CLIOwin 7 PCI User's Manual - Audiomatica

10 MLS & LOG CHIRP
10.1 INTRODUCTION
Within this menu two different technique are available that yields to the final result, the
complex transfer function of a generic device. They are MLS and LOG CHIRP Analysis.
While the internal processing is quite different the result is the same and this justify
keeping them together. Advantages of each approach will be described later in this
chapter briefly, leaving to the bibliography for details.
MLS stands for Maximum Length Sequences, is a powerful well established technique
that allows you to carry out analysis of linear systems recovering the Impulse
Response of the device using a fast cross-correlation algorithm . It is therefore a Time
based analysis. Frequency domain information is obtained calculating the Fast Fourier
Transform, hereafter FFT, of the impulse response.
LOG CHIRP analysis uses a log-swept sine chirp as stimuli. The Frequency Response is
obtained with a deconvolution process and the impulse response with an Inverse FFT
of the Frequency Response
Both approaches carry a crucial piece of information in the time domain, the Impulse
Response. MLS & LOG CHIRP is therefore particularly well suited for recovering the
anechoic sound pressure response of a loudspeaker. i.e. the frequency response of a
loudspeaker as if it where positioned in an anechoic room, while carrying out the
measurement in a normal room. Just as importantly MLS & LOG CHIRP allows complete
evaluation of room acoustic parameters.
Within this Menu the user will be able to switch from time domain to frequency domain
and back using the powerful post processing tools CLIO provides. This allows the
collection of very sophisticated and complete information of any electro-acoustic
device. Both the theory behind all of this and the amount of parameters that affect the
measurement results make this Menu probably the most complicate to use. We will skip
the theory completely and after a concise description of the whole User interface we
will deal with real life applications.
10.2 MLS & LOG CHIRP CONTROL PANEL
Figure 10.1
Chapter 10 - MLS 109