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 Zircon
- Loudspeaker-Microphone Probe
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loudspeaker-microphone probe for measuring in situ the
absorption and reflection properties of surfaces. These may be
indoor surfaces, such as in concert halls and gyms, or outdoor
surfaces, such as road surfaces (ISO 13472-1), sound barriers
installed in a free field (NF S 31-089) and traffic noise
reducing devices (CEN/TS 1793-5).
Using the wall measurement
stand, the Zircon can be rotated horizontally and vertically,
and is provided with 10° step angle indications. When using the floor measurement
stand, the Zircon can be rotated vertically over 360°.
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click
here for a larger image
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The Zircon components are easy to dismantle and
transport in their flight cases.
Operation
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For wall measurements, a setup
including the Zircon Probe and the Zircon W-stand is used.
The Zircon is connected to an
analyzer such as Dirac running
on a notebook PC, with integrated sound device or external sound
device such as the Triton,
and using a power amplifier, such as the Amphion.
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The analyzer generates an excitation
signal, such as an MLS or sweep signal, which is fed to the
loudspeaker. The microphone picks up the direct and reflected
sound. From the sent and received signals, the analyzer
calculates the impulse response. From the impulse response, a
direct and a reflection part are extracted by windowing,
subtraction and other techniques. By comparing these signal
parts, the absorption and reflection properties of the
surface under test are obtained.
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| The low end of the
usable frequency range is determined by the (limited) length of
the time windows. The direct sound time window cannot be made so
long as to overlap the reflected response, whereas the reflected
sound time window is limited by the tail of the direct response,
and the parasitic reflections.
Both windows can be extended by using the subtraction technique
as described by E. Mommertz in 'Angle-dependent in-situ
measurements of reflection coefficients using a subtraction
technique' (Applied Acoustics, Vol.46, 1995, pp.
251-263).
For floor (e.g. road surface)
measurements, a setup
including the Zircon Probe and the Zircon F-stand is used.
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