Sawasdeee ka Voice Search

Posted by Keith Hall and Richard Sproat, Staff Research Scientists, Speech


Typing on mobile devices can be difficult, especially when you're on the go. Google Voice Search gives you a fast, easy, and natural way to search by speaking your queries instead of typing them. In Thailand, Voice Search has been one of the most requested services, so we’re excited to now offer users there the ability to speak queries in Thai, adding to over 75 languages and accents in which you can talk to Google.

To power Voice Search, we teach computers to understand the sounds and words that build spoken language. We trained our speech recognizer to understand Thai by collecting speech samples from hundreds of volunteers in Bangkok, which enabled us to build this recognizer in just a fraction of the time it took to build other models. Our helpers are asked to read popular queries in their native tongue, in a variety of acoustic conditions such as in restaurants, out on busy streets, and inside cars.

Each new language for voice recognition often requires our research team to tackle new challenges, including Thai.

• Segmentation is a major challenge in Thai, as the Thai script has no spaces between words, so it is harder to know when a word begins and ends. Therefore, we created a Thai segmenter to help our system recognize words better. For example: ตากลม can be segmented to ตาก ลม or ตา กลม. We collected a large corpus of text and asked Thai speakers to manually annotate plausible segmentations. We then trained a sequence segmenter on this data allowing it to generalize beyond the annotated data.
• Numbers are an important part of any language: the string “87” appears on a web page and we need to know how people would say that. As with over 40 other languages, we included a number grammar for Thai, that tells you that “87” would be read as แปดสิบเจ็ด.
• Thai users often mix English words with Thai, such as brand or artist names, in both spoken and written Thai which adds complexity to our acoustic models, lexicon models, and segmentation models. We addressed this by introducing ‘code switching’, which allows Voice Search to recognize when different languages are being spoken interchangeably and adjust phonetic transliteration accordingly.
• Many Thai users frequently leave out accents and tone markers when they search (eg โน๊ตบุก instead of โน้ตบุ๊ก OR หมูหยอง instead of หมูหย็อง) so we had to create a special algorithm to ensure accents and tones were restored in search results provided and our Thai users would see properly formatted text in the majority of cases.

We’re particularly excited that Voice Search can help people find locally relevant information, ranging from travel directions to the nearest restaurant, without having to type long phrases in Thai.

Voice Search is available for Android devices running Jelly Bean and above. It will be available for older Android releases and iOS users soon.