Speech Audiometry: The Development of Lithuanian Bisyllable Phonemically Balanced Word Lists for Evaluation of Speech Recognition  
[PERSON]  
1 State Research Institute Centre for Innovative Medicine, Santariskiu Str. 5, LT-08406 Vilnius, Lithuania; [EMAIL_ADDRESS]  
[PERSON]  
2 Clinic of Ear, Nose, Throat and Eye Diseases, Institute of Clinical Medicine, Faculty of Medicine, Vilnius University, M.K. Curlionio Str. 21, LT-03101 Vilnius, Lithuania; [EMAIL_ADDRESS] (J.L. ); eugenijus.les  
the frequency of the various speech sounds that normally occur in the language. Many sets containing monosyllabic words are available in English; among them are the word lists of the Central Institute of Deaf (CID W-22) and of Northwestern University (NU-6) [2]. The criteria of the selection of words for word recognition tests include an equivalent average difficulty and equivalent phonetic composition between the lists, an equivalent average difficulty within the lists and familiarity of the words [3]. Given that linguistic aspects impact how we perceive sound, it is crucial that test materials are written in the language spoken by the listeners in order to ensure the tests are accurate and efficient [4]. Although the basic principles of test development for speech audiometry remain the same across languages, the specific test materials differ due to phonetic characteristics and cultural contexts. A variety of word lists have been created in many different languages based on the specific features of the given language, such as Greek, Turkish, Polish, Korean, Mandarin, Tamil, Cantonese and Arabic [5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18]. Lithuanian belongs to the Baltic branch of the Indo-European language family. Lithuanian is one of the two living Baltic languages, along with Latvian, and forms the eastern branch of the Baltic languages family. It is also one of the 24 official languages of the European Union. Today, Lithuanian is spoken by almost 4.5 million people all over the world, with the majority of them (about 3 million) living in Lithuania. The largest Lithuanian diisporas are concentrated in the United States of America, the United Kingdom, Norway, Germany and Denmark. The Lithuanian language has two dialects, which in turn are classified into six sub-dialects and 12 speeches [19]. The most important features of the Lithuanian phonological system are the free distinctive stress (i.e., the stress distinguishes words and their forms); the tone system (i.e., Lithuanian is a tonal language and has two contrasting intonations--rising and falling--distinguishing different meanings); and the vowels in the vowel system of the standard Lithuanian language feature two phonological lengths (i.e., short and long vowels are independent phonemes and their contrast plays the role of distinction). The Lithuanian language is a flexional language where grammatical relations between words are expressed by inflections [20]. A reduction in endings is not common to the standard Lithuanian language; vowels and consonants are retained in the endings, so two-syllable words do not get shortened, except in certain dialects. Most words in standard Lithuanian have two, three or four syllables. There are only a few monosyllabic nouns or verbs in their infinitive form in the Lithuanian language. Word lists for speech audiometry tests in the Lithuanian language were first developed several decades ago [21]. Polysyllabic words from those lists were both used for the speech recognition threshold (SRT) and for the WRS measurement. The set of words consisted of 20 items per list. The choice and the specific applicability of the words raised certain concerns: Although the frequency ratios between vowel, diphthong and consonant phonemes have been assessed, neither specific phonemes nor their frequency ratios have been analyzed. The interrelation between two-syllable, three-syllable and four-syllable words has been defined; however, neither the structure nor the type of syllables has been analyzed.