Category: lectureNotes_cm2

For Wednesday’s (12/10) quiz over spectral processing, review the previous posts on intro to spectral processing, the Fourier transform, phase vocoding, and convolution. Important Concepts The quiz is not limited to the listed items below, but these concepts will go a long way towards helping you master the important material. Intro to Spectral Processing Audio…

Convolution is a fundamental process in digital audio processing. Even if you do not specifically know that the process is happening, you know the effects of the process. Filtering, reverberation, and cross synthesis all illustrate convolution. For example, a filter convolves its impulse response (IR) with the input signal to produce filtered output. Sampling reverbs convolve…

Phase Vocoding allows for independent control of time duration and pitch.  Time Expansion/Compression with Phase Vocoding The conversion of an audio signal from the time domain to the frequency domain results in a series of frames containing bins of frequency and amplitude information. If you conceive of the FFT as producing a snapshot, a frozen picture of…

Background In 1822, Jean Babtiste Joseph, Baron de Fourier developed the theorem any periodic signal could be represented as the sum of individual sine waves. The number of sine waves needed could be infinite, and each sine wave would have its own frequency, amplitude, and initial phase. The process of calculating the frequencies present in…

Audio Domains Up until this point, we’ve been talking about audio processing and synthesis in the time domain. Spectral processing takes place in the frequency domain. In the time domain, we represent sound as changing amplitude (y value) over time (x value). In the frequency domain, sound is represented as changing amplitude (y value) over…

Overview Any sound can be thought of as containing discrete particles/time segments (grains) Duration of an individual grain is short – usually 1 ms to 100 ms. Within an individual grain, sound parameters are fixed. Change occurs as you progress from grain to grain. Parameters of Individual Grains Playback speed Index location (location in soundfile…

Short Quiz on Friday, 11/14. Topics: Granular Synthesis Filters (general, and Digital)

Two issues have come up from early attempts to upload, attribute, and geotag samples on Freesound.  Geotagging is much easier than I have made it out to be. You don’t need to use Google Earth at all. It’s built in to Freesound. Once you’ve uploaded a sample, and it has passed moderation (which only takes…

in no particular order… Interesting compositions tend to have more than one layer of activity going on at any given time. In traditional acoustic classical music we may think of this as harmony and melody, but it could also include multiple contrapuntal lines, or a slow background harmonic movement, a middle ground harmonic accompaniment. For…