ASTM E413-22 Classification for Sound Insulation Rating

The standard "ASTM E413-22 Classification for Sound Insulation Ratings" developed by the American Society for Testing and Materials (ASTM) describes methods for calculating single-number acoustic ratings for laboratory and field measurements of sound attenuation obtained in one-third octave bands.

The name given to a single-numbered rating is assigned by the test method that calls this rating. Test methods that call this rating include:

Test method E90: The single-numbered rating is called the sound transmission class.
Test method E336: The single-numbered ratings are noise insulation class, normalized noise insulation class and apparent sound transmission class.
Test method E596: The single-numbered rating is called the noise insulation class.
Test method E1414: The single numbered rating is called the ceiling attenuation class.

These single-number ratings are generally related to subjective impressions of sound transmission for speech, radio, television, and similar noise sources in offices and buildings. This classification method is not suitable for sound sources that have spectra that differ significantly from the sources listed above. Such sources include machinery, industrial processes, bowling alleys, power transformers, musical instruments, many music systems, and transportation noise such as motor vehicles, aircraft, and trains. For these sources, an accurate assessment of sound transmission requires a detailed analysis across frequency bands. A single-number sound transmission rating for building facade elements is given in ASTM E1332-22 Standard Classification for Outdoor-Indoor Sound Attenuation Rating.

The resulting single-figure ratings can be used to compare the potential sound insulation of partitions or floors tested under laboratory conditions, or the actual sound insulation between different suites in buildings. A partition constructed and tested in a building may have a lower rating than a partition tested in a laboratory due to side transmission or construction defects.

A similar rating procedure, described in the standard “ISO 717-1 Acoustics - Rating of sound insulation in buildings and structural elements - Part 1: Airborne sound insulation”, provides single-figure sound insulation ratings with a frequency range extending from 100 to 3150 Hz, with no maximum deficiencies specified for individual frequencies. For most partitions, the two ratings differ by only one or two points.

The procedure for classification is determined as follows:

The reference contour is defined by the set of values specified in the table provided in the standard.
The data to which the contour is to be fitted is rounded to the nearest integer. The degree of the contour in the table is zero. Other contours can be derived by adding the same integer to all values in the table.
The reference contour is fitted to the data by simultaneously increasing all values in the table in 1 dB increments until some of the data are less than the shifted reference contour.
The difference between the shifted reference value and the data at each frequency is calculated. If a measured data point is less than the reference contour, it is a defect, only defects are counted in the fitting procedure. The reference contour values are continued to be increased to the highest level that meets the following conditions:
- The sum of the deficiencies is less than or equal to 32 dB
- The maximum dropout at any frequency does not exceed 8 dB.
The single-number evaluation is given by the value of the shifted reference contour at 500 Hz.

For the presentation of results it is recommended that the data be plotted on the scale sizes recommended in this standard, together with the shifted reference contour. Such a presentation draws attention to the frequency regions of the data, which limit the single-number gradation. The recommended graphic scale sizes are 2 mm/dB for the ordinate and 10 mm per 1 to 50 frequency ratio for the logarithmic abscissa. It is recommended that the ordinate scale starts at 0 dB. If larger or smaller scale sizes are unavoidable, it is recommended to maintain the same aspect ratio of 10 dB per 1 to 25 frequency ratio.

Sound insulation ratings are usually classified using standardized systems that measure how well a material or building component (such as a wall, floor, or window) blocks or reduces sound transmission. The most common classification systems include the ASTM E413-22 standard, sound transmission class system. This standard provides a method for classifying the sound insulation performance of building elements using this system.

The sound transmission class is a single-number rating that indicates how well a building partition reduces airborne sound transmission. It is measured in decibels (dB). The higher the sound transmission class, the better the sound insulation.

The calculation method in this system includes the following steps:

Sound transmission loss is measured at standard frequencies (typically 125 Hz to 4000 Hz).
Sound transmission loss values are plotted to form a curve.
The sound transmission loss curve is compared with a standard reference contour defined in the standard.
The contour is shifted up or down the measured sound transmission loss curve by the following values:
- The contour does not exceed more than 8 dB at any frequency.
- Their total negative deviation is not more than 32 dB.
The degree of sound transmission loss is the value after the reference contour has been optimally shifted.

The degree of sound transmission loss is interpreted as follows:

25: Normal conversation is easily heard (thin walls or uninsulated doors)
Between 30-35: Loud speech is understandable (basic interior walls)
Between 40-50: Loud speech is only faintly audible (good residential walls/floors)
Between 50 and 60: Loud sounds are barely audible (luxury apartments/offices)
Above 60: Excellent insulation (recording studios, luxury venues)

Sound transmission loss focuses on mid- and high-frequency sound, so it may not adequately represent low-frequency noise, such as bass, HVAC hum, or traffic noise.

Our organization, which has been trying to support businesses from every sector with its testing, measurement, analysis and evaluation studies carried out in a wide range for years, has a strong staff that closely follows the developments in the world in the field of science and technology and constantly improves itself. In this context, testing services in accordance with the "ASTM E413-22 Classification for Sound Insulation Rating" standard are also provided to businesses.