Calibration matters: I. Sound level meter basics

Calibration is an essential component of audiology practice to ensure the accuracy of the equipment for audiometric tests and the transferability of test results across different clinics and countries. The ability to check the accuracy of the equipment and the ambient noise levels allows clinicians to monitor the functions of their equipment, to reduce noise distractors in the testing environment, and to have confidence in their test results, especially in humanitarian or field test settings. Sound level meters are the primary instruments to measure the sound pressure levels of the transducers and the test rooms used for audiometric testing. The International Electrotechnical Commission released a 3-part IEC 61672 standard of the specifications of sound level meters in 2013, and it is adopted by the standards organizations of many countries. This first installment of the tutorial series references this international standard and discusses basic acoustics concepts, calibration principles, and key functions of sound level meters in the application of audiometric calibration. Subsequent installments will discuss how to measure the ambient noise levels, how to determine whether a test room is suitable for testing hearing thresholds using different transducers, and how to determine whether different transducers of audiometers meet the national or international standards.