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Radiation Analysis


Far field SPL-response generated in a half spaceSCN, NFS, POL, RMA, HMA, SCN-NF
Directivity index, sound power responseSCN, NFS, POL, HMA, SCN-NF
Polar and balloon plotNFS, POL, SCN-NF
In-phase component (constructive contribution to SPL)SCN, RMA, HMA
Anti-phase component (destructive contribution to SPL)SCN, RMA, HMA
Quadrature component (no contribution to SPL)SCN, RMA, HMA

The transfer function Hc(jω, ρ, rc) and geometry measured by laser scanning at points r with sufficient resolution on the radiator’s surface are the basis for predicting the sound pressure in the far field using boundary element methods or simplified approaches. The Rayleigh equation is the basis for a radiation analysis showing the contribution of each point on the radiator’s surface to the sound pressure in the far field. The analysis also shows the contribution of individual modes (e.g. radial and circumferential). This information is important for detecting the causes of cancellation problems causing significant dips in the SPL and power response and for optimizing the directivity of the loudspeaker.


The figure to the left shows the coincidence of a significant dip in the sound pressure response (blue curve in left diagram) and sufficient accumulated acceleration level AAL (brown curve in left diagram) reveals acoustical cancellation of the volume velocity q1 and q2 generated by outer and inner part of the radiator (right diagram).

KLIPPEL R&D SYSTEM (development)



Scanning Vibrometer System (SCN)

SCN module predicts the sound pressure level at any point in the far field using the scanned geometry and mechanical vibration of the radiator. This data is the basis for calculating the polar radiation characteristics, sound power and directivity index. The analysis can be performed as post processing without hardware components (only dongle required). 

Near Field Scanner (NFS)

The NFS captures the entire sound field at any point in 3D space. The automatic measurement in the near field can be performed in a normal room (non-anechoic) and the software visualizes far field characteristics (sound pressure, sound power, directivity index, directivity balloon) as well as the near field characteristics (sound pressure distribution).

Polar Far-Field Measurement (POL)

POL far field measurement is performing a traditional directivity measurement of loudspeaker and microphones in an anechoic room. Using turntables or microphone arrays, the directivity pattern is measured at discrete point on sphere to determine the far field characteristics (sound pressure, sound power, directivity index, directivity balloon) of the device under test.

Higher Modal Analysis (HMA)

HMA performs modal analysis of distributed vibration data (like from Klippel SCN). It decomposes the total vibration into the contribution of separate modes, described by modal parameters (resonance frequency, damping coefficients, gain) and mode-shapes (characteristic vibration patterns). It visualizes cone deformation and simplifies the systematic analysis of mode interaction and sound radiation. 

Rocking Mode Analysis (RMA)

RMA analyses undesired rocking modes of the diaphragm which can cause impulsive distortion. It determines imbalances in the distributions of mass, stiffness and electromagnetic force factor, the main root causes for rocking motion. It also quantifies the excitation force caused by each of these effects and supports the user to find the location of the disturbance on the diaphragm.



Audio Engineering Society 
AES2 Recommended practice Specification of Loudspeaker Components Used in Professional Audio and Sound Reinforcement 
AES56 Standard on acoustics – Sound source modeling – Loudspeaker polar radiation measurement

International Electrotechnical Commission 
IEC 60268-5 Sound System Equipment, Part 5: Loudspeakers

Papers and Preprints

W. Klippel, et al., “Distributed Mechanical Parameters of Loudspeakers Part 2: Diagnostics,” J. of Audio Eng. Soc. 57, No. 9, pp. 696-708 (2009 Sept.).

F. J. M. Frankort, “Vibration Patterns and Radiation Behavior of Loudspeaker Cones,” J. of Audio Eng. Soc., Volume 26, No. 9, pp. 609-622 (September 1978).

W. Klippel, et al., “Distributed Mechanical Parameters of Loudspeakers Part 1: Measurement,” J. of Audio Eng. Soc. 57, No. 9, pp. 500-511 (2009 Sept.).

A. J. M. Kaizer, “Theory and Numerical Calculation of the Vibration and Sound Radiation of Cone and Dome Loudspeakers with Non-Rigid Diaphragms,” presented at the 62nd Convention of the Audio Eng. Soc., March 1979, Preprint 1437.

J. Backman, “Low-frequency Polar Pattern Control for Improved In-room Response,” presented at 115th Convention of Audio Eng. Soc., October 2003, Paper no. 5867.

J. Baird, et al., “The Analysis, Interaction, and Measurement of Loudspeaker Far-Field Polar Patterns,” presented at 106th Convention of Audio Eng. Soc., May 1999, Paper no. 4949.

M. Karjalainen, et al., “Comparison of Numerical Simulation Models and Measured Low-Frequency Behavior of a Loudspeaker,” presented at the 104th Convention of the Audio Eng. Soc., May 1998, Preprint 4722.

J. Wright, “Finite Element Analysis as a Loudspeaker Design Tool,” Paper MAL-11; Conference: AES UK Conference: Microphones & Loudspeakers, The Ins & Outs of Audio (MAL); March 1998.

A. Kaizer, “Calculation of the Sound Radiation of a Nonrigid Loudspeaker Diaphragm Using the Finite-Element Method,” J. of Audio Eng. Soc., Volume 36, No. 7/8, pp. 539-551; July 1988.