Used almost exclusively in negative expressions like 音沙汰がない to mean 'no news' or 'no contact' from someone. Often implies a lack of communication over a period of time.
I haven't heard anything from him.
I still haven't heard back from the company I applied to.
Compound of 音 (sound, news) and 沙汰 (tidings, affair). The exact historical derivation is uncertain, but the combination has long been used to mean 'news' or 'communication'.