Small, discreet lapel microphones attached directly to an actor's clothing. Captures primarily the wearer's voice with minimal room reflections and background noise. Often used as backup mic or primary solution for tight camera framing or mobile scenes.
Technical Fundamentals
A lavalier microphone (also called "lav", "body mic", or "wireless mic") is a small, lightweight clip-on microphone that is attached directly to the actor's body. Unlike a boom mic, which captures sound from a distance, the lavalier sits close to the mouth (typically 10-20 cm below the chin) and primarily captures the wearer's voice.
Typical Lavalier Specifications
| Property | Standard Value | Remark |
|---|---|---|
| Size | 3-6 mm diameter, 2-3 cm length | Discreet, can be hidden in clothing |
| Weight | 1-3 g (capsule only) | Barely noticeable for actors |
| Frequency Response | 50 Hz - 16 kHz | Optimized for human voice (not bass) |
| Pickup Pattern | Omnidirectional or Cardioid | Omnidirectional captures more ambient sound |
| Sensitivity | -35 to -42 dBV/Pa | Typically lower than boom mics |
| Maximum SPL | 130+ dB SPL | Can handle loud shouts |
| Self-Noise | 20-30 dB-A | Slightly higher than boom (acceptable close to mouth) |
| Cable Weight | Fine nylon/plastic, 1-2 mm | Barely visible under clothing |
Wireless Technology for Lavaliers
The lavalier system consists of three components:
- Transmitter (worn by the actor)
- Frequency: typically 1.9-2.4 GHz (ISM band, license-free in EU/USA)
- Transmission Power: 50-100 mW
- Battery: AA/AAA, runtime 6-12 hours
- Weight: 100-200 g (small enough to be hidden in a pocket)
- Examples: Sennheiser EW 500 Series, Shure ULXD, Audio-Technica 3000 Series
- Receiver (with the sound mixer)
- Range: typically 100-300 m (depending on environment)
- Multiple channels possible (mono or stereo, depending on the number of lav mics)
- Power Supply: AC adapter or batteries
- Display: Shows frequency, signal strength, battery status
- Antenna
- Whip antennas (practical) or helix antenna (better for range)
- Positioning: Elevated at the mixer's location
Frequency Response and Characteristics
A typical lavalier microphone has a shaped frequency response to provide optimal dialogue quality:
- 50-100 Hz: Reduced (high-pass filter to minimize body noise)
- 100-250 Hz: Flat (fundamental voice range for deep voices)
- 250-2 kHz: Slightly boosted (presence, intelligibility)
- 2-5 kHz: Moderate boost (sibilance region)
- 5+ kHz: Reduced (less "air", but also less sibilance)
This presence peak is intentional: a lavalier needs to sound aggressive to leverage its proximity to the source.
Practical Setup and Placement
Where is the Lavalier Placed?
Standard Position:
- 10-20 cm below the chin, on clothing (chest/shirt)
- Angle: Slightly angled upwards towards the mouth (45 degrees)
- Distance from Mouth: 15-25 cm (closer = more proximity effect, louder; further = more room tone)
Alternative Positions (depending on the scene):
- Tie or Sweater: More discreet, but further from the mouth
- Under the shirt on the chest: Very hidden, but muffled (only for special scenes)
- Lapel of a Jacket: Classic, visible but acceptable
- Shoulder under jacket: For action, when proximity to the mouth is unimportant
Cable Routing
The thin lavalier cable needs to be routed from the microphone to the transmitter:
- Clothing Integration: The cable is hidden inside the clothing
- Transmitter Position: Typically in the back pocket of trousers or attached to the hip (with a clip)
- Cable Securing: Attached to the actor's body with small pieces of tape or Velcro to minimize movement noise
- Testing: Test for cable friction noise before recording
Windscreen and Pop Filter
Since the lavalier is close to the mouth, it needs protection:
- Windscreen: Small foam cap around the microphone (reduces plosives and breath sounds)
- Pop Filter: Sometimes an additional mesh cover
- Material: Fine nylon or mesh, barely visible even up close
Common Problems and Solutions
| Problem | Audible Result | Cause | Solution |
|---|---|---|---|
| Clothing Noise ("Rustling") | Scratchy noise with movement | Cable rubbing against clothing, or lav moving | Secure cable with tape/Velcro, use windscreen |
| Cable Clicking ("Handling Noise") | Clicking sounds with movement | Transmitter moving in pocket | Secure transmitter in a rigid holder, not loose |
| Proximity Effect (Bass Boom) | Muffled, bass-heavy voice | Microphone too close to mouth | Position 5-10 cm further away, or apply EQ later |
| Sound Too Quiet | Whispers barely audible | Weak transmitter or lavalier too far away | Check transmitter battery, move microphone closer |
| Radio Interference ("Dropouts") | Short interruptions, "glitch" sounds | RF interference or poor range | Reposition antenna, change frequency, move receiver closer |
| Overload on Loud Dialogues | Distorted, strained-sounding voice | Transmitter input level too high | Reduce transmitter input level |
| Voice Sounds "Thin" and High | Incorrect pitch, unnatural | Incorrect crossover or lack of bass | EQ adjustment in post-production, or position closer |
Equipment Standard for Lavalier Systems
Professional Wireless Systems
Sennheiser EW 500 Series (Industry Standard)
- Frequency Range: UHF (600-700 MHz or 1.9-2.3 GHz)
- Range: up to 250 m
- Price: €2000-€4000 per channel
Shure ULXD Wireless (Premium, digital transmission)
- Frequency: Digital, 1.9 GHz band
- Range: up to 300 m
- Latency: under 2 ms (imperative for live applications)
- Price: €3000-€5000 per channel
Audio-Technica 3000 Series (More affordable, solid)
- Frequency: UHF, many channels available
- Range: up to 200 m
- Price: €1500-€3000 per channel
Lavalier Capsules (Microphones)
Sennheiser MKE 2 (Omnidirectional, neutral)
- Price: €100-€200
- Frequency Response: 50-16 kHz
- Good for natural voice
Shure WL93 (Cardioid, aggressive)
- Price: €150-€250
- Frequency Response: 50-20 kHz
- More presence, less room tone
Audio-Technica AT831cW (Condenser, modern)
- Price: €200-€300
- Good for wide dynamic range processing
Accessories
- Batteries: AA/AAA Alkaline or NiMH Rechargeable
- Tape: Gaff tape or Velcro for securing
- Cable Organizers: For managing wireless signals at the mixer
- Antenna Splitters: For connecting multiple receivers to a central antenna
Industry Workflow for Lavalier Usage
Before the Shoot: Lavalier Test
- Check Wireless Range: Signal strength ("-40 dBm" is good, "-70 dBm" is weak)
- Transmitter Battery: Fully charge or insert a new battery
- Microphone Test: "Pop sound" into the capsule to check function
- Headphone Check: Sound mixer listens on headphones and confirms signal
During Fitting: Mounting on Actor
- Clothing Check: What outfit is the actor wearing? Where is the best hiding position?
- Marking: Mark the exact spot with tape or marker where the lavalier will sit
- Cable Routing: Hide under clothing, secure with tape
- Transmitter Pocket: Securely in the back pocket of trousers or on a hip belt
- Live Check: Actor speaks a few lines, sound mixer confirms: "Good signal, sounds good"
Between Takes: Adjustments
- Too muffled? → Lavalier a few cm closer to the mouth
- Too much clothing noise? → Secure with more tape or move to a different spot
- Radio interference? → Reposition antenna or switch to a different frequency
After the Shoot: Backup Recording
The sound mixer saves the lavalier signal on a separate channel as a backup. In editing, the sound editor will later choose: boom mic or lavalier, depending on the recording quality.
Practical Checklist for Lavalier Operation
- [ ] Wireless transmitter is fully charged or has a new battery
- [ ] Receiver shows stable signal strength (-30 to -50 dBm ideal)
- [ ] Lavalier microphone is positioned 10-20 cm below the chin
- [ ] Cable is hidden under clothing and secured with tape
- [ ] Transmitter is securely in the trouser pocket, not loose
- [ ] Windscreen is on the microphone
- [ ] Perform live voice test ("Testing 1-2-3")
- [ ] Sound mixer confirms level and sound quality via headphones
- [ ] Record lavalier signal separately (as backup alongside boom)
- [ ] For costume changes: reposition and test lavalier
- [ ] After several hours: check battery status
Lavalier vs. Boom Mic: When to Use Which?
| Scenario | Best Choice | Reason |
|---|---|---|
| Static Dialogue Scene | Boom Mic | Better sound quality, less clothing noise |
| Action Sequence with Running | Lavalier | Boom cannot follow, lavalier provides consistent levels |
| Extreme Close-Up | Lavalier | Boom would be in frame |
| Outdoor Shooting with Wind | Boom Mic | Better wind protection possible |
| Tight Interior Spaces | Boom Mic | Better control over room reflections |
| Scene Start with Multiple Actors | Both (Mono) | Boom for wide sound, lavalier as backup |
Summary
The lavalier microphone is an indispensable tool in professional audio workflows, but with compromises:
Advantages:
- Consistent, loud dialogue levels
- Independent of boom position
- Allows for tight camera framing
- Reliable in action scenes
Disadvantages:
- Clothing noise ("Rustling")
- Proximity effect and bass boom
- Setup time for mounting
- Potential for radio interference
Best practice: Always use both systems (boom + lavalier). This gives the sound mixer maximum flexibility and security against bad recordings in post-production.