Acoustic Environment Design

1. Main points to consider in acoustic environment design

2. Perspective on how sound travels (airborne vs. structure-borne)

Airborne sound: Sound insulation materials (gypsum board, sound insulation sheets)
Structure-borne sound (floor impact sound): Vibration isolation materials, floating floor structures, cushioning materials
It is important to distinguish between material selection and structure from this perspective

3. Acoustic properties of building materials (sound absorption coefficient, sound insulation performance, reflectance)

For building materials, acoustic properties such as sound absorption coefficient (α value), transmission loss (sound insulation performance, in dB), and reflectance (ratio of reflected sound) are experimentally measured for each material and thickness, and are often displayed as standards.

1. Sound absorbing materials (absorb sound to suppress reverberation)
Glass wool: Standard sound absorbing material filled inside walls and ceilings (inexpensive, good workability)
Rock wool: Sound absorption + thermal insulation for factories and gymnasiums (good moisture resistance)
Melamine foam: High sound absorption + flame retardancy (recording rooms, studios, etc.)
Urethane foam: Flexible material used for simple sound absorption or DIY
Sound absorbing panels (fiber/wood-based): Installed exposed in rooms.
Used in conference rooms, halls, music rooms, etc.
Sound absorbing cloth (fabric): Interior finishing material + sound absorption (conference rooms, offices)
Wood wool cement board: Installed directly on ceilings and walls. Sound absorption + fire resistance + design

2. Sound insulation materials (block or stop sound)
Gypsum board (multi-layer): Main component material for walls and ceilings. Layering increases sound insulation
Sound insulation sheet (lead/polymer-based): Applied to other materials to reinforce sound insulation performance (thin)
Concrete (RC): Very high sound insulation, effective for housing and studios
ALC panel: Moderate sound insulation. Used for exterior walls and partitions
Particle board: Contributes to sound insulation as a structural material. Used for floating floors or intermediate layers of walls, etc.
Wood (plywood): Design + moderate sound insulation (used depending on the space)

3. Vibration isolation and transmission suppression materials (prevent transmission of vibration sound)
Vibration isolation rubber: Used for floating floors, suspended ceilings, and vibration isolation of equipment
Floating floor structural materials: Suppress floor-transmitted sound with vibration isolation materials + mass materials (particle board, etc.)
Viscoelastic damping sheet: Suppresses resonance of structural materials (vibration damping)
Duct silencers: Padding, board materials, etc., that suppress sound from air conditioning equipment

4. Other construction materials that affect sound
Soundproof doors/airtight fittings: Important for preventing sound leakage from gaps
Sound insulation sashes (double windows): Essential for sound insulation of openings (housing, conference rooms)
Acoustic diffusers: Eliminate uneven reverberation (uneven surface materials, wooden panels)
Carpets/rugs: Suppress floor reflection (hotels, theaters, etc.)
Acoustic blinds: Sound absorption + mobility (offices, temporary spaces)

4. Acoustic performance of typical building materials

Detailed numerical values are summarized in the following standards and databases
・JIS A 1405-1, 1409 (Japanese architectural acoustics testing standards)
・JAS (Japanese Agricultural Standards, sound absorption coefficient of wood)
・Manufacturer technical data (e.g., Asahi Kasei, Daiken, Yoshino Gypsum, etc.)
・Architectural Acoustics Handbook (academic societies and specialized books)

5. Recommended acoustic building materials by component surface

6. Recommended acoustic building materials by room use in housing

7. Locations requiring sound absorption measures and materials in acoustic environment design

8. Design of the ratio between sound absorbing surfaces and reflecting surfaces (intentional reflection design)

Excessive sound absorption can lead to a "dead" space, which can conversely be uncomfortable.
In conference rooms, studios, and auditoriums, sound field control design such as "front reflection + rear sound absorption" is required.
is required.

9. Practice and application of acoustic environment design

1. Airtightness of openings (windows/doors) and gaps
　Even if sound insulation measures are perfect, sound may leak from door gaps or sashes
　→ Reinforce with soundproof doors / airtight gaskets / double-pane sashes, etc.
2. Consideration of sound source placement and directivity
　If sound sources (speakers or human voices) are directed straight at walls or windows,
　unpleasant reflections are likely to occur
　→ Adjusting the angle of sound sources / installing reflection control panels / strategic speaker placement is important
3. Influence of ceiling height and shape
　Atriums and high ceilings increase reverberation, causing sound to diffuse too much and reducing clarity
　Dome ceilings or inclined surfaces can cause a **focusing (sound concentrating at one point)** phenomenon
　→ Distributed placement of sound absorption or control of ceiling material reflectivity is necessary
4. Background noise from equipment (HVAC/mechanical rooms)
　Steady noise (low frequency) from ventilation fans, air conditioners, and mechanical rooms interferes with conversations, etc.
　→ Equipment measures such as soundproofing mechanical rooms / silencers in ducts / floating floor structures are essential
5. Sound privacy (sound leakage/sound interference)
　In offices and medical facilities, leakage of conversations and hearing others' sounds become issues
　→ Combined use of sound-absorbing booths / masking sound (white noise) / sound-insulating partitions is effective
6. Variable sound field design (multi-purpose spaces)
　For single-room multi-purpose spaces (e.g., meetings and musical performances), switching reverberation time is ideal
　→ Utilize movable sound-absorbing panels / variable reflectors / motorized sound-absorbing blinds, etc.
7. User subjectivity and comfort
　Beyond physical acoustic performance, psychological evaluations such as "feeling noisy" or "hard to hear"
　are also important
　Especially in educational, medical, and elderly facilities, both "too quiet" and "too reverberant"
　can be uncomfortable
8. Maintainability and durability
　If sound-absorbing materials powder or discolor due to aging, it leads to performance degradation and hygiene issues
　→ Material selection (melamine, PET, etc.) / periodic inspection when installed exposed is recommended

10. Terms (related to acoustic environment design)

T60 (Reverberation Time): The time (in seconds) it takes for the sound pressure level to decay by 60dB after the sound stops.
　　An indicator of how "reverberant" a space is. There are optimal values for each purpose.

α value (Sound Absorption Coefficient): The ratio indicating how much incident sound is absorbed (0.00 to
　　1.00). The closer to 1.00, the higher the sound absorption. Often measured at 500Hz.
Sound Insulation Performance (Transmission Loss): A value (dB) representing how much sound is attenuated when passing through walls, etc.
　　The higher the value, the higher the sound insulation.
Reflectivity: The proportion of incident sound that is reflected without being absorbed or transmitted.
　　High reflectivity makes a space "reverberant."
Airborne Sound: Sound transmitted through the air, such as voices and music. Spreads by passing through walls, doors, etc.
　　Sound insulation measures are required.
Structure-borne Sound: Sound heard as vibrations (footsteps, mechanical vibrations, etc.) travel through the building.
　　Vibration isolation and floating floor structures are required.
Sound-absorbing Material: Materials that absorb sound to suppress echoes
　　(e.g., glass wool, melamine foam, etc.).
Sound-insulating Material: Materials that prevent sound from passing through (e.g., gypsum board, sound insulation sheets, RC walls, etc.).Vibration-isolating Material: Materials for blocking or attenuating structure-borne sound (vibration)
　　(e.g., vibration-isolating rubber, vibration-isolating hangers, etc.).
Diffusion Material: Materials that scatter sound reflections to make the sound field uniform
　　(e.g., uneven wood, QRD, etc.).
Dead Space: A space with excessive sound absorption and almost no echo.
　　In acoustic environment design, if sound-absorbing materials are used excessively, there is almost no sound reflection in the space, resulting in a state called a "dead space."
　　In this state, the following problems may occur:
　　・Voices and sounds do not travel far
　　・Speech sounds muffled or weak
　　・The way your own voice sounds changes, making it difficult to speak
　　・Auditory fatigue occurs easily, making long stays uncomfortable
　　・Music and performances lose their natural resonance and sound unnatural

Focusing Phenomenon: A phenomenon where sound is heard concentrated at one point due to dome shapes or the shape of reflecting surfaces.　　A type of acoustic defect.

White Noise (Masking Sound): Noise intentionally played to make surrounding sounds harder to hear.　　Used for sound privacy protection.

11. Acoustic environment design checklist: A list of items to check to avoid oversights during the design phase

12. Disclaimer

※ The information contained in this document is based on general knowledge, practical experience, and publicly available materials regarding architectural acoustics and environmental design, and does not guarantee complete applicability to all design and construction sites.
※ Numerical values such as sound absorption coefficients and sound insulation performance are reference values based on representative experimental data or manufacturer-published materials, and may vary depending on actual usage conditions, construction precision, and spatial configuration.

※ Regarding material selection, construction method adoption, structural design, etc., please always follow the latest JIS and JAS standards, various guidelines (e.g., Architectural Institute of Japan, Acoustical Society of Japan, etc.), and the actual conditions of the construction site and the judgment of experts.

※ This document is for educational and awareness purposes and does not guarantee or recommend the performance, effectiveness, or commercial value of specific products, manufacturers, or building materials.

※ Some of the images, charts, terms, cited literature, etc., included may belong to copyright holders. When reusing or redistributing, please ensure appropriate citation and source attribution.