Spherical Beamforming Systems - Uses, Features and Benefits - Measurement and Calculation

Oct 12, 2026

Spherical beamforming provides omnidirectional noise maps from a single measurement in any acoustic environment, enabling complete noise visualization rather than partial surroundings. Using a spherical array of microphones and cameras, it superimposes noise measurements onto directional pictures and works in both free-field and reverberant conditions. The document details system uses, feature set, calibration, measurement setup on a hard sphere, and the calculation via spherical harmonics with algorithms FAS and SHARP.

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Uses, Features and Benefits

Measurement and Calculation

Calibration

Performance

Application Examples

PRODUCT INF O RMAT ION Spherical Beamforming Systems based on Spherical Beamforming Type 8606 Spherical Beamforming is one of a suite of systems developed for noise source identification. Based on one simple measurement, the system provides a complete, omnidirectional noise map in any acoustic environment. Unlike other measurement methods that only map part of the surroundings, spherical beamforming uses a spherical array of microphones and cameras to simultaneously measure noise levels and take pictures in all directions. When the results are displayed, the noise measurements are superimposed on the pictures to create an acoustic map. Spherical beamforming does not make any assumptions about the nature of the acoustic environment and can therefore be used in both free-field and reverberant environments. The system is commonly used to make overview maps in confined and semidamped spaces such as vehicle, train and aircraft cabins. Uses, Features and Benefits Uses • Wide frequency range measurements • Vehicle interior noise measurements • Squeak and rattle testing • End-of-line wind box vehicle testing • Aircraft and train cabin noise measurements • Industrial plant noise measurements • Source location in rooms and factory halls Features • Quick snapshot measurement • Omnidirectional coverage • Independent of acoustic environment • Two algorithms implemented: – Filter and Sum (FAS), patent pending – Spherical Harmonics Angularly Resolved Pressure (SHARP) Benefits • Saves time via rapid evaluation of noise problems • Easy to use • Easy to mount inside a vehicle • Robust array with many applications • Boosts low-frequency resolution with FAS Measurement and Calculation Fig. 1 Car seat fixture for spherical array Fig. 2 Typical 36-channel system. Spherical beamforming systems are supplied as customer-specified projects The measurement is performed using an array of 36 or 50 microphones mounted on the surface of a hard sphere. The microphone positions on the sphere are numerically optimized to maximize the dynamic depth of the map. The sphere is usually placed at a typical (sound) impact position, for example, in the driver’s seat of a vehicle using the car seat fixture for spherical array (Fig. 1) . The calculation decomposes the observed sound field into its spherical harmonic components and then estimates the directional contributions by recombining these spherical harmonics. WB-3477 Split Box 1 11 2 10 3 9 4 8 5 6 7 Brüel & Kjær * Ordered via Project Sales † Optional support for fixture between car seats (WA-1678-xxx) ** Optional 50 m cable with extra power supply Splitter Box WB-3477 Software LAN Cable 090170/3 LAN-XI System: 3660-C Frame with 1 × 2831-A Battery Module 3 × 3053-B 12-ch. Modules 3 × UL-2112-120 Car Seat Fixture† WA-1647-W-xxx* Spherical Array WA-1565-W-020* USB Cable (5 m**) Small Computer Systems Interface (SCSI) Cable WQ-2552 B 7/6-'89 K Calibration Fig. 3 Calibration of the spherical array The spherical array and complete measurement system are easily calibrated using Pistonphone Type 4228 with a single-channel “stethoscope” adaptor (Fig. 3) . Performance The angular resolution provided by the spherical beamforming algorithms FAS and SHARP are roughly the same (see Table 1) . However, FAS provides considerable improvement in the maximum side lobe (MSL) level and, in conjunction with a low-frequency boost (LFB) algorithm, increases the angular resolution at low frequencies. Table 1 Comparison of resolution (–3 dB), in degrees, between FAS and SHARP beamforming for a sphere with diameter 19.5 cm | Algorithm | 100 Hz | 200Hz | 500 Hz | 1kHz | 2kHz | 4kHz | 6kHz | 8kHz | 10 kHz | 12kHz | | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | | FAS (36 and 50 ch. ) | 145 | 105 | 68 | 48 | 32 | 24 | 16 | 13 | 10 | 8 | | FAS with LFB (36 ch. ) | 110 | 95 | 68 | 48 | 32 | 24 | 1

FAQs

What does spherical beamforming produce from a single measurement?

It provides a complete, omnidirectional noise map in any acoustic environment by measuring noise levels in all directions.

How does spherical beamforming differ from other measurement methods?

It uses a spherical array to simultaneously measure noise levels and capture images in all directions, then combines measurements with the pictures to form an acoustic map.

Which algorithms are implemented and how do they affect performance at low vs. high frequencies?

The system implements Filter and Sum (FAS) and Spherical Harmonics Angularly Resolved Pressure (SHARP). FAS improves maximum side lobe levels and, with a low-frequency boost, increases low-frequency angular resolution; SHARP is limited at higher frequencies and FAS is recommended above 6.4 kHz.

Oct 12, 2026

Upload by Aria Callaghan