Sonority refers to the relative loudness of a sound. Vowels have the highest sonority and consonants have a lower level of sonority (Roach, 2009, p. 62). This chapter examines the distinction between the least sonorous sounds of the sonority hierarchy, that is the plosives /b, d, g, p, t, k/ (Collins & Mees, 2013, p. 81). Gimson (2008) distinguishes voiced plosives /b, d, g/ from their voiceless counterparts /p, t, k/ by the frequency of energy of the voice which is low in voiceless plosives (p. 162). However, they have more energetic articulation than voiced plosives and what distinguishes them most in the context of words is aspiration (Collins & Mees, 2013, p. 87).
Aspiration occurs when fortis plosives /p, t, k/ are followed by a burst of air which is released through the vocal folds (Roach, 2009, p. 27). In English, plosives /p, t, k/ are aspirated when initial in a stressed syllable followed by a vowel (Collins & Mees, 2013, p. 87). The aspiration is the strongest in velar plosive /k/ where it sounds almost as [χ] realized by /ch/ in Czech and Slovak, weaker aspiration is in alveolar /t/ where the character of the sound may be described as hissing, and bilabial /p/ has the weakest aspiration (Melen, 2010, p. 30). Aspiration is only realized before vowels and does not exist in unstressed syllables (Melen, 2010, p. 30). If the voiceless plosives /p, t, k/ follow /s/ in a stressed syllable, they have no aspiration. This is a case of phoneme neutralization (Collins & Mees, 2013, p. 76). Thus, words such as scar, school, stamp, star, speak, space are pronounced without aspiration.
The phenomenon of aspiration is very important and Czech and Slovak should aim their attention on careful distinguishing of fortis and lenis plosives when speaking, especially due to the fact that Czech and Slovak pertain to the group of languages without aspiration (Collins & Mees, 2013, p. 88; Bázlik, 2012, p. 50). These two Slavic languages rely particularly on voicing as the main feature of opposition of fortis and lenis plosives (Gimson, 2008, p. 318). Therefore, the realization of the word pat without initial aspiration is understood as bat by an English listener (Gimson, 2008, p. 318). Czech and Slovak speaker also often incorrectly over-aspirate the voiceless plosives in the middle, non-stressed positions.
A specific case of aspiration worth mentioning is the loss of unstressed vowel in the first syllable after voiceless plosives /p, t, k/. The vowel is substituted by the aspiration which takes up the middle portion of the syllable (Roach, 2009, p. 114). This results in the following pronunciations of words such as [pʰˈteɪtəʊ], [tʰˈmɑːtəʊ], [kʰˈneəri], [tʰˈdeɪ], and [pʰˈhæps] (Roach 2009, p. 114). Czech and Slovak speakers do not necessarily have to use this type of elision but knowing it will improve their ability to understand spoken English.
3.1.2 Devoicing of the post-alveolar approximant /r/
An interesting case of a phoneme losing its voicedness according to its environment is demonstrated on the phoneme /r/. It is a voiced, post-alveolar approximant (Gimson, 2008, p. 221). However, if the phoneme /r/ follows accented voiceless plosives /p, t, k/, it loses its voicedness and becomes voiceless. In syllable-initial consonantal clusters of two phonemes /pr-, tr-, kr-/, the sound [r] is voiceless and fricative and the two phonemes merge into one unit (Gimson, 2008, p. 221). Gimson (2008) explains the importance of distinguishing the opposition between voiced and voiceless plosives which is primarily indicated by the degree of voicing the phoneme /r/ (p. 224). If the sequences /br-, dr-, gr-/ are not to be confused with /pr-, tr-, kr/, the phoneme /r/ should be a completely devoiced fricative /ɺ̥/ after voiceless plosives, especially when accented, as is clearly heard in the pairs pray, bray; try, dry; crow, grow (Gimson, 2008, p. 224). The difference of the devoiced /r/ after the voiceless consonants /p, t, k/ is clear when similarly pronounced words in English, Czech and Slovak are compared (Melen, 2010, p. 34); for instance English cry, pronounced as [kɺ̥aɪ] and the Czech and Slovak word kraj [kraj] (region), or the English word proud, pronounced as [pɺ̥aʊd] and Czech and Slovak proud [proʊd] (stream).
3.1.3 Devoicing of the lateral /l/
A devoiced allophone of /l/ occurs after voiceless consonants /p, k/, in a stressed syllable (Roach, 2009, p. 49). It is important to distinguish the sequences /pl, kl/ from /bl, gl/ mainly by a clear aspiration cue of the voiceless /p, k/ followed by a devoiced /l/ (Gimson, 2008, p. 219). In this position, the devoiced /l/ is pronounced as a fricative (Roach, 2009, p. 49). Thus, if the word plot is pronounced with a fully voiced /l/, it may be understood as blot. Other pairs of words where the difference depends on the pronunciation of a voiced or voiceless /l/ are for example plight, blight; plead, bleed; clue, glue; class, glass (Gimson, 2008, p. 219).
Czech and Slovak /l/ is similar to the English clear /l/ and does not have allophones of the dark /ɫ/ or the voiceless /l̥/ found in the sequences /pl, kl/ (Melen, 2010, p. 37). Examples of Czech words with a voiced /l/ are plot [plot] (fence), plakat [plakat] (to cry), plést [plɛːst] (to knit), klusat [klʊsat](to trot) and Slovak plameň [plamεɲ] (flame), ploský [ploskiː] (flat), klas [klas] (ear).
3.1.4 Devoicing of the labial-velar semivowel /w/
The devoicing of the phoneme /w/ takes place when it follows accented /p, t, k/. The devoiced phoneme is then realized in transcription as a voiceless labial-velar fricative /ʍ/ (Gimson, 2008, p. 229). The noise produced in the pronunciation of sequences where /ʍ/ follows /p, t, k/ may be defined as a friction (Roach, 2009, p. 51). Thus, the following words contain a devoiced fricative /ʍ/: queen, quick, tweak, whereas words such as weak, wick contain a voiced /w/ (Roach, 2009, p. 51).
3.1.5 Devoicing of the palatal semivowel /j/
The same phenomenon occurs when the phoneme /j/ follows voiceless plosives /p, t, k/ in an accented syllable. The phoneme /j/ loses its voicing and becomes fricative (Roach, 2009, p. 51). Similarly as with the phoneme /w/, words such as pure, tune, queue, cue, cute are realized with a devoiced /j/ but words such as you, your have a fully voiced /j/ (Collins & Mees, 2013, p. 98).
3.1.6 Glottal fricative /h/
The negligence in distinguishing between a voiced and voiceless consonant pairs frequently occurs when Czech and Slovak speakers replace the English [h] with Czech or Slovak version of this sound. It is essential to stress the difference between the English sound [h] and its corresponding sound in Czech and Slovak. English /h/ is voiceless while Czech /h/ is a voiced consonant, very intense, paired with the voiceless phoneme /ch/ (Melen, 2010, p. 36). Slovaks tend to incorrectly devoice [h] at the beginning of articulation after a pause, thus the articulation starts with a voiceless aspiration and then follows shortened voiced [h] (Kráľ, 1984, p. 125).
The quality of the sound [h] is unstable and often depends on the quality of the following vowel (Vachek, 1973, p. 52). Vachek (1973) also refers to the definition of Daniel Jones who called the phoneme /h/ “the voiceless variant of the immediately following vowel sound” (p. 52). The articulators are in the position for the vowel which follows the sound [h] and the friction is produced by a strong airstream (Collins & Mees, 2013, p. 94). Since the upper part of the vocal tract is shaped for the articulation of the following vowel, various types of the friction may be heard (Gimson, 2008, p. 204). Melen (2010) asserts that English [h] is such a subtle voiceless sound that it is sometimes realized as a mere breathy beginning of the following vowel (p. 36).
Although English /h/ occurs only as a voiceless phoneme followed solely by a vowel, some speakers pronounce it as a slightly voiced allophone in accented syllable-initial positions, for instance in such words as ahead, perhaps, behind (Gimson, 2008, p. 204).
The phenomenon which frequently occurs in English is the elision of /h/ in unstressed formal, grammatical words, such as have, him, her in phrases I have seen him, or I have told her (Vachek, 1973, p. 54). These words are the “weak form”, that is a reduced form used in continuous speech, realized usually as /ə/ (Melen, 2010, p. 46). This loss of the sound [h] is common in formal speech; however, children are often wrongly corrected by parents and teachers when they elide /h/ in unstressed position due to the insecurity connected with h-dropping in England and Wales (Collins & Mees, 2013, p. 127). Czech and Slovak speakers do not often realize this duality of “strong” and “weak” forms and due to the invariable voicedness of the Czech and Slovak phoneme /h/ they consider English /h/ as always voiced and pronounce it as a voiced sound in unstressed functional words (Bázlik & Miškovičová, 2012, p. 65). Thus, Czech and Slovak speakers must respect the English breathy /h/ in initial position and distinguish between English, Czech (and Slovak) words such as hut [hʌt] – had [had](snake), hot [hɒt]- hod [hot](throw), heel [hiːl] – hýl [hiːl] – hýľ [hiːʎ](bullfinch) (Melen, 2010, p. 36).