Sports Arena: PA Coverage Across 15,000 Seats

The Challenge: 12 dB Variation Across 15,000 Seats

The Metro Arena, a 15,000-seat multi-purpose indoor venue, hosted everything from basketball games to concerts and corporate events. While the main distributed speaker system was installed during construction five years earlier, complaints about sound quality had grown steadily. Specific issues included: announcements that were deafening in the lower bowl but inaudible in the upper tier, unintelligible speech under the balcony overhang, and a noticeable echo effect in the delay ring coverage zone.

With a major international event approaching, the arena management commissioned a comprehensive acoustic survey and system optimisation to bring the PA up to professional standards.

Measurement: 50-Position SPL Survey

Using SonaVyx SPL metering with A-weighted Leq measurement at 50 positions distributed across all seating tiers, the engineering team mapped the sound pressure level distribution throughout the arena. Pink noise at the system's normal operating level was used as the test signal.

The SPL map revealed severe coverage inconsistencies:

• SPL range: 80 dBA (upper tier rear) to 92 dBA (lower bowl front) — a 12 dB variation
• Under-balcony seats: 78 to 82 dBA, consistently 8 to 10 dB below adjacent unobstructed seats
• Delay ring coverage: Erratic levels with localised hot spots and nulls

Complementary STIPA measurement at 20 critical positions showed:

• Average STI: 0.48 (below the 0.50 minimum)
• Under-balcony worst case: 0.35 (bad)
• Upper tier rear: 0.42 (poor)
• Lower bowl centre: 0.62 (good)

Diagnosis: Three Coverage Gaps

The SonaVyx AI diagnostic identified three distinct problem zones:

1. Under-balcony shadow zone: Approximately 2,000 seats received no direct sound from the main cluster. The balcony soffit blocked the line of sight to the central speaker arrays. These seats relied entirely on reflected sound, resulting in low levels and poor intelligibility.
2. Delay ring misalignment: Impulse response measurement at 8 delay ring positions showed timing errors ranging from 8 to 22 ms. The delay settings appeared to have been calculated from architectural drawings rather than measured, and the main cluster's acoustic centre did not match the assumed position.
3. Level imbalance between tiers: The main cluster was aimed primarily at the lower bowl, with insufficient tilt toward the upper tier. The inverse-square-law level reduction with distance was not compensated.

Solution: Fill Speakers, Delay Correction, Zone EQ

• Under-balcony fill speakers: 12 compact ceiling-mounted speakers installed under the balcony soffit, each covering approximately 160 seats. Level and delay individually set using SonaVyx measurements.
• Delay ring realignment: All 8 delay ring zones re-measured with SonaVyx IR delay finder and corrected to within ±1 ms of the target arrival time.
• Zone-specific EQ: Transfer function measurements at representative positions in each zone guided targeted EQ corrections: high-frequency boost for the upper tier (compensating for distance and air absorption) and low-mid reduction for the lower bowl (reducing reverberation from the nearby concrete surfaces).

Results: 4 dB Variation, 100% STI Compliance

Before/after comparison at all 50 SPL positions and 20 STI positions:

Metric	Before	After
SPL variation (50 positions)	12 dB	4 dB
Minimum SPL	78 dBA	85 dBA
Maximum SPL	92 dBA	89 dBA
Average STI (20 positions)	0.48	0.58
Minimum STI	0.35	0.51
Under-balcony STI	0.35	0.55
Positions below STI 0.50	9 / 20	0 / 20

The 4 dB variation represents a 67% improvement and meets the industry best-practice target of 6 dB or less. Every measurement position now exceeds the 0.50 STI minimum. The under-balcony seats experienced the largest improvement, going from an average of 0.35 to 0.55 STI — a transformation from unintelligible to clearly understandable.

Lessons Learned

• Measure at enough positions: The 50-position SPL survey revealed coverage patterns that a handful of measurements would have missed. The SonaVyx trace store feature made comparing all 50 positions efficient.
• Under-balcony areas always need fill speakers: No main system adjustment can overcome a physical acoustic shadow. Dedicated fill speakers are the only solution.
• Delay settings must be measured, not calculated: Architectural drawing dimensions do not account for the acoustic centre offset of speaker arrays or the actual propagation path. SonaVyx IR-based delay measurement provided the true values.
• Zone EQ is essential at scale: Different seating tiers in a large arena have different acoustic environments. A single system EQ cannot optimise for all zones simultaneously.