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This example is a tonic arpeggio, Do-Mi-So-Do, with continuous glides between the tones to illustrate the dynamic properties of the auditory image. There is a short, fast version of the arpeggio and a long, slow version of the arpeggio. In the short, fast version, each of the tones, Do, Mi, So, Do, is 0.3 seconds in duration and the acoustic properties of the sound are fixed during each tone. In the long, slow version the tones and glides are 1.2 seconds in duration. The auditory figures in this event are static for the duration of each tone; between tones the auditory figure morphs from one note to the next. The instrument is once again a click train and the period of the starting Do is 8 ms (125 Hz), so the spacing of the figures in the simulated auditory image is 8 ms for the starting Do.

A fast tonic arpeggio (time-interval format) with glides as an example of a compound auditory event

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A slow tonic arpeggio (time-interval format) with glides between the notes as an example of a compound auditory event

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Between the tones, the inter-click period decreases linearly with time down to the period of the next tone. At the same time, the pulse rate increases and we hear the pitch glide up continuously to the next note in the arpeggio where it stabilizes again briefly. In the simulated auditory image, we see the auditory figures march across, horizontally towards the origin of the time-interval dimension as each glide proceeds, and the rate shift matches the rate of the glide that we hear. During the glide, the magnitude of the figure decreases slightly and the details of the auditory figures become somewhat blurred, particularly at the longer time intervals. This is because the auditory figures produced by successive cycles of the sound are changing position slightly and so each frame of the video is presenting an average of a sequence of 4-6 slightly different auditory figures. Nevertheless, the rate of clicks is high relative to the integration time of the auditory system and so we see a blurring version of the figures gliding smoothly from one tone to the next, just as we see characters move smoothly in animated cartoons. As each glide terminates on the next note of the arpeggio, we hear pitch firm up and we see the figures in the simulated auditory image sharpen up.

The temporal parameters that control the dynamics of auditory perception are described in Chapter 3.2, along with the details of how they are instantiated in the computational version of AIM. The details of the motion of the auditory figures can be examined in detail by downloading the video and playing it in slow motion.

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