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Radiation analysis

Characteristics:

KLIPPEL R&D System
Far field SPL-response generated in a half spaceSCN; NFS, POL
Directivity index, sound power responseSCN, NFS, POL
Polar and balloon plotNFS, POL
In-phase component (constructive contribution to SPL)SCN
Anti-phase component (destructive contribution to SPL)SCN
Quadrature component (no contribution to SPL)SCN

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.

KLIPPEL R&D SYSTEM (development)

Module

Comment

Scanning Vibrometer (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). 

Example:

The figure above shows the sound pressure related decomposition technique where the total vibration is separated into in-phase, anti-phase and quadrature components which provide a constructive, destructive and no contribution to the total sound in the sound field.
The figure above shows the sound pressure related decomposition technique where the total vibration is separated into in-phase, anti-phase and quadrature components which provide a constructive, destructive and no contribution to the total sound in the so
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).
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
The figure above shows the results of a paper cone’s radiation analysis. The SPL response of the in-phase component which generates the sound pressure is always 15 dB higher than the anti-phase component which contributes destructively to the total output. The in-phase component occupies the inner part of the cone, but the size shrinks with rising frequency which increases the radiation resistance.
The figure above shows the results of a paper cone’s radiation analysis. The SPL response of the in-phase component which generates the sound pressure is always 15 dB higher than the anti-phase component which contributes destructively to the total outp

Standards:

  • IEC Standard IEC 60268-5 Sound System Equipment, Part 5: Loudspeakers
  • AES2-1984 AES Recommended practice Specification of Loudspeaker Components Used in Professional Audio and Sound Reinforcement
  • AES56-2008 AES standard on acoustics – Sound source modeling – Loudspeaker polar radiation measurement



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.