Mobile soundproof enclosure with changeable internal room shape and optional ventillation noise cancelling device consisting of a frame that can be assembled and disassembled by a single person without using tools and that in disassembled state is small enough to fit in a trunk of a car; a cover made with flexible sound absorbent sheet material creating completely enclosed room with double walls with air space in between, corner sound traps made with flexible sound absorptive sheet material that can be individually positioned to change internal shape of the room and an air vent noise cancelling device made with flexible sound absorbing sheet material having inlet portion, which enters a center portion at an angle, the center portion larger than the inlet portion and outlet portion which exits the center portion at an angle; the whole enclosure can be disassembled to compactly fold for easy storage or transportation.