Selective attentional biases arising from one sensory modality manifest in others. The effects of visuospatial attention, important in visual object perception, are unclear in the auditory domain during audiovisual (AV) scene processing. We investigate temporal and spatial factors that underlie such transfer neurally. Auditory encoding of random tone pips in AV scenes was addressed via a temporal response function model (TRF) of participants' electroencephalogram (N = 30). The spatially uninformative pips were associated with spatially distributed visual contrast reversals (“flips”), through asynchronous probabilistic AV temporal onset distributions. Participants deployed visuospatial selection on these AV stimuli to perform a task. A late (~300 ms) cross‐modal influence over the neural representation of pips was found in the original and a replication study (N = 21). Transfer depended on selected visual input being (i) presented during or shortly after a related sound, in relatively limited temporal distributions (<165 ms); (ii) positioned across limited (1:4) visual foreground to background ratios. Neural encoding of auditory input, as a function of visual input, was largest at visual foreground quadrant sectors and lowest at locations opposite to the target. The results indicate that ongoing neural representations of sounds incorporate visuospatial attributes for auditory stream segregation, as cross‐modal transfer conveys information that specifies the identity of multisensory signals. A potential mechanism is by enhancing or recalibrating the tuning properties of the auditory populations that represent them as objects. The results account for the dynamic evolution under visual attention of multisensory integration, specifying critical latencies at which relevant cortical networks operate.

Surroundings continually propagate audiovisual (AV) signals, and by attending we make clear and precise sense of those that matter at any given time. In such cases, parallel visual and auditory contributions may jointly serve as a basis for selection. It is unclear what hierarchical effects arise when initial selection criteria are unimodal, or involve uncertainty. Uncertainty in sensory information is a factor considered in computational models of attention proposing precision weighting as a primary mechanism for selection. The effects of visuospatial selection on auditory processing were investigated here with electroencephalography (EEG). We examined the encoding of random tone pips probabilistically associated to spatially-attended visual changes, via a temporal response function model (TRF) of the auditory EEG timeseries. AV precision, or temporal uncertainty, was manipulated across stimuli while participants sustained endogenous visuospatial attention. TRF data showed that cross-modal modulations were dominated by AV precision between auditory and visual onset times. The roles of unimodal (visuospatial and auditory) uncertainties, each a consequence of non-synchronous AV presentations, were further investigated. The TRF data demonstrated that visuospatial uncertainty in attended sector size determines transfer effects by enabling the visual priming of tones when relevant for auditory segregation, in line with top-down processing timescales. Auditory uncertainty in distractor proportion, on the other hand, determined susceptibility of early tone encoding to automatic change by incoming visual update processing. The findings provide a hierarchical account of the role of uni- and cross-modal sources of uncertainty on the neural encoding of sound dynamics in a multimodal attention task.