User`s manual

9 FFT, RTA AND “LIVE” TRANSFER FUNCTION
9.1 INTRODUCTION
By selecting the FFT command from the main menu bar, it is possible to carry out
Fourier analysis of the input signal to determine its frequency content using the
Fast Fourier Transform (FFT).
The ability to process two channels simultaneously, to select the appropriate
sampling frequency and the possibility of triggering with respect to the generated
signal make this control panel a flexible and valuable instrument. Finally, there is
also a very useful facility to quickly and easily swap back and forth between the
time and frequency domains.
The FFT processed data coming from the two input channels can be displayed as
narrowbands, 1/3 (or 1/6) octave bands (turning the instrument into what is
generally called a real-time analyzer or RTA) or, referencing one to the other, as
live transfer function (you may also use music as stimulus).
What you get are three different instruments in one.
9.2 NARROWBAND FFT ANALYZER
Fig. 9.1 The FFT control panel
Pressing the FFT button you select the narrowband FFT analyzer. Fig. 9.1 shows the
FFTcontrol panel (while processing a sinusoidal input signal). The narrowband FFT
analyzer is a general purpose instrument that can be applied to the frequency and
time analysis of any kind of electroacoustical signal.
There now follows a description of the FFT control panel toolbar and settings.
For a detailed description of the graphical display (common also to other
measurement control panels) and its capabilities please refer to Chapter 6. For a
description of the available shortcuts please refer to section 4.5.2.
9 FFT, RTA AND “LIVE” TRANSFER FUNCTION 99