Acoustic Flooring for Noise Control

Whether it be at work, in school or at home, Australians spend 90% of their time indoors, underscoring the importance of creating comfortable and productive indoor environments. Acoustic comfort is one of several critical design elements that contributes to indoor environmental quality and healthy living spaces. Poor acoustic control within an indoor environment can have a significant impact on the health, wellbeing and comfort of occupants and impair work and academic performance. Project teams that take a holistic approach to sustainable building design need to address acoustic performance as a high priority. The absorption and transmission of sound in a building is directly impacted by the type of building materials selected for indoor environments. Flooring, as one of the most abundant surfaces in any building, can have a massive impact on indoor acoustics. For spaces with demanding acoustic requirements, such as offices and classrooms, acoustic flooring – flooring that has been specially designed for superior impact sound reduction and sound absorption – has emerged as an effective solution to improving the overall acoustic performance of new and refurbished installations. In this whitepaper, we take a closer look at the impact of internal acoustics on occupant health, wellbeing and comfort. We also examine specifying flooring for acoustic performance and the various considerations integral to the design process.

POOR NOISE CONTROL AND HEALTH In general, noisy indoor environments have been shown to be detrimental to health and lead to increase levels of stress. Persistent noise disturbances at home can interrupt sleep, which can increase fatigue and lead to heart disease and hearing impairment. Some studies also highlight a potential link between noise and an increased risk of cardiovascular disease. Poor acoustic environments also have a negative impact on mood, personal relationships and overall mental health. Research indicates that exposure to excess noise can exacerbate existing mental health issues, such as anxiety. 

WORKPLACES A research survey conducted by OnePoll on behalf of Tarkett Australia, found that 32% of respondents across Australia selected noise as the most pressing issue in the workplace. A majority of respondents (72%) noted that noise impacted their ability to work. Several international studies have established a strong and significant correlation between changes in office productivity and sound. One study highlighted that as noise levels within a workplace increased, performance levels decreased while rates of error increased. This is likely attributed to the effect excess noise has on concentration, stress and annoyance, and other negative cognitive effects with respect to reading, attention, problem solving and memory. 

SCHOOLS In a classroom environment, research shows that poor acoustics can impact speech comprehension and student learning outcomes. Several studies emphasise that children are more impaired than adults by noise in tasks involving speech perception and listening comprehension, as well as memory recall, reading and writing. The effects of noise on children with language or attention disorders and second-language learners are even more pronounced. In noisy environments, speech intelligibility is degraded making teaching and learning harder. In a 30-student classroom generating 50dB of ambient noise, the teacher is required to speak at 65dB to be understood, which is above normal talking levels. Students who do not understand speech tend to lose concentration and become disconnected from the learning experience, hampering academic progress and wasting valuable teaching time.

BASICS OF SOUND

Sound travels in waves creating vibrations in air, water and materials. The key attributes of sound are speed, wavelength and amplitude. Speed (also referred to as “sound pitch” or “frequency”) is measured in the number of wave cycles occurring in one second, which is expressed as Hertz (Hz). The audible range of sound for humans is between 20 Hz to 20,000 Hz. Wavelength is the size of a sound wave, measured from one peak to the next. Amplitude (also referred to “sound intensity”, “loudness” or “volume”) is measured in Decibels (dB), with each increase of 10dB resulting in an apparent doubling of loudness.Sound transmission refers to sound passing through building elements and materials. When sound travels within an indoor space and hits a surface, be it a wall, floor or ceiling, sound is either reflected off the surface, absorbed into the surface or transmitted through the surface. Reverberation is the sound that reflects or echoes within a space. “Reverberation time” is “the time it takes for sound to decay by 60 dB after an abrupt termination”.A high reverberation time can contribute to spaces that are loud, muffled and noisy, whereas rooms designed for speech typically have a low reverberation time.

GOOD ACOUSTICS VS. POOR ACOUSTICS In general, good acoustics can be determined with reference to reverberation time, overall noise levels, speech intelligibility and how these factors affect users within a space. Mitigation of noise disturbances from inside and outside of a building is characteristic of good acoustic design. 

On the other hand, the following are typical indicators of poor acoustic design:

• excess noise from outside the building entering the space; 

• uncontrolled noise from adjacent spaces; and 

• lack of sound control in the space itself. The type of room and its intended purpose is a critical consideration when assessing acoustic design. Spaces that require peace and quiet (e.g. workspaces, libraries and study rooms) will usually require acoustic solutions that absorb sound, whereas lecture halls, on occasion, require targeted reverberation to project speech out to the audience. As a general rule, reducing the amount of reverberation within a space will allow for greater speech intelligibility and concentration levels.

The Australian Building Codes Board (ABCB) distinguishes between airborne noise and structure-borne noise (also known as “impact noise”). Airborne noise travels through the air through a direct or open path between the noise source and the listener. Structure-borne or impact noise is generated by vibrations induced in the ground and/or structural elements, often by impact or contact with vibrating machinery. The noise control method will depend on the type of noise being addressed. Airborne noise needs to be contained through noise absorption. Noise absorption refers to the “loss of sound energy when sound waves come into contact with an absorbent material such as acoustic wall paneling or carpet”. Impact noise can be mitigated using vibration resistance or damping. In the context of flooring, acoustic floor covering designed for impact resistance is one approach to preventing the transmission of impact noise through a building structure. Internal acoustics including reverberation and noise transfer are greatly affected by the characteristics of the surfaces separating, enclosing and within an interior space. As flooring makes up a significant proportion of a room’s total surface area, the characteristics of floor coverings and materials should be considered carefully. In general, hard reflective materials such as ceramic tiles, wood and vinyl are not good at absorbing mid-high frequency reverberating sound. A softer floor covering or a floor covering specially designed for acoustic performance (i.e. acoustic flooring) can better absorb excessive reverberation. Floor coverings with acoustic properties such as cushion back vinyl or carpet tiles are ideal for reducing the impact noise and noise transfer generated by foot traffic within a space. Floor coverings can play a major role in controlling acoustics with specific applications requiring targeted solutions to achieve the desired acoustic performance.

AUSTRALIAN BUILDING CODES, STANDARDS AND GUIDELINES:

 The National Construction Code specifies airborne and impact noise requirements with respect to flooring for various building types. In relation to the acoustic performance of floor systems in Class 2, 3 and 9c buildings, the key provisions are found in Part F5 of the NCC Volume One. Under the NCC, floors must insulate against the transmission of airborne and impact generated sound sufficient to prevent illness or loss of amenity to the occupants. Verification methods are tests, inspections, calculations or other methods prescribed by the NCC to determine whether a solution complies with the relevant performance requirement. The methods outlined in FV5.1 and FV5.3 of the NCC Volume One apply to the transmission of airborne and impact generated sound through floors and require in-situ testing in accordance with AS/ISO 717.1:2004 Acoustics - Rating of sound insulation in buildings and of building elements Airborne sound insulation and AS/ISO 717.2:2004 – Acoustics - Rating of sound insulation in buildings and of building elements Impact sound insulation. F5.4 of the NCC Volume One provides a Deemed-to-Satisfy solution for the sound insulation of floors. For other building types, such as educational facilities and offices, AS/NZS 2107:2016 Acoustics - Recommended design sound levels and reverberation times for building interiors provides design criteria for creating a healthy and comfortable indoor acoustic environment. According to AS/NZS 2107:2016, educational spaces should have reverberation times at the lower end of the range to promote a quiet environment that is conducive to teaching and learning. Hard flooring surfaces contribute to longer reverberation times, which can impact speech intelligibility. In such environments, acoustic flooring is ideal. The Association of Australasian Acoustical Consultants provides guidelines for acoustic design for commercial buildings. While the specific acoustic requirements of such buildings differ from educational spaces, the focus remains on minimising external and internal noise intrusion, minimising impact and vibration noise and ensuring acoustic separation between adjoining rooms. 

DESIGNING TO MEET NOISE REQUIREMENTS Acoustic design requires consideration of a range of design features working in combination. A bare concrete slab would provide comparatively little acoustic performance, but adding acoustic floor covering can significantly improve sound absorption in the room and reduce impact sounds. Other design elements such as insulation and ceiling systems all contribute to overall acoustic performance. Designers and specifiers require knowledge of the sound absorption of various products, especially solutions that exceed the minimum requirements. During the design phase, collaborating with an acoustic design consultant and leading manufacturers can help achieve the desired acoustic environment. Testing and acoustic modelling is required to assess the acoustic performance of designs and built-up systems. Note that there are several Australian and International Standards relevant to measuring the acoustic performance of flooring. 

COMFORT AND ERGONOMICS When selecting acoustic flooring, acoustic performance should not come at the cost of ergonomics and walking comfort. While more comfortable underfoot, softer and more elastic floors can provide more resistance when moving furniture and/or machinery, increasing physical strain. Rolling resistance, which refers to force resisting motion when a body rolls on a surface, must be balanced with walking comfort. Rolling resistance is highly dependent on floor surface and materials. Leading acoustic flooring solutions deliver low rolling load resistance while maintaining high acoustic performance and underfoot comfort. 

DURABILITY, MAINTENANCE AND CLEANING For high traffic environments, it is important to select flooring that is durable and resistant to wear and tear that could compromise its performance. Floors that are resistant to staining and damage will also ease maintenance and cleaning requirements. These characteristics will ensure that the flooring solution offers a long service life with reduced costs for cleaning, maintenance and repairs.