my question has nothing to with the category,
Is whistling haram? or makhroo? does Islam allows it or not?
The ruling of the whistling will depend on the reason and how it is used. If it is used for example by a lost person to identify his whereabout or for the purpose of instructions or to call someone by conveying the sound then it is permissible. If it is used in the context of music, it will be prohibited.
And Allah knows best.
Mufti Ikram ul Haq
Fatwa Center of America