I meditate in a silent space.
音 means there is sound, while 無音 means there is no sound at all, i.e. silence.
無音 means the absence of sound in general (e.g. a silent video), while 無言 specifically refers to a person not speaking.
Compound of 無 (mu, 'without') and 音 (on, 'sound'). The exact historical derivation is uncertain, but the meaning is transparent from its components.