Acoustic Privacy for Open Space Offices, Phone Booths, and Mobile Pods : Why ISO 23351 Sets the New Standard

What is ISO 23351?

ISO 23351-1:2020 is an international standard designed to measure how effectively a small enclosed space can reduce the spread of speech to its surroundings.

The main parameter it uses is:

DS,A – Speech Level Reduction
(Measured in decibels — dB)

A higher DS,A value means better speech privacy, which is increasingly important in modern open-plan offices and collaborative workspaces.

Why Speech Privacy Matters in Today’s Offices

Open-plan offices may encourage collaboration and optimize space usage, but they also come with acoustic challenges:

Overlapping conversations
Lack of private zones for sensitive discussions
Reduced ability to concentrate due to background noise

This is where dedicated enclosed spaces — such as meeting rooms, management cabins, or high-partition desks — need to meet certain speech isolation criteria. ISO 23351 provides an objective benchmark for evaluating how effective these spaces are at providing acoustic privacy.

How ISO 23351 Measures Acoustic Performance

The standard quantifies:

DS,A – Speech Level Reduction
(How much conversational sound is blocked from escaping the enclosed space)

ISO 23351 Performance Categories

Category	DS,A (dB)	Speech Privacy Level
A	≥ 30	Excellent – Conversations not audible
B	25 – 29	Very Good – Only faint speech cues heard
C	20 – 24	Moderate – Speech is unclear but audible
D	15 – 19	Poor – Speech is intelligible
E	< 15	No Privacy – Clear conversational leakage

Practical Applications of ISO 23351 in Office Design

1. Assessing Existing Enclosures

The standard is useful for evaluating if existing spaces like small meeting rooms, HR offices, or executive cabins are performing well in terms of acoustic containment.

2. Guiding Partition and Wall Selection

ISO 23351 supports architects and project teams in selecting acoustically tested partitions or demountable wall systems, instead of relying solely on thickness or materials.

3. Inclusion in Tenders and Green Building Criteria

The DS,A value can serve as an official acoustic performance indicator in design specs, especially for:

LEED, WELL, or GBI certifications
Government or corporate project tenders

Latest Applications: Privacy Pods & Phone Booths

With open-plan offices becoming the norm, many companies have turned to privacy pods, mobile work pods, or phone booths to regain acoustic separation without permanent construction.

ISO 23351 is the defining benchmark used by manufacturers and designers to demonstrate how well their enclosures prevent speech leakage — crucial in determining whether a phone booth or pod truly supports private conversations.

Tip: Not all pods are created equal. Always ask for the DS,A rating if you’re comparing acoustic pods or booths for your office.

Conclusion

In the age of hybrid work and open-concept layouts, acoustic privacy is no longer optional. It plays a vital role in maintaining productivity, confidentiality, and employee wellbeing.

ISO 23351-1 offers a clear, measurable framework for designing and assessing these spaces — from full-height partitions to modular pods. With speech privacy being a critical factor in modern work environments, this standard is fast becoming an essential tool in the architect’s acoustic playbook.