High fidelity or hi-fi refers to the reproduction of sound and image that is very faithful to the original. That is without noticeable amount of noise and distortion.
... of English alveolars like t, but with the tongue curled back) (t, th, d, dh, n)
Dental (tongue against teeth, like Spanish) (t, th, d, dh, n)
Labial (with the lips[?]) ...