The BBC is being forced to make musicians play more quietly during Proms concerts and rehearsals to comply with an EU safety directive.
Under the directive which came into effect in April, the broadcaster must ensure performers are not exposed to excessive levels of noise.
Noise control officers have been sitting in on rehearsals to take volume measurements and ensure orchestras keep below 140 decibels – the noise of a gunshot of firecracker.
A spokesman said: "If they go over this danger level we have to ask them to play more quietly."
The BBC has also been forced to erect screens between the musicians and hand out earplugs to make sure performers are not exposed to excessive noise.
