I use Audacity just about every week, to record myself and to record my students. Audacity is available for free, it is open software designed by volunteers and given to the world. It shows sound as spectrograms; I use the to help students become aware of sounds, which can be very helpful when learning English pronunciation.
Sometimes we just can’t hear sounds that don’t exist in our first languages until we are made aware of them; we have sort of acoustic deafness to certain sounds. By 18 months, babies have begun to disregard sounds that don’t bring them food or protection or shelter or responses from caretakers. They begin narrowing down their acoustic focus to those vocal sounds that are meaningful in their first language, and eventually they may not be able to hear sounds they were once able to hear as babies.
So, learning the pronunciation of a new language might mean learning to be aware of some sounds again. People believe their own eyes, and when I record myself saying certain sounds and students see the difference in the spectrograms, it has a stronger impact. From this awareness, we can begin to work on listening recognition and then articulation of the new sounds. Here’s an Audacity recording to show how differently F, V, and B are, so students can begin to emulate these shapes. The first is Fat, the second Bat, and the third Vat. You can clearly see the air of the initial f sound in fat, the flat beginning of bat formed by closed lips which stop any initial sound, and the gradually increasing voicing of the V in the third word, vat.
Students can record themselves and compare their own productions of Fat, Bat, and Vat, experimenting with their sound until they approximate spectrograms shaped more like these. This initial phase of becoming aware, and experimenting to learn how to control sound, is very important to adult learners. Peggy Tharpe teaches, coaches, and publishes about English pronunciation and intonation. She believes that if you understand why something is happening, you're better able to address it and change it. She teaches the "why" of pronunciation as well as the "what" and "how".