Unexpected results using octaveFilter

I'm aiming at obtaining a 1/3 octave band frequency signal for specific centre frequencies. I want to use Matlab's octaveFilter functionality but I was expecting to get a single 1/3 octave band peak at 1000 Hz, but instead far left and far right of 1000 Hz very positive sound pressure levels were computed.

What do I wrong?

        Fs = 48000;                         % Sampling rate
        t = 0:1/Fs:1-1/Fs;                  % Time vector of 1 second
        f = 1000;                           % Frequency of signal
        dpres = sin(2*pi*f*t);              % Signal in [Pa]

        frCen = [100 300 600 800 1000 1200 1300 1600];

        [Spl,frCen] = CompOctSplFreq(dpres,frCen)

        figure()
        semilogx(frCen,Spl,'ro-')
        title('1/3-Octave Filtered SPL over Frequency')
        xlabel('Center Frequency of Octave Band Filter [Hz]')
        ylabel('SPL [dB]')        

                function [Spl,frCen] = CompOctSplFreq(dpres,frCen)

                    % Reads singal in pressure over time
                    freqNum = length(frCen);
                    Fs = length(dpres);

                    % Setting up the 1/3-octave filters for all center frequencies
                    for f = 1:freqNum
                        octaveFilterBank{f} = octaveFilter(frCen(f),'1/3 octave','SampleRate',Fs,'FilterOrder',12);
                        % Filtering the signal with the corresponding filters
                        dpresFiltered(:,f) = octaveFilterBank{f}(dpres');
                        % Getting the average for each filter frequency band
                        drms(f) = sqrt(sum(dpresFiltered(:,f).^2)/length(dpresFiltered(:,f)));
                    end

                    % Converting the root mean square pressure to SPL            
                    pRef = 20e-06;                      % Reference pressure            
                    Spl = 20*log10(drms/pRef); 

                end