HBK 4250

Wideband Volume Velocity Sources

Ready to use Volume Velocity Sources incorporating special
two-microphone design for precise, in situ measurement of volume velocity in real time. Suitable for a range of acoustic environments from enclosed condition close to tyres or engine components, or open conditions some distance from a reflecting surface

Request Price

Volume velocity sources (VVS) are used as ‘acoustical shakers’ to measure acoustic frequency response functions – sound pressure per unit volume velocity – typically in connection with noise source contribution analysis. Uniquely, HBK volume velocity sources use a special dual-microphone probe to measure accurate volume velocity directly in real time.

HBK 4250 wideband volume velocity sources cover the full acoustic frequency range with two powerful drivers to maximize signal-to-noise in real-world conditions, and three probes providing calibrated volume velocity in the low-, mid-
and high-frequency ranges.

The driver units are designed to handle real-world measurement scenarios with high transmission loss or background noise that cannot be reduced, such as in outdoor situations.
Built-in overload protection ensures robust performance.

When used with BK Connect® software, volume velocity is monitored and measured in real time. Vibro-acoustic frequency response functions – sound pressure per unit force – can be measured using the reciprocal method and acceleration per unit volume acceleration.



  • Wideband omnidirectional acoustic radiation for assessment of both airborne and structure-borne generated phenomena
  • Accurate in situ measurement of output volume velocity using a pair of low-noise, ¼-inch microphones
  • Dual-microphone design minimizes near-field effects of the test object for optimum measurement accuracy
  • High-power output for measurement on vehicles with high transmission loss or when background noise conditions are sub-optimal
  • Measurement of frequency response functions at vehicle source systems (engine bay, tyres etc.) with the use of a low-emission, 3-metre hose
  • Quick-release coupling system for switching probes or hose-probe assemblies on the driver
  • Microphones with CCLD and TEDS for quick setup
  • Built-in overload protection circuit
  • Can be used with BK Connect software for real-time volume velocity measurements:
    • Use VVS Measurements Type 8442 for frequency response measurements related to a pass-by source path contribution model
    • Use Data Processing Type 8403 for general NVH measurements