1.
If you say that a person or their words go unheard, you are expressing criticism because someone refuses to pay attention to what is said or take it into consideration. (WRITTEN)
His impassioned pleas went unheard...
ADJ: usu v-link ADJ, ADJ after v, also ADJ n [disapproval]
2.
If you describe spoken comments or pieces of music as unheard, you mean that most people are not familiar with them because they have not been expressed or performed in public.
...a country where social criticism was largely unheard until this year.
ADJ
3.
If someone's words or cries go unheard, nobody can hear them, or a particular person cannot hear them. (WRITTEN)
Martin's weak cries for help went unheard until 6.40pm yesterday.
ADJ: usu v-link ADJ