4.3 Multi-Channel Assignment and Channel Isolation

What multi-channel recording does

A channel is a distinct audio path stored separately or separately addressable within the recording. Multi-channel capture can place the judge, witness, counsel tables, and other sources on different tracks. During playback, a transcriber can emphasize one track and reduce competing sources. The U.S. Courts digital-audio guidance describes channel isolation as the ability to listen to one channel while turning off others and identifies four-channel capability as a federal courtroom baseline, subject to specified exceptions. That federal requirement is useful context, not a universal rule for every AAERT assignment.

Plan the map

Build the map from actual participants and room geometry. A common conceptual plan might be:

The labels are examples; follow local naming standards. Additional channels might cover jury voir dire, interpreter, lectern, public comment, remote return, or backup mix. Do not label a track with a participant's role until the physical input is verified. A swapped cable can make a neat screen label dangerously wrong.

The assignment should maximize useful separation without creating unmanageable complexity. Feeding every microphone equally to every track defeats isolation. At the other extreme, placing a mobile speaker on only one fixed microphone can lose speech when the person moves. Coordinate seating, microphone coverage, and participant instructions.

Isolation is not silence

Microphones in the same room will capture some sound from other sources. Acoustic bleed differs from accidental electronic duplication. Bleed arrives through the air and changes with distance and room acoustics. Electronic duplication may produce nearly identical waveforms on several tracks because routing sends one input everywhere. Listen and inspect routing rather than assuming all shared sound is an error.

Useful isolation depends on:

• close, appropriate microphone placement;
• sensible pickup patterns;
• moderate gain that does not amplify the whole room unnecessarily;
• physical distance between sources when feasible; and
• correct bus, input, and track assignments.

Remote and hybrid routing

A videoconference creates at least two directions: local voices sent to remote participants and remote voices returned to the room. The recording needs both without feeding the far end back into itself. An echo-cancelled conference output, a platform's isolated tracks, or an approved mix-minus design may be used depending on the system. The reporter need not design an advanced broadcast system on the exam, but must recognize the hazards:

• the room hears the remote witness, yet the recording software receives only local microphones;
• the same remote source is recorded on multiple delayed paths, causing echo;
• a laptop's built-in microphone duplicates the installed room feed;
• headphones monitor the platform, not the file being written; or
• an automatic input change after reconnection sends audio to an unarmed device.

Test by speaking from each source and playing back the recorded track, not merely watching meters.

Document and monitor

A channel map should connect physical microphone, interface input, software track, and participant area. Include it in the job setup or approved notes so relief staff and transcribers can understand the record. When participants move, an interpreter joins, or a sidebar begins, reassess coverage and annotate the change.

During the proceeding, solo or isolate channels briefly under the approved monitoring method to verify that each remains healthy. Never mute an active track in the recording while intending only to mute it in headphones. Know the difference between monitor mute, input mute, track arm, and solo controls.

Failure reasoning

If the witness track fails but other microphones contain intelligible witness bleed, preserve all files and report the fault. Do not claim the intended channel worked. The presiding authority determines how to proceed; the reporter can explain the technical facts and available capture. If no usable source exists, prompt action prevents a longer unrecoverable gap.

Exam application

Suppose Channel 2 is labeled WITNESS but playback reveals counsel, while Channel 3 carries the witness. Do not relabel only the screen and forget the job history. Verify the physical route, correct the map through the approved process, and tell downstream users which interval used the earlier labels. If the audio itself is complete, transparent documentation can preserve usability. Concealing the swap or moving audio destructively between master tracks would create a larger integrity problem than the original configuration error.