Abstract
The present paper puts forward a novel technique of customizing the shape of the fade-in sound effect. In audio engineering, the most common fade-in shapes are of linear, logarithmic and exponential type. Since the valuation of the outputs of the transcendental functions (e.g. exponential and logarithm) is very time consuming, their employment with a view to imposing how the audio level has to change over time is mainly suitable for off-line volume processing, e.g. in various digital audio editors. In this paper, to depict the fade-in shape, we consider that the audio volume is the output of a function of time variable that is neither linear nor transcendental. In order to enable a smooth increasing in the audio level i.e. a smooth transition from silence, without notable “glitches”, the employed function is defined so that the initial instantaneous rate of change equals zero. More precisely, without taking into account the linear fade-in shape, we advance a method of fade shaping that is suitable for fast processing in real-time. Straightforward implementations in pure JavaScript are provided to the reader with the purpose of immediate use. Discretization is achieved by associating the “timeupdate” HTML DOM media event with the audio element.
Mathematics Subject Classification: 94A12, 94A29, 68N15, 68N19, 97P40
Keywords: Audio volume, Real-time processing, Fade-in audio effect, Fade-in shape, Programming techniques, JavaScript
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