Introduction

The pure-tone air-conduction audiogram determines the lowest sound levels a worker can hear at given test frequencies. There are various instrument types for determining these levels, as discussed in the previous chapters. In this chapter the different methods are discussed. All methods are based on presenting to the worker (listener) a sound level or tone from just audible to just inaudible. The workers threshold will be somewhere between these two levels. There are two main testing methods: manual audiometry, and automated audiometry. In both methods the modified Hughson-Westlake method is used. Hughson-Westlake is a pure tone test procedure or method. In this method the threshold of hearing is defined as 2 out of 3 (or 3 out of 5) correct responses during the ascending portion of the tone presentation.