52 dBA of HVAC, Glass Block Daylight, and a Soft-Spoken Witness on Glasses
A hearing is held in a converted municipal courtroom: 10-ft acoustic-tile ceiling, carpet, a supply return that measures 52 dBA at the witness stand, and an audible 120 Hz hum. The witness is soft-spoken and sits 8 feet from the camera. The examining attorney projects and sits 4 feet to the witness's left, just outside the frame. One wall is glass block admitting daylight; the wall behind the witness is dark walnut paneling. The witness wears rimless glasses. You have one camera with two XLR inputs, a lavalier, a cardioid shotgun, a boundary mic, and one 1x1 LED panel with a softbox. House lights are dimmable fluorescents.
1. Choose and justify a microphone strategy using only the gear listed, including gain structure and redundancy.
Read the worked answer
The two voices have opposite problems: the witness is close but quiet, the attorney is loud but off-camera. One mic cannot serve both well.
- Primary - lavalier on the witness, clipped high on the lapel or collar with a strain relief loop. It is the only option that keeps the witness's level constant as he turns his head, which matters given the room's low ceiling and reflective paneling.
- Second input - boundary mic on the table between witness and examiner, positioned to pick up the attorney's questions without being in frame. A shotgun from the camera position would be working at 8 feet through room reflections and would favor whoever faces the lens.
- Gain: set the witness channel so normal speech peaks around -12 dBFS, leaving headroom for laughter or a raised voice; set the attorney channel lower. Record 24-bit/48 kHz.
- Redundancy: use the camera's second track at a lower level as a safety against clipping, and check the hearing aid for feedback or clothing rustle before going on record.
Test both channels through headphones, not by looking at meters alone.
2. The glass block is directly behind the witness and he wears rimless glasses. Describe your lighting decision and the specific failure modes you are preventing.
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The backlight is the problem, and the glasses are where the mistakes become visible.
- Do not light into the window. Flag, diffuse, or simply block the glass block if the room allows, or reposition so the window is a rim rather than the background. Otherwise the camera exposes for the window, and the witness becomes a dark silhouette against a white field - the classic unwatchable legal video.
- Key light close and high: LED with softbox about 45 degrees off the lens axis, just above the witness's eye line, at a distance where the source is large relative to his face. Soft, not merely bright.
- Glasses: raise the key and angle it downward so the reflection leaves the frame; if a reflection persists, ask counsel - on the record - whether the witness can adjust his chin slightly. Never wave your hand at the witness yourself.
- Color and flicker: color-match the LED to the ambient (tungsten-balanced panel against daylight will read orange), white balance on a gray card under final conditions, and set shutter to the local mains standard to avoid fluorescent and LED flicker bands.
Every one of these is visible to a jury months later; none can be fixed in post.
3. The 120 Hz hum and the air handler bother you. How far can you go in reducing them, and how do you document what you did?
Read the worked answer
You can reduce noise; you may not quietly alter the substance of the record.
- Ask first, through the proper channel. Request via counsel, on the record, that the air handler be switched off for the session. If the building refuses, note the refusal and the time.
- Move what you control: reposition the boundary mic away from the return, orient the cardioid's null toward the vent, and keep cables away from dimmer packs and power runs that add hum.
- Record room tone for 30 seconds at the start and after any change, so a later reviewer can tell what the room sounded like.
- Post-processing: a high-pass or narrow notch can be defensible for monitoring or for a separate listening copy, but it must be documented and must not strip speech energy. If the deliverable is presented as the unaltered original, deliver the unaltered original.
The safe rule: any processing that touches the evidence is disclosed in writing with the deliverable, and the untouched master is preserved.