Stage machinery noise – What limits are appropriate?

Machinery noise is a widespread problem in almost every technology branch. Especially in sensitive environments such as operas and theaters it has to be limited to appropriate levels. Even though reference values for background noise levels in auditoria are readily available in literature these limits consider steady-state noise conditions that are not applicable to the occasional use of stage machinery during performance. In parallel stage machinery noise is often addressed in tenders, but there is no consensus about the limitation values to report. This raises the question which stage machinery noise levels can be considered acceptable under realistic conditions. To answer this question extensive sound level measurements were conducted during live performance in German opera houses and speech theaters. This presentation will discuss different analysis strategies of measured data and identify frequency dependent limits for stage machinery noise that are suitable for different types of performances, e.g. opera, ballet or speech theater. Based on these limits the design of stage machinery can be more economic while achieving better acoustic quality at the same time.