Chapter - 1

Key Words: Recording, Microphone type, Ambient noise, Gain staging, Mono, Stereo, Surround

Recording Requirements

🎯 Learning Objectives

By the end of this topic, you should be able to:

  • Understand the essential technical and acoustic requirements for high-quality recording.
  • Identify how microphone type, placement, and environment affect recording fidelity.
  • Explain the role of signal chain components such as preamps, interfaces, and monitoring systems.
  • Recognize how room acoustics and ambient noise influence microphone selection.
  • Apply proper gain staging, distance, and orientation techniques to avoid distortion and coloration.
  • Select the right recording configuration (mono, stereo, surround) based on session goals and source type.

Introduction:

In any audio system, the microphone is the first link in the signal chain — it determines how faithfully sound is captured.
The recording requirements depend on the application: whether capturing speech, music, ambient sound, or scientific measurements.
Understanding microphone specifications, placement, and environmental factors ensures accurate and high-quality recordings.

Fundamental Recording Requirements:

To achieve consistent and high-fidelity recordings, consider these key requirements:

Signal domain illustration
Figure. Recording Requirements

Frequency Response

The frequency response defines how accurately a microphone reproduces the amplitude of sound across frequencies:

H(f)=Vout(f)Pin(f)H(f) = \frac{V_\text{out}(f)}{P_\text{in}(f)}

Where:
H(f)H(f) = transfer function (response)
Vout(f)V_\text{out}(f) = output voltage
Pin(f)P_\text{in}(f) = input sound pressure

A flat response (±2±2 dB) across 2020 Hz to 2020 kHz is ideal for measurement microphones, while tailored responses are desirable for vocals or instruments (e.g., presence boost at 55 to 88 kHz).

Sensitivity and Gain Staging:

Microphone sensitivity determines the output level for a given sound pressure level (SPL).
It is usually expressed in millivolts per Pascal (mV/Pa) or dBV/Pa.

For example:

S=20log⁡10(Vout1 Pa) dBV/PaS = 20 \log_{10}\left(\frac{V_\text{out}}{1\ \text{Pa}}\right)\ \text{dBV/Pa}

Condenser mics: typically –32 to –44 dBV/Pa Dynamic mics: typically –52 to –58 dBV/Pa

Proper gain staging ensures that quiet signals are amplified without introducing noise or distortion.

Impedance Matching:

Every microphone has an output impedance, and the preamplifier has an input impedance.
For optimal signal transfer and minimal distortion:

Zin≥10×ZmicZ_\text{in} \ge 10 \times Z_\text{mic}

This ensures minimal loading and flat frequency response.
Low-impedance (150–600 Ω) microphones are preferred for long cable runs since they are less susceptible to noise pickup.

Dynamic Range and SPL Handling:

The dynamic range defines the microphone’s usable range between the noise floor and the maximum SPL (Sound Pressure Level) before distortion.

💡 Tip: When recording loud sources, enable a –10 dB or –20 dB pad switch (if available) to prevent overload.

Signal domain illustration
Figure. Dynamic Range and SPL Handling

Directionality and Polar Patterns:

The directional characteristics of microphones affect how they capture sound from various directions.
In mathematical form, a cardioid can be represented as:

R(θ)=0.5(1+cos⁡θ)R(\theta) = 0.5(1 + \cos\theta)

Where θ\theta is the angle relative to the front axis.

Signal domain illustration
Figure. Directionality and Polar Patterns

Environmental & Practical Considerations:

  1. Ambient Noise: Choose directional mics or soundproof the environment.
  2. Room Acoustics: Use acoustic panels, reflection filters, or reverb control for cleaner recordings.
  3. Microphone Placement: Distance and angle affect proximity effect, tonal balance, and phase relationships.
  4. Phantom Power: Condenser and MEMS microphones require +48 V (via XLR).
  5. Mechanical Isolation: Use shock mounts and pop filters to reduce vibrations and plosives.
  6. Temperature & Humidity: Affects diaphragm tension and electronics — store microphones properly.

Application-Based Recommendations:

Signal domain illustration
Figure. Recommendations

🎨 Interactive Demo

🎤 Microphone Response

📈 Frequency Response

📡 Polar Pattern

Microphone

Microphone Selector Tool

Move slider to adjust the expected mic distance to source.
High values favor directional, low-sensitivity mics (dynamics / cardioids).

Large-diaphragm Condenser (Cardioid)

score 75
Type: Large-diaphragm Condenser
Polar: Cardioid
High sensitivity and detail; needs phantom power. Use pop-filter and shock mount for vocals.
Why suggested?
  • Matches source: Studio Vocal (lead), Spoken Voice / Podcast, Acous
  • Good for: Treated studio, Conference room

Small-diaphragm Condenser (Cardioid)

score 45
Type: Small-diaphragm Condenser
Polar: Cardioid
Excellent transient response — good for detailed miking and stereo pair jobs.
Why suggested?
  • Matches source: Acoustic Guitar, Drum Overheads / Room, Instrument
  • Good for: Treated studio, Untreated room / bedroom

Omnidirectional Condenser

score 30
Type: Condenser (Omni)
Polar: Omnidirectional
Captures room ambience accurately; less proximity effect than cardioids.
Why suggested?
  • Matches source: Orchestra / Ensemble, Room/ambient recordings, Fie
  • Good for: Treated studio, Outdoors / field
Inputs:
Source: Studio Vocal (lead) — Environment: Treated studio — Distance: 0.25 m — Noise: 3 — Tone: Neutral
Notes: This tool uses heuristics to recommend microphone types and polar patterns based on common practice. It’s intentionally conservative — treat suggestions as starting points and always audition mics and placements in context.

Microphone Visualizer

Microphone Selection
Audio Preview
Distance affects HF roll-off and overall gain; angle influences stereo panning. Use an uploaded audio sample to audition changes in real time.
Display Options
Legend
Condenser

Frequency Response

Polar Pattern (shaded by source angle)

Source angle
0°

Key Takeaways

  • Recording quality depends on the synergy between microphone, source, and acoustic space.
  • A well-treated recording space reduces reflections, flutter echoes, and low-frequency buildup.
  • Microphone placement determines tonal balance, stereo width, and spatial depth — small movements can cause large sonic changes.
  • Proper gain staging ensures a clean signal with optimal headroom (no clipping, no excessive noise).
  • Phantom power (48V) is required for condenser and some active ribbon microphones.
  • Use pop filters, shock mounts, and isolation to reduce mechanical and plosive noise.
  • Monitoring through studio-grade headphones or reference speakers is critical for accurate recording decisions.
  • Environmental factors (temperature, humidity, wind) can subtly affect microphone performance and diaphragm sensitivity.

🧠 Quick Quiz

1) What is the most important first step before pressing 'record' in a studio session?

2) Why is room treatment critical for microphone recordings?

3) What is the function of phantom power (48V)?

4) What happens if input gain is set too high during recording?

5) Why should you use a pop filter when recording vocals?