#3D Sound Intensity, Sound Pressure and Particle Velocity Probe


Weles Acoustics WA301 is a general purpose 3D sound intensity probe which relies on direct measurement of sound pressure and triaxial particle velocity. The WA301 consists of four transducers: a conventional mems microphone and three orthogonally positioned Weles particle velocity sensors. Almost full acoustic bandwidth (20 Hz to 10 kHz) can be analyzed from just one measurement - no spacers required to measure sound intensity in the probes operating frequency range. Detailed information regarding any sound field can be extracted without introducing any constraints on the measurement - all acoustic quantities are measured directly.

Each WA301 probe is delivered with a Weles BOX. Connection between the probe and the BOX is established with a 7-pin LEMO cable. The BOX is designed to provide power to all sensing elements built into the probe. Furthermore, the Weles BOX acts as an interface between any data acquisition system that is meant to process analog signals provided by the probe. For WA301 probe four signals are provided over four BNC connectors: sound pressure and triaxial particle velocity (X, Y and Z axis as sepearate analog signals).

Download full datasheet here


  • Near field and Far field sound source localization and ranking – highest performance and accuracy is achieved with particle velocity measurements
  • 3D Particle velocity mapping
  • 3D Sound intensity mapping
  • Sound power measurement
  • Sound pressure measurement
  • 3D Sound field visualization


Parameter Particle Velocity X, Y and Z axis Sound Pressure Sound Intensity X, Y and Z axis
Frequency range (±2 dB) 20 Hz to 10 kHz 20Hz to 10 kHz 20Hz to 10 kHz
Total self-noise (20Hz - 10 kHz) 46 dB (A) 30 dB (A) 46 dB (A)
Dynamic range upper limit (<3% THD) 136 dB SVL 136 dB SPL 136 dB SIL
Output Voltage Swing 10 Vpp 10 Vpp -
Temperature range, operation -20 to 85 oC -20 to 85 oC -20 to 85 oC
Temperature range, storage -40 to 85 oC -40 to 85 oC -40 to 85 oC
Temperature coef. @250 Hz -0.0517 dB/oC -0.0235 dB/oC -0.0517 dB/oC
Static pressure coef. @250 Hz < 0.5 dB/kPa < 0.5 dB/kPa < 0.5 dB/kPa
Humidity coef. @250 Hz 0.06 dB/%RH 0.05 dB/%RH 0.06 dB/%RH
Maximum DC airflow 1.5 m/s
Connector type Lemo 7p EGG-1B-307
Weight 78g (WA301 Probe)/380g (Weles BOX WA301)
Dimensions 153.4/12.7/40mm Length/Tube diameter/Sphere diameter
CE/RoHS compliant Yes/Yes








Sound intensity is defined as the product of sound pressure and particle velocity. The WA301 sound intensity probe consists of four acoustic transducers: sound pressure microphone and three orthogonally positioned Weles particle velocity sensors. Each particle velocity sensor is responsible for measurements in a different axis – X, Y and Z respectively. Since the particle velocity and sound pressure are measured directly, the three-dimensional sound intensity vector can be determined in the entire frequency range covered by WA301 probe. No standards yet exist for measuring 3D sound intensity with PU probes.

Weles Acoustics designs and manufactures particle velocity transducers. Particle velocity is a physical quantity that together with sound pressure fully characterizes any sound field. Intrinsic characteristics of particle velocity physics coupled with distinctive features of the Weles sensor make it a unique tool for sound source localization. Working principle of the particle velocity sensor is similar to a hot wire anemometer. The sensor consists of several thin platinum strings. These strings are heated to a near incandescent temperature. Passing sound waves alter the temperature, and in turn the electrical resistance of the heated strings. The resulting voltage difference is proportional to the acoustic particle velocity.


The Weles particle velocity sensor is directional. Its polar pattern resembles a figure-of-eight. It is a bi-directional transducer. Thanks to this trait, each particle velocity sensor can be employed to measure the particle velocity in one axial direction. The sensing elements of the WA301 3D PU probe are enclosed in a spherical housing. The diameter of the sphere is 4 cm. The spherical housing is engineered to provide maximum acoustic transparency within the probes operating frequency range. Furthermore, the spherical shape ensures that the housing itself does not alter the measured sound field. All sensing elements of the WA301 PU probe are positioned at the center of the sphere and occupy a volume of approximately 0.216 cm3.


drawing The casing of WA301 3D sound intensity probe is built out of high quality stainless steel. The head of the probe was engineered to provide maximum acoustic transparency while maintaining protection for all sensing elements from particles of dust, sand or oil. The robust and durable spherical housing encloses 3D printed mechanical sound amplifiers that are built around the Weles particle velocity sensors and the microphone.

The mechanical amplifiers are designed to increase the signal-to-noise ratio of velocity transducers. All sensing elements of the WA301 PU probe are positioned at the center of the spherical housing. Thanks to this unique architecture, sound intensity is measured almost exactly at the same point. The distance separating all sensing elements is smaller than 6mm making the WA301 a very compact and capable solution. Additional layer of protection for the sensing elements is realized by a foam insert which fills the inside of the WA301 spherical housing. The purpose of the foam insert, apart from protecting from particle ingress, is to decrease the impact of DC airflow on particle velocity measurements.

WA301 probe is built, assembled and tested by Weles Acoustics. Each probe is calibrated and mechanically tested to withstand minor shocks and excessive vibration – This PU sound intensity probe is built to endure. See specification for details.


The WA301 PU Sound Intensity probe comprises the following items:

  • WA301 3D Sound Intensity probe
  • Weles BOX WA301
  • 7 pin male LEMO to 7 pin male LEMO cable
  • 5V Power supply
  • Protective case
  • Calibration certificate

Weles Acoustics reserves the right to change specifications without notice.