4204 Reference Sound Source

Reference Sound Source Type 4204 is a calibrated source of sound power with very well defined operating characteristics and a predictable performance. It is rugged, compact and stable, and is therefore suitable for both field and laboratory use.

Type 4204 is intended for use as a reference source for determination of the sound power output of equipment by the various comparison methods including the method described in ISO 3741, and by the survey methods described in ISO 3747. It is also useful in the field of building acoustics to determine the sound absorption and sound insulation of a room.

The reference sound source consists essentially of a specially designed centrifugal fan driven by a powerful asynchronous motor. The motor is of the external rotor type, and due to the high moment of inertia of the rotor it has a very constant speed of rotation. The motor is mounted on a cast aluminium base, shaped to minimize reflections. The complete assembly of motor and fan is mounted in a cylindrical safety grid fitted with two carrying handles.