ISO 23351-1:2020

Overview

ISO 23351-1:2020 - Acoustics - Measurement of speech level reduction of furniture ensembles and enclosures - Part 1: Laboratory method defines a reproducible laboratory procedure to quantify how much a furniture ensemble or enclosure reduces the speech level of an occupant speaking inside it. The outcome is a single-number speech level reduction (A-weighted) across the frequency range 125 Hz–8 000 Hz, based on differences in measured sound power levels with and without the product in a reverberation room.

Key topics and technical requirements

• Test principle: Measure sound power level in two scenarios - (1) sound source in an empty room (product absent) and (2) sound source placed at the occupant position inside the product. Level reduction is the per-octave difference (125 Hz–8 kHz).
• Speech level reduction: Single-number quantity representing reduction in A-weighted sound power of standard (genderless) speech across the full frequency range.
• Measurement environment: Tests are performed in a reverberation room complying with ISO 3741.
• Sources: Use an artificial mouth (preferred) or an omnidirectional sound source where required; directivity and specifications follow referenced standards.
• Specimen and positioning: Entire furniture ensembles or enclosures tested as a unity; not intended for single components (screens, chairs, cupboards, absorbers). Each specimen is measured in at least two distinct room positions (≥1.7 m apart) and averaged.
• Reference box: Product placed within a smallest box-shaped surface for consistent comparison.
• Reporting and annexes: Standard requires documented test conditions, instrumentation, and acoustical data; annexes provide calculation examples, precision guidance and application notes for room acoustic design.

Applications and who uses it

ISO 23351-1:2020 is used by:

• Furniture and enclosure manufacturers to quantify and compare acoustic performance of meeting pods, phone booths, workstations, and partially enclosed furniture.
• Acousticians and test laboratories performing standardized lab measurements of speech privacy performance.
• Architects, office planners and facility managers specifying products to achieve target speech privacy in open-plan and activity-based offices.
• Product specifiers and procurement teams evaluating alternatives on a common technical basis.

Practical uses include product selection, R&D for improved speech privacy, certification and marketing claims based on a standardized lab metric, and incorporation of measured values into room-acoustic simulations.

Related standards

• ISO 3741 (referenced) - determination of sound power levels in reverberation test rooms.
• Other ISO building/room acoustic standards (e.g., ISO 3382 series) are relevant for source directivity and reverberation guidance.

Keywords: ISO 23351-1:2020, speech level reduction, acoustics, furniture ensembles, enclosures, laboratory method, speech privacy, sound power level, A-weighted, reverberation room.