Always ask for a certificate of calibration of the independent Accreditation Council-certified laboratory for vibration, preferably in percentages and not in dB. Never settle for a certificate from the supplier alone, regardless of how impressive the ISO certification stamps appear. Certifications with understandable evidence in percentages are best. Always ask for an independent Accreditation Council calibration certificate with the general scientific agencies in the Netherlands. Check your calibration certificate--a deviation of more than 5%, respectively (about 0.5 dB at any frequency 2-100 Hz) means that you no longer meet the SBR directive cq. DIN 45669 requirements. Below are the results of calibration in a lab of the Accreditation Council AuroVibe with SBR A filter.