5.1 Microphone types and placement

Microphones are the backbone of audio recording in narrative documentaries. From dynamic to condenser, shotgun to lavalier, each type serves a unique purpose. Understanding their characteristics and placement techniques is crucial for capturing high-quality sound.

Proper microphone selection and positioning can make or break your audio. Factors like pickup patterns, proximity effect, and the 3-to-1 rule play vital roles in achieving clear, balanced recordings. Accessories like windscreens and shock mounts further enhance audio quality and protect your gear.

Types of microphones

• Microphones are essential tools for capturing audio in narrative documentary production
• Different types of microphones are suited for various applications and recording situations
• Choosing the right microphone depends on factors such as the sound source, environment, and desired audio quality

Dynamic vs condenser mics

• Dynamic microphones are rugged, reliable, and well-suited for capturing loud sound sources (drums, amplifiers)
• They have a simple design with a moving coil attached to a diaphragm, which generates an electrical signal when sound waves hit it
• Condenser microphones are more sensitive and capture a wider frequency range, making them ideal for recording vocals, acoustic instruments, and subtle sounds
• They require phantom power to operate and have a thin, electrically-charged diaphragm that vibrates when exposed to sound waves

Shotgun mics for distance

• Shotgun microphones are highly directional and designed to capture sound from a specific direction while rejecting noise from the sides
• They are commonly used in film and video production for recording dialogue and sound effects from a distance
• Shotgun mics have an interference tube that helps to focus the sound pickup pattern and minimize off-axis noise
• Examples of shotgun mics include the Sennheiser MKH 416 and the Rode NTG3

Lavalier mics for interviews

• Lavalier microphones, also known as lapel mics, are small, discreet microphones that can be clipped onto clothing
• They are ideal for recording interviews, presentations, and dialogue in situations where the microphone needs to be close to the speaker
• Lavalier mics are often omnidirectional, meaning they pick up sound equally from all directions
• Popular lavalier mics include the Sennheiser EW 112P G4 and the Rode Lavalier GO

Wireless vs wired mics

• Wireless microphones transmit audio signals wirelessly using radio frequencies, allowing for greater mobility and flexibility in recording
• They consist of a transmitter (worn by the speaker) and a receiver (connected to the recording device)
• Wired microphones are directly connected to the recording device via cables, providing a stable and reliable connection
• Wired mics are less prone to interference and battery issues compared to wireless systems

Microphone pickup patterns

• Microphone pickup patterns describe the directional sensitivity of a microphone and how it responds to sound from different directions
• Understanding pickup patterns helps in selecting the appropriate microphone for a given recording situation
• Pickup patterns affect the microphone's ability to isolate sound sources and reject unwanted noise

Omnidirectional pattern

• Omnidirectional microphones have a 360-degree pickup pattern, meaning they capture sound equally from all directions
• They are ideal for recording ambient sound, room acoustics, and multiple sound sources
• Omnidirectional mics are less sensitive to wind noise and handling noise compared to directional microphones
• Examples of omnidirectional mics include the DPA 4060 and the Shure SM58

Cardioid pattern

• Cardioid microphones have a heart-shaped pickup pattern, with maximum sensitivity at the front and reduced sensitivity at the sides and rear
• They are the most common type of microphone used in various recording applications, including vocals, instruments, and dialogue
• Cardioid mics provide good isolation of the main sound source while rejecting unwanted noise from other directions
• Examples of cardioid mics include the Shure SM57 and the Neumann TLM 103

Supercardioid and hypercardioid patterns

• Supercardioid and hypercardioid microphones have narrower pickup patterns compared to cardioid mics, with increased directionality and rejection of side noise
• They have a small rear lobe of sensitivity, which can be used to capture room ambience or strategically placed to minimize feedback
• Supercardioid and hypercardioid mics are often used in live sound reinforcement and film production for improved isolation and noise rejection
• Examples include the Sennheiser MKH 50 (supercardioid) and the AKG C414 XLS (hypercardioid)

Bidirectional (figure-8) pattern

• Bidirectional microphones, also known as figure-8 mics, have equal sensitivity at the front and rear, with minimal pickup from the sides
• They are often used for recording duets, interviews, or capturing the natural ambience of a room
• Bidirectional mics can be used in conjunction with the mid-side (MS) stereo recording technique
• Examples of bidirectional mics include the Shure KSM44A and the AKG C414 XLS (in figure-8 mode)

Microphone placement techniques

• Proper microphone placement is crucial for achieving optimal sound quality and minimizing unwanted noise
• The distance and angle of the microphone relative to the sound source can significantly impact the recorded audio
• Experimenting with different microphone positions and techniques can help capture the desired sound and create a sense of space and depth

Proximity effect

• The proximity effect is the increase in low-frequency response when a directional microphone is placed close to the sound source
• It can be used to add warmth and depth to vocals or instruments, but excessive proximity effect can result in a boomy or muddy sound
• To control the proximity effect, adjust the distance between the microphone and the sound source or use a high-pass filter to reduce low frequencies
• The proximity effect is more pronounced in directional microphones (cardioid, supercardioid, hypercardioid) compared to omnidirectional mics

3-to-1 rule for multiple mics

• The 3-to-1 rule is a guideline for placing multiple microphones to minimize phase cancellation and comb filtering effects
• It states that the distance between two microphones should be at least three times the distance from each microphone to the sound source
• Following the 3-to-1 rule helps ensure a clear and coherent sound when using multiple microphones on the same source
• For example, if two microphones are 1 foot away from a sound source, they should be at least 3 feet apart from each other

Mic placement for dialogue

• When recording dialogue, place the microphone close to the speaker's mouth (6-12 inches) to capture a clear and intimate sound
• Use a boom pole or a mic stand to position the microphone above the speaker's head, aiming it towards their mouth
• If using a lavalier microphone, attach it to the speaker's clothing, about 6-8 inches below their chin
• Avoid placing the microphone too close to the speaker's mouth to prevent plosives and excessive sibilance

Mic placement for narration

• For narration or voiceover recording, position the microphone 6-12 inches away from the speaker's mouth, slightly off-axis to minimize plosives
• Use a pop filter or windscreen to further reduce plosives and breath noise
• Record in a quiet, acoustically treated room to minimize unwanted reflections and background noise
• Encourage the narrator to maintain a consistent distance from the microphone throughout the recording

Mic placement for ambient sound

• When capturing ambient sound or room tone, place the microphone at a distance from the sound source to record a balanced and natural sound
• Use an omnidirectional or bidirectional microphone to capture a wide and immersive soundscape
• Position the microphone at ear level to simulate the listener's perspective
• Avoid placing the microphone too close to reflective surfaces or noise sources, such as air conditioning units or electrical appliances

Microphone accessories

• Microphone accessories are essential for improving sound quality, reducing unwanted noise, and protecting the microphone from damage
• They can also enhance the microphone's functionality and make it easier to use in various recording situations
• Investing in high-quality microphone accessories can significantly improve the overall audio quality of your recordings

Windscreens and pop filters

• Windscreens are foam or furry covers that fit over the microphone to reduce wind noise and protect the microphone from moisture and dust
• They are essential when recording outdoors or in windy environments to minimize rumble and distortion caused by wind
• Pop filters are mesh screens placed between the microphone and the sound source to reduce plosives (hard "p" and "b" sounds) and breath noise
• They help to disperse the air from plosives, preventing them from hitting the microphone capsule directly

Shock mounts for isolation

• Shock mounts are designed to isolate the microphone from handling noise and vibrations transmitted through the mic stand or boom pole
• They consist of an elastic suspension system that absorbs shocks and mechanical noise, preventing them from reaching the microphone
• Shock mounts are particularly useful when recording in environments with heavy foot traffic, or when using a microphone on a boom pole or stand
• Examples of shock mounts include the Rycote InVision USM and the Rode SM2

Mic stands and booms

• Microphone stands and booms are used to position the microphone at the desired height and angle relative to the sound source
• Stands come in various heights and designs, including straight stands, boom stands, and desktop stands
• Boom arms allow for greater flexibility in positioning the microphone, especially when recording instruments or multiple sound sources
• C-stands and boom poles are commonly used in film and video production to suspend the microphone above the sound source

Cable management and organization

• Proper cable management and organization are essential for maintaining a tidy and efficient recording setup
• Use cable ties, velcro straps, or cable organizers to keep microphone cables neat and tangle-free
• Label microphone cables with tape or cable markers to easily identify which microphone they belong to
• Invest in high-quality, shielded microphone cables to minimize interference and ensure reliable signal transmission
• Regularly inspect and maintain microphone cables to prevent damage and ensure optimal performance

Audio recording considerations

• In addition to microphone selection and placement, several other factors contribute to the quality of the recorded audio
• Understanding and optimizing these aspects can help you achieve professional-sounding results and avoid common audio issues
• Paying attention to signal levels, monitoring, and recording formats can ensure that your audio is clean, clear, and ready for post-production

Signal-to-noise ratio

• The signal-to-noise ratio (SNR) is the ratio of the desired audio signal to the level of background noise in a recording
• A high SNR means that the desired audio is much louder than the noise, resulting in a clean and clear recording
• To improve the SNR, use high-quality microphones, record in a quiet environment, and position the microphone close to the sound source
• Use noise reduction techniques, such as acoustic treatment, noise gates, and software noise reduction, to further minimize background noise

Gain staging and levels

• Gain staging is the process of setting the appropriate signal levels throughout the recording chain to ensure optimal audio quality and avoid clipping or noise
• Set the microphone preamp gain so that the average signal level is around -18 dBFS (decibels below full scale) to allow for headroom and prevent clipping
• Use a limiter or compressor to control sudden peaks in the audio signal and prevent distortion
• Monitor the audio levels using a meter or the recording device's display to ensure that they remain consistent and within a safe range

Monitoring and headphones

• Monitoring the audio signal through headphones or studio monitors is crucial for ensuring that the recording is clean, clear, and free of any issues
• Use closed-back headphones to isolate the sound and prevent audio leakage from the headphones into the microphone
• Set the monitoring level to a comfortable volume that allows you to hear the audio clearly without causing ear fatigue
• Listen for any unwanted noise, distortion, or dropouts in the audio signal and address these issues promptly

Recording formats and bit depth

• Choose an appropriate recording format and bit depth based on the intended use of the audio and the available storage space
• Common audio file formats include WAV, AIFF, and MP3, with WAV and AIFF being uncompressed formats that offer higher quality
• Higher bit depths (24-bit or 32-bit) provide a greater dynamic range and lower noise floor compared to 16-bit recordings
• Consider the compatibility of the recording format with your editing software and the final delivery requirements of your project

Common microphone problems

• Even with proper microphone selection and placement, various issues can arise during the recording process
• Identifying and addressing these common problems can help you maintain high-quality audio and avoid costly retakes or post-production fixes
• Being aware of potential issues and implementing preventive measures can save time and ensure a smoother recording experience

Handling noise and vibrations

• Handling noise occurs when the microphone or its cable is touched or moved, resulting in unwanted rumbling or thumping sounds
• To minimize handling noise, use a shock mount to isolate the microphone from vibrations and avoid touching the microphone or cable during recording
• Secure the microphone cable to the stand or boom pole using tape or cable ties to prevent it from rubbing against surfaces or swinging
• Encourage on-screen talent to avoid touching or adjusting the microphone during takes

Wind and environmental noise

• Wind noise can cause distortion and low-frequency rumble when recording outdoors or in drafty environments
• Use a windscreen or a furry windshield (dead cat) to reduce wind noise and protect the microphone from air movement
• When recording in noisy environments, use directional microphones (cardioid, supercardioid, or hypercardioid) to focus on the desired sound source and reject unwanted noise
• If possible, record in a quiet location away from traffic, air conditioning units, or other noise sources

Electromagnetic interference (EMI)

• Electromagnetic interference (EMI) can cause buzzing, humming, or clicking noises in the audio signal due to nearby electronic devices or power sources
• Keep microphones and audio cables away from power cables, transformers, and electronic devices such as cell phones, computers, or fluorescent lights
• Use balanced XLR microphone cables to reduce the impact of EMI and ensure a clean audio signal
• If necessary, use a ground lift adapter or a power conditioner to eliminate ground loop hum caused by multiple devices connected to different power outlets

Feedback and mic placement

• Feedback occurs when the sound from a loudspeaker is picked up by a microphone and re-amplified, creating a loud, high-pitched squealing noise
• To prevent feedback, avoid placing microphones directly in front of or close to loudspeakers
• Use directional microphones (cardioid, supercardioid, or hypercardioid) to minimize the pickup of sound from the sides and rear, reducing the likelihood of feedback
• Monitor the sound levels and adjust the microphone placement or speaker volume to find the optimal balance and avoid feedback
• Employ equalization (EQ) techniques, such as cutting frequencies prone to feedback or using a feedback suppressor, to further reduce the risk of feedback