ACOUSTICS IN SCHOOLS

Effective learning depends on effective communication between teachers and students. It has been established by a number of experts, and certainly some common sense, that excessive noise creates a barrier to effective learning. Ambient noise in schools such as conversations in hallways, sound systems, students in other classrooms and mechanical equipment can hamper student concentration and interfere with student/teacher communications. And background noise causes teachers to raise their voices, which results in vocal strain over time.

Good acoustics in school settings contribute to overall indoor environmental quality, improve learning outcomes, and reduce the need for teachers to raise their voices to be heard. Photo courtesy of CertainTeed Gypsum

 

The US Green Building Council (USGBC) has been a strong leader for the promotion of highly sustainable school environments through the LEED ® for Schools Program. Within that specialized version of the LEED ® rating system, acoustic performance is a specific criterion in two cases. First, there is mandated Prerequisite 3 – “Minimum Acoustical Performance. The stated intent of this pre-requisite is “To provide classrooms that are quiet so that teachers can speak to the class without straining their voices and students can effectively communicate with each other and the teacher.” While it would seem to many that this is a basic and commonly achieved criteria, the built condition in many school buildings indicates otherwise. Beyond the basic pre-requisite requirement, there is also an additional IEQ Credit 9 – “Enhanced Acoustical Performance”. The stated intent of this credit is “To provide classrooms that facilitate better teacher-to-student and student-to-student communications through effective acoustical design.” In other words, it acknowledges the design efforts of improving acoustical design beyond the minimum pre-requisite level to achieve better environments for speech communication and education.

The basis for demonstrating compliance with the LEED® for schools acoustic performance requirements is ANSI Standard S12.60-2002, “Acoustical Performance Criteria, Design Requirements and Guidelines for Schools”. This national standard has been used independently as a basis for determining currently acceptable levels of acoustic performance in schools. It addresses all aspects of acoustical design beginning with the establishment of some very stringent thresholds for background or ambient noise. Specifically, for core learning spaces of 20,000 cubic feet or less, the one-hour steady-state background noise levels should not exceed 35 dBA, while those over 20,000 cubic feet should not exceed 40 dBA. This is the same “faint” level of sound that one would experience in a quiet office. There is a caveat however that if the noisiest one-hour period during which learning activities take place is dominated by transportation noise, these maximum noise limits can each be increased by 5 dB. The LEED prerequisite requirements follow these same ANSI thresholds for size and dB levels of background noise, although it is only stated to address HVAC equipment noise.

In terms of isolating noise through STC ratings, the ANSI standard is quite prescriptive. It lists minimum STC ratings for single or composite wall, floor/ceiling and roof/ceiling assemblies that separate an enclosed core learning space (e.g. classrooms) from an adjacent space. These ratings vary from STC 45 – 60 depending on the nature of the adjacent space. For example STC 45 is acceptable between classrooms and corridors, but STC 50 is required between other core learning spaces between a classroom and the outdoors.  If the core learning space is adjacent to a toilet room or bathing room, the requirement bumps up to STC 53. And, not surprisingly, if the core learning space is adjacent to a larger, louder space such as a music room, equipment room, cafeteria, pool, etc., then the minimum acoustical performance standard is STC 60. There are similar ratings for ancillary learning spaces as opposed to core learning spaces, which are slightly relaxed compared to the ones listed above, but they are dependent on the nature and use of the adjacent space.

Standard S12.60-2002 goes on to identify specific Impact Insulation Class ratings and recommendations for classroom learning spaces including the following:

• IIC ratings for floor-ceiling assemblies above core learning spaces should be at least IIC-45 and preferably IIC-50 as measured on floors without carpeting.
  
  
• In new construction, a gymnasium, dance studio, or other spaces with high floor impact activities shall not be located above core learning spaces.
  
  
• In existing facilities IIC-65-70 (depending on the volume of the space below) is recommended if gymnasia, dance studios or other spaces with high floor impact activities are located above core learning spaces.

Finally, the standard addresses Reverberation Time by acknowledging that it is possible to calculate the reverberation time of sound within a space based on the interior surface qualities of a room. Using the process identified in ANSI S12.60-2002 to conduct these calculations, the resulting educational spaces must meet the following levels in order to comply:

• The maximum reverberation time for core learning spaces with internal volumes of greater than 10,000 cubic feet should not exceed 0.6 seconds.
  
  
• For core learning spaces with internal volumes of more than 10,000 but less than 20,000 cubic feet the maximum reverberation time is 0.7 seconds.
  
  
• Reverberation time for spaces with more than 20,000 cubic feet of internal volume is not specified, however, guidelines are given in Annex C of the standard.

If an existing space or room is being investigated, then it can be tested with acoustical equipment specifically intended for measuring RT. For a new space, calculations must be relied on to determine what the RT will be in the proposed space.

Noise reducing gypsum board can be used to contribute to the acoustical performance in all of these aspects and demonstrate compliance with LEED® for Schools and ANSI Standard S12.60-2002. It specifically reduces sound transmission from adjacent spaces to make it easier for teachers to be heard and students to learn. As a result, it reduces distractions so students can pay closer attention and learn more effectively while keeping the lines of communication between students and teachers clear and open. For teachers, it reduces voice strain and increases the effectiveness of their teaching.