Alright I'm going to continue with fricatives we briefly talked if you
watched part 1 and part 2 this is part 3 of the continuation of fricatives. I briefly
talk about fricatives in my second lecture where we talked about what
fricatives are like what are the 5 articulatory positions of the fricatives. We talked about
a fricative being a non-resident consonant and if it's a non-resident
consonant you have a limited formant structure for that but it is a
continuant and continuant is something that can be prolonged say if you go |s| |z|
those are sounds that can be prolonged so it's called continuant. So a fricative is an
example of a non-resident continuing speed sound. It's got restricted air flow
the restriction is caused by the constrictions and occlusions within the
vocal tract it has a presence of an audible noise. If i don't have to
repeat the sounds again but any time you try to produce a fricative it has no
audible noise. And the fricative noise originates at your articulatory
constriction and you have voiced vs. voiceless cognates and we talked about those
briefly in your previous part. And I'm not going to go over this again but we
wanted to talk about how a fricative is being produced. Now the concern or the
major focus for this lecture is going to be on the acoustic cues so we talked
about the nasals that was our first consonant sound which is classified
based on a manner of articulation. So the formant of articulation was nasals,
fricatives, stops, and affricates so we talked about the nasals we're talking
about the fricatives. If you talk about all these fricatives you make this audible
noise the first cue that stands out for fricative is the energy in the high frequency
region.
Ok, so if you produce a sound |s| and I measure the frequency of this acoustic sound or
of the speed sound there's going to be energy in the high frequency region. The
next thing that you observed since it's a non-resonant sound there is little or
no form and structure and it's basically more so often noise
rather than exact speed sound. For example if I produce these and if for the
not it was part of a speed sound it's going to be just like noise like a hissing sound of a snake. |f|
You know just kind of those sounds are sounds that are not going to be known
as speed sounds if you don't produce it in the context of speech
ok. Now the source as I said for the production of the fricatives is going to
be one at the level of the constriction of the vocal tract. So if i go |s| |f| those two
sounds are produced the constriction happens at the level of the vocal tract
only their voiceless sounds you're not bringing your vocal folds together. But
there are certain fricatives that have source of the level of the vocal folds
and the level of constriction at the vocal tract for example |z| |v|.
Those are sounds that have sourced the level of the vocal folds because you're
vocal folds have to vibrate to produce voice sounds and there is a
constriction of the level of the vocal tract ok. Now let me just show you a
spectrogram before i come to this slide.
Ok, so if I were to produce the sound |s| |z| right here only difference if
you look at the energy concentration so this is a spectrogram so your x-axis is
the time in your y-axis the frequency the darker the striation that you see on
the spectrogram indicates how intense or how loud those sounds are. So for example
if I see the difference between and I'm sorry those are the voiceless cognates
of the fricative pair and if you see the same region of high
frequency greater than 4,000 Hertz the same thing the energies greater than
4,000 Hertz for |z| the as well so what is the difference between these two sounds? If
you look at the very bottom
do you see this little thing right there where the |z| is? That is the vibration of
the vocal folds which can be seen as fundamental frequency, right? So voice
sound can be seen as the vibration of the vocal folds and the voiced indication
is right there as bar and there is no vibration of the vocal folds here so
there is no voiced piece right there.
Ok ,so that is the difference between |s| and |z|. All right, S and Z have a very narrow band
of frequency and high-energy noise as the spectrogram said the energies about
4,000 Hertz for S and Z the only difference you're going to have a voiced bar that's
called voiced bar right there for this and there is no bar for the voiceless sound
because your vocal folds don't vibrate. For Shh its energy's around 2,000 Hertz because
the point of articulation is further back in the mouth. So just go produce
these two sounds for me |s|
Shh observe the tongue position change for these two sounds. So the point of
articulation for shh is further back in the mouth so the resonating
cavity anterior to that is longer. So remember how even though the formant
structure there is no formant it's a non resonant sound the rule of how the
articulators are placed in the mouth will modify the frequency. So longer
the tract lower the frequencies right? So longer cavity resonates to lower
frequencies so that is why Shh has lower frequency than |s|.
Ok, so we're talking about the cavity anterior alright in front of your
articulator. So if you talk about there's really not much space in front of your
tongue which is the anterior to the tongue point of constriction but if you go
back and go shh there's more space in front of your articulator and that
what makes it resonate to lower frequencies. So the key point with a
fricative is that you need to know the point of articulation of the fricative you need
to know how the articulators constrict to produce this
sounds. It's a non-resonant sound it is a continuant sound the acoustic cue is
energy in the high frequency and there is little or no formant structure. The
acoustic energy for S and Z are higher about 4,000 Hertz but for shh the energy's around
2,000 Hertz the difference is because of the change in the cavity size alright?
As i said the perceptual energy for S is 4000 the perceptual energy for shh is 2000
that's how we perceive the difference between S and shh is because of the
difference in the acoustic energy.
Alright, so here we go again if i look at the spectrogram S is a voiceless so there's
no voice bar and the Z is voice that you see a voice bar down there
similarly for the shh and zz there's not much intensity so that is not a
voice bar but this is
definitely voice bar. The frequencies are about 2,000 hertz so if you see there's
more frequency starting at 2000 hertz if this was S your frequency only started
about four thousand hertz.
Ok, so in some what I want you to understand is where are the sound
sources for these speech sounds. So let's just focus about fricatives here.
Fricatives have source at the vocal tract and their aperiodic if there is
no vocal fold involvement. So they are voiceless fricatives which include the
|s| |shh| |f| ok?
The source is a level of the vocal folds and the vocal tract the resonator
becomes the vocal tract but it's a periodic and aperiodic sound because your vocal
folds are vibrating. Anytime your vocal folds vibrate you know that it's going
to be a periodic component because it's going to be fundamental frequency and
there's going to be harmonics. So for a voiced fricatives which is the |z| |f| those
sounds are voiced fricatives their sound is mixed periodic and aperiodic and their
source is the vocal folds and the vocal tract. This table is an important table
because I will be asking you an example of what the source is what the
resonators whether it's the sound is an aperiodic or a mixed periodic in
aperiodic sound giving an example. So for example i will say |B| is an
example of an aperiodic sound true or false? The answer response because it's mixed
periodic and aperiodic because for the sound |b| there is a vibration of your vocal
folds and there's a constriction of the level of vocal tract as well where
you're completely seeing off your lips.
Ok so that was a very brief thing because we already had talked about the
fricatives. So in sum fricatives are non resonant costants but they're
continuant consonants. The non resonant because of the
construction and occulsions that happens in your vocal tract because of your
articulators. The source can be at two different levels if it's a voiced sound
the source is at the vocal folds and the vocal tract, but if it's a voiceless
sound the source of the sound is only at the level of the vocal tract.
The acoustic energy for
fricatives is the high frequency energy, energy of high-frequency, for example
for |s| and |z| the energy is greater than 4,000 Hertz for |sh| the energy is around
2,000 Hertz. The difference how you can tell a difference between |s| and |z|
or |sh| and |jhhh| on the spectrogram is presence of the voice bar that you see
at the very bottom on the spectrogram right here that indicates a voice sound
versus a voiceless sound. The voice bar is because of the vibration of the vocal
folds so that in sum brings us to an end of fricatives and how fricatives
are identified on the spectrogram. So we've talked about nasals, we've talked
about fricatives. For your next class i'll be talking about stops affricates
and we'll also be talking about some super segmentals. Alright hopefully you're
getting the concept i want you to sit through i want you to look at this
listen to the lecture and tell me give me examples of voiced and voiceless
cognates for fricatives. Tell me if nasals are voiced or voiceless. Ok so
here's the list i want you to tell me if nasal voiced or voiceless I want you to tell
me if fricatives are voiced or voiceless and if their voiced and voiceless
cognates give me examples of a voiceless and voiced cognate and tell me what is
the difference that is identifiable between other discriminates between
voiced and voiceless fricative on a spectral plan. Ok so let's go over that
again i want to tell me if
nasals are voiced or voiceless sounds. I want you to tell me give me an example of a
voiced and voiceless cognate of a fricative and tell me on a spectrogram how would
you identify the difference between a voiceless and voice fricative alright.