Simultaneous Interpretation

12 min read·Last updated 1 September 2026

Simultaneous interpretation is the rendering of a speech into another language, orally and in real time, by an interpreter. It requires a different skill, a different kind of preparation and usually a different technical setup from written translation.

What is simultaneous interpretation?

While the speaker talks, the interpreter listens, understands and delivers into the target language at the same moment. There is no pause between the two: before the speaker has finished a sentence, the interpreter has already said its first half. This is work beyond knowing two languages; it demands the ability to sustain listening and speaking at once.

Its most familiar form is live broadcasting: when a speech is given at an international summit, you hear its equivalent in your own language as it happens. At conferences with foreign participants, interpretation booths are installed. The real-time interpretation carried out in those booths lets the speakers and guests in the hall understand each other instantly.

Simultaneous versus consecutive

The two services are often confused, yet the choice directly determines the duration, the cost and the setup of your event. The basic distinction is this: in simultaneous interpretation the speech does not stop; in consecutive interpretation it does.

When deciding, ask one question: is the duration of the event fixed? If your programme is planned to the minute and speeches cannot be broken up, simultaneous interpretation is required. If the programme is flexible and the audience is small, consecutive is both simpler and less costly.

Where is it used?

Simultaneous interpretation is used wherever speech cannot be stopped, or where stopping it would be costly.

Technical setup

Simultaneous interpretation cannot be delivered without the right setup. If the interpreter cannot hear the room cleanly, quality falls regardless of the interpreter. That is why, in planning an event, the setup matters as much as the choice of interpreter.

1. 01

   The booth

   A sound-insulated booth lets the interpreter work unaffected by room noise and keeps their own voice out of the hall. A view of the stage matters: the speaker's gestures and the presentation screen complete the meaning.

2. 02

   Audio source

   The feed to the interpreter should come directly from the sound desk, not from the hall speakers. Speaker audio carries reverberation and reduces intelligibility.

3. 03

   Receivers and headsets

   Listeners follow the interpretation on channel-selectable receivers. The number of participants and languages determines how many receivers are needed.

4. 04

   Technical support

   Having a technician monitoring the setup throughout means a channel or microphone problem during the session is resolved in minutes.

5. 05

   Rehearsal

   Levels, channels and the booth connection are tested before the event begins. Where no rehearsal happens, problems surface during the first speech.

Why two interpreters?

Simultaneous interpretation carries a continuous and intense cognitive load: the interpreter speaks while listening and listens while speaking. The period over which that load can be sustained without a break is limited. This is why international practice places two interpreters in the booth, working in rotation at set intervals.

An interpreter who does not rest begins to compress: first the details go, then the subordinate clauses. This is not a shortcoming of the interpreter but the nature of the work. For short sessions a single interpreter may be enough; for full-day programmes two is standard. Share your programme with us and we will determine together how many are needed.

interpreters per booth on full-day programmes

2interpreters per booth on full-day programmes

a separate receiver channel per target language

1 channela separate receiver channel per target language

chances the listener has to rewind

0 replayschances the listener has to rewind

Preparation before the event

The quality of simultaneous interpretation depends largely on how well the interpreter could prepare beforehand. An interpreter who has seen the speech in advance enters the booth having researched the terminology and knowing where the speaker will place emphasis.

Confidentiality of these documents is not an obstacle: materials sent are used solely for preparation and are not shared after the event. If you would like a confidentiality agreement signed, simply say so at the outset.

What determines quality?

Quality here is not measured word by word. For the listener there is only one test: could they understand what the speaker said, while the speaker was saying it? Meeting that test depends on four things.

1. 01

   Intelligibility

   Tone, pace and pronunciation have to be followable. An interpretation that is accurate but not understood does not exist as far as the listener is concerned.

2. 02

   Completeness

   The main argument and the critical details must both come through. Numbers, dates and names cannot be dropped.

3. 03

   Managing the lag

   How many seconds the interpreter stays behind the speaker is a matter of balance. Too close distorts meaning; too far behind makes the interpretation impossible to follow.

4. 04

   Command of the field

   In a technical session a term must be recognised the instant it is heard; there is no time to think. That is why the interpreter is chosen to match the field of the event.

How is it priced?

Unlike written translation, interpretation is calculated on time rather than pages. The factors that determine the price are the duration of the event, the language pair, the number of target languages, how many interpreters are required, the city and whether the technical setup is included.

Because these vary from one event to the next, we do not quote a figure here. Send us your programme and language requirements; we will prepare two quotes, with and without equipment, so you can compare if you would prefer to source the setup from your own supplier.

Language combinations at multilingual events

For an event with a single foreign language the setup is simple: one booth, two interpreters, one receiver channel. As the number of languages rises the setup does not grow in a straight line; which language is rendered into which becomes a planning question of its own.

In practice there are two approaches. In the first, a booth working directly in each language pair is installed for every target language. In the second, relay is used: one booth renders the source into a common language, and the other booths work from that rendering into their own targets. For language pairs where interpreters are hard to find, relay may be the only workable route.

Common planning mistakes

Most problems in simultaneous interpretation begin not on the day but in the planning. The points below are the easiest to fix and the most frequently skipped.

1. 01

   Briefing the interpreter at the last moment

   If the programme was settled a week earlier, there is no reason for the presentation files to arrive on the morning of the event. A draft sent early is worth more than a final version sent late.

2. 02

   A booth with no view of the room

   Placed at the back of the hall without sight of the screen, the booth gives the interpreter sound alone. An interpreter who cannot see the slide the speaker is pointing at cannot carry a reference to the table on screen.

3. 03

   Forgetting video and recorded audio

   If the audio of a video in the programme is not fed to the booth from the desk, the interpreter works from the reverberant sound of the hall speakers. Sending the video's script in advance is the safest route.

4. 04

   Leaving question time unplanned

   Questions from the floor are often asked without a microphone and never reach the booth. Providing a roving microphone, or having the moderator repeat the question, saves this part of the session.

5. 05

   Leaving break times to the speaker

   Handovers inside the booth happen at set intervals. Where the programme has no natural pauses, the handover lands mid-speech and listeners read the change of voice as a break in continuity.

What to watch for by type of event

What simultaneous interpretation demands varies with the type of event. The table below shows the factor that governs planning for the event types we work on most often.

Once you share the type and the programme of your event, we determine together which factor governs the planning. This is one of the rare cases where a ten-minute conversation at the quotation stage saves hours on the day.

Hybrid events: the hall and remote participants together

A share of events now runs both in a hall and online. For simultaneous interpretation that means handling two audiences at once: participants in the room listening on receivers, remote participants on the platform's interpretation channel. Carrying the same interpretation to both channels without lag adds a layer to the setup.

The critical point in a hybrid setup is which audio the interpreter hears. If the interpreter is in a booth in the hall, the remote speaker's audio has to be fed directly into the booth; picked up from the hall speakers, that remote sound arrives twice compressed and reverberant. In the reverse case, where the interpreter joins remotely, every microphone in the hall has to be connected to the broadcast feed.

Rehearsal matters more at hybrid events than at single-venue ones, because problems usually arise not in one device but in the link between devices. Testing both channels under real participant conditions beforehand prevents the kind of failure that cannot be recovered mid-session.

Frequently asked questions