Reverberant Room and Semi-anechoic Chamber

La Reverberant Room of the Engineering Department of the University of Ferrara is an acoustic laboratory in which a diffuse sound field, almost constant within the entire volume, can be generated. The walls of the room, constituded by heavyweight building structures in order to increase the sound reflection, are non-orthogonal. Four static acoustic diffusers are hanging from the ceiling. Moreover, a rotaing diffuser can also placed inside tha chamber.

This laboratory allows for the measurement of the sound absorption coefficient of materials or systems, and for the sound power of sound sources. The reverberant room is connected through an opening window to a small semi-anechoic chamber. This window is used to measure  the sound radiation and sound transmission on pannels and components.

Main characteristcs:

• Reverberant Room:

• Volume ≈ 250 m³
• Schroeder frequency: fs = 330 Hz
• Uneven geometry: the room boundaries, walls, floor and ceiling, are not orthogonal nor parellel to each other.
• Acoustic Diffusers:
• 4 static acoustic diffusers hanging from the ceiling:
• Dimensions: 2.0 x 2.2 m
• Radius of curvature: 5.0 m
• Thickness: 2.0 cm
• Front surface ≈ 4.40 m²
• Material: MDF
• Low design frequency: 80 Hz
• 1 rotating diffuser (dynamic)
• Dimensions: 2.0 x 1.5 m
• Thickness: 2.5 cm
• Front surface ≈ 3.00 m²
• Rotation frequencies: within the range 0.13-0.36 Hz
• Opening window, between the reverberant room and a semi-anechoic chamber, for sound transmission loss measurments. The window's size can be adjusted by means of wood frames:
• Large window: 125 x 150 cm
• Medium window: 90 x 90 cm
• Small window: 50 x 50 cm

Acoustic equipment:

• Multi-channel acquisition system SINUS controlled by SAMURAI® software;
• Fixed microphone positions: 6 ICP ½ inch Bruel and Kjaer microphones;
• Rotating boom microphone: ½ inch Larson & Davis microphone with Brüel & Kjær Type Boom 3923 rotating system, for sound power measurements according to the EN ISO 3741 standard;
• Bruel and Kjaer sound intensity probe;
• Three LookLine D203 dodecahedron sound sources powered with LookLine DA204  amplifiers  and signal generators.
• Two sound sources specifically design for high freqeuency noise emission (for transmission loss);
• Thermo-hygrometer and electronic barometer.

Service equipment:

• Remote control from an external control room;
• Mono and three-phase electric power system;
• HAVC system to mantain constant temperature and humidity inside the room.

Testing:

• Sound power measurements according to the ISO 3741 standard;
• Diffuse incidence sound absorption measurements according to the ISO 354 standard;
• Experimental evaluatio of sound transmission loss by means of sound intensity measurements, or according to spefic product standards.