Revision 1. February 2017
A08C - ACOUSTICAL ISSUES
A08C-1 General
A08C-2 Airborne noise
A08C-3 Impact noise
A08C-4 Resonating noise
A08C-5 Noise reduction
A08C-2 Airborne noise
A08C-3 Impact noise
A08C-4 Resonating noise
A08C-5 Noise reduction
Preface:
The following information on acoustical issues pertaining to flooring has been compiled from various sources and is provided as general information only. Individuals using this information are advised to contact design authorities, research agencies, and product manufacturers for specific requirements and information in regard to flooring systems and materials to be used for their project specific requirements.
1 • GENERAL
.01 The maintenance of acceptable acoustical levels and the reduction of noise in residential, commercial, or institutional environments is essential in order to maintain privacy, comfort, and freedom from distracting and unwanted noise and to enable the occupants of a space to live, eat, sleep, and/or work without disrupting others or being disrupted themselves.
.02 As the reduction or control of sound at the source or individual noise generating activities is not part of the acoustical equation in regard to flooring, other means must be employed to achieve an acceptable acoustical environment. This involves the three basic methods in noise reduction: absorbing, blocking, and/or covering-up or masking.
.03 Before any of these methods are reviewed to determine which ones may be implemented to reduce unwanted sound or noise it is essential to understand the three types of sound associated with flooring materials:
The following information on acoustical issues pertaining to flooring has been compiled from various sources and is provided as general information only. Individuals using this information are advised to contact design authorities, research agencies, and product manufacturers for specific requirements and information in regard to flooring systems and materials to be used for their project specific requirements.
1 • GENERAL
.01 The maintenance of acceptable acoustical levels and the reduction of noise in residential, commercial, or institutional environments is essential in order to maintain privacy, comfort, and freedom from distracting and unwanted noise and to enable the occupants of a space to live, eat, sleep, and/or work without disrupting others or being disrupted themselves.
.02 As the reduction or control of sound at the source or individual noise generating activities is not part of the acoustical equation in regard to flooring, other means must be employed to achieve an acceptable acoustical environment. This involves the three basic methods in noise reduction: absorbing, blocking, and/or covering-up or masking.
.03 Before any of these methods are reviewed to determine which ones may be implemented to reduce unwanted sound or noise it is essential to understand the three types of sound associated with flooring materials:
- Airborne Noise: This sound is any airborne vibration such as voices, sound systems, etc that travels through the wall assembly into the adjacent room or area and/or through the flooring system and into the room or area below.
- Impact Noise: This is sound is vibration generated by footfalls or objects coming in contact with the flooring surface that is transmitted into the adjacent room or area and/or through the flooring system and into the room or area below.
- Resonating Noise: This sound is that portion of impact or airborne noise that reverberates or echoes within the room.
2 • AIRBORNE NOISE
.01 Airborne or audible noise is defined as voice, music, machine, or any other noise not related to impact sound. Such noise may be measured in three different ways:
.01 Airborne or audible noise is defined as voice, music, machine, or any other noise not related to impact sound. Such noise may be measured in three different ways:
- Sound Transmission Class (STC): This rating system is based on a laboratory-conducted measurement of the resistance of a building element such as a floor or wall to the passage of audible sounds. The higher the STC number the better sound barrier.
- Field Sound Transmission Class (FSTC): This rating system is based on a field-conducted measurement of the resistance of a building element such as a floor or wall to the passage of audible sounds. The higher the FSTC number the better sound barrier. Current Code requirements only define STC rather than FSTC ratings as the applicable requirement. Test methods used to determine sound transmission classification ratings are ASTM E90 for testing and ASTM E413 for classification.
- Noise Reduction Coefficient (NRC): This rating system is based on laboratory conducted measurements to determine the average of the mid frequency sound absorption coefficients of a material measured at frequencies of 250, 500, 1,000 and 2,000 Hz rounded to the nearest 5% and ranges from zero (perfectly reflective) to one (perfectly absorptive). This is perfectly acceptable for speech, but can be inadequate for music (and other low-frequency sounds). In addition, because the lab is a perfect environment that is rarely duplicated in everyday applications, some products will not test the same in the field. Certain factors, such as installation variables, are not accounted for in laboratory testing.
3 • IMPACT NOISE
.01 The control of impact noise differs greatly from that of airborne noise.
.02 Impact noise or sound is generated by the impact of one body striking another such as the noise of footsteps, hammering, moving furniture, and objects falling on flooring surfaces. Such sound travels through the floor assembly (floor covering and structure) with little loss of energy if the structure is continuous and rigid. Increasing either the mass of the flooring structure (e.g. increasing a concrete floor slab thickness or adding an additional layer of gypsum board to the ceiling surface below) or altering the floor structure by "isolating" floor component members one from another so that it is not a continuous assembly will reduce impact noise.
.03 There are three rating systems or methods that have been used to determine impact noise:
.05 For a more thorough explanation of controlling the transmission of impact sound through floors refer to the National Research Council publication "Construction Technology Update No. 35 available on NRC's website (www.nrc.ca/irc).
.01 The control of impact noise differs greatly from that of airborne noise.
.02 Impact noise or sound is generated by the impact of one body striking another such as the noise of footsteps, hammering, moving furniture, and objects falling on flooring surfaces. Such sound travels through the floor assembly (floor covering and structure) with little loss of energy if the structure is continuous and rigid. Increasing either the mass of the flooring structure (e.g. increasing a concrete floor slab thickness or adding an additional layer of gypsum board to the ceiling surface below) or altering the floor structure by "isolating" floor component members one from another so that it is not a continuous assembly will reduce impact noise.
.03 There are three rating systems or methods that have been used to determine impact noise:
- Impact Noise Rating (INR): The earliest single-number rating system obtained by standard / controlled testing methods was called the Impact Noise Rating (INR) system. This system has since been replaced by the Impact Insulation Class (IIC) rating system which for the sake of this discussion has values that are generally 50 points above the corresponding former INR values.
- Impact Insulation Class (IIC): This is a measurement obtained by a standard / controlled laboratory testing methods (ASTM E492 for testing and ASTM E989 for classification) which classify or rate a flooring assembly in regard to amount of impact sound transmitted through the assembly. Each rating is called an impact insulation class (IIC) with the higher the IIC number the better the impact insulation.
- Field Impact Insulation Class (FIIC): This is a companion measurement obtained by a standard / controlled field-testing methods (ASTM E1007 for testing and ASTM E989 for classification) which classify or rate a flooring assembly in regard to amount of impact sound transmitted through the assembly. Each rating is called a field impact insulation class (FIIC), with the higher the FIIC number the better the impact insulation.
- A standard laboratory test method (ASTM E2179) has been developed to determine the effectiveness of floor coverings in reducing impact sound transmission through concrete floors.
.05 For a more thorough explanation of controlling the transmission of impact sound through floors refer to the National Research Council publication "Construction Technology Update No. 35 available on NRC's website (www.nrc.ca/irc).
4 • RESONATING NOISE
.01 Although resonating sound within a room or space is an essential element in the acoustical quality of the space, at the present time there are no established testing methods for testing this acoustical property. There are, however, proposed methods that are currently under evaluation by various organizations.
.01 Although resonating sound within a room or space is an essential element in the acoustical quality of the space, at the present time there are no established testing methods for testing this acoustical property. There are, however, proposed methods that are currently under evaluation by various organizations.
5 • NOISE REDUCTION
.01 In considering the three basic methods used in noise reduction: absorbing, blocking, and/or covering-up or masking sound, only two can be used in regard to flooring as the third, masking or covering up noise, is not applicable in flooring acoustics, as this can only be achieved by "electronic" means.
.02 Noise Blocking: This method of noise control involves blocking clear paths for the transmission of sound from one space to another. This can be achieved by providing
physical barriers without gaps to prevent sound from flanking the barrier. In ceiling and wall assemblies this may entail the use of multiple layers of gypsum board,
resilient channels, insulation, caulking and sealants, acoustical seals at all openings (such as acoustical threshold and seals in door openings), etc. In regard to flooring this
may mean providing flooring assemblies with acoustical separation of the floor structure elements, such as using a floating floor system in hardwood flooring or using
dampening pads and panel type sub-floor, cork expansion joint strips, etc., in hardwood sports flooring, as well as caulking all flooring penetrations and perimeter gaps.
Note: Mechanical fasteners (nails and screws) should not penetrate any sound barrier material as the integrity of the sound control material will be jeopardized. Impact sound will travel through the fastener to the surface below, and will negate the effectiveness of the sound control system. In addition the isolation membrane should run up any vertical face enough to isolate the hard surface flooring from the vertical surface to eliminate the transmission of noise to another part of the building or surface.
.03 Noise Absorption: Adding absorptive floor covering materials will reduce the energy and therefore the volume of sounds reflected off their surfaces and back into the room or area. Hard flooring materials are more reflective and result in a more reverberant environment. Carpeting greatly reduces footfall and impact noise, but typically provides only minimal absorption of frequencies in human speech. The use of an absorptive cushion under carpet and hardwood flooring and cushion backed resilient flooring will have a greater effect in absorbing these frequencies as well as aiding in the reduction of impact noise. The use of absorptive floor covering materials is the best method of noise reduction of the three basic methods.
.04 The National and Provincial Building Codes require that there be an acoustical separation (sound control) between each dwelling unit and every other space within a building. This encompasses sound travelling through both wall and floor / ceiling assemblies. The minimum sound transmission class (STC) rating requirement is noted and various construction assemblies have been assigned sound rating classifications (I, II, or III) based on minimum STC ratings for each class. These "airborne" sound ratings do not include the contribution of any floor covering materials in increasing these ratings (i.e., improving the STC ratings), nor do they consider impact noise at all.
.05 The acoustical properties of flooring materials and related installation systems vary. To determine what these properties are various ASTM and ISO acoustical testing methods are used as the criteria to determine acceptable sound transmission standards in regard to impact and airborne noise.
.06 When evaluating flooring material acoustical ratings it is important to carefully evaluate the testing methods used. In addition, any reports of sound test results should include a description of the entire wall and floor / ceiling assembly.
When reviewing acoustical performance claims made by flooring material manufacturers ensure that these are substantiated by independent testing data. This is particularly important when comparing one product to another and to ensure that you are getting what you pay for. There are many factors which contribute to the acoustical rating of a floor assembly. However, one must also consider the impact of dropped ceiling constructions below, continuity of acoustical insulation, affect of in-floor duct and piping systems, floor penetrations, and any other construction anomalies that will disrupt the acoustical assembly and mitigate against achieving the acoustical ratings required. The choice of flooring materials particularly acoustical underlayments will have an impact on the acoustical performance of a floor system. This should not however be the sole deciding factor in trying to achieve a particular floor assembly acoustical rating.
.01 In considering the three basic methods used in noise reduction: absorbing, blocking, and/or covering-up or masking sound, only two can be used in regard to flooring as the third, masking or covering up noise, is not applicable in flooring acoustics, as this can only be achieved by "electronic" means.
.02 Noise Blocking: This method of noise control involves blocking clear paths for the transmission of sound from one space to another. This can be achieved by providing
physical barriers without gaps to prevent sound from flanking the barrier. In ceiling and wall assemblies this may entail the use of multiple layers of gypsum board,
resilient channels, insulation, caulking and sealants, acoustical seals at all openings (such as acoustical threshold and seals in door openings), etc. In regard to flooring this
may mean providing flooring assemblies with acoustical separation of the floor structure elements, such as using a floating floor system in hardwood flooring or using
dampening pads and panel type sub-floor, cork expansion joint strips, etc., in hardwood sports flooring, as well as caulking all flooring penetrations and perimeter gaps.
Note: Mechanical fasteners (nails and screws) should not penetrate any sound barrier material as the integrity of the sound control material will be jeopardized. Impact sound will travel through the fastener to the surface below, and will negate the effectiveness of the sound control system. In addition the isolation membrane should run up any vertical face enough to isolate the hard surface flooring from the vertical surface to eliminate the transmission of noise to another part of the building or surface.
.03 Noise Absorption: Adding absorptive floor covering materials will reduce the energy and therefore the volume of sounds reflected off their surfaces and back into the room or area. Hard flooring materials are more reflective and result in a more reverberant environment. Carpeting greatly reduces footfall and impact noise, but typically provides only minimal absorption of frequencies in human speech. The use of an absorptive cushion under carpet and hardwood flooring and cushion backed resilient flooring will have a greater effect in absorbing these frequencies as well as aiding in the reduction of impact noise. The use of absorptive floor covering materials is the best method of noise reduction of the three basic methods.
.04 The National and Provincial Building Codes require that there be an acoustical separation (sound control) between each dwelling unit and every other space within a building. This encompasses sound travelling through both wall and floor / ceiling assemblies. The minimum sound transmission class (STC) rating requirement is noted and various construction assemblies have been assigned sound rating classifications (I, II, or III) based on minimum STC ratings for each class. These "airborne" sound ratings do not include the contribution of any floor covering materials in increasing these ratings (i.e., improving the STC ratings), nor do they consider impact noise at all.
.05 The acoustical properties of flooring materials and related installation systems vary. To determine what these properties are various ASTM and ISO acoustical testing methods are used as the criteria to determine acceptable sound transmission standards in regard to impact and airborne noise.
.06 When evaluating flooring material acoustical ratings it is important to carefully evaluate the testing methods used. In addition, any reports of sound test results should include a description of the entire wall and floor / ceiling assembly.
When reviewing acoustical performance claims made by flooring material manufacturers ensure that these are substantiated by independent testing data. This is particularly important when comparing one product to another and to ensure that you are getting what you pay for. There are many factors which contribute to the acoustical rating of a floor assembly. However, one must also consider the impact of dropped ceiling constructions below, continuity of acoustical insulation, affect of in-floor duct and piping systems, floor penetrations, and any other construction anomalies that will disrupt the acoustical assembly and mitigate against achieving the acoustical ratings required. The choice of flooring materials particularly acoustical underlayments will have an impact on the acoustical performance of a floor system. This should not however be the sole deciding factor in trying to achieve a particular floor assembly acoustical rating.