Manner of Articulation
Stop - Complete closure of the oral cavity. [p], [t], and [k] are examples of oral stops because the nasal cavity is closed as well (i.e. there is no airflow through the nose). [m] and [n] are examples of nasal stops because the nasal cavity remains open allowing airflow through the nose.
On a spectrogram oral stops are chracterized by a gap in the formants during the closure, followed by a sharp resumption at the release. Stops can be aspirated in which case the release will be followed by random enrergy distributed over all frequencies.
Fricative - Narrowing of the distance between two articulators so that the airstream is partially obstructed and a turbulent airflow is produced, as in English [z] in "zoo." The turbulent airflow produced by a fricative sounds like a hissing noise.
On a spectrogram, a fricative looks like random noise distributed over many frequencies. Different fricatives have energy concentrated in different frequency ranges.
Nasal - A sound in which the soft palate is lowered so that there is no velic closure and air may go through the nose, as in English [m] in "my."
Nasals resemble vowels on a spectrogram because they are both sonorants. A key to telling nasals and vowels apart is that nasals have a wider first formant band.
Lateral - An articulation in which the airstream flows over the sides of the tongue, as in English [l] in "leaf."
Laterals also resmemble nasals and vowels on a spectrogram.
Tap - A rapid movement of the tongue tip upwards to contact the roof of the mouth, then returning to the floor of the mouth along the same path. This sound occurs in English in the middle of words like "ladder" or "writer."
Where a tap occurs on a spectrogram, there will be a brief interruption between two vowels.
Approximant - An articulation in which one articulator is close to another but to a lesser degree than for a fricative., as in English [w] in "wet."
Diphthong - A vowel in which there is a change in quality during a single syllable, as in English [ai] in "high."
On a spectrogram, this will look like a long vowel where the formants change in the middle.
Affricate - A stop followed by a fricative at the same place of articulation.
On a spectrogram, this looks like a gap in the pattern, as in the closure for a stop. Then there is a long narrow line, where the articulators come apart. Then there is a pattern of white noise corresponding to the fricative energy. The fricative noise should be longer than that for an aspirated stop.