Any prodigious sound or noise which is exempt from social proscription. Originally, such natural phenomena as thunder, volcanic eruptions, storms, and so on, were regarded as sacred noise, as they were believed to represent divine combats or divine displeasure with humankind.
By analogy, the expression may be extended to social noises which, during certain periods of history, have escaped the attention of noise abatement legislators, e.g. church bells, industrial noise, moozak, amplified pop music, etc.
(Source - Barry Truax - Handbook for Acoustic Ecology CD-ROM Edition. Cambridge Street Publishing, 1999 - CSR-CDR 9901)