What Is Array Beamforming?
Array beamforming is a powerful acoustic technology used to "listen" to the ocean. It helps scientists detect and track marine mammals by filtering out background noise and pinpointing the direction of underwater sounds. Think of it as a highly sensitive underwater microphone system that can focus on specific sounds while ignoring others.
Why Use Arrays Instead of a Single Microphone?
A single underwater microphone (called a hydrophone) represents what we now consider a Gen 2 approach to ocean listening. While it can pick up sounds, it struggles in noisy environments and lacks directional awareness.
Modern beamforming arrays – Gen 3 and Gen 4 technologies – offer a transformative leap forward:
- Noise Rejection: Filters out unwanted sounds from ships, wind, and other marine life.
- Directional Listening: Determines where a sound is coming from, helping locate vocalizing animals.
This is achieved through a process called beamforming, which combines signals from multiple hydrophones to enhance sounds from a specific direction while suppressing others.
How Does It Work?
Arrays use spatial filtering to isolate sounds. Here's how:
- Aperture Length & Sensor Spacing: The size and spacing of the hydrophones affect how well the array can "focus" on sounds.
- Frequency Sensitivity: Arrays are tuned to detect low-frequency whale calls.
- Shading Functions: These mathematical tools help refine the array's listening ability.
The result? A system that can detect whale calls more consistently, at longer distances, and with more precision than Gen 2 single hydrophones. Many of the calls immediately apparent to array detection would be nearly invisible to earlier-generation systems.
Built for the Ocean
Designed and manufactured to industry-leading standards, ThayerMahan's arrays represent the peak of linear array performance – Gen 4 and beyond.
- Variants: 32-channel and 64-channel models
- Design: Low-drag, laminar flow hydrophone jackets
- Precision Sensors: Measure heading, depth, and pitch
- High Sensitivity: Detects faint whale calls with -199 dBV re 1μPa sensitivity
- Efficient Power Use: Less than 2W total for a 32-channel array
What Can We See with Beamforming?
Beamforming produces rich visual data products:
- BTR (Bearing-Time Record): Shows when and where sounds occur.
- FRAZ (Frequency-Azimuth Surface): Displays sound energy by direction and frequency.
- Scissorgram: Like a spectrogram, but tracks sound along a directional path.
These tools help researchers visualize and interpret underwater soundscapes in real time – capabilities that simply weren't possible with Gen 2 systems.
Real-World Impact
Real-World Impact
Beamforming arrays have revolutionized marine mammal monitoring: Beamforming arrays are a generational leap in marine mammal monitoring
- Detection Range: Up to 3–10x farther than single hydrophones
- Area Coverage: Up to 100x greater
- Localization: Multiple arrays can triangulate whale positions
- Density Estimation: Measure how many animals are vocalizing in an area
For example, in a 1.5-hour period in the Kauai-Ni'ihau Channel, a single hydrophone detected 599 whale vocalizations. A beamforming array detected 6,899 - a dramatic improvement.
Why It Matters
With increasing offshore wind development and other human activities, ocean noise is rising. This makes it harder to hear and protect endangered species like the North Atlantic Right Whale. Beamforming arrays help overcome this challenge by:
- Filtering out human-made noise
- Enhancing detection of faint whale calls
- Supporting conservation through better data
Array beamforming is a game-changer in ocean acoustics. By combining advanced engineering with smart signal processing, it allows scientists to hear the ocean more clearly, detect marine mammals more reliably, and protect their habitats more effectively.
Whether you're a curious learner or a seasoned researcher, this Gen 4 technology opens a window into the underwater world - one sound at a time.
