Free speech analysis software
There are several software packages for the analysis of speech signals available free of charge via the internet. Which one you want to use will depend on your particular needs.
The following is simply the opinions of one user, and is not in any way meant to be read as an official evaluation. We are indebted to the creators of this software for all the work they have put into the development of the software without financial reward.
Available from University College London, written by Mark Huckvale. Probably the simplest and easiest to use. It's ideal for introducing students to acoustic analysis on computer, and it takes up very little disk space.
Quite easy to use, and capable of delivering more functions than WASP. The display format is more flexible, and it's easy to change between monochrome and colour spectrograms, and to set the frequency range displayed. The pitch-tracker works well, and can be set to be restrained within a particular frequency range. The labelling of segments can be done with proper IPA symbols selected from IPA Chart-type displays. There is a quite a lot of other phonetic software that can be downloaded and used in conjunction with this. Students like it, in my experience. The only drawbacks are that positioning the cursors is awkward, requiring some practice, and the package is not as flexible as some others in allowing you to design your own functions.
This is the "big brother" of WASP. It is extremely powerful, well documented and very regularly updated and improved. As well as analysis, it will also let you do speech synthesis and experiments with speech recognition. Beginners tend to find it intimidating, however, and on the whole it is not recommended for people with limited computing skills. For the suitably skilled, it can be used more or less as a programming language, and many programs can be "pipelined" together so that a particular research application can be "tailor-made". There is a users' email support group that gives helpful advice.
For some people, Praat is more of a way of life than a software package. It is very widely used by top-level researchers, has most of the good features of SFS (see above) and in addition will teach you all about Optimality Theory! Praat enthusiasts contribute extra programs or functions, so it keeps growing. Email support for users in difficulty is good. As with SFS, though, learning it is a difficult challenge for those with little computing expertise.
Not really free software in the sense of the above, but you can download a free trial copy of CoolEdit 2000 with some of its functions disabled, and if you later want to buy it you can do so over the internet. At $69, it's incredible value. Although its spectrograms look awful, this package lets you do all sorts of useful things, such as convert from one recording format to another, reduce background noise, slow down the replay without changing the pitch, cut and paste bits of waveform, and loads of other things.
WaveSurfer is an Open Source tool for sound visualization and manipulation. It has been designed to suit both novice and advanced users. WaveSurfer has a simple and logical user interface that provides functionality in an intuitive way and which can be adapted to different tasks. It can be used as a stand-alone tool suited for a wide range of tasks in speech research and education. Typical applications are speech/sound analysis and sound annotation/transcription. WaveSurfer can also serve as a platform for more advanced/specialized applications. WaveSurfer can be extended through plug-ins or be embedded in other applications. Another option is to control it remotely.