https://tts.langeek.co/read?text=Ynk&hash=2cc60022c3035ca401091b765d1aed76b3e4a7e9&lang=en&cache-only=0

https://tts.langeek.co/read?text=aW4&hash=d9f99e59087477e0ce749c9005cc1d3a28dfe1d6&lang=en&cache-only=0

These prepositions indicate how something is done or through what channel or medium it is achieved.