Dual axis plot for the same data, left = linear -1 0 +1, right side= linear in dB -0db inf +0db

Acoustic wave form plot, amplitude range -1 to 0 to +1 (left side), in dB, -0dB to inf to +0dB (right side). The right and left side would correspond to each other. Zero on the amplitude side equals infinity on the dB side. The plot displays fine except that I'm not able to get the right side to range from -0dB to inf to +0dB. Any ideas would greatly appreciated. Thank you.

[Dyuman Joshi]

"-0dB to inf to +0dB"

I, for one, can't make sense of this.

[Jonathan Broyles]

Ok, the y plot scale on the left is from -1 to +1 which represents the actual values of each sample(amplitude) of data with 0 in the center. In terms of, lets say, digital audio recordings, the -1 is the same as 0dB representing the maximum negative component/amplitude of the signal, the 0 would be the same as infinity representing zero amplitude, and the +1 would be 0dB (or 0dBV), which is the maximum positive component/amplitude value. The maximum values are what can be represented by the digital recording's amplitude resolution.

To illustrate, do you have access to Adobe Audition or iZotope Audio Editor or DC Forensics or AVS Audio Editor or the like? Open/load an audio recording, if setup for dB, the vertical scale has inf (infinity) as the center and dB values numerically increasing from there in both directions.

(Since I'm not a math person, I'm staying away from botching a math description of dB.)

I need to have a similar scale on the right side of my plot.

Thank you.

Answer 1

[Mathieu NOE]

hello

something like that ?

% dual plot (linear scale left , dB scale right)
yleft_ticks = (-1:0.1:1);
yleft_ticks_labels = num2str(yleft_ticks',3);
yright_ticks = 20*log10(abs(yleft_ticks));
yright_ticks_labels = num2str(yright_ticks',2);

% create plot with yyaxis
x = linspace(0,10);
y = 0.5*sin(x)+0.1*randn(size(x));
yyaxis left
plot(x,y)
ylim([-1 1]);
ylabel('Mag (linear)')
set(gca, 'YTick', yleft_ticks,'YTickLabel', yleft_ticks_labels );
yyaxis right
plot(0,0)
ylim([-1 1]);
ylabel('Mag (dB)')
set(gca, 'YTick', yleft_ticks,'YTickLabel', yright_ticks_labels );

[Jonathan Broyles]

Wow. Fast and perfect.. All I needed to do was change the number ticks and PRESTO! Perfect!

Thank you very much for your quick accurate answer!

[Mathieu NOE]

glad I could be of some help

as always, my pleasure !