The Klippel SCN Near Field Add-On (SCN-NF) enhances the measurement capabilities of the Klippel SCN Scanning Vibrometer with automated sound pressure measurements in the near field of transducers and compact audio devices. The radiated direct sound into half-space is determined with high accuracy based on acoustic holographic methods also used in the Klippel NFS Near Field Scanner System. Due to the holographic nearfield measurement approach no anechoic room is required for precise measurements and the most relevant transducer measurements can now be done on the same hardware, in an average office room.
The SCN-NF adds 2pi acoustical measurement capabilities to the same Scanning Vibrometer platform used for laser scan diaphragm vibration. The SCN hardware is extended with a microphone in addition to the existing laser sensor. Automated axis control ensures repeatable, precise and fast positioning of the microphone and laser sensors, in combination with a round baffle for measuring transducers up to 10" (30 cm) in diameter, or compact (smart) speakers.
As Klippel explains, comprehensive near- and far-field radiation data, such as directional characteristics, sound power and sound pressure output at any point in the 3D half-space, can be calculated with this solution. This data is extrapolated from a double shell acoustic measurement and holographic processing for direct sound separation.
Holographic measurements are based on a model based on spherical wave components, weighted by spherical harmonics and frequency dependent coefficients, providing a full solution for the acoustic wave equation. For this holographic model, multiple nearfield sound pressure measurements are performed on the plane surrounding the sound source and used as boundary values. This holographic model then describes the radiated acoustic wavefield of the measured sound source in a tridimensional format.
This is the same technology used in Klippel's Near Field Scanner (NFS), now available for the much smaller SCN hardware. The SCN-NF is perfect for comprehensive transducer analysis because it integrates everything necessary into a space-efficient unified hardware that can quickly perform multi-domain measurements.
The SCN equipped with the new SCN Near Field Add-On allows users to obtain accurate results with undersized baffles, creating a virtual infinite baffle with the described acoustical holography. As Klippel also details, setups using much larger and often still insufficient baffles can be replaced, and mechanical, electrical and acoustical measurements can be performed in a normal reverberant room such as a home office, all in a very compact space.
A half-space setup is the typical operating condition of compact loudspeaker devices or smart speakers which are usually placed on a larger structure, typically a table. These devices should therefore be measured in such a setup in order to provide meaningful data. With the SCN Near Field Add-On the device can be simply positioned on the add-on baffle for a comprehensive full scan with 400 measurement points performed in approximately 1 hour. Key results are accurate frequency and sound power response, while the optional Near Field Analysis Module further detailing the listeners field.
With the SCN Near Field Add-on, Klippel has created a multifunctional device with multiple sensors and domains using the SCN hardware to enable users to perform a variety of different measurements without having to constantly change their measuring device. As a result, Klippel has expanded its SCN Vibrometer Scanner into a SCN Multi-Scanning Workbench. The multifunctional measurement device supports the IEC 60268-21 and IEC 60268-22 standards.
More information about the possibilities using the Klippel SCN Near Field Add-On will be presented in the second KLIPPEL LIVE webinar series "Electrical and Mechanical Measurement of Transducers and Systems according IEC 60268-22," by Dr. Wolfgang Klippel. This will be followed by another KLIPPEL LIVE webinar focusing on the SCN Multi-Scanning Workbench possibilities and its associated products.
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