Aerial “Loudspeaker”: Drone-Based Acoustic Hailing Systems Transform Long-Range Communication

In the advancement of smart-city development and modern emergency management, a new class of equipment that integrates low-altitude aviation platforms with acoustic transmission technology—the drone-mounted acoustic hailing system—has emerged as a pivotal tool for solving long-distance communication challenges. As a core component of low-altitude acoustic communication systems, it combines aerial mobility, wide-area coverage, and high-SPL acoustic projection. Through directional sound-beam design, it eliminates the spatial constraints and blind zones of traditional ground-based loudspeakers.Mounted on drones, the system rapidly reaches complex terrains, dense crowds, or signal-disrupted zones, enabling long-range, high-fidelity voice transmission. It bridges the communication gap between air and ground, becoming an “aerial information terminal” for emergency command, public-order management, and refined urban governance—delivering efficient, flexible, and precise acoustic communication solutions that embody the value of low-altitude and acoustic technologies in modern governance.

A drone hailing system is a high-SPL acoustic projection device mounted on an unmanned aerial platform, designed as a long-range, high-fidelity voice transmission terminal. Its essential function is to deliver voice messages accurately and clearly to designated areas.Taking the RA21Z model as an example, it delivers a peak SPL of 154 dB and a continuous SPL of 144 dB during stable operation. This exceptionally high acoustic intensity forms the fundamental basis for long-range sound propagation.

Sound pressure level is a key indicator of acoustic propagation intensity. Using everyday sound references provides intuitive context:
• Normal conversation is around 60 dB—soft and suitable for close-range dialogue.
• 70 dB resembles the ambient noise of a busy street; intelligible but easily masked by interference.
• A motorcycle engine at about 95 dB creates a harsh mechanical rumble, uncomfortable over time.
• 110 dB is comparable to front-row concert levels, chainsaws, or high-pressure water jets—sharply penetrating and attention-grabbing even outdoors.
• Above 120 dB approaches the threshold of pain, similar to aircraft takeoff noise at close range, with potential for hearing damage.

The RA21Z’s high SPL allows it to maintain strong acoustic output even at several hundred meters to over a kilometer from the source, ensuring clarity and intelligibility at long distances. Its coverage performance extends across multiple dimensions to suit diverse operational scenarios

• Distance Dimension:
  At a typical drone cruising altitude of 100 m, the RA21Z maintains 110 dB within a 200 m radius—a level clearly distinguishable above ambient noise. Even at 1000 m radius, it remains within effective transmission range.
• Area Dimension:
  The system supports multiple operational modes for flexible coverage.
  – Dispersal Mode: covers an area equivalent to 18 football fields
  – Broadcast Mode: covers up to 440 football fields
  This enables both localized warning actions and large-scale public notifications.

Across acoustic performance, coverage capability, platform adaptability, user experience, and environmental robustness, the RA21Z outperforms mainstream products on the market.

• Acoustic Performance: Higher SPL, Superior Voice Fidelity

With a 154 dB peak SPL and 144 dB continuous SPL, the RA21Z exceeds typical industry levels. Its effective acoustic power is 4–8× that of competing products (every 6 dB increase doubles acoustic energy).A wide frequency response of 500 Hz–5 kHz ensures that even at 1 km, output remains around 70 dB, preserving speech clarity and detail while enhancing penetration in noisy environments.

• Coverage Capability: Dual-Mode Switching, Far Greater Efficiency

The RA21Z offers both Dispersal Mode (18-field coverage) and Broadcast Mode (440-field coverage).At a 100 m cruising altitude, it sustains 110 dB within a 200 m radius, remaining effective up to 1 km. Most competitive products support only a single mode, with effective coverage typically limited to a 250 m radius (~28 fields), and SPL dropping below 70 dB at long range. Our system delivers ~15× greater area coverage efficiency.

• Platform Adaptability: Lightweight, Compatible with More Drone Models

The RA21Z uses high-power-density speakers and a lightweight mechanical structure, keeping weight within industry-optimal levels. It is compatible with multirotor, fixed-wing, and hybrid UAV platforms, supporting quick-mount installation and universal interface standards.

Competing systems often:
– support only specific drone models
– require excessive payload capacity
– offer insufficient SPL
– or add weight due to external modules, reducing drone endurance

RA21Z maintains high SPL without compromising flight time, allowing stable integration even on medium- and small-payload drones.

• Intelligent User Experience: Faster, Simpler, More Reliable

Features include real-time broadcasting, onboard voice storage, and one-button mode switching. It supports both remote-controller operation and app control, requiring minimal setup for rapid deployment. Integrated anti-howling algorithms and environmental noise suppression ensure clear audio even in close-range broadcasting. Competitors often rely on proprietary software, suffer from signal blind spots, have limited audio functions, or require multiple setup steps—slowing emergency response. The RA21Z operates without network dependency, enabling instant recording and playback in urgent scenarios.

• Environmental Robustness: Built for Harsh Conditions

With IP65 protection, excellent dust- and water-resistance, and a –20°C to 50°C operating temperature range, the RA21Z includes triple safeguards: temperature, over-current, and power protection. Many competing devices fall at IP54 or lower, are vulnerable to rain and dust, or can’t operate under extreme temperatures. The RA21Z runs reliably in harsh climates, emergency rescue missions, and outdoor inspections—extending service life by 30% or more compared with typical products.

From lifesaving emergency communication to refined smart-city management, drone hailing systems are redefining the boundaries of information delivery. With ultra-high SPL output, flexible dual-mode area coverage, broad platform compatibility, intuitive operation, and robust environmental resistance, our system fully unlocks the value of airborne acoustic communication.

Looking forward, we will continue to advance the integration of acoustics and low-altitude technologies, optimizing product performance and delivering more reliable, efficient aerial acoustic communication solutions for emergency response, public safety, and urban governance—building a more seamless “aerial information bridge” for the cities of tomorrow.