Weighted Level Difference (Dw) a single integer number found by comparing the measured spectrum with the ‘standard’ curves in BS EN ISO 717 for airborne and impact insulation.
The Dw value is where the curve meets the 500 Hz curve and the unfavourable deviation is 32 dB. Dw will be identical to DnT,w when T = 0.5 seconds.

According to BS 8233, weighted level difference is used to characterize the insulation between rooms in building as they are. Values cannot normally be compared with measurements made under other conditions.

Weighted Normalised Level Difference (Dn,w). The weighted level differences (D) measured on-site, vary due to the different room sizes encountered. Normalising the results to a reference absorption minimises these differences. Dn,w is also known as weighted normalised noise reduction.

Weighted Standardized Level Difference (DnT,w), single number value of the airborne sound insulation between room, used to characterize the sound insulation between rooms in buildings.
On site results will include flanking sound so the test is for the total transmission between the rooms, not just the partition.

Weighted Apparent Sound Reduction Index (R’w) a single number rating of airborne sound insulation between rooms, over a range of frequencies – field measurement.

ISO 16283-1: Field measurement of sound insulation in buildings and of building elements — Part 1: Airborne sound insulation
ISO 717-1: Rating of sound insulation in buildings and of building elements — Part 1: Airborne sound insulation

Noise Isolation Class (NIC) is a single number rating of the degree of speech privacy achieved through the use of an acoustical ceiling and sound absorbing screens in an open office. NIC has been replaced by the articulation class rating method.

The Normalized Noise Isolation Class (NNIC) is the sound isolation performance of a partition measured in the field according to ASTM E336, normalized to account for the reverberation time in the room.

The Apparent Sound Transmission Class (ASTC) is the sound isolation performance of a partition measured in the field according to ASTM E336, normalized to account for different room finishes and the area of the tested partition (i.e. compare the same wall measured in a bare living room and an acoustically dry recording booth).

ASTM E336: Standard Test Method for Measurement of Airborne Sound Attenuation between Rooms in Buildings (tested on field).
ASTM E413-16 Classification for Rating Sound Insulation

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.

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 Noise Rating (NR) serves as a standard way to measure and specify noise in buildings and occupied spaces.

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

The Noise Criterion (NC) were 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 E1686
Standard Guide for Applying Environmental Noise Measurement Methods and Criteria

ASTM E 1374-02: Standard Guide for Open Office Acoustics.

Weighted standardized Impact Sound Pressure Level (L’nT,w) a single number quantity used to characterise the impact sound insulation of floors, based on field measurement of L’nT.

ISO 16283-2: Field measurement of sound insulation in buildings and of building elements — Part 2: Impact sound insulation (tapping machine and rubber ball)

The Apparent Impact Insulation Class (AIIC) is the insulation index of the apparent impact noise of a floor or ceiling assembly on site.

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).

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.

IEC 60268-16: IEC 60268-16 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.