Acoustic pods are usually sold on a single headline number — sound insulation in decibels — but that figure alone says surprisingly little about whether a pod will actually work for its intended use. A booth can block plenty of outside noise and still be a poor place to take a call, or reduce noise well but leave conversations inside muddy and hard to follow. Understanding the four numbers that actually matter makes it much easier to compare pods on paper.

Sound Insulation Tells You What Stays Out, Not What Happens Inside

Sound insulation, usually written as DS,A and measured in dB(A), describes how much external noise a pod's shell attenuates. Finch's Silent Bubble is rated at ≥30dB(A), which is enough to bring typical open-plan office background noise (55–65dB) down to a level well below normal conversation volume inside the pod. This figure matters for privacy — it is what stops a call inside the pod from being overheard outside, and what keeps office chatter from bleeding in — but it says nothing about how clear speech sounds once you're inside.

Speech Transmission Index (STI) Is the Number That Predicts Call Quality

STI, scored from 0 to 1, measures how intelligible speech remains after passing through a space's acoustics and any electronic transmission chain. An STI of 0.85 or higher (Silent Bubble's rating) sits in the "excellent" band under IEC 60268-16, meaning a listener on the other end of a video call hears clear, natural speech rather than a boxy or muffled voice. A pod can have strong sound insulation and still deliver a poor STI if its internal surfaces cause excessive reflection or resonance — which is why the two figures need to be read together, not as substitutes for each other.

Reverberation Time (RT60) Is What Makes a Pod Feel Comfortable to Talk In

RT60 measures how long sound takes to decay by 60dB after the source stops — in plain terms, how "boomy" or "dead" a space sounds. Silent Bubble's 0.3–0.4 second RT60 sits in the range recommended for small meeting and call spaces: long enough that the room doesn't feel unnaturally muffled, short enough that voices don't echo or blur together on a recording. This is also the figure that matters most for anyone using a pod for podcast recording or voiceover work, where excessive reverberation is the hardest artefact to remove in post-production.

Ventilation Noise Is the Spec Most Pods Don't Publish

A well-sealed, well-insulated pod with a noisy fresh-air fan defeats its own purpose within twenty minutes of continuous use. Silent Bubble's fresh-air system is rated at ≤30dB(A) during operation — quiet enough that ventilation noise doesn't become audible on a call or a recording, and low enough that the pod remains comfortable for extended single-person use without the stuffiness that under-ventilated booths develop.

Reading a Pod's Spec Sheet

Taken together, these four figures — sound insulation, STI, RT60, and ventilation noise — describe a pod's acoustic performance far more completely than sound insulation alone. A pod intended for calls, video meetings, focused work, or recording should be evaluated against all four before installation, particularly in open-plan offices where a single poorly-specified pod can undermine confidence in acoustic solutions generally.

Finch Electronic Solutions — Melbourne, Australia
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