Custom Font

I am trying to use the font Humanist 521. I upload the file (hum521n.tff) , and then I insert the following code in theme.scss:

@font-face {
font-family: hum521n;
src: url('hum521n.ttf');
}

Then I change the font code to set the font:

$fonts: hum521n;
$form_field_font: hum521n;
$headline_font: hum521n;

The font isn't working. What am I doing wrong?