Normal drywall walls are not acoustically insulated. They offer fundamental separation at most. This is an issue in offices, studios, even homes where the need to control privacy or noise levels is necessary. A single material does not create true soundproofing but rather is a composite of mass, isolation and absorption.
Sound can travel via air gaps, structural connections and loose joints. A one-layered dry-wall partition is easily penetrated by sound. The only way this is solved is by making it increasingly thicker provided there are gaps and vibration paths.
The initial step towards successful soundproofing is a two-layered drywall construction on either side of a metal frame. High-density insulation (mineral wool or fiberglass) is placed in the cavity to absorb the sound waves. The drywall is decoupled to the frame by resilient channels or isolation clips which prevent the transfer of vibration.
Sealing is critical. Minor cavities around edges, electrical boxes or joints will be sound leaks. All perimeter joints are closed using acoustic sealants. Doors and windows too are to be treated--an untreated door will be a weak point in all the partitions.
Mineral wool is also used because of its density and resistance to fire. Mass is added by means of double gypsum boards, and prevents sound. To achieve greater performance, staggered stud frames or double-wall systems may be utilized, but this is more expensive and thicker.
The greatest fallacy is believing that a room can be soundproofed by the addition of one more board or foam panels. There will be little results without the concern of structure-borne sound and air gaps. The other problem is poor workmanship- boards out of line and unsealed joints ruin performance.
It involves a system-based measure that integrates insulation, mass, and isolation to soundproof drywall partitions. No quick and easy. With a well-planned and implemented design, a substantial amount of noise can be mitigated, but it is not realistic to assume total silence unless proper construction is implemented.