ISO 23351 Acoustics - Measurement of Sound Level Reduction of Furniture Assemblies and Enclosures

The “ISO 23351 Acoustics - Measurement of sound level reduction of furniture sets and enclosures” standard, developed by the International Organization for Standardization (ISO), consists of the following subsections published under the same title:

• The standard "ISO 23351-1 Part 1: Laboratory method" describes a laboratory method to facilitate comparisons between furniture ensembles and enclosures regarding their ability to reduce the speech level of a person speaking inside the product. In this method, the sound power level is measured in two scenarios: without the product and with the product.

During the first scenario, the test signal is generated by a sound source in an empty room without the product present. During the second scenario, the test signal is generated by a sound source inside the product at the person's location. Level reduction is the difference between the sound power levels measured in the two scenarios in the 1/1 octave frequency bands between 125 Hz and 8000 Hz. Speech level reduction is a single-number quantity that expresses the corresponding reduction in the A-weighted sound power level of standard speech across the entire frequency range between 125 Hz and 8000 Hz.

The method is applicable to any furniture group or enclosure that serves one or more people and forms a unit used to provide enhanced speech privacy. This method is not intended for single components used in workstations, such as screens, storage units, desks, lighting fixtures, cabinets, bookcases, standard chairs, wall units, or ceiling units.

The test is conducted in an echo chamber. The criteria for the test chamber are contained in the ISO 3741 standard. A product tested according to this standard must have a predefined size, geometry, and bill of materials. Occupant positions must be clearly identifiable. The test specimen must be tested in at least two positions within the test chamber. The distance between the two positions must be at least 1,7 m. The distance is measured from the midpoint of the test specimen. The reported level reduction is the arithmetic average of the position-specific level reduction values.

The test specimen should be installed in the same manner as it would typically be installed for occupant use. Operable components, such as doors or windows, should be in normal operating condition. The pressure drop through ventilation openings should be the same as under normal operating conditions. If the test specimen includes operable components, such as doors or windows, these components should be opened and closed at least five times immediately before testing to ensure proper operation. If the test specimen has several distinct operating conditions, such as those caused by operable doors or windows or adjustable ventilation openings, it may optionally be tested in different positions. The operating conditions should be clearly stated in the test report. A workstation should be tested to include all components used in the specific workplace configuration.

• The standard "ISO 23351-2 Part 2: Field method" describes a method for determining the apparent speech level attenuation of furniture assemblies and enclosures under field conditions that meets an engineering degree of accuracy. This method is applicable to all furniture assemblies or enclosures that can be used by one or more people. This method is not intended for individual components used in workstations, such as a screen, a storage unit, a desk, a lighting fixture, a cabinet, a bookcase, a standard chair, a wall absorber, or a ceiling absorber.

For the purposes of this standard, the following terms and definitions apply:

• Apparent level reduction refers to the frequency dependent measure that describes how much the test object reduces its sound power level in 1/1 octave frequency bands from 125 Hz to 8000 Hz.
• Apparent speech level reduction refers to the reduction in A-weighted speech sound power level caused by the test object.
• Artificial mouth refers to the instrument used as a sound source to measure the apparent level reduction of furniture assemblies.
• An enclosure refers to a single object that provides improved sound insulation for a person moving within it. Examples of enclosures include mobile phone booths for a single person, mobile work booths for one to two people, and mobile meeting booths for several people.
• A furniture ensemble refers to the installation of single furniture or furniture elements that provide improved sound insulation for a person moving within. Furniture ensemble can also be called partial enclosures. Furniture ensemble can include, for example, traditional workstations consisting of screens, storage units, and a desk, workstations, meeting rooms, partially enclosed sofa groups, and partially enclosed chairs.
• The measurement surface refers to the imaginary box-shaped envelope that contains the test object during the second test scenario and the microphone positions or scan paths in both scenarios. The measurement surface is not a tangible object.
• An omnidirectional sound source is an instrument used as a sound source to measure the apparent level reduction of enclosures.

In short, the purpose of the ISO 23351 standard is to provide a standardised method for measuring and comparing the speech level reduction of furniture assemblies and enclosures such as acoustic partitions, workstations and telephone booths to improve speech privacy in environments such as open offices.

Our organization, which has been supporting businesses across all sectors for years through a wide range of testing, measurement, analysis, and evaluation activities, has a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services in accordance with the ISO 23351 Acoustics - Measurement of Sound Level Reduction in Furniture Sets and Enclosures standard.