Acoustic holography is an excellent technique to visualize structure borne sound. It requires the microphone array to be positioned in the near field of the sound source. With a near field microphone array like the Fibonacci the holography methods SONAH and HELS can be used to generate acoustic maps of the sound pressure, sound intensity or particle velocity. Due to its microphone layout and both wide angle and normal cameras the Fibonacci not only excels at standard beamforming but also at near field acoustic holography.

Fibonacci AC Pro
72 / 96 / 120 channel system 

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. This array can be operated with the mcdRec data recorder.

Array body diameter79 x 79 x 17 cm
Weight9 kg
Video camera

2x Baumer VLG-22C (1x wideangle lens)

Resolution1920 x 1080 (Full HD)
MicrophonesElectret condenser capsule
+ special designed preamplifier
Frequency response100 Hz – 15 kHz (< 0.5 dB)
20 Hz – 20 kHz (< 3 dB)
Max. sound pressure level130 dB at 3 % THD
Noise level27 dB(A)
Sensitivity20 mV/Pa
Channels72/96/120
Recommended measurement distanceSONAH: 10 – 20 cm
HELS: 0 – 10 cm
BF: > 0.8 m
Acoustic maps from ...72 channels: 9 dB – 130 dB
96 channels: 8 dB – 130 dB
120 channels: 7 dB – 130 dB
Recommended mapping frequencies

SONAH: 40 Hz – 2 kHz
HELS: 30 Hz – 400 Hz
BF:
72 channels: 285 Hz – 20 kHz
96 channels: 245 Hz – 20 kHz
120 channels: 262 Hz – 20 kHz

Dynamic range
(Distance to the source: 1 m;
calculation points: 90.000)

72 channels: 14 dB – 20 dB
96 channels: 15 dB – 22 dB
120 channels: 16 dB – 25 dB

up to 50 dB with advanced algorithms

Ingress protection codeIP20
Cable length to data recorderup to 20 m (on request: 50 m)
Operating environment0 °C to 45 °C, up to 80 % RH (Baumer)

For near field and far field applications

This array can be used for beamforming as well as for holography (HELS and SONAH) applications. Depending on the chosen method, the recommended measurement distance is between 0 and 10 meters. The area of application is between 30 Hz for holography measurements up to 25 kHz for beamforming measurements. owing to the arrangement of microphones, near field and far field measurements can be conducted with only one array.

The array design is optimized to provide the highest spatial resolution as well as map dynamic possible given the number of microphones used. Additionally, the array design effectively minimizes partial reflections, sound pressure doubling effects on the surface, and resonance effects between the measured object and the array.

The microphones used are calibrated to ensure stable sound pressure levels (+/- 0.5 dB). The array is connected to the data recorder via differential SymBus microphone connector cables. This technology allows for long microphone cables (max. 20 m). The array comes with two Baumer Ethernet cameras. The included high-end Manfrotto tripod allows a set up in almost any measurement environment imaginable. Array and tripod are supplied in a transport case and bag, respectively.

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