Traditionally, room acoustic measurements are based upon sound pressure microphones only. With the invention of the Microflown sensor , acoustic particle velocity has become a directly measurable quantity. Since then, many new applications have been developed for various markets. The applications are based on the fact that particle velocity based approaches may provide additional information. Together with a regular sound pressure sensor, the whole acoustic vector can now be measured. Sound probes combining both sound pressure and particle velocity sensors can be used for a variety of room acoustics applications as well.
In-situ measurements of acoustic impedance and absorption of separate structures
Microflown Technologies offers a complete solution to measure the acoustic properties of materials with its In-situ absorption setup. This method is a true alternative for the well known Kundt's method or reverberant room method. Taking (destructive) samples is no longer required, and also the absorption of sound waves under oblique angles of incidence, as they occur in practice of course, can finally be tested. The system can even measure, next to material samples, complete assembled parts.
Localization of the direction of the direct sound source and early reflections in a hall
This application allows the mapping of the direction of incoming early reflections versus time. Early specular reflections influence the perception of a signal in a room, whether it is the sound of a symphony in a large concert hall, a singer in an opera house, or a speaker in a classroom. With a sound pressure microphone a scalar quantity is obtained, which provides no directional information. When the particle velocity is also measured in three directions the 3D intensity can be calculated. Intensity is a vector indicating the direction of energy flow, thus the location of the direct source and early reflections can be determined. Such measurements have been studied as early as 2002, by Meyer sound laboratories.
Energy density measurements
Energy density can be used in the calculation of most room acoustics parameters like decay time, clarity, definition, and center time. Using only p^2 as an estimation parameter often leads to errors and variation between measurement positions, as sound pressure is a place dependent quantity. Acoustic energy is a place independent quantity, thus more uniformity can be achieved by including the kinetic energy term of velocity as well. The pressure-velocity probes can be used in diffuse fields, as they are not affected by a high pressure-intensity index. This is a significant advantage over p-p intensity probes.
Quantification of diffusion
This application is the quantification of the degree to which a sound field is diffuse. A metric can be developed relating the degree of diffuseness to the amount that the timeaveraged intensity, pressure and energy are related to each other. Because PU probes can be used in conditions with a high pressure-intensity index, these quantities can reliably be measured in a diffuse field.
3D intensity visualization around objects
This application is the visualization of the sound vector field. Usually an extremely complex sound field is present because of the many different scattering and absorbing surfaces. To gain further insight into the true behavior around objects a theatre seat has been analyzed. In one plane a many measurements were taken with a three dimensional intensity probe and the intensity vector field is visualized.
- Acoustic particle velocity enabled methods to assess room acoustics (PDF)
Published at the Euronoise 2009, J. Botts, E. Tijs, H-E de Bree, E. Arato
- Statistical properties of kinetic and total energy densities in reverberant spaces (PDF)
Published at the JASA 2010, F. Jacobsen, A. Rodriguez Molares
- Measurement of total sound energy density in enclosures at low frequencies (PDF)
Published at the Acoustics 2008, F. Jacobsen
- The coherence of reverberant sound fields (PDF)
Published at the ASA 2010, F. Jacobsen, T. Roisin
- Measurement of sound power and absorption in reverberation chambers using energy density (PDF)
Published at the JASA 2007, D. Nutter
- Automotive & Ground Vehicles
- Appliances & Electronics
- Aerospace & Aviation
- End of line control
- Room Acoustics
- Environmental Noise
- MEMS Testing
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