he’s alarmed to hear two loud knocks on his apartment door. The startling timbre of their aggressive knocking helps the audience connect with Neo’s ominous feeling of being watched.

Insidious 3, Who Framed Roger Rabbit – Knocking on a wall

The timbre of knocking sounds on a wall are usually more hollow. They could carry an intimate connotation when the knock comes from a neighbor rather than an outside visitor, like in the scene below from The Summer I Turned Pretty.

A series of soft knocks are exchanged between young lovers in neighboring bedrooms. They can’t share the same room, but the sound is a reassuring sign that they are aware of each other and not too far away.

An almost identical scene plays out in the supernatural thriller Insidious: Chapter 3, when the main character Quinn knocks on her bedroom wall to connect with her neighbor, Hector. She hears a response knock and swoons, taking out her cell phone to begin texting him. But she quickly learns that Hector is not at home. It comes out that the knocking sound came from an evil spirit.

These two examples demonstrate how the same sound effect can have opposite meanings.

Knocking on a wall can also represent the pursuit of someone in hiding. This scene from Who Framed Roger Rabbit show a villain named Judge Doom pursuing the main character. Each knock is followed by a period of pause and listening, to see if someone behind the wall reacts. Judge Doom knocks with a metal-tipped cane, changing the timbre of the sound from the usual bare knuckle knocking sound to a harder and higher pitched tone.

A Beautiful Mind, Marshall, Bobby Fischer – Knocking on a table

Knocking on a table carries a completely different set of meanings from doors and walls. It’s often a sign of authority and endings. The intensity of the knocking sound effect often conveys the intention behind the person making the statement.

An obvious example of this is the knocking of a judge’s gavel against the podium’s sound block. In the scene above, a defendant is declared not guilty and an immense feeling of relief washes over the audience. But the same fateful knock can also carry a guilty sentence and have the opposite effect.

Like a gavel, games of chess are finalized when one player knocks over their king in a sign of resignation. The light timbre of this knocking sound effect can carry immense weight, as in the climactic scene above from Searching for Bobby Fischer.

In this scene from A Beautiful Mind, the professor’s resignation is met by a moment of warm and supportive knocking sound effects, as each of his colleagues places their pen down on the table in a show of support. As each pen drops, its gentle knock against the wooden table reiterates their humble and singular appreciation for him.

Wolf of Wallstreet, Three Stooges – Knocking against body parts

Characters have known to occasionally knock on body parts. The pairing of a hollow knocking sound with characters being tapped on the head might be used for comedic effect, to imply that person is being absent minded.

Knocking on human heads was a common trope in the Three Stooges. Notice that in some cases, the knocking sound effect resembles a popping bubble. The use of unlikely sounds adds to the absurdity and humor of these scenes.

The scene above from Wolf on Wallstreet shows two men in business suits knocking repeatedly on their chest in a tongue-in-cheek moment of solidarity. Similar gestures are common in scenes where a warrior is asserting their strength and confidence.

Stranger Things, Harry Potter – Knocking in coded rhythms

A tap-t-t-tap-tap pattern on someone’s door is a classic way to let people know you’re a friendly visitor. But there are other examples in films where characters knock to convey secret messages. The scene below, from Stranger Things, features a character named Will tapping out Morse code to secretly communicate a phrase to his friends.

Playing on this theme, the movie Harry Potter and the Order of the Phoenix features this scene where three knocks of a wizard’s staff are required to open up the entrance to Grimmauld Place.

How to create and use knocking sound effects

Instead of recording and using audio directly from a movie set, knocking sound effects are recreated in a foley studio using materials that match the scene. For a wooden door, sound designers use large blocks of wood to capture similar resonance and tone.

The source of the knock, whether someone’s bare knuckles or a metal cane, will also be taken into consideration when recording foley. When syncing up with your scene, each knock needs to placed to precisely match the movements on screen.

If you don’t have access to a foley studio, you can download the royalty-free knocking sounds we’ve provided in this article. Pick up a free copy of Audio Design Desk to make it even easier to select and place sounds on your video timeline.