The smaller the bird the smaller the voice.

Love Birds make tweeter sounds.

Budgies tweeter and squack.

Cockatiels tweet, chatter and sing (most beautiful voice I have ever heard.

Macalls can be heard all over the neighborhood.
You can close your bedroom door on a little bird and no one will notice that it is there, but your mother will get used to the little noises and they won't bother her.
When my windows are open the neighbors say

Rambo and

Myrtle sound like two little kids.