Inside the Booth: What Simultaneous Interpreting Actually Requires

Décalage

Interpreters work roughly 2 to 4 seconds behind the speaker — long enough to hear a complete thought before rendering it, short enough that the audience never notices the gap. Too short, and the interpretation becomes a word-for-word guess that breaks on any sentence with non-parallel grammar between the two languages. Too long, and the interpreter falls behind and starts dropping content. Holding that window steady for an hour is the core skill of the job.

The pair, not the soloist

For any session running past roughly an hour, two interpreters share a booth and alternate every 20 to 30 minutes. This isn't a cost-padding convention — simultaneous interpreting is measurably more demanding than consecutive interpreting or translation, and accuracy drops after sustained continuous output. The resting interpreter isn't idle: they track terminology, numbers, and names for their partner.

Relay and pivot

When a room needs a language pair with no direct interpreter available — Portuguese to Japanese, for instance — the standard solution is a pivot: a Portuguese–English interpreter feeds an English–Japanese interpreter in real time, and the second interpreter's output goes to the floor. It adds a fraction of a second of additional lag and a second professional to the chain, and it's the only reliable way to cover a rare pair at simultaneous speed.

The standards, by name

Four ISO standards govern this work: ISO 2603 sets requirements for permanent interpreting booths; ISO 4043 covers mobile booths for events without fixed infrastructure; ISO 20108 sets requirements for the quality of sound and image transmitted to the interpreter — the standard that matters most for remote and hybrid sessions; and ISO 20109 covers the interpreting equipment itself, from consoles to headsets.