The EASA TCDS does not show it as it was not required at the time of certification.
They have a detailed list of types here in an excel sheet, but specifically state the SA342 does not require one:
http://easa.europa.eu/system/files/d...8140418%29.xls
The Swiss are very big into noise (and emission) levels, so they may have something through e-mail contact, though not listed on their website:
FOCA - Aircraft Noise certification
Interestingly, the LBA website shows an application form for a Noise Certificate, which seems to imply they will provide it for you:
http://www.lba.de/SharedDocs/Downloa...ublicationFile