How to play beep before each trial

I have 80 audio files and I want to play beep before each audio starts as a cue.

Should I add "Beeper(400, [0.3], [0.5]);" in the loop, or outside of the loop?

for i=1:length(audio_files)
    aud_file=strcat('C:\toolbox\aud_file\',audio_files(i).name);
% load sound file (make sure that it is in the same folder as this script) 
    [soundData freq]=audioread(aud_file);
% opens sound buffer at a different frequency
    pahandle = PsychPortAudio('Open', [], [], 2, []);
% loads data into buffer
    PsychPortAudio('FillBuffer', pahandle, soundData');
% how many repititions of the sound
    repetitions=1; 
%starts sound immediatley
    PsychPortAudio('Start', pahandle, repetitions,0);
% stop
    PsychPortAudio('Stop', pahandle, 1,0);
%wait
    WaitSecs(3);    
%close
    PsychPortAudio('Close', pahandle);  
end

[Walter Roberson]

You should have a Beeper() call at the point where each trial is about to start.

[Takara Sumoto]

Thank you but it didn't work.

for i=1:length(audio_files)
    aud_file=strcat('C:\toolbox\aud_file\',audio_files(i).name);  
% load sound file (make sure that it is in the same folder as this script) 
    [soundData freq]=audioread(aud_file);
% opens sound buffer at a different frequency
    pahandle = PsychPortAudio('Open', [], [], 2, []);
% loads data into buffer
    PsychPortAudio('FillBuffer', pahandle, soundData');
% how many repititions of the sound
    repetitions=1;   
%Beep
Beeper(400);
%starts sound immediatley
    PsychPortAudio('Start', pahandle, repetitions,0);
% stop
    PsychPortAudio('Stop', pahandle, 1,0);
%wait
    WaitSecs(3);    
%close
    PsychPortAudio('Close', pahandle); 
end

[Walter Roberson]

I wonder if before all of this, you should create a PsychPortAudio filled with the sound of the beep, and then 'Start' it each time instead of using Beeper ? You would close it after all of trials.

[Takara Sumoto]

If I made a code like this below, I can only play beep once before all the audio files are played. (Just for trial, I add 3 audio files instead of 80.)

% opens sound buffer at a different frequency
    pahandle = PsychPortAudio('Open', [], [], 2, []); 
% generate a beep
    beepWaveform = MakeBeep(1000,.250,44100); 
% make stereo 
    beepWaveform = repmat(beepWaveform, 2, 1);
% fill buffer
    PsychPortAudio('FillBuffer', pahandle, beepWaveform); 
% how many repititions of the sound
    repetitions=1;
%starts sound immediatley
    PsychPortAudio('Start', pahandle, repetitions,0);  
% stop
    PsychPortAudio('Stop', pahandle, 1,0);
%wait
    WaitSecs(1);
%close
    PsychPortAudio('Close', pahandle);     

%randomaize
    a=randperm(3);
    for i=1:length(audio_files)
    aud_file=strcat('C:\toolbox\aud_file\',audio_files(a(i)).name);   
% load sound file (make sure that it is in the same folder as this script) 
    [soundData freq]=audioread(aud_file);
% opens sound buffer at a different frequency
    pahandle = PsychPortAudio('Open', [], [], 2, []); 
% loads data into buffer
    PsychPortAudio('FillBuffer', pahandle, soundData');
% how many repititions of the sound
    repetitions=1;
%starts sound immediatley
    PsychPortAudio('Start', pahandle, repetitions,0);  
% stop
    PsychPortAudio('Stop', pahandle, 1,0);
%wait
    WaitSecs(1);
%close
    PsychPortAudio('Close', pahandle); 
    end

[Walter Roberson]

% opens sound buffer at a different frequency
    pabhandle = PsychPortAudio('Open', [], [], 2, []); 
% generate a beep
    beepWaveform = MakeBeep(1000,.250,44100); 
% make stereo 
    beepWaveform = repmat(beepWaveform, 2, 1);
% fill buffer
    PsychPortAudio('FillBuffer', pabhandle, beepWaveform); 
% how many repititions of the sound
    repetitions=1;


%randomaize
    a=randperm(3);
    for i=1:length(audio_files)
    aud_file=strcat('C:\toolbox\aud_file\',audio_files(a(i)).name);   
% load sound file (make sure that it is in the same folder as this script) 
    [soundData freq]=audioread(aud_file);
% opens sound buffer at a different frequency
    pahandle = PsychPortAudio('Open', [], [], 2, []); 
% loads data into buffer
    PsychPortAudio('FillBuffer', pahandle, soundData');
    
%starts beep sound immediatley
    PsychPortAudio('Start', pabhandle, repetitions,0);  
% stop beep
    WaitSecs(1);
    PsychPortAudio('Stop', pabhandle, 1,0);
    
% how many repititions of the sound
    repetitions=1;
%starts sound immediatley
    PsychPortAudio('Start', pahandle, repetitions,0);  
% stop
    PsychPortAudio('Stop', pahandle, 1,0);
%wait
    WaitSecs(1);
%close
    PsychPortAudio('Close', pahandle); 
    end

%close beep
    PsychPortAudio('Close', pabhandle);