How to make the harmonic complex tones sound comfortable? I'm trying to create a complex tone, which is consisted by several sine waves with a 220Hz fundamental frequency and 6 multiplied harmonics (at 440Hz, 660Hz, 880Hz, 1100Hz, 1320Hz, 1540Hz).
My code below generated a tone. However, it sounds very uncomfortable, and its waveform and spectrogram picture also look much intensive.
fs = 44100;      % [Hz] 
T = 0.5;          % [s] 
x = 0:1/fs:T;   % [s] 
 
f = 220;        % [Hz]
y = 1*sin(2*pi*f*x);
f1 = 0.2*sin(2*pi*440*x);
f2 = 0.2*sin(2*pi*660*x);
f3 = 0.2*sin(2*pi*880*x);
f4 = 0.2*sin(2*pi*1100*x);
f5 = 0.2*sin(2*pi*1320*x);
y1 = y + f1 + f2 + f3 + f4 + f5
fname = 'sin_220.wav';       
audiowrite(fname,y1,fs);  


I found that one research group have shared similar tone materials, in which, the sine waves were synthesized regularly and sound pleasant.

My question is how to make adjustments to the code so that it looks like this.
In Octave: plot(y1);

audiowrite will effectively clip floating point sample values to range -1 ... 1. This will sound unpleasant. You can divide your data by its maximum absolute value, before writing the audio file, to normalize it to that range.