10. Results case studies ‐ maintenance.

Maintenance
Noise source	Intervention	Follow‐up	Initial noise level	Noise level after	Reference ID
Dough mixer	Maintenance modifications to a mixing machine	not reported	94 dB	91 dB	HSE 2013
Compressed air in soft drinks factory machines	Regular maintenance of machines to reduce noise from air leaks	not reported	High noise levels	Noise levels reduced by 3 to 4 dB
Gearboxes on mixing machine	Lubricating gearboxes	not reported	80–85 dB	Noise levels reduced by 1.5 dB
Compressed‐air exhausts on vacuum‐wrapping machines	Fitting and maintaining silencers on wrapping machines	not reported	88–90 dB	Below 85 dB
	Number of cases: 4		mean before	mean after	mean reduction
	Noise level dB		88.5 dB	85.7 dB	3 dB