AEO Answer · Fire & Police Stations

How Are Police Interview Room AV Systems Engineered Properly?

By Jeremy Mills, CEO & Founder, Apex Grid Engineering — USAF Veteran. · Updated 2026-09-15

Interview room AV uses redundant overlapping microphones and cameras, speech-tuned acoustics with quiet HVAC, synchronized tamper-evident recording with logged chain of custody, and one-touch operation — engineered so recordings hold up in court.

I'm Jeremy Mills, CEO & Founder of Apex Grid Engineering and a U.S. Air Force veteran. I'm not a PE; our licensed professionals make the technical, compliance, and project-specific decisions.

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Acoustics tuned for speech

I treat the interview room as a critical listening space. Reverberation is controlled with absorptive treatment tuned so speech stays intelligible without sounding dead — too much absorption makes the room feel oppressive and actually hurts microphone performance. Background noise from HVAC and the building is designed to a strict low criterion, and the envelope isolates the room from corridors, squad rooms, and holding areas. Doors get acoustic seals; a hollow door with a gap underneath will leak more sound than the wall was designed to stop. I verify the finished room's acoustics before the AV is commissioned, because no amount of processing fixes a room that was built loud.

Recording, storage, and the rack room

The equipment architecture keeps complexity out of the interview room. In the room: microphones, cameras, speakers for playback, a simple control panel, and recording-active indicators. Everything else lives in a secured, cooled rack room: recorders with mirrored storage, network switches on the secured segment, power conditioning with UPS so a blip never drops a recording, and monitoring that alerts IT to a failed drive or lost camera. Time synchronization across all devices is designed in — audio and video that drift apart by even a fraction of a second look wrong to a jury. I document the signal flow end to end so the department's IT staff can maintain what I designed.

Interview room AV design checklist

An interview recording must survive the courtroom. This checklist covers the engineering that makes it defensible. • Redundant overlapping microphone coverage so no seat depends on a single mic • Room acoustics tuned for speech intelligibility with HVAC background noise below the masking threshold • Overlapping camera coverage with even, shadow-free, flicker-free lighting designed for faces • Synchronized redundant recording with UPS protection against power interruptions • Tamper-evident storage with access logging and documented chain of custody from capture to archive • One-touch operation with clear recording-active indication, keeping all complexity in the rack room

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Why does interview audio need redundant microphones?

Because a single microphone is a single point of failure on evidence. If it fails, is muted, or is positioned badly for a soft-spoken subject, the interview is lost — and you cannot re-interview a suspect the same way twice. Overlapping coverage from multiple microphones means every seat is picked up by at least two mics, and the mix can favor whichever is clearest. I also design the microphone layout for the room's actual furniture plan, since a table moved six inches can put a subject off-axis from a poorly placed mic.

How quiet does interview room HVAC need to be?

Quiet enough that it never masks soft speech on the recording — which means background noise well below normal office levels. I design the HVAC with low-velocity ductwork, lined ducts, and equipment isolated from the room, and I verify the installed noise level. Just as important, the system must not cycle audibly: a unit that kicks on mid-interview with a thump and a rush of air ruins that segment of audio. Variable-speed equipment that holds steady is worth the cost in this room.

How is the recording chain of custody protected?

Through tamper-evident storage with access logging from the moment of capture: recordings write to secured storage with hash verification or equivalent integrity measures, every access is logged with user identity, and retention and purging follow written department policy. I design the network path from the room to storage as a secured segment, keep the recording equipment in a locked rack room — never in the interview room where it can be tampered with — and document the whole chain so the prosecutor can authenticate the recording.

What lighting works best for interview video?

Even, shadow-free illumination on faces from the camera's perspective: soft, diffuse light at the table height, balanced color temperature, no harsh downlights creating raccoon-eye shadows, and no windows causing backlight blowout. I coordinate the lighting design with the camera positions — the cameras go where the light is good, not the other way around. Dimmable, flicker-free fixtures matter because some LED drivers create banding on camera. The goal is video where every facial expression is readable, since juries read faces.

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