CEA Microphone Techniques and Placement 1 — Questions and Answers
Question 1: What polar pattern captures sound equally from all directions with no directional preference?
- Cardioid
- Figure-8 (bidirectional)
- Hypercardioid
- Omnidirectional (Correct answer)
Correct answer: Omnidirectional
An omnidirectional polar pattern has equal sensitivity at all angles (360°). Omnidirectional microphones capture the full sonic environment of a space, exhibit no proximity effect, and are often chosen for capturing room ambience and orchestral recordings.
Question 2: For recording an acoustic guitar, what is the generally recommended microphone placement to capture a balanced tone with both warmth and articulation?
- Directly at the sound hole to maximize bass resonance
- Pointing at the 12th fret from approximately 6–12 inches away to balance body warmth and string detail (Correct answer)
- At the rear of the body to capture room ambience
- Pointed at the bridge saddle from 1 inch away for maximum attack
Correct answer: Pointing at the 12th fret from approximately 6–12 inches away to balance body warmth and string detail
Placing a microphone at the 12th fret captures a blend between the bass-heavy resonance of the sound hole and the bright, articulate transients from the strings and frets, yielding a naturally balanced acoustic guitar tone. Close placement at the sound hole creates excessive low-frequency buildup.
Question 3: What does the 'hypercardioid' polar pattern offer compared to a standard cardioid?
- A wider front acceptance angle with less rear rejection
- A narrower front acceptance angle with greater side rejection, but a small rear lobe of sensitivity (Correct answer)
- Equal sensitivity in all directions like an omnidirectional pattern
- Rejection of sound from both front and rear with maximum sensitivity at 90 degrees
Correct answer: A narrower front acceptance angle with greater side rejection, but a small rear lobe of sensitivity
Hypercardioid microphones have a narrower front pickup angle (acceptance angle ≈ 105°) providing better isolation from sides compared to cardioid (131°), but they have a small rear lobe of sensitivity (maximum rear rejection at 150° rather than 180°). They are used in live sound for rejection of stage monitors.
Question 4: What is the 'ORTF' stereo microphone technique, and what are its standard specifications?
- Two omni microphones spaced 1 meter apart to capture a wide stereo image
- Two cardioid microphones with capsules spaced 17 cm apart and angled 110 degrees apart, simulating the human ears (Correct answer)
- An M/S arrangement using a cardioid and figure-8 microphone in a coincident configuration
- Two figure-8 microphones crossed at 90 degrees in a Blumlein pair configuration
Correct answer: Two cardioid microphones with capsules spaced 17 cm apart and angled 110 degrees apart, simulating the human ears
ORTF (Office de Radiodiffusion Télévision Française) is a near-coincident stereo technique using two cardioid microphones with capsules spaced 17 cm apart and angled 110 degrees apart, approximating the distance and angle of the human ears to produce a natural, wide stereo image.
Question 5: When recording drums, what technique is used to minimize phase interference between the kick drum close mic and the overheads?
- Using omnidirectional microphones on all drum positions
- Applying the 3:1 rule and checking phase alignment by mono-summing the close mics with the overheads (Correct answer)
- Placing the overhead microphones directly above the snare drum
- Engaging the high-pass filter on the kick mic at 200 Hz
Correct answer: Applying the 3:1 rule and checking phase alignment by mono-summing the close mics with the overheads
Phase issues between the kick close mic and overheads arise from different time-of-arrival to each mic. The 3:1 rule (overhead distance ≥ 3× kick mic distance to the drum) reduces leakage. Phase coherence is verified by checking for low-frequency cancellation when summing tracks to mono.
Question 6: What microphone technique is recommended to avoid plosive sounds ('p' and 'b' sounds) when recording vocals?
- Engaging the low-cut filter on the microphone
- Positioning the microphone slightly off-axis (at an angle) or using a pop filter 2–6 inches in front of the microphone (Correct answer)
- Using a dynamic microphone instead of a condenser
- Reducing the input gain to lower the sensitivity to plosive bursts
Correct answer: Positioning the microphone slightly off-axis (at an angle) or using a pop filter 2–6 inches in front of the microphone
Plosives are bursts of low-frequency air pressure that cause thumps in vocal recordings. Placing a pop filter (mesh or foam screen) 2–6 inches from the microphone and angling the microphone slightly off-axis deflects the burst of air while preserving tonal quality.
CEA Microphone Techniques and Placement 1
What polar pattern captures sound equally from all directions with no directional preference?