Sound basics

Learning goal

You will be able to record the voice of someone speaking intelligibly in a video you shoot with your stills camera. You will explain why the camera's own microphone often falls short, and choose between a directional microphone mounted on top of the camera and a lavalier microphone clipped to the speaker's clothing. You will compare how the microphone's distance from the mouth affects the sound with the inverse square law in light, and notice and reduce, before the shoot, hard surfaces that echo and humming machines. You will set the recording level so that the sound doesn't clip even at its loudest moments, listen with headphones during the shoot, and record a few seconds of room tone to fill gaps in editing. When putting a lavalier microphone on someone, you will respect their body and clothing, and choose the look of the microphone and its accessories according to the person's skin and clothing.

The question

The bakery's anniversary video is projected on a screen at the family's home. Everyone smiles at the slow-motion flour shot. Then comes the part where the baker talks about the bakery and the trade they learned from their father. The image is sharp, the light warm, the framing careful; but the speech mixes with its own echo in the tiled room, the oven's constant whine sits under every sentence, and at one point the sound of a tray hitting the counter drowns out the whole speech. Their daughter asks twice, "what are they saying?"

At the club, a member says people don't mind a slightly soft frame much, but don't put up with speech they can't understand for more than a few seconds. Does the audience forgive bad picture or bad sound? Why does sound recorded with the same camera come out so bad?

Context

In the module's first lesson we defined ambient sound and suggested listening to the room before pressing record (Lesson 24.1). In the stop concept lesson, too, you saw the inverse square law as light dropping to a quarter when the distance from a small source doubles (Lesson 8.8). Sound behaves in a similar way, and this similarity is the shortest way to understand where the microphone should go.

Photographers are meticulous about the image but often leave the sound to the camera. Yet in a video, speech is what carries the story. This lesson deals with the most effective and cheapest ways of improving sound: bringing the microphone closer to the speaker and quieting the surroundings.

Simple explanation

Why isn't the camera's microphone enough?

The camera's own microphone is small, built into the body and designed to listen equally to sound coming from every direction. If the camera is two or three meters from the speaker, the baker's voice and the oven's hum reach the microphone at almost the same strength. On top of that, because the microphone is attached to the camera's body, the lens's focus motor, fingers touching the buttons and the camera's own sounds also get into the recording.

An external microphone is a separate microphone connected to the camera or a recorder and used to record the speaker's voice more cleanly than the camera's own microphone. An external microphone's real strength comes from being able to be placed closer to the speaker than the camera, or from being able to listen to a particular direction.

Sound, like light, weakens fast with distance. In an open space, when the distance from the speaker doubles, the sound level drops by about six decibels; this is the sound counterpart of the inverse square law in light. Halving the distance, on the other hand, strengthens the speech by the same amount, but the hum in the background stays where it is. That is why the first rule of sound recording is to bring the microphone closer to the speaker; no setting can clean up speech recorded from a distance afterward.

Which microphone is chosen for what?

A directional microphone is a microphone that picks up mostly the sound in front of it and hears sound coming from the sides and the back less. It is often mounted on top of the camera and faces the way the lens faces. It gives good results if the speaker is close to the camera and the surroundings aren't very noisy; but the farther it is from the speaker, the more it again starts to gather the sound of the surroundings. Detaching it from the camera and bringing it close on the end of a pole just above the speaker's head, outside the frame, makes it much more effective.

A lavalier microphone is a small microphone clipped to the speaker's clothing, at a place near the chest. Because it sits only a hand's span from the mouth, it picks up speech clearly louder than the sound of the surroundings, and the distance doesn't change even if the person moves. It can be wired or wireless. Rubbing against clothing can create rustles; securing the microphone and not leaving its cable loose reduces this.

Putting on a lavalier microphone means working close to someone's body. Explaining where you will put the microphone and asking the person, letting them put it on themselves if possible, and talking about it in advance if the cable needs to be run under the clothing make the shoot a safe place. The microphone's look is considered too. A black microphone disappears on dark clothing and stands out on light clothing. Microphone covers and tapes sold as skin color are often made only for a light tone; on dark skin this light-colored piece, instead of hiding, sits like a stain. Choosing the microphone and its accessories according to the person's own skin or clothing, or hiding it under the clothing, makes this care the same for everyone.

How are the surroundings and the level managed?

Even the best microphone takes the sound of the surroundings into the recording. Before the shoot, turning off the fridge or the ventilation, keeping the oven door closed, shutting a door improves sound in the cheapest way. Bare walls, glass and tiles reflect sound and create echo; laying a rug in the room, hanging blankets on the walls the camera doesn't see, or moving the speaker to a corner with curtains and furniture reduces echo.

Recording level is the setting that decides how much the sound coming from the microphone will be amplified during recording. If the level is too low, speech stays thin, and when it is raised afterward the background rises too; if it is too high, a laugh or the sound of a tray hits the recording's ceiling and clips. Clipped sound is like a sky blown out to white in a photo: the lost information doesn't come back. Setting the level so that it doesn't touch the ceiling even at the loudest moments of speech, and listening with headphones throughout the shoot, makes it possible to notice the problem before the shoot ends.

Room tone is a few seconds of ambient sound recorded with no speech, at the same place and with the same settings. When you cut out a silence between two sentences in editing, the background sound stops suddenly and the ear notices it at once. Room tone recorded in advance is placed in these gaps and preserves the continuity of the sound.

Visual evidence

You record the part the baker will narrate again. Before the shoot you turn off the fridge, ask for the oven door to stay closed, and move the speaking from in front of the bare walls to in front of the flour sacks and the shelves full of bread. You show the baker a lavalier microphone and ask where you should put it; they put it on the inside of their apron themselves.

The light beige of the microphone's cover stands out next to the baker's dark skin; you switch to a black cover that hides in the apron's dark fabric. You set the recording level on a test sentence in which the baker laughs so that it doesn't touch the ceiling, and listen with headphones. At the end of the shoot, while everyone stands quietly, you record half a minute of room tone.

Listening to the new recording side by side with the first, the difference is striking. In the first recording the baker's voice comes from afar and echoing, the hum continuing under every sentence. In the new recording the voice is close and warm, the hum almost inaudible; even when a tray hits the counter, the sound doesn't clip. When the gap between two sentences is filled with room tone in editing, the transition can't be noticed.

Common mistakes

Summary

The camera's own microphone mixes speech with ambient sound because it is far away and listens to every direction; because sound, too, weakens fast with distance, dropping about six decibels in an open space when the distance doubles, bringing an external microphone, directional or lavalier, closer to the speaker is the most effective improvement. Sources of hum in the surroundings are quieted, echo is reduced with soft surfaces, the recording level is set so as not to clip even at the loudest moments and listened to with headphones, and room tone is recorded for editing; the lavalier microphone is put on after asking the person, and the microphone and its accessories are chosen according to the person's skin and clothing.

Mini assignment

In this assignment you will record speech with different methods and compare them.

1. Record a friend's one-minute account with the camera's own microphone, from two meters away.
2. Record the same account with an external microphone if you have one, or if not, by holding a phone close to the speaker outside the frame; compare the two recordings with headphones.
3. List the sources of hum and the echoing surfaces at the shooting location, quiet one and soften one, repeat the recording, and at the end take half a minute of room tone.
4. If you used a lavalier microphone, ask the person where it should be put; note how the microphone and its cover look on their skin or clothing.

Check yourself

• Can you tell with your ear the difference between the camera's microphone and a microphone close to the speaker?
• Did your recording level stay unclipped at the loudest moments?
• Did you put on the microphone after asking the person, and choose its look according to their skin and clothing?

Glossary

Mini quiz

1. What is the first and most effective way of improving a sound recording?

• A) Turning the recording level all the way up
• B) Using the camera's microphone
• C) Cleaning up the speech afterward
• D) Bringing the microphone closer to the speaker

2. In an open space, if the microphone's distance from the speaker doubles, about how much does the sound level drop?

• A) It doesn't drop at all
• B) About six decibels
• C) By half, three decibels
• D) More than ten decibels

3. When the silence between two sentences is cut in editing, the background sound stops suddenly. What should have been recorded in advance?

• A) Room tone
• B) Echo
• C) A high recording level
• D) The camera's own sound

4. A light-colored microphone cover sold as skin color sits like a stain on a dark-skinned person's neck. What is done?

• A) Leaving the cover as it is
• B) Bringing the microphone closer to the person's face
• C) Choosing the microphone and cover according to the person's skin or clothing, or hiding it under the clothing
• D) Lowering the recording level

Answers

1. D — Speech recorded from a distance can't be cleaned up afterward; closeness separates speech from ambient sound.
2. B — Sound, like light, weakens with distance; in an open space it drops about six decibels when the distance doubles.
3. A — Room tone is placed in the cut gaps and preserves the continuity of the background sound.
4. C — If the accessory's color is chosen according to the person's skin and clothing, it hides equally well for everyone.

Summary card

• The audience forgives a blurred image, not sound it can't understand.
• Bring the microphone closer to the speaker: directional or lavalier.
• Quiet the hum, soften the echo.
• Set the level so it won't clip, listen with headphones, record room tone.
• Put on the lavalier after asking; choose the accessory by the person's skin and clothing.

Bridge to the next lesson

The sound was clean now, and your friend wanted one more shot: the journey of the baker taking the hot bread tray out of the oven and carrying it to the window at the front of the shop. When they walked behind the baker holding the camera in their hand, the image swayed with every step, the framing bouncing up and down. The tripod, on the other hand, didn't move from its place and couldn't follow the baker. How does handheld footage look professional? The next lesson tells about camera movement with a gimbal, slow pans and static shots.