In addition, Zwicker's loudness (N) was highly correlated with the annoyance from high-speed train noise in both the audio-only and audio-visual conditions.
In these experiments, the recognition rate of a set of utterances (words, syllables, or sentences) by a group of observers, is computed under at least two different conditions, namely, unimodal auditory and bimodal audio-visual conditions [33].
We directly compared activity in response to the audio-visual conditions with that in response to the AO condition, as only the modulation of auditory responses was of interest for the current purposes.
The P2 component was significantly influenced by Condition, F 2, 72) = 7.30, p = .001, ηp² = 0.17, driven by the Bonferroni corrected difference (p < .05) between AO and both audio-visual conditions; the N1 component was not influenced by Condition (p = .128).128
The experiments consisted of three parts: 1) visual-only condition, 2) audio-only condition, and 3) combined audio-visual condition.
In the "audio-visual" condition, a synchronized combination of the visual and auditory stimulus was presented for 200 msec., always on the same side (left visual hemifield/left speaker or right visual hemifield/right speaker).
In addition, the visual images significantly influenced the noise annoyance, and LAeq and NF were the dominant factors affecting the annoyance from high-speed train noise in the combined audio-visual condition.
However, in the current data set the attenuation of P2 amplitude was greater for the audio-visual Mismatch condition than for the congruent Audio-visual condition.
To further assess the changing relationship between Conditions over Age, a linear regression was run with Age as a predictor of the difference between AO and each audio-visual condition for N1 and P2.
For latency, the ANOVA revealed a main effect of Condition, F 2, 72) = 5.14, p = .008, ηp² = 0.13, driven by the difference (p < .05) between the AO and each audio-visual condition, AO > AV = MM.
Notably, after Bonferroni correction P2 showed significant (p < .01) modulation between all levels of Condition, whereas N1 only showed a difference between AO and each audio-visual condition, at p < .01 (see Figure 2).
