ASTM E2235-04(2020)

Standard Test Method for Determination of Decay Rates for Use in Sound Insulation Test Methods

SIGNIFICANCE AND USE
5.1 Several ASTM test methods to evaluate the sound-insulating properties of building elements require the measurement of room sound absorption as part of the procedure. The room sound absorption in these standards appears in an equation in the form 10 log (x/A), where x is a quantity with the same units as A, m2. Room sound absorption is calculated from the decay rate using Eq 1.  
5.2 The requirements of this standard have been chosen so the uncertainty associated with the measurement of room sound absorption will be acceptably small so long as the logarithm of the absorption is being used in calculations.  
5.3 Other test methods should specify explicitly that they make use of this test method.  
5.4 Where measurement requirements in the parent standard differ from those given here, the requirements in the parent standard shall be satisfied.  
5.5 This test method shall not be used when room sound absorption or decay rate is to be used directly to satisfy some criterion, for example in a room that must not be overly reverberant so speech will be intelligible.
Note 1: The uncertainty of the room sound absorption obtained will usually be too high and additional measurements are necessary.  
5.6 Any companion standard may specify the use of the procedures in this method for determining whether the decay rates in a room are slow enough to satisfy the requirements of the companion standard. The measured decay rates shall still be used only to calculate the logarithm of the room absorption.
SCOPE
1.1 This test method covers the measurement of sound decay rate in rooms and the calculation of the sound absorption of the room and its contents. The sound absorption so calculated may be used in calculations in sound insulation test methods.  
1.2 The method shall be used only in conjunction with other test methods where the logarithm of the sound absorption is used in formulas. It is not sufficiently precise for use in situations where room sound absorption is to be used without taking logarithms.  
1.3 For laboratory measurements of the sound absorption of materials and objects, Test Method C423 should be used.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Mar-2020
• ICS: 91.120.20 - Acoustics in building. Sound insulation
• Technical Committee: E33 - Building and Environmental Acoustics
• Drafting Committee: E33.01 - Sound Absorption

Relations

• Replaces: ASTM E2235-04(2012) - Standard Test Method for Determination of Decay Rates for Use in Sound Insulation Test Methods
• Effective Date: 01-Apr-2020
• Refers: ASTM E90-23 - Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements
• Effective Date: 01-Dec-2023
• Refers: ASTM E336-19a - Standard Test Method for Measurement of Airborne Sound Attenuation between Rooms in Buildings
• Effective Date: 01-Oct-2019
• Refers: ASTM E336-19 - Standard Test Method for Measurement of Airborne Sound Attenuation between Rooms in Buildings
• Effective Date: 01-Jan-2019
• Refers: ASTM E966-18a - Standard Guide for Field Measurements of Airborne Sound Attenuation of Building Facades and Facade Elements
• Effective Date: 01-Nov-2018
• Refers: ASTM E966-18 - Standard Guide for Field Measurements of Airborne Sound Attenuation of Building Facades and Facade Elements
• Effective Date: 15-Jan-2018
• Refers: ASTM E336-17a - Standard Test Method for Measurement of Airborne Sound Attenuation between Rooms in Buildings
• Effective Date: 15-Nov-2017
• Refers: ASTM E336-17 - Standard Test Method for Measurement of Airborne Sound Attenuation between Rooms in Buildings
• Effective Date: 01-Jul-2017
• Refers: ASTM E90-09(2016) - Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements
• Effective Date: 01-Dec-2016
• Refers: ASTM E1007-16 - Standard Test Method for Field Measurement of Tapping Machine Impact Sound Transmission Through Floor-Ceiling Assemblies and Associated Support Structures
• Effective Date: 01-Oct-2016
• Refers: ASTM E336-16a - Standard Test Method for Measurement of Airborne Sound Attenuation between Rooms in Buildings
• Effective Date: 01-Oct-2016
• Refers: ASTM E336-16 - Standard Test Method for Measurement of Airborne Sound Attenuation between Rooms in Buildings
• Effective Date: 01-Jan-2016
• Refers: ASTM E336-15 - Standard Test Method for Measurement of Airborne Sound Attenuation between Rooms in Buildings
• Effective Date: 01-Sep-2015
• Refers: ASTM E1007-14 - Standard Test Method for Field Measurement of Tapping Machine Impact Sound Transmission Through Floor-Ceiling Assemblies and Associated Support Structures
• Effective Date: 01-Sep-2014
• Refers: ASTM E336-14 - Standard Test Method for Measurement of Airborne Sound Attenuation between Rooms in Buildings
• Effective Date: 15-Apr-2014

Overview

ASTM E2235-04(2020): Standard Test Method for Determination of Decay Rates for Use in Sound Insulation Test Methods provides a systematic approach for measuring sound decay rates in rooms and calculating sound absorption. The standard is essential for accurate assessment of the sound-insulating properties of building elements, particularly when used in conjunction with other sound insulation test protocols. The key outcome of this method is the reliable determination of room sound absorption, which is subsequently used in logarithmic form in formulas as part of broader acoustic performance evaluations.

This international standard aligns with globally recognized practices as recommended by the World Trade Organization (WTO) Technical Barriers to Trade (TBT) Committee, ensuring consistency and comparability across different countries and applications.

Key Topics

• Measurement of Sound Decay Rate: Defines how to systematically capture the decline in sound pressure levels in a room after a sound source is switched off, across multiple frequency bands.
• Calculation of Room Sound Absorption: Uses the decay rate to determine the total sound absorption, applying it in the context of sound insulation performance.
• Precision and Applicability: Emphasizes the method’s precision when used with logarithmic functions in calculations and highlights limitations if used for direct room absorption assessments.
• Microphone and Loudspeaker Positioning: Specifies the placement and quantity of microphones and sound sources to ensure representativeness and repeatability in measurement.
• Instrument Requirements: Outlines the essential characteristics and functionality for analysis instruments, including compliance with related ANSI and ASTM standards.
• Measurement Conditions: Details requirements for controlling or documenting variables such as temperature, background noise, and frequency range to maintain result integrity.

Applications

ASTM E2235-04(2020) is widely utilized within the field of building acoustics to support:

• Sound Insulation Testing: The standard underpins other ASTM methods for evaluating airborne and impact sound transmission through walls, floors, facades, and other building elements. Test results inform the design and specification of partitions, floor-ceiling assemblies, and façade systems.
• Laboratory and Field Assessment: Applies in both controlled laboratory settings and on-site evaluations to ensure the sound-absorbing characteristics of environments or components meet relevant standards.
• Normalization of Sound Pressure Levels: Facilitates the elimination of room absorption effects to accurately assess the intrinsic acoustic properties of materials or assemblies.
• Supporting Regulatory Compliance: The method is essential for demonstrating compliance with building codes, acoustic performance regulations, and certification programs focused on occupant comfort and privacy.

NOTE: This standard should not be used in applications where direct measurement of room sound absorption or decay rates is required for critical listening environments such as speech intelligibility rooms, due to insufficient precision. For direct measurement of material sound absorption, refer to ASTM C423.

Related Standards

ASTM E2235-04(2020) is referenced and complemented by several other standards in building and environmental acoustics, including:

• ASTM E90: Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements
• ASTM E336: Measurement of Airborne Sound Attenuation between Rooms in Buildings
• ASTM E492: Laboratory Measurement of Impact Sound Transmission Through Floor-Ceiling Assemblies
• ASTM E1007: Field Measurement of Tapping Machine Impact Sound Transmission Through Floor-Ceiling Assemblies
• ASTM E1414: Airborne Sound Attenuation Between Rooms Sharing a Common Ceiling Plenum
• ASTM C423: Sound Absorption and Sound Absorption Coefficients by the Reverberation Room Method (recommended for direct material measurements)
• ASTM C634: Terminology Relating to Building and Environmental Acoustics
• ANSI S1.4, S1.6, S1.11: Specifications for sound-level meters, preferred frequencies, and band filters for acoustical measurements

For further details or to obtain official copies, visit the ASTM International website at www.astm.org.

Keywords: sound decay rate, sound absorption, sound insulation, building acoustics, ASTM E2235, reverberation, acoustic testing.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E2235 − 04 (Reapproved 2020)
Standard Test Method for
Determination of Decay Rates for Use in Sound Insulation
Test Methods
This standard is issued under the fixed designation E2235; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
This test method is part of a set of methods used to evaluate the sound-insulating properties of
building elements. It is intended for use in conjunction with methods for measuring the transmission
of sound through a partition or partition element in a laboratory or in a building. These methods
include the laboratory measurement of airborne sound transmission loss of building partitions and
elements(TestMethodE90),themeasurementofsoundisolationinbuildings(TestMethodE336),the
laboratory measurement of impact sound transmission through floors (Test Method E492), the
measurement of impact sound transmission in buildings (Test Method E1007), the measurement of
sound transmission through building facades and facade elements (Guide E966), and the measurement
of sound transmission through a common plenum between two rooms (Test Method E1414).
1. Scope mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
1.1 This test method covers the measurement of sound
decay rate in rooms and the calculation of the sound absorption
2. Referenced Documents
of the room and its contents. The sound absorption so calcu-
lated may be used in calculations in sound insulation test
2.1 ASTM Standards:
methods.
C423 Test Method for SoundAbsorption and SoundAbsorp-
tion Coefficients by the Reverberation Room Method
1.2 The method shall be used only in conjunction with other
C634 Terminology Relating to Building and Environmental
test methods where the logarithm of the sound absorption is
Acoustics
used in formulas. It is not sufficiently precise for use in
situations where room sound absorption is to be used without E90 Test Method for Laboratory Measurement of Airborne
taking logarithms.
Sound Transmission Loss of Building Partitions and
Elements
1.3 For laboratory measurements of the sound absorption of
E336 Test Method for Measurement of Airborne Sound
materials and objects, Test Method C423 should be used.
Attenuation between Rooms in Buildings
1.4 This standard does not purport to address all of the
E492 Test Method for Laboratory Measurement of Impact
safety concerns, if any, associated with its use. It is the
Sound Transmission Through Floor-Ceiling Assemblies
responsibility of the user of this standard to establish appro-
Using the Tapping Machine
priate safety, health, and environmental practices and deter-
E966 Guide for Field Measurements of Airborne Sound
mine the applicability of regulatory limitations prior to use.
Attenuation of Building Facades and Facade Elements
1.5 This international standard was developed in accor-
E1007 Test Method for Field Measurement of Tapping
dance with internationally recognized principles on standard-
Machine Impact Sound Transmission Through Floor-
ization established in the Decision on Principles for the
Ceiling Assemblies and Associated Support Structures
Development of International Standards, Guides and Recom-
E1414 Test Method for Airborne Sound Attenuation Be-
tween Rooms Sharing a Common Ceiling Plenum
ThistestmethodisunderthejurisdictionofASTMCommitteeE33onBuilding
and Environmental Acoustics and is the direct responsibility of Subcommittee
E33.01 on Sound Absorption. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved April 1, 2020. Published April 2020. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2003. Last previous edition approved in 2012 as E2235 – 04 (2012). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/E2235-04R20. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2235 − 04 (2020)
2.2 ANSI Standards: 5.3 Other test methods should specify explicitly that they
S1.4 Specification for Sound-Level Meters make use of this test method.
S1.6 Standard Preferred Frequencies, Frequency Levels, and
5.4 Wheremeasurementrequirementsintheparentstandard
Band Numbers for Acoustical Measurements
differ from those given here, the requirements in the parent
S1.11 Specification for Octave-band and Fractional-Octave-
standard shall be satisfied.
Band Analog and Digital Filters
5.5 This test method shall not be used when room sound
absorption or decay rate is to be used directly to satisfy some
3. Terminology
criterion, for example in a room that must not be overly
3.1 Definitions of the acoustical terms used in this test
reverberant so speech will be intelligible.
method are given in Terminology C634.
NOTE 1—The uncertainty of the room sound absorption obtained will
3.2 Definitions of Terms Specific to This Standard: usually be too high and additional measurements are necessary.
3.2.1 output interval, ∆t; [T]; s—of a real-time analyzer, the
5.6 Any companion standard may specify the use of the
time between successive outputs of sound pressure levels
procedures in this method for determining whether the decay
during a single decay measurement.
rates in a room are slow enough to satisfy the requirements of
the companion standard. The measured decay rates shall still
4. Summary of Test Method
be used only to calculate the logarithm of the room absorption.
4.1 Sound decay rate in rooms is a function of frequency so
6. Sound Source Requirements
measurements are made in a series of frequency bands. Bands
of random electrical noise are used as signals to drive loud-
6.1 Sound sources shall be loudspeaker systems driven by
speakers in the room until the sound pressure level reaches a
power amplifiers.
steady state. When the sound is then turned off, the sound
NOTE 2—Loudspeaker systems should be omnidirectional. In practice,
pressure level decays at a rate determined by the sound using multiple driver elements to cover different frequency ranges and
placing sources in trihedral corners of the room will be adequate.
absorption in the room. The decay rate is measured in each
frequency band by measuring the slope of a straight line fitted
7. Sound Source Positions
to the average decay curve. The absorption of the room and its
7.1 At least one source position shall be used in the room.
contents is calculated from the Sabine formula:
NOTE 3—Where more than one source position is used, decay rate data
Vd
may be collected for each source position in sequence and then the decay
A 5 0.921 (1)
c
rates averaged. Alternatively, multiple loudspeakers may be activated
simultaneously. If this is done, the sound power emitted by the loud-
where:
speaker sources should be approximately equal. Separate electronic noise
generators and amplifiers for each system are not necessary.
A = sound absorption, m ,
V = volume of reverberation room, m ,
8. Electrical Signal
c = speed of sound, m/s, and
d = decay rate, dB/s.
8.1 Theelectricalsignalfedtoeachpoweramplifiershallbe
a band of random noise with a continuous spectrum covering
4.1.1 The speed of sound changes with temperature and it
the frequency range over which measurements are made.
shall be calculated for the conditions existing at the time of test
from the equation:
9. Frequency Range
c 5 20.047=273.151t m/s (2)
9.1 The frequency range of the measurements shall be that
specified in the companion standard for which the measure-
where:
ments are being made.
t = room temperature, °C.
9.2 Bandwidth—For each test band, the overall frequency
5. Significance and Use
response of the electrical system, including the filter or filters
in the source or microphone systems, shall satisfy the specifi-
5.1 Several ASTM test methods to evaluate the sound-
cations given in ANSI Specification S1.11 for a one-third
insulating properties of building elements require the measure-
octave band filter set, Order 3 or higher, Type 1.
ment of room sound absorption as part of the procedure. The
NOTE 4—The shape of the filter response curve can influence the
room sound absorption in these standards appears in an
minimum decay rate that can be measured. This problem is dealt with by
equationintheform10log(x/A),where xisaquantitywiththe
the requirement in 13.5.
same units as A,m . Room sound absorption is calculated from
the decay rate using Eq 1.
10. Microphone Requirements
5.2 The requirements of this standard have been chosen so
10.1 A microphone used to measure decay rate shall be
the uncertainty associated with the measurement of room
omnidirectional with a 61 dB random-incidence amplitude
sound absorption will be acceptably small so long as the
response within any one-third octave band for all frequencies
logarithm of th
...