The Phonetics of Standard German Stops - Phonetic Properties of Standard German

Phonetic Properties of Standard German

2.2 The Phonetics of Standard German Stops

Apart from PoA, German distinguishes stops according to a laryngeal con-trast which is sometimes described as a concon-trast between voiced /b, d, g/

and voiceless /p, t, k/ (e.g., Hall 2000:81). As explained above, phoneti-cally, voiced stops are defined as being produced with vibrating vocal folds during the closure phase. Voicelessness, on the other hand, is characterised by the absence of vocal fold vibration. Kohler (1995:81f.) notes that German /b, d, g/ are fully voiced only intervocalically. Lax stops in other positions are partially or fully devoiced. He further states that the distinction between the tense and the lax stop series is maintained through the presence (in the case of/p, t, k/) or absence (in the case of /b, d, g/) of aspiration.

Various phonetic studies on stop production confirm that the German la-ryngeal contrast is rather a contrast of voiceless unaspirated versus voiceless aspirated stops than of voiced versus voiceless ones. In a production exper-iment on intervocalic posttonic stops as for instance in Ka/b/el ‘cable’ or Sta/p/el ‘stack’, Braunschweiler (1997:362) finds that the main factor for laryngeal distinctions in German word-medial stops is ACT. Even though he observes some cases in which lax stops exhibit closure voicing, he points out that most lax stops are produced without prevoicing and display a short voicing lag with a mean ACT of 15.5 ms. For tense stops he finds a longer voicing lag with a mean ACT of 50.5 ms. Besides, Braunschweiler (1997) does not explicitly state the presence/absence of closure voicing, a further indicator that this factor is not of primary relevance in the production of the German laryngeal contrast.

Braunschweiler’s (1997) data support what has been found by others before. Jessen (1998:48ﬀ.) provides a comprehensive summary of the liter-ature on the phonetics of German stops from the early 1970s to the mid 1990s. As Jessen is interested in three specific contexts, namely stops in utterance-initial position, posttonic word-medial stops before schwa, and stops following voiceless obstruents, he focuses on these environments in his overview. His survey of previous research suggests that there are variations depending on factors like methodology, regional provenance of the speakers of the individual studies, definition of how voicing and aspiration are to be measured and so forth. Still, the overall picture emerging from this com-parison is rather homogeneous and leads to the conclusion that the German tense/lax opposition is maintained by a significant diﬀerence in ACT in all three contexts of interest. Tense stops in utterance-initial, word-medial and post-voiceless-obstruent position are clearly aspirated and have relatively high ACT values, while lax stops in all three contexts show considerably

2.2 The Phonetics of Standard German Stops 25 shorter voicing lags and thus can be labeled unaspirated. Unlike ACT, clo-sure voicing is not found to be a reliable means to maintain the opposition in production. Significant diﬀerences with regard to closure voicing are found only in intervocalic position. Word-medial lax stops are most times fully or at least partially voiced, tense stops are voiceless.

Jessen’s (1998) own production experiments on German stops in inter-vocalic position, utterance-initially and following voiceless obstruents sub-stantiate this pattern. He reports that the German tense/lax opposition is reliably maintained by aspiration in all three contexts. With a mean value of 67.3 ms for tense and 21.7 ms for lax stops, ACT seems to be the distinctive factor also in his study. With regard to closure voicing, Jessen (1998:87f.) reports considerable within- as well as cross-subject variation without a clear pattern. Lax stops consistently display closure voicing only in intervocalic position. Utterance-initially and after voiceless obstruents, a minority of the lax stops are produced with vocal fold vibration during the closure phase.

In an experiment by Jessen & Ringen (2002), word-medial posttonic intervocalic lax stops consistently show full or at least partial closure voicing while the tense stops are all produced without vocal fold vibration during closure. Word-initial productions of lax /d/ following /s/, however, are all realised as voiceless.¹⁷ Like in the studies presented above, Jessen & Ringen (2002) find consistent diﬀerences in ACT for tense (mean 40.1 ms) and lax stops (mean 13.7 ms).

In sum, these studies support the assumption that phonetically the Ger-man laryngeal contrast should not be described as a contrast of voiced versus voiceless stops, but rather as a contrast of voiceless unaspirated (short voic-ing lag) versus voiceless aspirated (long voicvoic-ing lag) stops. Accordvoic-ingly, ACT can be seen as the most important phonetic correlate to distinguish the two stop series in production. The data presented in chapter 5 pro-vide further support for this assumption and show that ACT is a strong cue for the German tense/lax contrast also in perception (see also Pohl &

Grijzenhout 2010).

2.2.1 More Phonetic Correlates of Laryngeal Contrasts Besides ACT and closure voicing, there are other phonetic properties that might contribute to the distinction of two stop series. Steriade (1997), among others, lists closure duration (henceforth CD), length and F₁ tran-sition of a preceding vowel, duration and amplitude of the release burst as

17No other stops were investigated in this position.

well as F₀ and F₁ transitions into a following vowel as potential phonetic correlates that may be used to distinguish laryngeal stop contrasts. Jessen (1998) further mentions the amount of breathy voice at the beginning of the following vowel. These correlates will be briefly inspected below, drawing mostly on findings from speech production.

To begin with, CD values may diﬀer in tense and lax stops. Braun-schweiler (1997) finds significant CD diﬀerences for German tense and lax stops word-medially, in a posttonic intervocalic environment. /p, t, k/ are produced with on average 20% longer CDs than/b, d, g/(78 ms vs. 62.5 ms).

However, CD values for the two categories overlap considerably, suggesting that – at least on its own – CD is not a reliable parameter to distinguish German tense and lax stops. Also, in accordance with Kohler (1984), Kuz-la & Ernestus (2007) find that CD is an acoustic correKuz-late of the German tense/lax contrast only in medial but not in word-initial position. CD val-ues of German tense and lax stops are also examined by Kohler & K¨unzel (1978). They report considerably longer CDs for tense (126 ms) than for lax stops (59 ms). However, tense stops in their experiment are produced in word-final position while lax stops occur in a "V @-context. Therefore, their data for tense and lax stops are comparable only to a limited extent.

As Braunschweiler (1997:370) suggests, the final position might induce an additional lengthening of the closure which is not given in medial position.

The length of the preceding vowel has been shown to play a crucial role in the distinction of English tense and lax stops, especially in utterance-final position. Ladefoged (2006:58f.), for example, points out that vowels preceding lax stops are longer than vowels preceding tense stops in English.

Due to contrast neutralisation in final position, this context is irrelevant in German. Nonetheless, significant diﬀerences in preceding-vowel length are found for German stops in other than final contexts. Braunschweiler (1997) observes that stressed vowels preceding word-medial lax stops are about 20%

longer than stressed vowels preceding word-medial tense stops. Yet, there is extensive overlap between the tense and the lax category. Consequently, both preceding vowel length and CD cannot be considered as unambiguous cues to perceptually distinguish the German stop contrast. Experimental perception data presented in chapter 5 (see also chapter 8) will demonstrate that CD is not a suﬃcient cue to distinguish the German tense/lax contrast.

Preceding-vowel length on its own has to be ruled out as a strong cue for the perceptual diﬀerentiation of the laryngeal contrast since vowel length is phonemic in German (also cf. Braunschweiler 1997). Accordingly, length-ening the vowel in Matte ["mat^h@] ‘mat’ with all other phonetic properties unchanged will not lead to the perception of Made ["ma:t@] ‘maggot’, but

2.2 The Phonetics of Standard German Stops 27 rather of Mate ["ma:t^h@] ‘yerba mat´e’ (a South American plant often used for tea). Besides, the preceding vowel is of minor relevance for the present investigation, which focuses on pretonic stops following schwa. Decisive ef-fects of the preceding vowel are assumed to occur in full vowels only, but not in reduced ones such as schwa. For the same reason, formant transitions from the preceding vowel will not be discussed in detail (see also below).

Steriade (1997) does not clarify what exactly what is meant by burst duration. In some studies, burst duration is equated with ACT (e.g., van Alphen & Smits 2004; Warner et al. 2004). Others subdivide the release phase into burst and aspiration (e.g., Reetz 1999; Jessen & Ringen 2002; see also Mikuteit 2006). The burst can be very short and abrupt or somewhat longer, but as Bettina Braun (p.c.) assures, it is assumed to be fairly over-lapping for tense and lax stops and thus not a very strong perceptual cue to category distinction. Regarding burst amplitude, it is generally agreed upon that lax stops are produced with lower burst intensity than tense ones.

However, this seems to be the case rather for contrasts between prevoiced and voiceless unaspirated stops than when the tense/lax opposition is imple-mented as a contrast between voiceless aspirated and voiceless unaspirated stops: Jessen (1998:119) points out that burst amplitude does not serve as a consistent cue to distinguish voiceless unaspirated from voiceless aspirated stops and, furthermore, that it is diﬃcult to measure for voiced stops (see also Jessen 1998:262f.). Edwards (1981) reports to find no apparent diﬀer-ences in burst duration between tense and lax English stops. Accordingly, this parameter is not listed as a useful indicator to perceptually distinguish laryngeal contrasts (Edwards 1981:544). Instead, it seems to provide infor-mation helpful in PoA distinction, since labial stops have considerably lower burst amplitudes than alveolar and velar stops (Edwards 1981:542).

As shown, for example, by Mikuteit (2006; for posttonic intervocalic stops) and Jessen (1998; for utterance-initial stops), vowels following tense stops are produced with a higher fundamental frequency (F0) than vowels after lax stops. Kingston & Diehl (1994) refer to a so-called ‘low frequency property’ observable in lax but not in tense stops. Apart from closure voic-ing, this property may be realised in terms of low F0 and low F1 values in vowels adjacent to the stops in question. Kingston & Diehl (1994) argue that this low frequency property can be observed not only for stops with a voicing lead. Periodicity of a vowel following prevoiced stops sets in at a lower value than in vowels following voiceless unaspirated stops. The same F₀ relation is claimed to be found when vowels following voiceless unaspirated stops are compared to vowels following voiceless aspirated stops. However, as Kingston & Diehl (1994) admit, such patterns seem to be language-specific.

Moreover, they seem to be strongly influenced by intonation contour as well as by the presence of closure voicing. In a production experiment with speakers of American English, Ohde (1984) finds nearly identical F₀ val-ues at the onset of voicing for vowels following voiceless unaspirated and voiceless aspirated stops, which, in turn, are both significantly higher than F₀ onset in vowels after voiced stops. For German, Jessen (1998:104, 262) finds highly variable results across speakers. He reports that in most cases in which lax stops are produced without closure voicing, F₀ values do not diﬀer significantly for vowels following tense and lax stops. Accordingly, F₀ appears not to serve as a strong cue to categorically distinguish voiceless unaspirated from voiceless aspirated stops.

Besides fundamental frequency and closure voicing, Kingston & Diehl (1994) mention the first formant in vowels adjacent to stops as another po-tential component of the so-called ‘low frequency property’ that is assumed to characterise lax stops. Similarly, Steriade (1997) speaks of the transition of F₁ into a following vowel as a potential phonetic correlate that can be found in the production of laryngeal contrasts. The presence of formant transitions at the oﬀset of stop consonants is directly linked to ACT. In stops with a short voicing lag, the rise of the first formant from the conso-nantal release to a vowel’s steady state frequency occurs after the onset of voicing of the following vowel. In stops with a long voicing lag, by contrast, the transition is already essentially completed before voice onset. In other words, the voicing lag provides more time for the spectral change to occur before the onset of regular vowel periodicity. As Stevens & Klatt (1974) show with synthetic stimuli and American English listeners, ACT and F₁ transitions are cues for the laryngeal contrast that stand in a trading rela-tionship in perception, that is, the ACT boundary might be slightly shifted depending on F₁ transitions (see also Lisker et al. 1977). Note however, that they argue mono-directionally: If an F₁ transition after voicing onset is perceived, this is regarded as a negative cue for aspiration. Thus, if such a transition is present in the following vowel, the preceding consonant cannot be a voiceless aspirated consonant. However, if the F₁-cue is missing, this is not seen as a necessary indicator for a voiceless aspirated stop. Regardless, F₁ must be considered as a minor, ancillary cue to perceptually distinguish tense/lax contrasts. Formant transitions in (preceding and following) vowels are first and foremost PoA indicators and may play only a supporting role in marking laryngeal contrasts.

Jessen (1998:108ﬀ.) mentions another parameter that can be measured in productions of tense and lax stops in German, namely the amount of breathy phonation at the onset of a following vowel. It can be observed,

2.2 The Phonetics of Standard German Stops 29 for example, in the first and second harmonics of the sound signal and is directly related to the degree of glottal aperture during stop production.

Thus, breathy phonation at vowel onset is a by-product of aspiration and as such it is not considered as an independent cue to phoneme perception.

The parameters listed in the present section may influence the German laryngeal contrast in addition to the strong ACT cue. To a certain extent they are aﬀected by factors such as segmental and prosodic environment, speech style or speech rate. In particular, temporal parameters might vary depending on speech rate, but the overall relations are assumed to remain relatively stable. Some of these influencing factors are mentioned below.

2.2.2 The Segmental and Prosodic Context

A comprehensive survey of studies investigating stops in diﬀerent phonolog-ical contexts is provided by Jessen (1998). Kohler (1995) also gives some detailed descriptions of the realisation of tense and lax German stops in various positions. In the following, only a brief overview will point out the crucial aspects of German tense and lax stops in diﬀerent environments.

The German laryngeal contrast is maintained in word-initial and -medial position but it is neutralised word-finally.¹⁸ Tense stops in initial position are aspirated, lax stops are unaspirated and mostly produced without closure voicing, especially in utterance-initial position. In intervocalic post-stressed position, the ACT diﬀerence between tense and lax stops is reduced, but still contrastive. Furthermore, lax stops in this position often display full or partial closure voicing. Since glottal pulsing during closure is attested nearly exclusively in this context – and not even consistently – it is suggested that closure voicing in the lax German stops in this position can be attributed to passive voicing, induced by the surrounding highly sonorant phones. Thus, closure voicing in intervocalic lax German stops may have an enhancing function to emphasise the laryngeal contrast but it is not mandatory for its maintenance. In medial stops preceding stressed vowels, the ACT diﬀerences are very pronounced with a large amount of aspiration in the tense stops

18Neutralisation might also occur in /s, S/+stop clusters like in the words Spiel [Spi:l]

(‘game’) andSkelett[sk@"lEt] (‘skeleton’), in which the tense stops are produced without aspiration. Note that there are no words beginning with /s, S/+/b, d, g/. Such phoneme combinations might, however, be found at morpheme boundaries as inWaschb¨ar["vaS.p

˚æ5]

(‘raccoon’) (see also Iverson & Salmons 1999). Some argue that aspiration is also absent in other consonant-stop clusters. For instance, Wiese (2000:270) suggests, that clusters like /tr/ and /pl/ are produced without aspiration, the contrast to /dr/ and /bl/ being maintained by other parameters. But since the present work does not focus on consonant clusters, this issue will not be further discussed.

and usually no closure voicing in the lax ones. In final position, the German laryngeal contrast is neutralised. This contrast neutralisation is often de-scribed as ‘final devoicing’ but given that even lax stops are mostly voiceless in German, it might better be referred to as ‘final laryngeal neutralisation’

(e.g., Wagner 2002).¹⁹ Examples of (near) minimal pairs for German tense and lax stops in initial, medial and final position are provided in table 2.4.

Position in word Item UR SR Gloss

Initial Paar /p/ [p^h] ‘couple’

Bar /b/ [p] ‘nightclub’

Intervocalic posttonic Laken /k/ [k^h] ‘sheet’

lagen /g/ [k]∼[g] ‘to lie’ ^{PAST PL.}

Intervocalic pretonic Athen /t/ [t^h] ‘Athens’

ade /d/ [t] ‘bye bye’

Final Rat /t/ [t] ‘council’

Rad /d/ [t] ‘wheel’

Table 2.4: Examples for the German tense/lax contrast in initial, medial and final position of a word.

As hinted at before, the segmental context is not the sole influencing factor on the realisation of tense and lax stops. The prosodic position also aﬀects stop production. Sol´e (2007:314) provides an overview which shows that in English, ACT values of tense stops are higher in prosodically more prominent positions than in less prominent positions (in stressed vs. unstressed sylla-bles, in focused vs. non-focused position, in accented vs. unaccented syllables and in domain-initial syllables vs. syllables within a prosodic constituent).

As Jessen (1998:328) remarks in a footnote, it is sometimes claimed that German tense stops are aspirated only in foot-initial and in utterance-final position (e.g., Hall 1992), an assertion that is disproved by his own data as well as by the findings of Braunschweiler (1997).

In a study using electropalatography (EPG) on initial /t/ in diﬀerent prosodic positions in English, French, Korean and Taiwanese, Keatinget al.

19Since word-final stops are not of primary interest in the present work, on-going debates about the completeness of neutralisation and the appropriate domain (phonological word, morpheme, or syllable, and within the syllable the coda as a whole or only the final segment) for its application are not discussed here. The interested reader is referred to Fourakis & Iverson (1984); Jessen (1998); Iverson & Salmons (1999); Wagner (2002);

Jongman (2004) and references cited there.

2.2 The Phonetics of Standard German Stops 31 (2003) find that all four languages exhibit domain-initial strengthening in terms of ‘linguopalatal contact’ and in ‘seal duration’, that is, CDs are longer in prosodically higher positions than at lower levels. An ACT-eﬀect is found only for Korean with longer ACTs at higher prosodic levels, showing that ACT is not necessarily aﬀected by prosodic prominence.²⁰

For German, Jessen (1998:61ﬀ.) points out that, with regard to ACT, no essential diﬀerences are reported for word-initial stops in utterance-initial as opposed to word-initial stops in utterance-medial position. In a production study on German word-initial stops preceding stressed /a/, Kuzla & Ernes-tus (2007) find that ACT in tense stops does not increase with higher levels in the prosodic hierarchy, but instead decreases from word (ACT: 58.1 ms) to intermediate phrase (53.4 ms) to intonation phrase (48.5 ms). The lax stops do not show an ACT eﬀect. Unlike ACT, CD increases with higher

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