Using these different assessment tools, an audiologist can identify how far any damage to the auditory system has progressed, and the impact caused in each of the five phases of communication decline.
To hear something, the sound must be loud enough. Damage to the auditory system causes the level at which sound becomes audible to be higher than normal, and is identified as a hearing loss. Standard Pure Tone Audiometry (PTA) is used to assess any decline in sensitivity to sound, testing the combined function of the outer, middle and inner ear.
Even in ideal listening environments, some people can struggle to understand speech. Free-field word recognition tests are used, presented through a calibrated loud speaker, to assess any decline in speech recognition.
Communicating in noisy environments is harder for everyone, but some people have more difficulty than others, and is the most common and important area of communication difficulty for many. The speech in noise test is used to measure the level of volume speech needs to be in relation to competing sounds, for someone to follow a conversation.
Everyone has a tolerance for background noise; a level at which they find noise uncomfortable. The Acceptable Noise Level (ANL) test is used to measure at what level an individual finds noise intolerable, relative to a conversation at a comfortable volume. This assesses any decline in acceptable noise levels.
Hearing and communication is highly complex, involving many processes and high-level brain function. For some, the damage to one or more of these processes will result in little benefit from hearing correction. Aided free-field word recognition tests are used to assess the potential for improvement through amplification.