ISO 23351, short for Acoustics - Measurement of speech level reduction of furniture ensembles and enclosures, currently consists of only Part 1: ISO 23351-1:2020 (Laboratory methods). It was officially published on 30 June 2020 as a globally harmonized test and classification standard for the speech privacy performance of silent booths, office pods and telephone booths. It specifically solves the problem that the acoustic performance of modular mobile enclosures could not be objectively compared in the past.

The fundamental differences between ISO 23351-1 and traditional sound insulation standards (ISO 717-1 / ISO 10140) are as follows:

ISO 717/10140 characterize the sound insulation Rₙ,w (sound pressure level difference) of building elements, focusing on blocking external noise from entering the space.

ISO 23351-1 measures the speech sound power reduction DS,A (the reduction in sound power radiated outward from a source inside the booth), which directly quantifies speech privacy and resistance to eavesdropping, making it much more relevant to the actual use of acoustic office pods.

Official grading system (generally used in the acoustic office cabin industry)

ISO 23351-1:2020 is the global gold standard for "voice privacy performance" in acoustic office cabins, and DS,A is a core indicator for measuring "whether others can hear you clearly."