This document discusses the main parameters used to classify consonant sounds: place and manner of articulation, state of the glottis (voiced vs voiceless), nasality, and laterality. It explains that place of articulation refers to where the active and passive articulators come together in the vocal tract. Manner of articulation describes how closely the articulators approach each other and can include stops, fricatives, approximants, and affricates. It also discusses how the vocal cords, soft palate, and sides of the tongue can be configured to modify sounds.

1. Manners of articulation
Place of articulation refers to where the narrowing occurs -- which active
articulator gets close to which passive articulator. Constriction
degree refers to how close they get. The main constriction degrees are:
stop: the active articulator touches the passive articulator and completely
cuts off the airflow through the mouth. English stops include:
[p], [d], [k], [m].

2. fricative: the active articulator doesn't touch the
passive articulator, but gets close enough that
the airflow through the opening becomes
turbulent. English fricatives include [f], [ ],
[z].
approximant: the active articulator approaches
the passive articulator, but doesn't even get
close enough for the airflow to become
turbulent. English approximants include [j],
[w], [ ], and [l].
affricate: Affricates can be seen as a sequence
of a stop and a fricative which have the same or
similar places of articulation. They are
transcribed using the symbols for the stop and
the fricative. If one wants to emphasize the
affricate as a "single" sound, a tie symbol can be
used to join the stop and the fricative
(sometimes the fricative is written as a
superscript).

3. State of the glottis
For now, we can simply use the terms "voiced" and
"voiceless" to answer the question of what the vocal
cords are doing:
In voiced sounds, the vocal cords are vibrating.
In voiceless sounds, the vocal cords are not vibrating.
Ultimately, we will see there are different ways of being
voiced or voiceless. The vocal cords can do a number
of things. They can:
be held so wide apart that the air makes no sound
passing through them. (This is nice when you have to
breathe 24 hours a day, but not as useful for speaking.)
be held closer together, so that the air passing through
them becomes turbulent. This quality of sound is
called breathiness. It is what is happening in
apsiration and in the sound [h].
be held together so that the air passing through them
causes them to vibrate. This is called voicing.
be held together so tightly that no air can pass through
at all, as in a glottal stop.

4. (By varying their tension and position, the vocal
cords can also produce many other effects like
breathy voicing, creaky voicing, and falsetto.)
What the vocal cords are doing is independent of
what the higher parts of the vocal tract are doing.
For any place of articulation and any degree of
stricture, you can get two different sounds: voiced
and voiceless. For example, [t] and [d] are formed
identically in the mouth; the difference is that the
vocal cords vibrate during a [d] but not during a [t].
(The obvious exception is the glottal place of
articulation -- you can't vibrate your vocal cords
while making a glottal stop.)
In each cell of the IPA chart, the symbol for the
voiceless sound is shown to the left and that for
the voiced sound to the right. Some rows only
have voiced symbols (e.g., nasals and
approximants). You can write the corresponding
voiceless sound using the voiceless diacritic (a
circle under the voiced symbol).

5.  Nasality
 The soft palate can be lowered, allowing air to flow
out through the nose, or it can be raised to block
nasal airflow. As was the case with the vocal cords,
what the soft palate is doing is independent the
other articulators. For almost any place of
articulation, there are pairs of stops that differ only
in whether the soft palate is raised, as in the oral
stop [d], or lowered, as in the nasal stop [n].
 Laterality
 When you form an [l], your tongue tip touches your
alveolar ridge (or maybe your upper teeth) but it
doesn't create a stop because one or both sides of
the tongue are lowered so that air can flow out
along the side. Sounds like this with airflow along
the sides of the tongue are called lateral, all others
are called central (though we usually just assume
that a sound is central unless we explicitly say it's
lateral).
 The side of the tongue can lower to different
degrees. It can lower so little that the air passing
through becomes turbulent (giving a lateral
fricative like [ ] or []) or it can lower enough for
there to be no turbulence (a lateral approximant).
The [l] of English is a lateral approximant.