octspace

Create logarithmic spacing with 1/N-th octave bands over a specified frequency range.

This function creates log spacing for 1/n octave frequency bands for the range of frequencies containing [Fmin, Fmax]. By default, the reference center-band frequency is set at 1 kHz and calculations are preformed using a Base 2 method, but can be changed using the variable input. The reference center-band frequency can be specified as any numerical value. Available calculation methods are Base 2 and Base 10.

REFERENCES TO ANSI, IEC, AND JIS STANDARDS.

• ANSI S1.11-2004: Specification for octave-band and fractional-octave band analog digital filters, class 1.
• IEC 1260 (1995 - 07): Electroacoustics - Octave-band and fractional-octave-band filters, class 1.
• JIS C 1514:2002: Electroacoustics - Octave-band and fractional-octave-band filters, class 1.

EXAMPLE:

% Create 1/6th octave band between 0.1 to 50 Hz and center reference frequency at 1 Hz.
fspan = octspace(0.1,50,6,'ref',1,'base',10);

% Generate plot with RS profiles
Freq = [0.1,1.3,8.3,33.3,50];
Horz = [0.48,4.8,4.8,3.6,3.6];
Vert = [0.201,2.01,2.01,0.81,0.81];
figure
loglog(Freq,Horz,'-*',Freq,Vert,'-*','LineWidth',2)
legend({'RS-Horizontal Motion','RS-Vertical Motion'},'AutoUpdate','off','Location','se')
title('Response Spectra showing 1/6th Octave Band Spacing')
xlabel('Frequency (Hz)')
ylabel('Response Acceleration (g)')
xlim([0.1,50])
ylim([0.1,10])

% Create patches for every other frequency band for visualization
for i=1:2:length(fspan.center)
    patch('Vertices',[fspan.low(i),0.1;fspan.low(i),10;fspan.high(i),10;fspan.high(i),0.1],...
        'Faces',1:4,'FaceColor',[1,0,0],'FaceAlpha',0.1)
end
set(gca,'children',flipud(get(gca,'children'))) % Reverse order of axes children