When selecting a soundproof room, you’ll inevitably encounter notations like “D-40” or “D-55.” These represent “D-values” for sound insulation performance, but the numbers alone may not mean much to many people.
This article explains what D-values are, how much sound reduction each level provides, and for those who’ve received noise complaints, which D-value will solve your problem.
D-Value Basics#
D-Value Definition#
A D-value represents Japan’s sound insulation performance grade. Officially called “sound transmission loss rating,” it indicates the sound insulation performance of walls, floors, etc.
Simply put, it’s a “number showing how many decibels quieter sound from the next room becomes.” For example, “D-50” means sound from the adjacent room becomes 50 decibels quieter.
Higher numbers indicate better sound insulation and less sound leakage. While typical residential walls rate D-3035, soundproof rooms generally rate D-4070.
Incidentally, there’s also a similar notation called “Dr-value,” which refers to “room-to-room sound pressure level difference rating,” indicating actual sound insulation performance between rooms. Catalog listings of “Dr-40” often show performance in actual use environments.
Understanding Decibels (dB)#
To understand D-values, you also need to know about “decibels (dB),” the unit measuring sound volume.
Decibels measure sound loudness but have different characteristics from regular numbers. Specifically, each 10dB increase roughly doubles perceived loudness.
This means reducing 40dB sound by 20dB results in 20dB, but this isn’t simply half the volume—it’s perceived as about one-quarter the loudness.
Generally, reducing sound by 10dB feels like “half the volume,” 20dB feels “considerably quieter,” and 30dB feels “almost inaudible.”
This perceptual understanding becomes important when selecting D-values.
D-Values and Actual Sound Relationship#
Let’s look specifically at how much effect different D-values have.
Typical residential wall (D-30):
- Conversation next door (60dB) → Heard as 30dB here
- 30dB is about “whisper” level
- Content is clearly audible
Soundproof room D-50:
- Piano playing next door (90dB) → Heard as 40dB here
- 40dB is about “inside a library” level
- Sound is audible but not bothersome
Soundproof room D-70:
- Drums next door (110dB) → Heard as 40dB here
- Even very loud sounds remain at quiet environment level outside
Thus, higher D-values mean even loud sounds inside remain quiet outside.
Daily Sounds and Decibel Guide#
Common Sound Decibel List#
To understand D-value effects, let’s first know the decibel values of everyday sounds.
Very Quiet Environment (0~30dB):
- 0dB: Minimum sound humans can detect
- 10dB: Butterfly wings, leaves touching
- 20dB: Leaves rustling, clock ticking
- 30dB: Residential area at midnight, whispering
Quiet Environment (30~50dB):
- 40dB: Inside library, downtown at midnight
- 50dB: Quiet office, home AC outdoor unit
Moderate Environment (50~70dB):
- 60dB: Normal conversation, sewing machine
- 70dB: Noisy office, busy street
Noisy Environment (70~90dB):
- 80dB: Busy street, karaoke, alarm clock
- 90dB: Large truck passing, karaoke booth, piano
Very Noisy Environment (90~110dB):
- 100dB: Nearby train, pachinko parlor, pile driver
- 110dB: Drums, rock concert, car horn nearby
Dangerously Loud (110dB+):
- 120dB: Aircraft takeoff nearby, thunder overhead
- 130dB: Pain threshold
D-Value Selection by Instrument#
Acoustic Instruments#
Piano:
- Volume: ~90dB
- Recommended D-value: D-50~60
- Ideal: D-55 or higher
- Notes: Grand pianos especially need higher performance
Violin/Viola:
- Volume: ~80-85dB
- Recommended D-value: D-45~55
- Ideal: D-50 or higher
Cello/Bass:
- Volume: ~85-90dB
- Recommended D-value: D-50~60
- Ideal: D-55 or higher
- Notes: Low-frequency measures also needed
Flute/Piccolo:
- Volume: ~85-95dB
- Recommended D-value: D-50~60
- Ideal: D-55 or higher
- Notes: High frequencies penetrate easily
Clarinet/Oboe:
- Volume: ~85-90dB
- Recommended D-value: D-50~60
- Ideal: D-55 or higher
Trumpet/Trombone:
- Volume: ~95-100dB
- Recommended D-value: D-60~70
- Ideal: D-65 or higher
- Notes: Especially loud instruments
Saxophone:
- Volume: ~90-95dB
- Recommended D-value: D-55~65
- Ideal: D-60 or higher
Percussion Instruments#
Drums:
- Volume: ~110dB
- Recommended D-value: D-65~80
- Ideal: D-70 or higher
- Notes: Vibration isolation essential
Taiko:
- Volume: ~110-120dB
- Recommended D-value: D-70~80
- Ideal: D-75 or higher
- Notes: Very high performance needed
Electric Instruments#
Electric Guitar/Bass:
- Volume: ~80-100dB (amp dependent)
- Recommended D-value: D-50~60
- Ideal: D-55 or higher
Electronic Keyboard:
- Volume: ~70-90dB
- Recommended D-value: D-45~55
- Ideal: D-50 or higher
D-Value Selection by Use Case#
Vocals/Voice Practice#
Light Vocals:
- Volume: ~70-80dB
- Recommended D-value: D-45~55
- Suitable for: Vocal practice, voice acting
Full-Volume Singing:
- Volume: ~85-95dB
- Recommended D-value: D-55~65
- Suitable for: Professional vocalists, opera
Streaming/Content Creation#
Talk/Commentary:
- Volume: ~60-70dB
- Recommended D-value: D-40~50
- Suitable for: Podcasts, VTubers, commentary
Gaming Streams:
- Volume: ~65-80dB
- Recommended D-value: D-45~55
- Suitable for: Including reactions and shouting
ASMR:
- Volume: ~30-50dB
- Recommended D-value: D-40~50
- Notes: Emphasis on blocking external noise
Music Production#
DTM/Composing:
- Volume: ~70-85dB
- Recommended D-value: D-45~55
- Suitable for: Headphone-based work
Recording:
- Volume: Varies by instrument
- Recommended D-value: D-50~60
- Notes: External noise prevention also important
Remote Work#
Video Conferences:
- Volume: ~60-70dB
- Recommended D-value: D-40~50
- Suitable for: Standard meetings
Confidential Calls:
- Volume: ~60-70dB
- Recommended D-value: D-50~60
- Notes: Voice leak prevention important
D-Value Selection by Living Environment#
Detached House#
Residential Area:
- Recommended D-value: D-45~55
- Reason: Distance to neighbors provides buffer
- Notes: Still consider time of day
Quiet Residential Area:
- Recommended D-value: D-50~60
- Reason: Higher environmental noise sensitivity
- Notes: Especially strict nighttime consideration
Apartment/Mansion#
Reinforced Concrete (RC):
- Building D-value: D-45~55
- Additional needed: D-45~60
- Total target: D-60~70
Steel Frame:
- Building D-value: D-35~45
- Additional needed: D-50~65
- Total target: D-60~70
Wood Frame:
- Building D-value: D-25~35
- Additional needed: D-55~70
- Total target: D-60~70
Urban vs. Suburban#
Dense Urban Area:
- Higher ambient noise: 50-60dB
- Can use relatively lower D-values
- Recommended: D-45~60
Quiet Suburban Area:
- Lower ambient noise: 30-40dB
- Need higher D-values
- Recommended: D-55~70
D-Value Cost Comparison#
Unit-Type Soundproof Rooms#
D-40~45 Grade:
- Price: 500,000-1,000,000 yen
- Suitable for: Light instruments, streaming
- Cost-performance: ★★★★★
D-50~55 Grade:
- Price: 800,000-1,500,000 yen
- Suitable for: Piano, wind instruments
- Cost-performance: ★★★★☆
D-60~65 Grade:
- Price: 1,200,000-2,500,000 yen
- Suitable for: Brass instruments, loud vocals
- Cost-performance: ★★★☆☆
D-70+ Grade:
- Price: 2,000,000-4,000,000+ yen
- Suitable for: Drums, professional use
- Cost-performance: ★★☆☆☆
Renovation#
D-50 Grade:
- Construction cost: 2-4 million yen (6 tatami)
- Suitable for: General instruments
D-60 Grade:
- Construction cost: 3-6 million yen (6 tatami)
- Suitable for: Brass, loud instruments
D-70+ Grade:
- Construction cost: 5-10 million+ yen (6 tatami)
- Suitable for: Drums, professional studios
Practical D-Value Selection Advice#
Start with Your Instrument#
- Check instrument volume (dB)
- Determine target outdoor volume (30-40dB target)
- Calculate necessary D-value
- Add safety margin (+5~10dB)
Consider Your Environment#
- Measure current building’s D-value
- Check distance to neighbors
- Assess ambient noise levels
- Determine final necessary D-value
Balance Budget and Performance#
- Don’t over-spec unnecessarily
- Prioritize based on actual use
- Consider future upgradeability
- Explore cost-effective alternatives
Common Mistakes in D-Value Selection#
Mistake 1: Choosing Too Low#
Problem: Sound still leaks, neighbors complain Solution: Always add 5-10dB safety margin
Mistake 2: Choosing Too High#
Problem: Unnecessarily expensive, diminishing returns Solution: Match actual needs, don’t over-invest
Mistake 3: Ignoring Building Performance#
Problem: Overlooking how building D-value affects results Solution: Consider total performance including building
Mistake 4: Forgetting Vibration#
Problem: Sound insulation good but vibration leaks Solution: Add vibration isolation for low-frequency instruments
Conclusion: Choosing the Right D-Value#
D-values represent sound insulation performance, and selecting the right level is crucial for your needs and environment.
Key Takeaways#
- Higher D-values = Better performance but higher cost
- Instrument volume determines minimum D-value
- Living environment affects requirements
- Always add safety margin
- Consider total cost including installation
Use this guide to select the optimal D-value for your situation. When in doubt, consult manufacturers or acoustic professionals for personalized recommendations.
The right D-value choice ensures a comfortable soundproof environment for years of musical enjoyment and creative activities without neighbor concerns.