Chapter 1 22 • If the noise level measured at the eardrum exceeds the level of 87 dBA when using hearing protection, direct action is required to reduce the noise level. Technical interventions Manytechnicaldevicesareavailabletofacilitatehearing.Thesecanpartiallycompensate for the listening difficulties that are associated with hearing loss. Conductive hearing loss can often be managed relatively well, but sensorineural and mixed hearing losses are much more difficult to manage (Michels et al., 2019). Fulfilling auditory tasks often remains to require increased attention, concentration, and effort for adults with hearing loss, even if technical devices are used to enhance hearing (Ohlenforst et al., 2017; Shinn-Cunningham&Best, 2008). For example, understanding speech in noise is often more difficult for adults with hearing loss – even when wearing hearing aids – compared to those with normal hearing (Cubick et al., 2018). Hearing aids Providing hearing aids is the primary intervention for adults with hearing loss (Hickson et al., 2013; Kochkin, 2009; Timmer et al., 2015). Essentially, hearing aids act to amplify sounds. A microphone detects a sound, which is processed and delivered as an acoustic signal directly into the external ear canal or through a hollow tube (Hampson, 2012). This amplification can be linear or non-linear and is most of the times non-linear (Dillon, 2008). In the case of linear amplification, all sounds of a given frequency are amplified equally irrespective of the level of the signal, or what other sounds are simultaneously present. In case of non-linear amplification, the amplification of a sound may differ between sounds with different sound levels, or when simultaneous sounds are present. To compensate for the reduced dynamic range in ears with sensorineural hearing loss and to reduce the distortion component of hearing loss, non-linear amplification is important. Earlier in this chapter, we mentioned that the range of levels that can be heard ánd tolerated is often smaller when hearing loss is present. Compression systems in hearing aids aim to adjust the dynamic range of sound levels in the environment to better match with the smaller dynamic range of an individual with hearing loss (Dillon, 2008). When compression is used, the amplification of sounds is automatically adjusted based on the level of the input signal, with higher sound
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