Math 5: Software
- SPRING 2007
A word about computer audio formats:
-
WAV (.wav, `Microsoft Wave format') is
high quality but gives large files
(1MB gives only 6 seconds of stereo CD-quality)
- MP3 (.mp3, 'MPEG 3') is a proprietary format,
compressed so gives much smaller files
(1MB gives a full minute of stereo CD-sounding-quality at default
'128 kbit' rate). For our purposes this quality will be fine.
- OGG (.ogg 'Ogg Vorbis') is a free (non-proprietary)
format, equally compressed as MP3, sounding equally good.
I strongly
recommend exporting to OGG (eg using audacity) for all your Aural postings.
Audio analysis, editing, conversion
- audacity
Great for basic editing, viewing, multitrack, applying effects,
power spectrum of a selection,
reading/writing/converting MP3, OGG, WAV formats.
[Windows,MacOSX,Linux]
Useful keystrokes:
- Ctrl-1 zoom in, Ctrl-3 zoom out timescale
- Highlight a (mono) sound, not too short,
then
Analyze->Plot Spectrum.
For better resolution change 512 to the largest size possible
(and choose a longer selection),
change
Linear frequency to Log frequency and make it
fill the screen.
- praat
Powerful tool for spectrograms, spectra, voice analysis,
formant extraction and modification (eg gender changing!)
Interface is dorky, but is worth it. Reads WAV, not MP3 or OGG.
[Windows,MacOSX,Linux]
Useful keystrokes:
(also see online help)
- Once you've loaded a sound object, choose
Edit,
switch off Formant, Pitch,
and switch on Spectrum->Show spectrogram
- Ctrl-n zooms to a (pink) selection
- Tab plays a selection
Spectrum->Spectrogram settings... I recommend
View range 0 to 2000 Hz, Window length 0.05 s or longer.
- Ctrl-l takes power spectrum of selection, very useful to
then zoom in on to measure partial frequencies.
- Raven
Professional audio analysis software, for playback,
spectrogram, spectrum. Comes in two versions: Raven Lite (free; does spectrogram but not spectrum),
and Raven Pro (free demo version runs for 10 mins;
otherwise $50 student license).
[Windows,MaxOSX]
- baudline
Beautiful interface, very flexible,
for recording, variable-speed playback, real-time spectrogram, spectrum.
Nearly as powerful as Raven or praat, easy to use, colorful, my favorite.
Reads WAV, OGG, not MP3.
[Linux]
Useful keystrokes:
- Pause start recording or stop, Alt-P play (highlighted section)
- Right-mouse-button brings menu up, eg to choose input source
- Alt-right, Alt-left zoom waveform timescale;
Alt-up, Alt-down zoom spectrogram timescale or waveform
amplitude
- Set
process->transform size->4096,
or larger, for good resolution on frequency axis.
- To take power spectrum of a selection:
displays->average
then use Middle-mouse-button to grab spectrum (then set
Clear->auto-clear)
- Middle-mouse-button on spectrogram
brings up variable harmonic series lines
- glScope
An elegant and useful little oscilloscope for real-time input only
by Luke Campagnola,
tweaked by yours truly. [Linux]
Useful keystrokes:
- spacebar toggle capture/restart
- 1,2 make line thinner/fatter
- Tab align view so trigger on right side
- wavesurfer
Spectrum (including averaged over a selection) and spectrogram, formants,
of sound files, and basic editing. Easy to use, not very flexible (eg
spectrogram length limited to 512 samples). [Windows,MacOSX,Linux]
Useful keystrokes:
- Amadeus II
Very nice real-time spectrogram and spectrum, editing, effects, conversion.
Trial version is free; $30 to buy.
WAV, MP3, OGG, many formats. [MacOSX only]
- MATLAB
Can read audio files into arrays of numbers for analysis, graphing, processing.
Very powerful programming environment; I don't recommend it for this
course unless you already use it.
See Matlab
help on my Math 46 site. [Windows,MacOSX,Linux]
Audio synthesis
