The acoustic valve sits in the nearside front wheel arch. It is fitted by Renault to meet EU noise emissions. Its connected to one of the intakes into airbox and a flap within the valve closes to restrict noise/airflow at certain engine speeds. As a modification, some might argue there is little to be gained, but removal is not too difficult and you remove the restriction in the intake (good!) and it's free (if you do it yourself!) and may aid performance if you choose to remap the ecu to take into account increased airflow at a later date.
