School Soundproofing Projects: Case Review and Technical Analysis

1. Lecture Halls and Large Classrooms: Indoor Reverberation Time Control

In large lecture spaces with hard reflective surfaces (such as concrete walls and whiteboards), sound wave reflection leads to prolonged indoor Reverberation Time (RT60), which in turn degrades speech intelligibility during teaching^[1].

Configuration of Sound-Absorbing Materials

For the large classrooms at The University of Hong Kong and the City University of Hong Kong, acoustic treatments focused on reducing reflected sound. The engineering utilized ENA Soundproof Cotton laid on the ceilings and the upper halves of both side walls. This porous material (NRC=0.3) converts sound energy, shortening the retention time of sound waves within the space, ensuring that back-row seats also receive clear acoustic reception, and reducing reliance on amplification equipment and sound spillover. (See Soundproofing Materials Guide for details)

2. Music Rooms and Multi-Purpose Spaces: Structure-Borne and Airborne Sound Insulation

Music rooms and activity spaces generate high-decibel instrumental sounds and low-frequency vibrations. School soundproofing planning for these types of spaces requires simultaneously cutting off airborne sound and structure-borne sound (such as floor slab vibrations caused by percussion instruments).

Mass Impedance and Room-in-Room Design Concept

In specific facilities at the Hong Kong International School and Hong Kong Design Institute (HKDI), the high-density ENA Soundproof Blanket NE200 (STC=23) was installed within the inner layers of the walls. According to the Mass Law^[2], this material provides sufficient acoustic impedance to limit low-to-mid frequency sound waves from penetrating into adjacent regular classrooms. Entrances and exits were replaced with soundproof doors equipped with automatic drop-down bottoms to ensure spatial airtightness. (See Music Studio Soundproofing for details)

3. Libraries and Study Areas: Low-Frequency Background Noise Attenuation

Academic libraries and study rooms have an extremely low tolerance for Background Noise (NC). External traffic flow and the operational sounds of internal electro-mechanical equipment (such as central air conditioning) are the primary factors affecting environmental tranquility.

Window Openings and Floor Slab Treatments

Some study spaces at the Hong Kong University of Science and Technology and The Hong Kong Polytechnic University are located facing streets or adjacent to plant rooms. In the engineering, soundproof curtains (STC 16.6-36.6) without chemical coatings were deployed over large glass window areas to physically mask and attenuate high-frequency external traffic sounds using mass. Simultaneously, composite soundproofing and sound-absorbing materials were laid on the walls adjacent to the plant rooms to reduce low-frequency conduction caused by air conditioning equipment.

4. Student Dormitories and Staff Areas: Door/Window Airtightness and Privacy Protection

The acoustic treatment of student dormitories and staff offices focuses on personal privacy protection and sound isolation from adjacent spaces. The gaps around door leaves are often the primary paths for sound leakage.

Door Leaf Airtightness Upgrades

In the dormitory and administrative area projects at The Hang Seng University of Hong Kong and Lingnan University, traditional wooden doors were replaced with soundproof doors (STC 35) featuring soundproof interlayers. The door frames are equipped with silicone sealing strips to reduce the infiltration of corridor foot traffic and conversational sounds, providing acoustic isolation that meets residential standards. (The treatment principles for such spaces are similar to hotel guest rooms; see School and Hotel Soundproofing and Residential Soundproofing Solutions for details)

5. Fire Safety and Indoor Air Quality Regulations for Educational Spaces

In addition to meeting acoustic data requirements, the physical and chemical safety of materials in school soundproofing engineering is also strictly regulated. Traditional fiberglass and flammable foam are no longer suitable for modern educational facilities due to risks of dust shedding and toxic gas volatilization^[3].

The ENA series acoustic materials selected for the aforementioned institutional projects all possess third-party inspection certifications. Regarding fire safety, they meet the BS-476 flame-retardant standards set by the Hong Kong Fire Services Department for indoor building materials; regarding chemical safety, the materials reach the Super E0 formaldehyde emission level. The characteristics of no dust shedding and no free formaldehyde ensure the respiratory health of students and staff in enclosed, air-conditioned environments.