Volume acceleration sound sources are sophisticated acoustic excitation devices. The source is capable of producing very high noise levels, more than sufficient for excitation of complete vehicles. The integrated volume acceleration sensor gives a real-time feedback of the source strength and can directly be used as a reference for FRF measurements without any post-processing.
The LMS low-mid frequency source is designed to be used in the 10 to 800 Hz frequency band which covers the most important frequency band in the noise source analysis in vehicle development. This source is typically used for Transfer Path Analysis of structureborne or airborne contributions, cabin vibro-acoustic modal analysis, Frequency Based Sub-structuring, etc.
If you think this sound source looks like a dummy, you are right. The Qlmf was deliberately made to simulate the acoustic properties of a person at low frequencies. Because most applications are for seat positions, the device is optimized for quick positioning on a seat with the acoustic center at ear location.
For linear systems, the reciprocity principle is applicable. As a vehicle can be seen as a linear system in practice the in- and output can be switched allowing to introduce acoustic energy at ear location and measure acceleration at many force input points like connection of suspension/exhaust/engine to the body. This will result in a shorter FRF acquisition time as it is not necessary to excite the system at every force input location by a hammer.
The unique properties of this low-mid frequency source include compact, human body diffraction simulation, omni-directional, time stable sensitivity& high noise levels. These features make this device extremely accurate and efficient for the analysis of transport vehicles like cars, vans, trucks, busses, trains and aircraft.
Since 1996 almost any OEM and many automotive suppliers in the world use these sources for improving the acoustic performance of their products on complete system level.
For making full use of the source, the LMS Qsources Measurement Amplifier is perfectly suited to amplify the excitation signal from the LMS SCADAS III.
Features
- Covers 10-800Hz frequency range with nearly constant noise energy spectrum.
- Time/environment-stable real-time volume acceleration reference signal.
- Human body diffraction simulation (50% male).
- Integrated electronic overload protection device.
Benefits
- Real-time volume acceleration sensor outputs source strength directly without postprocessing.
- Reciprocal FRF acquisition reduces measurement time significantly.
- Automatic overload protection stands for very robust test device.
- Easy positioning results in efficient data acquisition.
