Tone terracing
Encyclopedia
Tone terracing is a type of phonetic
downdrift
, where the high or mid tones
, but not the low tone, shift downward in pitch (downstep
) after certain other tones. The result is that a tone may be realized at a certain pitch over a short stretch of speech, shifts downward and then continues at its new level, then shifts downward again, until the end of the prosodic contour
is reached, at which point the pitch reset
s. A graph of the change in pitch over time of a particular tone resembles a terrace
.
Since the pitch of the low tone remains more-or-less constant at the lower end of the speaker's vocal range, while the other tones shift downward, the difference in their pitches narrows, eventually obscuring the tones altogether. At this point pitch reset is required if the tone system is to continue functioning.
Tone terracing is particularly common in the languages of West Africa
, where typically only the low tone causes downstep. However, a somewhat more intricate system is found in the Twi language of Ghana
. Twi has three phonemic tones: high, mid, and low. A word, and therefore a prosodic chunk of speech, may only start with a high tone or a low tone on its first syllable. As in many languages, a low tone starts out and remains at the bottom of the speaker's range. After a low tone, a subsequent high tone is downstepped. (A temporary exception occurs when a single low tone is found between two high tones. In this case the low tone is raised from its base value, but the second high tone is still downstepped, and subsequent low tones return to the base pitch.)
However, a phonetic downstep occurs between any two adjacent mid tones as well. In fact, a high tone is defined as any tone that is at the same pitch as a preceding high or mid tone; a mid tone will always be lower in pitch than a preceding high or mid tone. The result is that every instance of a mid or low tone shifts the upper end of the pitch range downward, until all pitches are reset at the end of the prosodic melody.
Table 1. The phonetic terracing effect in Twi of a series of mid tones. (Twi constrains the first tone to be either high or low.)
Table 2. The phonetic terracing effect in Twi of an alternating series of high and mid tones.
Table 3. The phonetic terracing effect in Twi of an alternating series of high and low tones.
From tables 2 and 3 it can be imagined that the tone sequences high-low-high and high-mid-high may be difficult for a non-native speaker to distinguish.
Phonetics
Phonetics is a branch of linguistics that comprises the study of the sounds of human speech, or—in the case of sign languages—the equivalent aspects of sign. It is concerned with the physical properties of speech sounds or signs : their physiological production, acoustic properties, auditory...
downdrift
Downdrift
In phonetics, downdrift is the cumulative lowering of pitch over time due to interactions among tones, called downstep, in a tonal language. It is distinct from the general lowering of the pitch during prosodic contours of a tonal or non-tonal language....
, where the high or mid tones
Tone (linguistics)
Tone is the use of pitch in language to distinguish lexical or grammatical meaning—that is, to distinguish or inflect words. All verbal languages use pitch to express emotional and other paralinguistic information, and to convey emphasis, contrast, and other such features in what is called...
, but not the low tone, shift downward in pitch (downstep
Downstep (phonetics)
In phonetics, downstep is a phonemic or phonetic downward shift of tone between the syllables or words of a tonal language. It is best known in the tonal languages of West Africa, but the pitch accent of Japanese is quite similar to downstep in Africa. Downstep contrasts with the much rarer upstep...
) after certain other tones. The result is that a tone may be realized at a certain pitch over a short stretch of speech, shifts downward and then continues at its new level, then shifts downward again, until the end of the prosodic contour
Prosodic unit
In linguistics, a prosodic unit, often called an intonation unit or intonational phrase, is a segment of speech that occurs with a single prosodic contour...
is reached, at which point the pitch reset
Pitch reset
In speech, phonetic pitch reset occurs at the boundaries between prosodic units.Over the course of such units, the median pitch of the voice declines from its initial value, sometimes reaching the lower end of the speaker's vocal range. At this point it must reset to a higher level if the person...
s. A graph of the change in pitch over time of a particular tone resembles a terrace
Terrace (agriculture)
Terraces are used in farming to cultivate sloped land. Graduated terrace steps are commonly used to farm on hilly or mountainous terrain. Terraced fields decrease erosion and surface runoff, and are effective for growing crops requiring much water, such as rice...
.
Since the pitch of the low tone remains more-or-less constant at the lower end of the speaker's vocal range, while the other tones shift downward, the difference in their pitches narrows, eventually obscuring the tones altogether. At this point pitch reset is required if the tone system is to continue functioning.
Tone terracing is particularly common in the languages of West Africa
West Africa
West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...
, where typically only the low tone causes downstep. However, a somewhat more intricate system is found in the Twi language of Ghana
Ghana
Ghana , officially the Republic of Ghana, is a country located in West Africa. It is bordered by Côte d'Ivoire to the west, Burkina Faso to the north, Togo to the east, and the Gulf of Guinea to the south...
. Twi has three phonemic tones: high, mid, and low. A word, and therefore a prosodic chunk of speech, may only start with a high tone or a low tone on its first syllable. As in many languages, a low tone starts out and remains at the bottom of the speaker's range. After a low tone, a subsequent high tone is downstepped. (A temporary exception occurs when a single low tone is found between two high tones. In this case the low tone is raised from its base value, but the second high tone is still downstepped, and subsequent low tones return to the base pitch.)
However, a phonetic downstep occurs between any two adjacent mid tones as well. In fact, a high tone is defined as any tone that is at the same pitch as a preceding high or mid tone; a mid tone will always be lower in pitch than a preceding high or mid tone. The result is that every instance of a mid or low tone shifts the upper end of the pitch range downward, until all pitches are reset at the end of the prosodic melody.
Table 1. The phonetic terracing effect in Twi of a series of mid tones. (Twi constrains the first tone to be either high or low.)
| (starting range) | syllable 1 : | syllable 2 : | syllable 3 : | syllable 4 |
|---|---|---|---|---|
| (high) | ||||
| (mid) | mid | |||
| mid | ||||
| mid | ||||
| (low) | low |
Table 2. The phonetic terracing effect in Twi of an alternating series of high and mid tones.
| (starting range) | syllable 1 : | syllable 2 : | syllable 3 : | syllable 4: | syllable 5 |
|---|---|---|---|---|---|
| (high) | high | ||||
| (mid) | mid | high | |||
| mid | high | ||||
| (low) |
Table 3. The phonetic terracing effect in Twi of an alternating series of high and low tones.
| (starting range) | syllable 1 : | syllable 2 : | syllable 3 : | syllable 4: | syllable 5: | syllable 6 |
|---|---|---|---|---|---|---|
| (high) | high | |||||
| high | ||||||
| (mid) | high | |||||
| low | ||||||
| (low) | low | low |
From tables 2 and 3 it can be imagined that the tone sequences high-low-high and high-mid-high may be difficult for a non-native speaker to distinguish.