You can configure your bot's voice from its Voice page in its Admin Console.
Bot Libre supports several different voices and languages, and a voice modifier to make a voice sound childish, robotic or others. Bot Libre also supports integration with HTML5 speech to use the web browser's voice. For HTML5 the voice will depend on the browser.
Your bot pioyu is currently set to use the US female voice with an echo modifier. Maybe remove the echo modifier. Also check if you have native HTML5 voices enabled, then you would be getting the web browsers voice.