Extent Of Frequency Modulation Research Articles

Postpartum whistle production in bottlenose dolphins

AbstractDespite much research on bottlenose dolphin signature whistles, few have investigated the role of maternal whistles in early calf development. We investigated maternal whistle use in the first weeks postpartum for captive dolphins. The overall whistling rate increased by a factor of ten when the calves were born and then decreased again in the third week of the one surviving calf. Adult whistles were distinguished from calf whistles based on the extent of frequency modulation and were further classified into signature and non‐signature whistles by comparison to a dictionary of known whistles. The average rate of maternal signature whistle production increased significantly from 0.02 whistles per dolphin‐minute before the calves were born to 0.2 and 0.3 whistles in weeks 1 and 2, decreasing again to 0.06 in week 3 for the mother of the surviving calf. Percent maternal signature whistles changed similarly. Signature whistle production by non‐mothers did not change when the calves were born. A likely function of this increase in maternal signature whistle production is that it enables the calf to learn to identify the mother in the first weeks of life.

Perceptual studies of violin vibrato

Although it seems obvious to violinists that vibrato has a large influence on the perception of violin tone quality, published studies of violin vibrato have mainly concerned its influence on the sound from a scientific point of view, i.e. the characterisation of its time-frequency properties. Work will be described to explore the link between the perception of vibrato notes, the extent of frequency modulation and the level of damping of the resonance modes of the violin. Damping influences the "peakiness" of the frequency response function. The test methodology is based on liveliness ratings and triadic comparisons, where subjects have to select the most similar and the most different pair in each triad (presentation of three sounds). The sounds of the corpus are synthesised using sawtooth waves with frequency modulation, whose amplitude is varied, filtered through a set of admittances corresponding to a reference violin and two modified violins, one with the damping of all modes increased, the other one with the damping decreased.