Braxen 1.0 (2025)

Abstract: With this paper, we release a Swedish pronunciation lexicon resource, Braxen 1.0, which is the result of almost 20 years development carried out at the Swedish Agency for Accessible Media (MTM). The lexicon originated with a basic word list, but has continuously been exanded with new entries, mainly acquired from university textbooks and news text. Braxen consists of around 850 000 entries, of which around 150 000 are proper names. The lexicon is released under the CC BY 4.0 license and is accessible for public use.

## introduction the mission of the swedish agency for accessible media (mtm) includes the production of accessible materials for individuals with print impairments, such as low vision or dyslexia. this work primarily involves converting books into accessible formats such as braille and talking books. the talking books are produced through either human narration or text-to-speech synthesis (tts). mtm uses tts to produce approximately 1 500 university textbooks annually and more than 120 newspapers on a near-daily basis. while commercial tts voices are used in this production, the complexity of non-fiction texts often necessitates additional support to ensure accuracy, mainly through pronunciation instructions. the pronunciation dictionary used at mtm, from which braxen is derived, is referred to as mtm-lex for clarity. the starting point of mtm-lex was centlex, a generalised swedish lexicon for speech technology developed at the academic-industrial centre of excellence ctt in the early 2000s @xcite . in 2005, as ctt approached the end of its 10year run, mtm made the decision to develop an in-house tts system for the production of talking books @xcite . the pronunciation lexicon in the mtm tts started with 55 000 entries from centlex, and was supplemented with around 35 000 entries acquired from svenska språknämndens uttalsordbok (suo), 67 000 ord i svenskan och deras uttal @xcite . suo was made publicly available by the institute for language and folklore under the cc-0 license in 2023 @xcite . mtm has since made significant changes and expansions to the lexicon to meet the substantial demands placed on a pronunciation lexicon used for tts synthesis of long and information-rich text, such as university textbooks. an in-house format for a phone alphabet used for phonetic transcriptions was developed and inflections of baseforms were added along with hundreds of thousands of new entries, mainly proper names and domain-specific vocabulary. as part of an active production process, mtmlex is continuously updated, primarily with words from swedish newspapers and university textbooks. mtm produces over 120 newspapers in spoken form, read aloud by tts. the lexicon is updated weekly with the 100+ most frequent news words that are not yet part of mtm-lex. these pronunciations are then forwarded to the tts system, either as a user lexicon or as ssml insertions in the newspaper document. in addition, mtm produces around 1 500 swedish and english university textbooks with speech synthesis annually. frequency lists are computed individually for most books, and new high-frequency words are added to mtm-lex. in this way, the lexicon is kept up-to-date with the current vocabulary of the news world, as well as with vocabularies from specific domains, such as medicine or law. the sharing of braxen has been approved by mtm's legal team. the lexicon can be downloaded here: http://www.github.com/ sprakbankental/braxen . ## initial release: braxen 1.0 braxen is not identical to the original mtm-lex and does not include all of its entries or information. firstly, only 5 of the original 27 fields are included in the first release (see section 4). the remaining fields are excluded for one of the following reasons: they are internal to mtm, unavailable for most of the lexicon entries, lacking in quality or consistency, or simply mere placeholders for future information. secondly, not all entries are included in the release. english proper names are included, but approximately 35 000 general english words are not. these words were originally transcribed to match the english variety of a specific swedish speaker, which was incorporated into the swedish tts system mentioned in section 1. as a result, the current pronunciations differ from more established transcription conventions of english. as with any lexicon, it is virtually impossible to guarantee complete accuracy. for example, all entries do not have complete pos information, partially due to the purpose of the resource. features that are less important in speech-oriented dictionaries, such as whether a word is an adjective or a perfect participle, have been given less attention. we are also aware that there are a small number of incorrect entries. to the best of our knowledge, this remains the best swedish resource of its kind available by some margin. the release includes full documentation and perl scripts for conversion between the native transcription format and ipa, as well as validation scripts. ## statistics this section presents statistics on a selection of features of general words (852 000 entries, examining the baseforms of the open part-ofspeech classes of general words, we count approximately 129 000 nouns, 8 000 verbs, and 16 000 adjectives, present and perfect participles. ## fields this section describes the five fields included in the initial release. ## phonetic-phonemic transcription this section describes the braxen transcriptions and the symbol set used to encode them. as braxen is primarily a pronunciation resource for real-world swedish speech technology, and particularly for tts synthesis of long, information-rich texts, much care has been taken to create transcriptions that are useful for this purpose. this goal takes precedence over strict adherence to any specific speech or language theory, and even over generality in terms of language independence. the braxen transcriptions are encoded using a symbol set based on four main design principles, some of which are language-specific. the symbol set can be converted to its ipa equivalent using tools included with the release. ## conclusions and future work this release of braxen 1.0 marks a step forward for swedish speech technology in that it provides an accessible and high-quality pronunciation lexicon for swedish speech technology applications. with its comprehensive symbol set tailored to swedish language needs and adherence to practical design principles, braxen is well-suited for tts synthesis and other real-world applications. while the current release offers robust functionality, several areas remain open for enhancement and expansion, and a range of activities are already on the list for upcoming releases: