The study of phonetics is not only about figuring out the differences between written and spoken language and creating such useful instruments as the IPA, it is also about describing the sounds that are made when a word is articulated.
One way to decribe sounds would be to define the physical characteristics of the sounds themselves... frequency, intensity, duration, etc. As you know by now, this would be part of acoustic phonetics. According to Skandera/Burleigh (2005), at least eight features are relevant to the description of speech, that fall into two categories. The first five features: loudness, pitch, tone of voice, duration and length, and air-stream mechanism are mainly relevant if we want to stay with acoustic phonetics and want to describe the physical aspects of English sounds and you have learned the most important facts on most of these features already.
The second category contains features that are both phonetically and phonologically relevant, since they can distinguish meaning. This is why these features, namely: intensity of articulation or voicing, place of articulation and manner of articulation, are also called distinctive or relevant features. They describe sounds mainly based on how they are produced and what organs are involved in changing the air-stream that moves up from our lungs through the vocal tract. Analysing the way sounds are made is, as you have learned already, the goal of articulatory phonetics and this is what we will focus on in the next three subchapters.
Voicing, in phonetics and phonology, generally refers to the vibration of the vocal folds and its impact on the quality of the sounds produced. Read more on the difference between voiced and voiceless sounds, and the difference between voicing and intensity of artiulation in this brief subchapter.
Place of Articulation In this subchapter we will have a look at how the different parts of our speech apparatus are involved in the production of consonant sounds. Depending on the place of their articulation, the different consonants can be put together in a group and be named according to where they are produced.
Manner of Articulation refers to the type or degree of closure of the speech organs and is defined by a number of factors such as for example whether the airstream passes through the nasal cavity in addition to the oral cavity (nasal vs. oral) and so forth. Apart from vowels, we
can identify a number of different manners of articulation, listed in this subchapter.