PMC

Spectrograms of a 4 second segment of audio, containing a series of coughs, showing stages of algorithm; a) 512 sample Fast Fourier Transform of audio data is taken every 16 samples and positive half of spectrum is plotted vertically using intensity of colour as contribution of frequency to signal. This spectrogram is shown underneath the audio waveform. b) Median frequency is calculated for each point in spectrogram and shown here superimposed. c) Threshold value for median frequency used to generate a ‘mask’ indicating which audio is to be removed, indicated graphically here as the faded sections. d) Timings for cuts of audio data adjusted to ensure ‘attack’ of sounds is captured.

All spectrograms represent unfiltered 4-s segments of WAV soundscapes passively recorded at station PPA001 in the Fazenda Pouso Alegre area (windowing function: Blackman-Harris; resolution: 512 bands; decibel range: 85 dB; the strongest target signals were equalized to –3 dB). A: flight calls of a lapwing patrolling its inundated territory; 28 Apr. 2013, 17:38 h (). B: display and agitated cackling of a pair flying over their inundated territory; 29 Apr. 2013, 16:35 h (). C: short series of cackling alarm calls of perched V. chilensis close to its nest; 31 May 2013, 14:31 h (). D: short series of agitated alarm calls of a lapwing flushed from its nest or close to it; 30 May 2013, 06:13 h (). E: excerpt of a long alarm call series of a V. chilensis flock mobbing a predator to defend their chicks; 16 Jun. 2013, 15:35 h (). F: segment of a long alarm call series of a pair or flock mobbing a potential predator or food competitor; 21 Jun. 2013, 12:28 h ().

The image histograms for R, G, B components a cover image, b stego image. The time series and histogram for c secret audio data, d obtained audio data

After identifying a series of event patterns in a group of subjects who watched a movie, we tested whether this same series of events occurred in a separate group of subjects who heard an audio narration of the same story. The movie and audio stimuli were not synchronized and differed in their duration. We restricted our searchlight to voxels that responded to both the movie and audio stimuli (having high intersubject correlation within each group). Movie-watching event patterns in early auditory cortex (dotted line) did not generalize to the activity evoked by audio narration, while regions including the angular gyrus, temporoparietal junction, posterior medial cortex, and inferior frontal cortex exhibited shared event structure across the two stimulus modalities. This analysis, conducted using our data driven model, replicates and extends the previous analysis of this dataset () in which the event correspondence between the movie and audio narration was specified by hand. The searchlight is masked to include only regions with intersubject correlation > 0.1 in all conditions, and voxelwise thresholded for above-chance movie-audio fit, q<10⁻⁵. See also .