His voice sounded very gentle.

Where did you get the source of sound for this song?

He is spending a lot of time on experimental research.

Quantum mechanics is a branch of physics that studies the behavior of microscopic particles.

Quantum chromodynamics is a part of particle physics that describes strong interactions.

He proposed a new theory about quantum mechanics.

He is majoring in quantum mechanics at university.

He became a prisoner of conscience because of his political beliefs.

I am majoring in biophysics at university.

I am majoring in physical chemistry at university.