Latentin prosodia-avaruuden analysointi ja puhetyylien hallinta suomenkielisessä end-to-end puhesynteesissä

Viime vuosina syväoppimisen saralla tapahtunut kehitys on mahdollistanut neuroverkkoihin perustuvan puhesynteesin, joka lähes luonnollisen puheen tuottamisen lisäksi sallii syntetisoidun puheen akustisten ominaisuuksien hallinnan. Tämä merkitsee sitä, että on mahdollista tuottaa eloisaa puhetta eri tyyleillä, jotka sopivat kyseiseen kontekstiin. Yksi tapa, jolla tämä voidaan saavuttaa, on lisätä syntetisaattoriin referenssi-enkooderi, joka toimii pullonkaulana mallintaen prosodiaan liittyvän latentin avaruuden. Tämän tutkimuksen päämääränä oli analysoida kuinka referenssi-enkooderin latentti avaruus mallintaa moninaisia ja realistisia puhetyylejä, ja miten puheennosten akustiset ominaisuudet ja niiden latentin avaruuden representaatiot korreloivat keskenään. Toinen päämäärä oli arvioida kuinka syntetisoidun puheen tyyliä voi kontrolloida. Tutkimuksessa käytettiin referenssi-enkooderilla varustettua Tacotron 2 syntetisaattoria, joka oli koulutettu yhden naispuhujan luetulla puheella usealla puhetyylillä. Latenttia avaruutta analysoitiin tekemällä pääkomponenttianalyysi puhedatan kaikista puheennoksista otetuille referenssivektoreille, jotta saataisiin esille puhetyylien keskeisimmät erot. Olettaen puhetyyleillä olevan akustisia korrelaatteja, tutkittiin pääkomponenttien ja mitattujen akustisten ominaisuuksien välillä olevaa mahdollista yhteyttä. Syntetisoitua puhetta analysoitiin kahdella tapaa: objektiivisella evaluaatiolla, joka arvioi akustisia ominaisuuksia ja subjektiivisella evaluaatiolla, joka arvioi syntetisoidun puheen sopivuutta liittyen puhuttuun lauseeseen. Tulokset osoittivat, että referenssienkooderi mallinsi tyylillisiä eroja hyvin, mutta tyylit olivat monisyisiä ja niissä oli merkittävää sisäistä vaihtelua. Pääkomponenttianalyysi erotteli akustiset piirteet jossain määrin, ja tilastollinen analyysi osoitti yhteyden latentin avaruuden ja prosodisten ominaisuuksien välillä. Objektiivinen evaluaatio antoi ymmärtää, että syntetisaattori ei tuottanut tyylien kaikkia akustisia ominaisuuksia, mutta subjektiivinen evaluaatio näytti, että mallinnus riitti vaikuttamaan sopivuuteen liittyviin arvioihin. Toisin sanoen spontaanilla tyylillä syntetisoitua puhetta pidettiin formaalia sopivampana spontaaniin tekstityyliin ja päinvastoin.In recent years, advances in deep learning have made it possible to develop neural speech synthesizers that not only generate near natural speech but also enable us to control its acoustic features. This means it is possible to synthesize expressive speech with different speaking styles that fit a given context. One way to achieve this control is by adding a reference encoder on the synthesizer that works as a bottleneck modeling a prosody related latent space. The aim of this study was to analyze how the latent space of a reference encoder models diverse and realistic speaking styles, and what correlation there is between the phonetic features of encoded utterances and their latent space representations. Another aim was to analyze how the synthesizer output could be controlled in terms of speaking styles. The model used in the study was a Tacotron 2 speech synthesizer with a reference encoder that was trained with read speech uttered in various styles by one female speaker. The latent space was analyzed with principal component analysis on the reference encoder outputs for all of the utterances in order to extract salient features that differentiate the styles. Basing on the assumption that there are acoustic correlates to speaking styles, a possible connection between the principal components and measured acoustic features of the encoded utterances was investigated. For the synthesizer output, two evaluations were conducted: an objective evaluation assessing acoustic features and a subjective evaluation assessing appropriateness of synthesized speech in regard to the uttered sentence. The results showed that the reference encoder modeled stylistic differences well, but the styles were complex with major internal variation within the styles. The principal component analysis disentangled the acoustic features somewhat and a statistical analysis showed a correlation between the latent space and prosodic features. The objective evaluation suggested that the synthesizer did not produce all of the acoustic features of the styles, but the subjective evaluation showed that it did enough to affect judgments of appropriateness, i.e., speech synthesized in an informal style was deemed more appropriate than formal style for informal style sentences and vice versa

Cooperation or Aid? A Corpus-Assisted Critical Discourse Analysis of Finland’s Development Policy

The current Finnish development policy, published in 2016, follows the United Nations 2030 Agenda for Sustainable Development and its 17 sustainable development goals. With the help of a few tools from corpus linguistics, this study conducts a critical discourse analysis of the policy, using Norman Fairclough’s three-dimensional method for CDA as its methodologicalframework and post-development theory as its main theoretical background. The study focuses on the definitions of development and its implementation as put forward by the policy, and how the policy text relates to its production and consumption as well as to the social and political context in which it is situated. Rather than working toward cooperation and participation which it promises, the policy reinforces the image of top-down aid dictated by institutions of the global North. It juxtaposes Finland as a giver and saviour with countries in the global South as vulnerable receivers of aid, granting little agency for the institutions,let alone the people of its development partners

Cooperation or Aid? A Corpus-Assisted Critical Discourse Analysis of Finland’s Development Policy

The current Finnish development policy, published in 2016, follows the United Nations 2030 Agenda for Sustainable Development and its 17 sustainable development goals. With the help of a few tools from corpus linguistics, this study conducts a critical discourse analysis of the policy, using Norman Fairclough’s three-dimensional method for CDA as its methodologicalframework and post-development theory as its main theoretical background. The study focuses on the definitions of development and its implementation as put forward by the policy, and how the policy text relates to its production and consumption as well as to the social and political context in which it is situated. Rather than working toward cooperation and participation which it promises, the policy reinforces the image of top-down aid dictated by institutions of the global North. It juxtaposes Finland as a giver and saviour with countries in the global South as vulnerable receivers of aid, granting little agency for the institutions,let alone the people of its development partners

Prosody under control: Controlling prosody in text-to-speech synthesis by adjustments in latent reference space

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