Acoustic Holography

Microphone Array for Holography and Beamforming

The Fibonacci array represents a new array family allowing near field and far field measurements with the same hardware. Two Baumer VLG22c cameras (one with an extra wide-angle lense for near field measurements) provide optimal reference images. The application area of this array ranges from 30 Hz for holography measurements to 25 kHz for beamforming measurements.

Fibonacci 120 AC Pro
Fibonacci 120 AC Pro: 120 channel system for beamforming and holography applications

Features

  • Supports beamforming as well as holography (HELS and SONAH) applications
  • Very light and stable, acoustically transparent array construction
  • Optimized array design for the highest spatial resolution and map dynamic
  • Effective minimization of partial reflections, sound pressure doubling effects on the surface, and resonance effects between the measured object and the array
  • Calibrated microphones ensuring stable sound pressure levels (+/- 0.5 dB)

Technical Data

Fibonacci 120 AC Pro

  • Array-body diameter: 0.95 m
  • Weight: 10 kg
  • SymBus microphone connectors via differential conditioning
  • Advanced disturbance tolerant ¼” symmetrically buffered electret pressure receivers (based on Sennheiser microphone capsule 4211)
  • Number of microphones: 120
  • Frequency response of the microphones: 20 Hz – 20 kHz (± 3 dB)
  • Dynamic range of microphones: 28 – 130 dB (A-weighted)
  • Acoustic maps from 23 – 130 dB
  • Max. equivalent sound level: 130 dB
  • Symmetrical output resistance: 100 Ω
  • Single map dynamic: 13 – 17 dB (CBF) using HDR 20 – 40 dB
  • Backward attenuation of array: > -20 dB
  • Connecting Array Cable length to data recorder: 1 – 20 m
  • Ingress protection code: IP20
  • Operating environment: 0°– 45°C, up to 80% r.h.
Holography SONAH

  • Recommended measurement distance: 10 – 20 cm
  • Recommended mapping frequencies: 40 Hz – 2 kHz
Holography HELS

  • Recommended measurement distance: 0 – 10 cm
  • Recommended mapping frequencies: 30 Hz – 400 Hz
Beamforming

  • Recommended measurement distance: 80 cm – 10 m
  • Recommended mapping frequencies: 300 Hz – 25 kHz