On-Air Audio Quality Verification

Broadcast Audio Quality Assurance

Broadcast audio quality depends on the entire signal chain from microphone to transmitter, but the monitoring environment is where all quality decisions are made. If the control room monitors are inaccurate, every mixing and processing decision will be compromised. Broadcast facilities must maintain calibrated monitoring environments that comply with international standards to ensure content sounds correct on consumer playback systems. SonaVyx provides the measurement tools to verify and maintain broadcast monitoring accuracy.

Applicable Standards

• EBU R128: Loudness normalization at -23 LUFS (±1 LU) for program delivery
• ITU-R BS.1116: Methods for subjective listening tests — specifies room criteria
• ITU-R BS.1770: Loudness metering algorithm
• EBU Tech 3276: Listening conditions for monitoring and quality control (RT60 0.2-0.4s, background noise ≤NR 15)

Control Room Verification Procedure

Step 1: Background Noise Verification

Broadcast control rooms require exceptionally low background noise. Use the SPL Meter with the NC curve display to verify compliance with EBU Tech 3276 requirements: NR 15 (approximately 25 dBA) for critical listening rooms, NR 20 (approximately 30 dBA) for general production rooms. The octave band analysis identifies specific noise contributors — computer fans, air handling units, and equipment rack ventilation are common offenders.

Step 2: Room Acoustics

Measure RT60 using the RT60 tool at the mix/monitoring position. Per EBU Tech 3276, the target RT60 is 0.2-0.4 seconds depending on room volume, with the ratio of RT60 across octave bands remaining within ±10% of the mid-band average. This frequency-independence of RT60 ensures the room does not color the tonal balance of program material. Measure at the primary monitoring position and at secondary positions used by producers and directors.

Step 3: Monitor Frequency Response

Use the Transfer Function to measure each monitor speaker individually at the listening position. The target is ±2 dB from 80 Hz to 16 kHz within the primary listening window. Measure left and right monitors separately, then both together to verify stereo imaging is not compromised by asymmetric room response. Check for low-frequency issues using the RTA mode with 1/12 or 1/24 octave smoothing to identify room modes that may require bass management or EQ correction.

Step 4: Reference Level Calibration

Broadcast facilities maintain reference monitoring levels — typically 85 dBC SPL for film/TV (per SMPTE RP 200) or 79 dBC for smaller rooms. Use the SPL Meter with C-weighting to verify that the monitor controller produces the correct SPL when fed a -20 dBFS pink noise reference signal. Each monitor should produce within ±0.5 dB of the target level. Document the monitor controller position and gain settings for the reference level.

Step 5: Comprehensive Assessment

Run the AI Diagnostic engine on the combined measurement data. For broadcast environments, the diagnostic evaluates frequency response flatness against tighter tolerances than live sound, checks for asymmetry between left/right monitors, identifies room modes, and assesses whether the noise floor is sufficient for the room's intended use (critical monitoring vs. general production).

Target Metrics for Broadcast Monitoring

• Background Noise: NR 15 (≤25 dBA) critical listening, NR 20 (≤30 dBA) production
• RT60: 0.2-0.4s (frequency-independent within ±10%)
• Monitor Response: ±2 dB (80 Hz - 16 kHz) at listening position
• L/R Symmetry: ±1 dB between left and right monitors
• Reference Level: 85 dBC (film/TV) or 79 dBC (small room) ±0.5 dB

Ongoing Quality Verification

Broadcast monitoring environments should be re-verified quarterly or after any room modifications. Use SonaVyx's Trending feature to track monitor response over time. Gradual degradation in high-frequency response may indicate driver fatigue, while changes in low-frequency response often point to room modifications or HVAC changes. The trending data provides early warning before monitoring accuracy degrades enough to affect on-air quality.