ion is passed along to connected nodes. Excitatory links exist between nodes at different levels, which can cause a node at the next level to fire. There are also inhibitory links between nodes within the same level, which allows highly activated nodes to inhibit competitive nodes with less activity. This results in one node taking all the activity. The flow of activation is not just from the feature detectors to the word level. The excitatory activation flows in both directions, which allows for information gathered at the word level to influence phonetic identification (Moore, 1997).Like humans the TRACE cannot identify a word until it has heard part of the next word. It can, however, better determine a where a word will begin when it is preceded by a word rather than a non-word. Although the model is influenced by word beginnings, it can recover from underspecification or distortion of a word’s beginning. The model is able to use activations of phoneme units in one part of the TRACE to adjust the connection strengths determining which feature will activate which phoneme. This model is called the TRACE because the pattern of activation left by a speech input is a trace of the analysis of the input at each of the levels (Elman and McClelland, 1986). Resistance of Speech to Corrupting InfluencesOne factor that can greatly affect speech perception is background noise. For satisfactory communication, the signal to noise ratio should be +6dB. When this does not occur, speech perception drastically drops. Moore (1997) stated that at a 0dB signal to noise ratio word articulation scores reach 50%. A second factor, which may affect speech perception, is a change in frequency spectrum. Many transmissions only pass a certain range of frequencies. This may leave some speech signals out since information by the speech wave is not confined to any particular frequency range.A third factor is peak clipping. If an amplifier is o...
