RT60 (Reverberation Time)

ASTM E2235: Standard Test Method for Determination of Decay Rates for Use in Sound Insulation Test Methods

ISO 3382-1: Specifies methods for the measurement of reverberation time and other room acoustical parameters in performance spaces

ISO 3382-2: Specifies methods for the measurement of reverberation time in ordinary rooms.

The RT60 reverberation test measures the time required for a sound to decrease in intensity from it’s original maximum level by 60 decibels. RT60 is measured in seconds and often stated as a single value. The actual measurements span the frequency band from 50 Hz to 8000 Hz with 1/1 or 1/3rd octave resolution. Rooms have individual absorption capabilities for each frequency, so the RT60 values within each band will vary.

Sound Transmission Class (STC)

ASTM E90: Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements (tested in laboratories).

ISO 10140-2:2010: Acoustics — Laboratory measurement of sound insulation of building elements
Part 2: Measurement of airborne sound insulation

ASTC / FSTC (Apparent STC / Field STC)

ASTM E336: Standard Test Method for Measurement of Airborne Sound Attenuation between Rooms in Buildings (tested on field).

ISO 16283-1:2014: Field measurement of sound insulation in buildings and of building elements — Part 1: Airborne sound insulation

The ASTC is determined in accordance with ASTM E413, Classification for rating sound insulation. The test was used with the XL2 Data Explorer software to determined the STC of the room.

NC (Noise Criterion)

ASTM E1686
Standard Guide for Applying Environmental Noise Measurement Methods and Criteria

ISO 1996
Description, measurement and assessment of environmental noise:
— Part 1: Basic quantities and assessment procedures
— Part 2: Determination of sound pressure levels

Established in U.S. for rating indoor noise, noise from air-conditioning equipment, etc. In Europe, it is common to use the Noise Rating Curve – NR.

This industry standard (also an ANSI standard) usually pertains to HVAC or mechanical noise impact. Occupant comfort is the goal of all HVAC designers. Sound (or noise) is a key parameter in measuring comfort.
ASTM E 1374-02: Standard Guide for Open Office Acoustics.

STI (Speech Transmission Index)

IEC 60268-16: IEC 60268-16:2011 specifies objective methods for rating the transmission quality of speech with respect to intelligibility. It provides a comprehensive manual for all types of users of the STI method in the fields of audio, communications and acoustics.

Speech Transmission Index (STI) is a measure of speech transmission quality. The STI measures some physical characteristics of a transmission channel (a room, electro-acoustic equipment, telephone line, etc.), and expresses the ability of the channel to carry across the characteristics of a speech signal. STI is a well-established objective measurement predictor of how the characteristics of the transmission channel affect speech intelligibility. The speech intelligibility is measured by playing a known signal (the STIPA test signal) through the PA and measuring the quality of that signal as it reaches each of the measurement positions.

SAC (Sound Absorption Coefficient)

ASTM C423: Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberation Room Method

ISO 354:2003: Specifies a method of measuring the sound absorption coefficient of acoustical materials used as wall or ceiling treatments, or the equivalent sound absorption area of objects, such as furniture, persons or space absorbers, in a reverberation room.

(It is not intended to be used for measuring the absorption characteristics of weakly damped resonators.)

IIC (Impact Insulation Class)

E492: Standard Test Method for Laboratory Measurement of Impact Sound Transmission Through Floor-Ceiling Assemblies Using the Tapping Machine (tested in laboratories).

ISO 10140-3:2010: Laboratory measurement of sound insulation of building elements — Part 3: Measurement of impact sound insulation (uses standard tapping machine)

AIIC / FIIC (Apparent IIC / Field IIC)

ASTM E1007: Standard Test Method for Field Measurement of Tapping Machine Impact Sound Transmission Through Floor-Ceiling Assemblies and Associated Support Structures (tested on field).

ISO 10052:2004: Field measurements of airborne and impact sound insulation and of service equipment sound — Survey method
ISO 16283-2:2015: Field measurement of sound insulation in buildings and of building elements — Part 2: Impact sound insulation (tapping machine and rubber ball)
(Note: Survey test methods for field measurements of airborne and impact sound insulation are dealt with in ISO 10052) 


A Class-1 NTI measurement set, comprising:

XL2 Audio & Acoustic Analyzer
M2230 Measurement Microphone
Minirator MR-Pro
Dodec Speaker DS2 Omni-directional sound source
Precision calibrator 94/114 dB & class 1 for 1/2″ Measurement Microphones
Power amp PA3 for Dodec DS2