The Disguise Self spell allows the caster to look like another creature. Due to my poor English skills I am not sure if this includes the voice or if it is just a visual matter.
No, the illusion is purely visual.
You make yourself—including your clothing, armor, weapons, and other belongings on your person—look different until the spell ends or until you use your action to dismiss it. You can seem 1 foot shorter or taller and can appear thin, fat, or in between. You can’t change your body type, so you must adopt a form that has the same basic arrangement of limbs. Otherwise, the extent of the illusion is up to you.
There's nothing there that would allow you to disguise your voice, or the clanking of your armour, or any other sound you make. You look different, in specified ways, and that's pretty much it. The word "look" applies purely to your visual appearance.
Disguise Self is visual only. If it were meant to change your voice it would specifically say so, much like Alter Self does:
You decide what you look like, including your height, weight, facial features, sound of your voice...