Absorption coefficient of acoustic materials is the most common
parameter to be measured, and the "Kundt Method" for plane waves represents
the standard since many years.
A recently introduced method using the two microphones transfer function technique
still employs the Kundt tube device in terms of frequency range for plane waves,
but it allows a very fast and precise measurements of alfa. The SCS 902A PC
based system equipped with the Kundt device options, allows for automatic determination
of alfa coefficient according to ISO and ASTM standard; a system based on a
very long experience gained in the automotive measurements need of alfa coefficient
in the last 15 years.
The Kundt device set includes the low and high frequency tubes with samples
holders, loudspeakers case and audio amplifier, two microphones and supply sets.
The small tube (high frequency) can be used as stand alone with its own loudspeaker
case, or alternatively be mounted on the bigger one (low frequency). The microphones
are connected to the PC system which also includes a random noise generator.
A user friendly software interface guides the user through the measurement and
the store and print operations of the results. No multilevel menus: a single
label with all the necessary information is stored along the results file, and
all data become very rapid to recall, print or search; customized version of
the results label are available for automotive industries. All data can be printed
and plotted directly in the SCS 902A software system, export functions are also
included in the Windows environment, allowing a fast and professional reporting
using document automation facilities in Microsoft Word, Excel or Acces.
Several measurements can be performed on a single sample or a group of samples
of the same material, in order to perform averaging and statistical functions
on the narrow band as well as 1/3 octave spectra of the alfa coefficient, or
to keep a track of a material development history and quality control based
on production time, aging, etc. A virtual no limited frequency range can be
achieved using different sets of tubes available, the two standard sets allow
the nominal (and most common) 100 Hz - 6 kHz full octave frequency range using
two samples diameter taken from the same material layer. Other related functions
can be calculated in the SCS 902A system like acoustic impedance. The user can
define the automatic procedure in the initial menu, in terms of calibration,
calculated function, results plotted and data to be stored, everything under
a single file name; the software takes care of the remaining; it is also possible
to recall stored measurements and repeat them on a new sample with the same
setup. The Kundt device ensemble for the SCS 902A system is available as a separated
set and it can be connected with other acquisition and analysis system.