If you are looking for specific attenuation results or testing services,
Because EN 50147-1 is a copyrighted harmonized standard, legitimate copies are not freely distributed on the open internet as public PDFs. en 50147-1 pdf
The reference measurement must be performed in a location with ambient noise at least 10 dB below the received signal. In dense urban environments, this is nearly impossible—hence many labs perform the reference measurement inside a larger shielded room or a TEM cell, which is a deviation allowed only with careful documentation. If you are looking for specific attenuation results