• Recall disruption produced by noise-vocoded speech: a study of the irrelevant sound effect

      Dorsi, Josh (2013-11-11)
      The Irrelevant Sound Effect (ISE) is the finding that serial recall performance is impaired under complex auditory backgrounds such as speech as compared to white noise or silence (Colle & Welsh, 1976). Much of the current research investigates the role of changing-state complexity of the background stimuli in ISE (e.g., Jones & Macken, 1993). This study investigated whether speech-specific qualities of the irrelevant background have an effect on the ISE. This was done using noise-vocoded speech, an acoustic transformation that removes many of the acoustic properties of speech while preserving the speech intensity profile. Experiment 1 compared serial recall accuracy resulting from white noise and noise-vocoded speech backgrounds and found that noisevocoded speech is more disruptive. Noise-vocoded speech preserves the intensity profile of nature speech with a number of amplitude channels; each channel matches the average intensity for the corresponding channel in natural speech. Experiment 2 systematically varied the resolution of noise-vocoded speech by adjusting the number of these channels. These results show that ISE varies based on the number of channels in noise-vocoded speech, but this change in disruption is not consistent across channel conditions. Results demonstrate that changing state complexity alone is not a sufficient explanation of ISE.