In audio, recording, and broadcast systems audio noise refers to the residual low level sound (usually hiss and hum) that is heard in quiet periods of programme. This is also known as white noise according to the Merriam Webster Definition. [5] There is a similar phenomena to "white noise" which emanates not only from audio recording equipment but from everything and more particularly, musical instruments (whether they are acoustic or electric). These noises are "impurities." When an instrument plays a pitch, even the most beautiful sounding instruments, there is noise (consisting of impurities) projected. Henry Cowell claims that technological advancements have brought machines closer to diminishing these unwanted noises, but have not been completely successful thus far. [6]
In audio engineering it can also refer to the unwanted residual electronic noise signal that gives rise to acoustic noise heard as hiss. This signal noise is commonly measured using A-weighting or ITU-R 468 weighting.