Classroom Acoustics

Roles and Responsibilities

Audiologists, acoustical consultants, speech-language pathologists (SLPs), classroom teachers, teachers of the Deaf and hard of hearing, and administrators may work as a team to improve acoustical conditions in classrooms and other learning spaces. See the American Speech-Language-Hearing Association’s (ASHA) Scope of Practice in Audiology (ASHA, 2018) and Scope of Practice in Speech-Language Pathology (ASHA, 2016b).

Audiologists

Appropriate roles and responsibilities for audiologists in relation to classroom acoustics include the following:

  • Understanding the principles behind sound acoustical design and the impact of classroom acoustics on educational outcomes
  • Educating others (e.g., the public, parents/guardians, students, other professionals) regarding classroom acoustical concerns, the effects of acoustics on listening and learning, and the need for the application of good acoustical design in the planning and building process
  • Developing and disseminating information concerning classroom acoustics to the general public and policymakers
  • Acting as a resource for teachers, parents/guardians, SLPs, principals, and administrators
  • Surveying classroom acoustical conditions, including measuring background noise in dBA, measuring or estimating reverberation time, and measuring or estimating signal-to-noise ratio and comparing these measurements to the American National Standards Institute (ANSI) standards
  • Developing and implementing strategies to target excessive noise and reverberation in classrooms and other learning spaces
  • Recommending acoustical treatments to the existing physical space
  • Recommending technologies to improve the classroom listening environment
  • Establishing efficacy of improvements in classroom acoustics
  • Providing aural (re)habilitation as indicated to minimize listening and learning barriers in the classroom
  • Monitoring and documenting the effectiveness of amplification and/or hearing assistive technologies
  • Managing hearing aid technology, hearing assistive technology systems (HATS), and other applicable technology
  • Performing visual inspection and listening checks on applicable equipment and instructing other professionals to do the same
  • Assisting families in improving the listening environment in the home
  • Advocating for the application of sound acoustical design in school planning and building processes at local, state, and national levels

As indicated in the Code of Ethics (ASHA, 2016a), audiologists who work in this capacity should be specifically educated and appropriately trained to do so.

Speech-Language Pathologists

Appropriate roles and responsibilities for SLPs in relation to classroom acoustics include the following:

  • Understanding the principles behind sound acoustical design and the impact of classroom acoustics on educational outcomes
  • Promoting efficient and effective education outcomes for students
  • Developing and implementing strategies to target excessive noise and reverberation in classrooms and other learning spaces
  • Encouraging the involvement of an audiologist or acoustical consultant to evaluate and make specific recommendations to accomplish acceptable classroom acoustics
  • Collaborating with the educational team to improve the classroom listening environment and implement strategies in the classroom to enhance the listening skills of all students
  • Providing aural (re)habilitation as indicated to minimize listening and learning barriers in the classroom
  • Completing daily checks of hearing aids and hearing assistive technologies
  • Supporting teachers in avoiding vocal abuse and overuse
  • Advocating for good acoustical design in the school planning and building process at local, state, and national levels

As indicated in the Code of Ethics (ASHA, 2016a), SLPs who work in this capacity should be specifically educated and appropriately trained to do so.

Collaboration With Other Professionals

There are several stakeholders with interest, knowledge, and skills in classroom (and other learning space) acoustics. These stakeholders include classroom teachers, teachers of the Deaf and hard of hearing, school administrators, and acoustical consultants. See ASHA resources on Interprofessional Education/Interprofessional Practice (IPE/IPP) and IPE/IPP Organizations, Reports, and Articles.

Classroom Teachers and Administrators

Classroom teachers are instrumental in identifying students who may be experiencing hearing loss or other types of listening problems and in referring those students to the appropriate professionals for further assessment. For students with identified hearing loss and/or listening problems, the classroom teacher may need to implement accommodations and strategies within the general education environment(s). Building administrators can be instrumental in providing resources and collaborating with teachers to improve classroom acoustics and students’ listening environments.

In classrooms where the acoustics are less than optimal, classroom teachers may find it beneficial/effective to use strategies that have typically been used for students with hearing loss, including

  • instituting prioritized seating away from extraneous noise;
  • optimizing visual communication during instructional periods with high academic content;
  • gaining students’ attention prior to delivering information;
  • using review strategies to identify key points;
  • encouraging students to practice active listening habits; and
  • involving students in managing the noise level in the classroom.

Acoustical Consultants

Acoustical consultants have a variety of educational backgrounds, including engineering and physics. Consultants use knowledge of room acoustics, noise control, acoustical isolation, and audio systems to ensure the efficient distribution of desirable sound as well as the suppression of undesirable sound in and around classrooms and other structures.

Examples of contributions made by acoustical consultants include the following:

  • Providing consulting services for new construction, including evaluating the design for interior room acoustics, interior and exterior acoustical isolation, mechanical system noise control, and performance sound reinforcement system design
  • Evaluating existing conditions in classrooms, including performing acoustical testing to determine the exact acoustical parameters of the room and comparing these to ANSI/Acoustical Society of America (ASA) standards
  • Making recommendations for corrective measures to meet acceptable criteria to the extent possible

Behavior of Sound In Rooms

Sound waves radiate in all directions from a source until they come to an obstacle (e.g., a wall). The intensity of a sound wave is a measurement of perceived loudness. The frequency of a sound wave is a measurement of perceived pitch.

Both the intensity and the frequency of the sound wave will affect the sound–surface interaction. When sound waves strike a surface, one or more of the following can occur (Seep et al., 2000):

Transmission—sound passes through the surface into the space beyond it.

Absorption—the surface absorbs the sound.

Reflection—the sound strikes and bounces off of the surface. Reflected sound can result in echoes, which can interfere with hearing and understanding speech. Echo types include

  • discrete echoes, such as when the teacher’s voice is continually bouncing off the back wall of a classroom; and
  • flutter echoes, when a sound bounces rapidly between two flat, hard surfaces, such as two walls or a floor and ceiling.

Diffusion—the sound strikes the surface and is scattered in many directions.

Measuring Sound In Rooms

Several types of measurements may be considered when assessing a room’s acoustical environment. Measurements can be taken in occupied or unoccupied rooms and compared to ANSI/ASA standards.

Reverberation time (RT)—a measurement of how quickly sound decays in a room, depending on the physical volume and surface materials of a room. The RT60 of a room is the time in seconds it takes for a sound of 60 decibels to die down completely.

Noise reduction (NR)—a measurement of the effectiveness of materials to decrease sound exposure. The NR of a wall measures the percentage of sound produced in one room that passes through the wall into the next room.

Noise reduction coefficient­—a measurement of the ability of a material to absorb sound.

Signal-to-noise ratio (SNR)—a comparison of a desired signal (sound) to the level of background noise. This measurement can be used to determine the level of speech intelligibility within a room (and in specific parts of a room). A positive SNR indicates that the signal of interest is louder than the background noise. In general, the more positive the SNR, the better the speech intelligibility.

Noise criterion (NC)—a measurement of relative loudness in a room with a range of frequencies. NC can be used to rate indoor noise (e.g., equipment noise).

Poor classroom acoustics can affect speech intelligibility (percentage of understandable speech) potential within a given learning space.

Surveying Classroom Acoustical Conditions

Educational audiologists and/or acoustical consultants are responsible for assessing classroom acoustics and associated student performance within the classroom. They are uniquely positioned to take acoustical measurements in the classroom and compare them to ANSI/ASA or other standards.

Acoustical assessments of classrooms and of student performance within their learning environments may include

  • formal noise and reverberation measurements;
  • behavioral performance measurements, including
    • speech recognition scores
    • teacher or student report forms
    • changes in student behavior, and
    • changes in achievement scores;
  • comparison of current acoustical conditions and performance measurements with acceptable standards; and
  • determination of the adequacy of the classroom for listening and learning.

Both audiologists and SLPs may be involved in gathering behavioral performance measurements, assessing changes in student behavior, and making recommendations regarding improving the listening environment.

Modifications to Improve Existing Acoustical Conditions

A classroom acoustics survey can help determine whether corrective action is needed. Recommendations are devised to meet acceptable criteria to the extent practical. Strategies for improving acoustical conditions may include

  • modifying the physical characteristics of the room;
  • using evidence-based techniques (i.e., real-ear or simulated real-ear measures) to ensure appropriately fit hearing aids and hearing assistive technologies for students;
  • purchasing a classroom audio distribution system (CADS); and
  • implementing habilitation and rehabilitation interventions (e.g., listening training, phonological awareness training, visual communication training, auditory–verbal training, monitoring classroom noise management).

Members of the school staff and the district’s facilities department may collaborate to improve acoustics. Measurements taken before the recommendations are implemented can be repeated after changes have been made to determine and document the effectiveness of the changes and improvements over time.

Classroom Audio Distribution Systems

Classroom audio distribution systems (CADS), formerly referred to as sound-field amplification systems, provide benefits to all listeners in a classroom. The ASA Panel on Public Policy (2013) states that “provided that sound field amplification systems are used in conjunction with ANSI S12.60, the ASA recognizes their usefulness for core classrooms to augment teachers’ voices as multimedia sound distribution systems” while noting that they should not be used as a replacement for suitable room acoustics.

When a CADS is considered, it is important to carefully assess the classroom acoustics and follow a systematic process to determine the most appropriate solution for a given classroom. Classroom acoustics are a significant factor influencing the efficacy of CADS (Dockrell & Shield, 2012).

Children with hearing loss may require personal frequency modulation (FM) systems for the best results, despite any CADS that may already be in place (Wolfe et al., 2013). In fact, in some cases, a CADS may negatively affect the results of a personal FM system (Wolfe et al., 2013). Involvement of an educational audiologist is important when considering, choosing, and installing a CADS, as well as when training is provided.

Interior Modifications

Modifications to the physical characteristics of a room or other learning space can improve the acoustical quality. It is important to consider the sound absorption qualities of various absorptive materials for ceilings, walls, and floors. An absorption coefficient and a noise reduction coefficient are used to measure the ability of a material to absorb sound (Seep et al., 2000). Examples of classroom modifications are listed below. Additional and more specific details can be found in classroom acoustical resources and guides (Canning et al., 2015; National Deaf Children’s Society, 2016; New Zealand Ministry of Education, 2016; Phinney & Woolworth, 2015; Seep et al., 2000).   

Ceilings

Acoustical panels on the ceiling may help improve the listening environment in the classroom, especially if there is a high ceiling. Any acoustical ceiling tile that is used should have a sound absorption coefficient rating sufficient to achieve the desired noise and/or reverberation reduction.

Floors

Where practical, installing carpet over a pad to absorb sound and dampen noise from students and from movement of classroom furniture is beneficial.

Furniture

Classroom furniture and movable screens can be used and manipulated to provide acoustical separation and break up sound reflections. Using felt or rubber caps on chair and table legs may help reduce noise as well, particularly if floors are not carpeted.

Lighting

Some fluorescent lighting systems emit a constant noise. Regular maintenance—and, when possible, the use of high-frequency lighting—can reduce and/or eliminate flickering and buzzing.

Mechanical Equipment Noise

High ambient noise from mechanical equipment—such as noisy HVAC systems—can be mitigated by adding custom-built enclosures around mechanical units, adding sound-lined ductwork to the unit, and addressing the location of the HVAC systems in relation to the learning spaces. Equipment such as computers, projection units, and aquarium pumps add to mechanical equipment noise.

Walls

Strategies for mitigating noise through modifications to existing walls include adding materials such as fabric-faced glass fiber wall panels, carpet, sound-absorbing panels, or acoustical ceiling tiles to the walls.

Windows and Doors

Strategies for mitigating noise through modifications to windows and doors include adding double-pane or storm windows, tight-fitting solid core doors, and window draperies/shades.

Exterior Modifications

Exterior noise also contributes to the background sound in a classroom. Modifications to reduce exterior noise include using exterior barriers and landscaping to deflect or absorb unwanted sounds and ensuring that building walls are free of cracks and receive regular maintenance.

New Construction

Acoustical design begins at the outset of the building planning, design, and construction process. It is likely easier to incorporate appropriate acoustical materials at the beginning of the process, rather than retrofit materials at a later date. A new school building’s architectural team may employ acoustical consultants to evaluate aspects of the design, such as interior room acoustics, acoustical isolation, and mechanical system noise control.

Acoustical consultants may advise on the following:

  • Interior room acoustics—selecting acceptable wall, ceiling, and floor materials or finishes for the classroom so that the reverberation time of the room meets or exceeds the reverberation design goal specified in the ANSI standard.
  • Background sound levels—performing various types of design calculations—supported, whenever necessary, with noise measurements—to determine if the ANSI-specified background noise level design goal can be met.
  • Mechanical noise—calculating sound levels in a classroom using the design documents provided by mechanical engineers and, if needed, recommending sound attenuation devices to meet the design goals.
  • Exterior noise—measuring the sound levels at the potential site of a new school, making recommendations for noise isolation or performance of exterior windows and wall sections, and making recommendations for sound insulation design (e.g., external walls, roof assembly).
  • Partition design—ensuring that partitions between the classroom and adjacent areas are designed or upgraded to meet ANSI standards.

Classroom Acoustics Standards and Legislation

ANSI Standards

The ANSI/ASA S12.60-2010 series of standards includes the following:

  • ANSI/ASA S12.60-2010 Part 1: American National Standard Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools, Part 1: Permanent Schools
  • ANSI/ASA S12.60-2009 Part 2: American National Standard Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools, Part 2: Relocatable Classroom Factors

These standards, based on the best scientific evidence available at the time of publication, “help school planners and designers provide good acoustical characteristics for classrooms and other learning spaces in which speech communication is an important part of the learning process” (ANSI/ASA, 2010, p. 2).

Standards include guidance on

  • performance criteria for background noise levels;
  • performance criteria for reverberation times;
  • noise isolation design requirements;
  • classroom audio distribution systems; and
  • compliance/conformance testing.

Building Codes

Guidelines and requirements for classroom construction and applicable facilities are determined on the state and local levels. International and national model standards are developed by the International Code Council and then are adopted by states or localities. In some states, guidelines are uniform; however, many states use guidelines as a basic blueprint. State requirements regarding standardized classroom size, materials, construction requirements, lighting, and similar factors may be found in the information regarding capital construction and/or building requirements available from the state’s department of education.

Content Disclaimer: The Practice Portal, ASHA policy documents, and guidelines contain information for use in all settings; however, members must consider all applicable local, state and federal requirements when applying the information in their specific work setting.