Microphone Testing Guide

Complete guide to testing microphones, evaluating frequency response, and diagnosing common microphone issues

Testing microphones properly ensures accurate recordings, clear communications, and reliable audio capture. This guide covers professional techniques for evaluating microphone performance across different use cases.

Quick Microphone Test Checklist

Visual Inspection

Check for physical damage, loose connections, damaged grilles or windscreens, and debris in the capsule.

Connection Test

Verify cable connections are secure, check for XLR/TRS pin damage, test with known-good cable if issues suspected.

Level Check

Speak at normal volume and distance, verify input levels reach -18dB to -12dB range, ensure no clipping occurs.

Noise Floor

Record 10 seconds of silence in quiet room, check for hiss, hum, RF interference, or electronic noise.

Frequency Response

Use AudioTest Pro's Tone Generator, play test tones across frequency range (100 Hz, 1 kHz, 5 kHz, 10 kHz), record and analyze spectrum.

Using AudioTest Pro for Microphone Testing

Method 1: Tone Generator + External Recorder

Set up microphone at standard test distance (6-12 inches for vocal mics)
Position speaker at same distance from microphone (on-axis)
Use Tone Generator to play reference tones (100, 500, 1k, 5k, 10k Hz)
Set consistent playback volume (~85 dB SPL)
Record each tone for 5-10 seconds
Use Spectrum Analyzer to compare recorded levels across frequencies

Method 2: Direct Spectrum Analysis

Connect microphone to your computer/interface
Open AudioTest Pro's Spectrum Analyzer
Select "Microphone" as input source
Grant microphone permission in browser
Speak, sing, or play sounds at consistent volume and distance
Observe frequency spectrum in real-time - should show balanced response

Method 3: Frequency Sweep Test

Use Frequency Sweep tool to generate 20 Hz - 20 kHz sweep
Play through reference speaker at consistent level
Record microphone output throughout sweep
Analyze recording to identify frequency response peaks/dips
Compare to manufacturer's frequency response specification

Common Microphone Issues & Solutions

Low Output / Weak Signal

Symptoms: Need to crank gain to maximum, still quiet.

Causes: Damaged capsule, faulty cable, incorrect phantom power, preamp issues.

Solution: Check phantom power (48V) is enabled for condenser mics, test with different cable, verify preamp/interface is working with known-good mic.

Hum or Buzz (50/60 Hz)

Symptoms: Low-frequency hum present even without sound source.

Causes: Ground loop, electromagnetic interference, unbalanced cables, bad power supply.

Solution: Use balanced XLR cables, check ground lift switches, separate audio cables from power cables, test in different outlet.

Distortion or Clipping

Symptoms: Harsh, crunchy sound on loud passages.

Causes: Gain too high, sound source too loud/close, capsule overload, preamp clipping.

Solution: Reduce gain, increase distance from source, use pad switch if available, check for clipping at multiple stages (mic → preamp → interface → DAW).

High Noise Floor / Hiss

Symptoms: Constant white noise/hiss in background.

Causes: Low-quality preamp, excessive gain, noisy power supply, poor shielding.

Solution: Use quality preamp with low noise floor, optimize gain structure, consider high-output dynamic mic or lower-noise condenser.

Intermittent Cutting Out

Symptoms: Signal drops in and out, crackling when cable moved.

Causes: Loose connection, damaged cable, worn XLR pins, failing phantom power.

Solution: Replace cable, clean XLR connections with contact cleaner, check for bent pins, test with different input.

Microphone Type Considerations

Dynamic Microphones (e.g., SM58, SM57)

• No phantom power needed - passive design
• Higher SPL handling - good for loud sources
• Less sensitive - need more gain
• Frequency response - typically rolled off below 80 Hz and above 15 kHz
• Testing - verify proximity effect (bass boost when close)

Condenser Microphones (e.g., AT2020, Neumann U87)

• Requires 48V phantom power - will not work without it
• More sensitive - captures detail and transients
• Extended frequency response - often 20 Hz to 20 kHz
• Lower SPL handling - can overload on very loud sources
• Testing - verify phantom power is present (48V ± 4V)

Ribbon Microphones (e.g., Royer R-121, AEA R84)

• Fragile - can be damaged by phantom power (some modern ribbons are safe)
• Very low output - needs lots of clean gain (60-70 dB)
• Figure-8 pattern - rejects sound from sides
• Smooth high end - warm, natural sound
• Testing - verify phantom power is OFF unless explicitly safe

Advanced Testing Techniques

Polar Pattern Verification

Test how microphone responds to sound from different angles:

Mount microphone on stand at consistent height
Position speaker at 0° (on-axis, directly in front)
Play 1 kHz test tone at consistent level
Record output level
Rotate microphone 30°, 60°, 90°, 135°, 180° and repeat
Plot results to visualize polar pattern

Proximity Effect Measurement

Measure bass boost at close distances (directional mics only):

Play 100 Hz tone through speaker
Record output at 12 inches distance
Move mic to 6 inches, record again
Move to 3 inches, record again
Compare bass levels - should increase closer to source

Self-Noise Measurement

Measure microphone's inherent noise floor:

Test in very quiet environment (noise floor below 30 dB SPL)
Connect mic with phantom power (if needed)
Set preamp gain to manufacturer's recommended level
Record 30 seconds of silence
Measure RMS level of recording
Compare to spec sheet (typically 10-20 dB-A for good condenser mics)