Soundproof Room Ventilation and Air Conditioning | Design and Practical Guide to Prevent Sound Leakage

Are you experiencing problems like “stuffy,” “hot,” or “musty” after installing a soundproof room?

Soundproof rooms have high airtightness, so if ventilation and air conditioning are not properly designed, comfort is significantly compromised. Furthermore, “stopping sound” and “allowing air through” are contradictory structures, so insufficient ventilation design can also cause sound leakage.

This article organizes the basic structure and principles of sound leakage countermeasures for soundproof room ventilation and air conditioning, and explains practical countermeasure methods in detail.

Introduction: Why “Air Flow” Becomes a Problem in Soundproof Rooms

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Ventilation and air conditioning problems in soundproof rooms arise from their structural characteristics.

Soundproof Room = High Airtightness → Ventilation, Heat Buildup, and Humidity Are Challenges

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Soundproof rooms have high airtightness to prevent sound from leaking outside. This airtightness causes the following problems.

①CO₂ Accumulation Due to Insufficient Ventilation

• CO₂ from breathing accumulates in sealed spaces
• Causes headaches and fatigue during long use
• Guideline: Discomfort occurs when CO₂ concentration exceeds 1,000ppm

②Heat Buildup

• Heat from human bodies and equipment cannot escape
• Room temperature can exceed 35℃ in summer
• Risk of heatstroke increases

③Humidity Rise

• Water vapor from breathing and perspiration accumulates
• Mold becomes more likely at 70%+ humidity
• Promotes deterioration of instruments and equipment

“Stopping Sound” and “Allowing Air Through” Are Contradictory Structures

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The most difficult aspect of soundproof room design is balancing “stopping sound” and “allowing air through.”

How Sound Travels

• Airborne transmission: Sound travels through air
• Structure-borne transmission: Sound travels through walls and floors

Ventilation Opening Problems

• Ventilation openings easily become “sound exits”
• Straight paths allow sound to leak directly outside
• Ensuring ventilation volume increases sound leakage risk

Solution Direction

• Create bends in ventilation paths (avoid straight lines)
• Install sound-absorbing layers in ducts
• Distribute ventilation openings

Basic Structure of Soundproof Room Ventilation and Air Conditioning

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Let’s understand the basic structure of ventilation and air conditioning in soundproof rooms.

Why Securing Ventilation Paths Is Difficult (Air and Sound Use the Same Path)

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The reason securing ventilation paths is difficult is that air and sound travel through the same path.

Problems with Standard Ventilation Fans

• Straight exhaust paths
• Sound leaks directly outside
• Soundproofing performance significantly decreases

Features of Soundproof Room-Specific Ventilation Fans

• Ducts with bent structures
• Sound-absorbing material filled inside
• Maintain soundproofing performance while ventilating

Ventilation Path Design Principles

1. Avoid Straight Paths: Create 90-degree or greater bends
2. Install Sound-Absorbing Layers: Place sound-absorbing material in ducts
3. Distribute Layout: Distribute ventilation openings to multiple locations

Differences from Standard Homes: CO₂ Accumulation and Temperature Rise Due to Sealed Structure

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The need for ventilation and air conditioning differs greatly between soundproof rooms and standard homes.

Standard Homes

• Natural gap ventilation occurs
• Ventilation possible by opening windows
• Easy to manage temperature and humidity

Soundproof Rooms

• Extremely few gaps
• Opening windows loses soundproofing effect
• Forced ventilation is essential

CO₂ Accumulation Measurement Data

• Standard homes: 400-600ppm (when ventilation is good)
• Soundproof rooms (no ventilation): 1,200ppm+ in 1 hour
• Guideline: Discomfort above 1,000ppm, health risk above 2,000ppm

Temperature Rise Measurement Data

• Standard homes: External temperature ±2℃
• Soundproof rooms (no ventilation): External temperature +5-10℃
• Can exceed 40℃ in summer

Role Division Between “Ventilation Systems” and “Air Conditioning (Air Conditioners)”**

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Ventilation and air conditioning have different roles. Understanding each role will help you choose what you really need.

Ventilation System Role

• Bring in fresh air
• Exhaust CO₂ and dirty air
• Adjust humidity (exchange with outside air)

Air Conditioning (Air Conditioner) Role

• Adjust temperature (cooling/heating)
• Dehumidify (during cooling operation)
• Circulate air

Relationship Between the Two

• Ventilation alone does not lower temperature
• Air conditioners alone do not improve air quality
• Combining both achieves a comfortable environment

Recommended System Configuration

• Ventilation fan: Continuous operation (low airflow)
• Air conditioner: Operate as needed
• Thermohygrometer: Environmental monitoring

How Sound Leakage Occurs Through Ventilation

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Understanding how sound leakage occurs through ventilation enables appropriate countermeasures.

Why Ventilation Openings Become “Sound Exits”

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Ventilation openings cause sound leakage because sound and air travel through the same path.

How Sound Travels

• Sound traveling through air (airborne transmission)
• Sound traveling through walls and floors (structure-borne transmission)

Ventilation Opening Problems

• Ventilation openings are air passages
• Airborne sound also goes outside
• Straight paths allow sound to leak directly

Sound Leakage Levels

• No ventilation opening: D-40 to 50 (soundproof room performance)
• Standard ventilation fan: D-20 to 30 (significant performance decrease)
• Soundproof ventilation fan: D-35 to 45 (maintains performance)

How Sound Travels (Airborne/Structure-Borne Transmission)

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Understanding how sound travels enables appropriate countermeasures.

Airborne Transmission

• Sound travels through air
• Sound leaks through ventilation openings and gaps
• Countermeasures: Create bends in ventilation paths, install sound-absorbing material

Structure-Borne Transmission

• Sound travels through walls and floors
• Vibration travels through structures
• Countermeasures: Floating floor structure, use vibration-damping materials

Sound Leakage in Soundproof Rooms

• Mainly airborne sound leakage is the problem
• Sound leakage from ventilation openings is largest
• Ventilation path design is important

Three Points to Prevent Sound Leakage in Ventilation Opening Design

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Following these three points in ventilation opening design can significantly prevent sound leakage.

①Avoid Straight Paths (Bent Structure)

Straight ventilation paths cause sound to leak directly outside.

Countermeasures

• Create 90-degree or greater bends
• Combine multiple bends
• More bends increase effectiveness

Effect

• Straight path: Large sound leakage
• One bend: About 5-10dB attenuation
• Two bends: About 10-15dB attenuation

②Install Sound-Absorbing Layers in Ducts

Placing sound-absorbing material in ducts can attenuate sound energy.

Countermeasures

• Attach sound-absorbing material to duct inner walls
• Sound-absorbing material thickness: 50mm+ recommended
• Materials: Glass wool, urethane foam, etc.

Effect

• No sound-absorbing material: Large sound leakage
• With sound-absorbing material: About 5-10dB attenuation
• Combined with bends: About 15-20dB attenuation

③Distribute Exit Locations

Concentrating ventilation openings in one location increases sound leakage.

Countermeasures

• Distribute ventilation openings to multiple locations
• Separate intake and exhaust openings
• Install away from sound source

Effect

• Concentrated layout: Large sound leakage
• Distributed layout: Sound leakage is distributed and overall attenuated

Soundproofing Specifications Required for Air Conditioning (Air Conditioners)

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Let’s explain how to choose and install air conditioners for soundproof rooms.

Noise and Vibration Countermeasures for Outdoor Units

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Air conditioner outdoor units are sources of noise and vibration.

Outdoor Unit Noise

• Operating sound: About 40-50dB
• Fan sound: About 30-40dB
• Compressor sound: About 50-60dB

Countermeasures

• Install soundproof covers
• Use vibration-damping rubber
• Install away from sound source

Recommended Installation Position

• At least 3m from sound source
• Away from neighboring houses
• Cover with soundproof cover

Importance of Ceiling-Directed Airflow and Wall Separation

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Air conditioner airflow direction affects soundproofing performance.

Benefits of Ceiling-Directed Airflow

• Away from sound source
• Good air circulation
• Less direct sound

Importance of Wall Separation

• Do not attach directly to wall
• Completely seal gaps
• Maintain soundproofing performance

Recommended Installation Method

• Ceiling-embedded type
• At least 10cm from wall surface
• Use soundproof ducts

Points for Choosing Air Conditioners: Quiet, Vibration-Damping, Heat Efficiency

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Let’s explain how to choose air conditioners suitable for soundproof rooms.

Quiet Performance

• Operating sound: 30dB or less ideal
• Fan sound: 25dB or less ideal
• Compressor sound: 40dB or less ideal

Vibration-Damping Performance

• Use vibration-damping rubber
• Design where vibration does not transmit to structure
• Choose low-vibration type

Heat Efficiency

• Soundproof rooms are sealed spaces, so 1-2 ranks higher capacity needed
• 1 tatami: 6-tatami air conditioner recommended
• 1.5 tatami: 8-tatami air conditioner recommended
• 2 tatami: 10-tatami air conditioner recommended

Features by Manufacturer

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Let’s compare features of major manufacturers.

Panasonic

• Outdoor unit quiet control function
• Quiet operating sound
• Easy to install in rental properties

Daikin

• Quiet airflow outlet design
• Compatible with small spaces
• Optimal for small soundproof rooms

Mitsubishi Electric

• Compatible with Lossnay ventilation fan
• Suitable for constant temperature management
• Also supports commercial use

Ventilation Opening and Soundproof Cover Design to Prevent Sound Leakage

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Let’s explain design methods for ventilation openings and soundproof covers to prevent sound leakage.

How Silencers (Sound-Absorbing Ducts) Work

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Silencers (sound-absorbing ducts) are devices that attenuate sound within ventilation paths.

Mechanism

• Place sound-absorbing material in ducts
• Change sound path with bent structure
• Convert sound energy to heat energy

Structure

• Outer: Sound-insulating sheet
• Inner: Sound-absorbing material (glass wool, urethane foam)
• Path: 90-degree or greater bends

Effect

• Sound leakage: About 10-15dB attenuation
• Ventilation performance: Maintained
• Installation: Incorporated into ducts

Commercial Soundproof Ventilation Openings and DIY Methods

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Soundproof ventilation openings include commercial products and DIY versions.

Commercial Soundproof Ventilation Openings

DIY Method

Materials

• Duct material (PVC pipe, etc.)
• Sound-absorbing material (glass wool, urethane foam)
• Sound-insulating sheet
• Ventilation fan unit

Procedure

1. Create 90-degree bends in duct material
2. Attach sound-absorbing material to duct inner walls
3. Cover outside with sound-insulating sheet
4. Connect ventilation fan

Notes

• Ensure ventilation capacity
• Minimize sound leakage
• Consider maintenance

DIY Structure of Soundproof Covers

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Making soundproof covers yourself can prevent sound leakage while keeping costs down.

Structure

• Outer: Sound-insulating sheet (5mm+)
• Inner: Sound-absorbing material (50mm+)
• Path: 90-degree bends

Effect

• 90-degree bends + sound-absorbing layer: 10-15dB attenuation
• Ventilation performance maintained
• Cost: About ¥5,000-10,000 in materials

Design Example: Ventilation System Layout for 1-Tatami Soundproof Room

[Outside Soundproof Room]
    ↓
[Soundproof Cover (90-degree bend)]
    ↓
[Sound-Absorbing Duct]
    ↓
[Ventilation Fan]
    ↓
[Inside Soundproof Room]

Points

• Install ventilation fan away from sound source
• Separate intake and exhaust openings
• Distribute to multiple ventilation openings

Ventilation and Air Conditioning Troubles and Improvements

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Let’s explain actual troubles and their improvement methods.

Checklist to Prevent “Stuffy,” “Hot,” and “Musty”

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A checklist to prevent common problems in soundproof rooms.

“Stuffy” Countermeasures

• □ Is ventilation fan operating normally?
• □ Is ventilation volume sufficient? (100㎥/h+)
• □ Measure CO₂ concentration (maintain below 1,000ppm)
• □ Is ventilation fan running continuously?

“Hot” Countermeasures

• □ Is air conditioner operating normally?
• □ Is air conditioner capacity sufficient? (1-2 ranks higher)
• □ Is outdoor unit heat building up?
• □ Is air being circulated with a circulator?

“Musty” Countermeasures

• □ Is humidity maintained at 50-60%?
• □ Is dehumidifier being used?
• □ Is moisture being exhausted with ventilation fan?
• □ Is regular cleaning being done?

Temperature and Humidity Management: Maintain 50-60% with Dehumidifier + Air Conditioning Linkage

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Temperature and humidity management is important for soundproof room comfort and equipment protection.

Recommended Environment

• Temperature: 24-26℃ (summer), 20-22℃ (winter)
• Humidity: 50-60%

How to Choose Dehumidifier

• Capacity: Choose according to soundproof room volume
• Quietness: 30dB or less ideal
• Continuous operation: Type that can operate 24 hours

Linkage with Air Conditioning

• Utilize air conditioner dehumidification function
• Use dehumidifier and air conditioner together
• Monitor with thermohygrometer

Effect

• Maintain humidity at 50-60%
• Prevent mold growth
• Prevent deterioration of instruments and equipment

Monthly Maintenance: Filter Cleaning and Sound-Absorbing Material Replacement

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Regular maintenance maintains ventilation and air conditioning system performance.

Monthly Maintenance Items

Ventilation Fan

• Filter cleaning (monthly)
• Duct interior cleaning (every 3 months)
• Operation check (monthly)

Air Conditioner

• Filter cleaning (monthly)
• Outdoor unit cleaning (every 3 months)
• Operation check (monthly)

Sound-Absorbing Material

• Check deterioration (every 3 months)
• Replacement (every 1-2 years)
• Cleaning (every 6 months)

Effect

• Maintain ventilation performance
• Prevent sound leakage
• Maintain comfort

Summary | Not Just “Stopping Sound” but “Moving Air”

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What determines soundproof room comfort is balancing “quietness” and “air flow.”

What Determines Soundproof Room Comfort Is “Quietness + Air Flow”

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Soundproof rooms need not just to stop sound, but to appropriately move air.

Important Points

• Ventilation system: Bring in fresh air
• Air conditioning system: Manage temperature and humidity
• Linkage of both: Achieve comfortable environment

Design Principles

• Create bends in ventilation paths
• Install sound-absorbing layers in ducts
• Distribute ventilation openings

Professional Design Considers Ventilation and Air Conditioning as a Set

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In professional design, it’s important to consider ventilation and air conditioning as a set.

Design Flow

1. Confirm soundproof room purpose and size
2. Calculate required ventilation volume
3. Select appropriate ventilation system
4. Design air conditioning system
5. Consider linkage between both

Recommended System

• Ventilation fan: Continuous operation (low airflow)
• Air conditioner: Operate as needed
• Thermohygrometer: Environmental monitoring

Related Article Links

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• → Product Article: “Creating a Quiet Soundproof Room with Lossnay Ventilation Fan | Mechanism, Introduction Examples, DIY Installation Guide”
• → Practical Article: “Soundproof Room Selection Checklist | By Purpose, Failure Prevention”

This article is based on the latest information as of 2025. Ventilation and air conditioning system specifications and prices may change, so please check with manufacturers and professionals for the latest information when actually introducing.