Bio is an interactive analysis program for SGI and Linux machines, which shows sonograms, spectrograms, oscillograms, pitch tracking, spectral gravity and noise content.
Bio can perform spectral analyses of sound of any length. The user can zoom in and out in the sonogram, and extract accurate amplitude and frequency values (the latter with the aid of a phase vocoder) by clicking in the image. The program also features an oscillosgram, as in a sound editor, a pitch tracker and a curve with estimated noise content.
Moreover, one can see a curve showing the spectral center of gravity (centroide), and in a separate window you can see the spectrogram for the time highlighted with the mouse. Segments of the sound can be played back. All data can be exported to text files for further analysis (eg. In Matlab), or PostScript.
How is the program useful?
Bio was originally written as a bioacoustic tool in conjunction with a research project on monkeys in Costa Rica, in which the program developer participated. Later, the program has also proved useful in musicological analysis and for educational purposes..
The integrated presentation of different measurement data provides a richly detailed but understandable impression of different aspects of sound, especially in combination with playback.
Hvordan does the program work?
As with Ceres, Bio is based on FFT (Fast Fourier Transform), which means that the spectral analysis is done in chunks with a fixed number of analysis channels, evenly spread along the frequency axis. In order to estimate the exact frequencies the partials, phase data is used.
The pitch tracker uses the same algorithm as Pitch Tracker (the program), and uses the frequencies of the partials, which the phase vocoder has estimated. The fundamental tone is identified by using a simple heuristic algorithm.
The noise content is estimated by measuring residual energy through linear predictive coding. Alternatively, one can choose a normalized measuring unit for spectral entropy.
Bio is designed and programmed by Øyvind Hammer.