!ask my opponent is asking me to say in plain voice every move I am doing. "I will play..." I want to concentrate on my game and not talk to him. Am I compelled by the rules to do so ? What if I refuse ?

No — you're not required to narrate every move in plain voice. Rules only require that changes to public information be acknowledged in an "understandable and observable way" — verbally, physically, or by agreed convention — and physically playing a card face-up is itself that acknowledgment (TR 502.6.a). You're also explicitly not required to assist your opponent in playing the game (TR 501.3); the one exception is that scoring points must be verbally announced.

If you refuse: as long as your actions are clear and observable, refusing to narrate is not a violation. However, if your opponent asks a direct question about public information ("what did you just play?"), you must answer honestly — refusing that is a Communication Violation (Warning, TR 703.5/502.7). If they're asking you to read out private/derived info like what a Hidden card is or your hand, you don't have to disclose it. If the demand continues, you can call a judge and keep playing normally in the meantime.