Jaaa For Linux

Jaaa is short from JACK and ALSA Audio Analyser, is an audio signal generator and spectrum analyser designed to make accurate measurements.

These two sets of buttons set the display view. One of these six buttons, or 'Bandw', 'Peak', or 'Noise' discussed below, has an orange LED at its left side. The LED indicates the 'currenty selected parameter' that usually can be modified in three ways:

- by typing a new value into the text widget, followed by ENTER, - by using the '' buttons to decrement or increment, - by mouse gestures.

'Min' and 'Max' set the min and max displayed frequencies. If either of these is selected then

a horizontal Drag Left changes 'Min', a horizontal Drag Right changes 'Max'.

'Cent' is the frequency at the middle of the x-axis. 'Span' is 'Max' - 'Min', changing this value preserves 'Cent'. If either of these is selected then

a horizontal Drag Left changes 'Cent', a horizontal Drag Right changes 'Span'.

'Cent' can also be set by Clicking in the frequency axis scale.

'Max' is the maximum value on the y-axis. 'Range' is the range of the y-axis. If either of these is selected then

a vertical Drag Left changes 'Max', a vertical Drag Right changes 'Range',

So for the last four mouse gestures, a Drag Left will scroll the display, while a Drag Right will zoom in or out. Maybe I will add and automatic selection of the axis based on the direction of the mouse gesture.

The analyser is based on a windowed FFT. Actually the windowing is performed by convolution after the FFT, and combined with interpolation. The windowing and interpolation ensure that displayed peaks will be accurate to 0.25 dB even if the peak falls between the FFT bins. More accurate measurements can be made using the markers.