When choosing a soundproof room, the most important number is the “Dr (Dr) grade”. (*Depending on the catalog, it may be written as “D-Value (D-chi)”, but the meaning is the same.)
This number represents “how much you can cut the sound you make inside that room”.
- The larger the number, the higher the performance (sound doesn’t leak).
- The smaller the number, the lower the performance (sound leaks).
In this article, we will explain the differences between the main grades Dr-30, Dr-35, and Dr-40 based on how they actually sound.
Formula for Soundproof Performance#
First, let’s learn the basic formula.
Volume inside the room (dB) － Dr grade (performance) ＝ Volume leaking outside (dB)
For example, suppose the sound of a piano is “90dB”.
- For a Dr-30 soundproof room: 90 - 30 = 60dB (outside sound)
- For a Dr-40 soundproof room: 90 - 40 = 50dB (outside sound)
If the sound leaking outside becomes about “50dB”, it becomes a level of “can I faintly hear it?” to the neighbors, and the risk of complaints is dramatically reduced.
Experience Level by Grade (How it sounds in the next room)#
Dr-30 (Standard / Entry)#
- Performance: The minimum line for general soundproof rooms.
- Experience:
- Voices: Almost inaudible.
- TV: Only a level where the sound becomes a little smaller.
- Piano: The song title is known, but it’s not noisy (feels like watching TV at a low volume).
- Target: Telework, piano practice during the day.
Dr-35 (Standard)#
- Performance: This is what the standard models of Yamaha and Kawai are.
- Experience:
- Voices: Not audible at all.
- Piano: About the level of small voices. Acceptable at night (until around 8 PM).
- Singing voice: Even if you sing seriously, it only sounds like mumbling next door.
- Target: Upright piano, singing, acoustic guitar.
Dr-40 (High Grade)#
- Performance: The highest peak of assembly-type soundproof rooms.
- Experience:
- Piano: Faintly audible. It blends into daily life sounds and doesn’t bother you.
- Brass instruments: The sharp sound of a saxophone also attenuates considerably.
- Target: Late-night piano practice, saxophone, trumpet, professional recording.
Dr-50 or more (Pro / Studio)#
- Performance: Impossible with unit types. A level that requires construction work.
- Experience: Almost silent. Even if you play drums, it’s a different dimension from the outside world.
- Target: Drums, live houses, commercial studios.
A difference of 5dB is a “Different World”#
You might think, “Dr-35 and Dr-40, it’s just a difference of 5, right?”. However, in the world of sound, it is said that “if 5dB is different, the hearing changes by 2 times”.
- A sound that was told “it’s a bit noisy” at Dr-35
- Changes to “I can’t hear it at all” when at Dr-40.
If your budget allows, choosing the higher grade (Dr-40) without hesitation will lead to peace of mind later on.
→ Related: What is the D-value required for piano soundproofing? See standards by type → Sound Insulation Performance D-Value Guide (Top)