Chamber for tesing acoustical transmission loss characteristics of sheet materials

A chamber for testing acoustical transmission loss characteristics of sheet materials comprising:

• means defining a first cylindrical enclosure oriented along a vertical axis;
• means for producing acoustical vibrations within said housing including a speaker electrically connected to a generator for driving said speaker over a predetermined range of frequencies within at least the frequency range of approximately 20-800 Hz;
• means for defining a second cylindrical enclosure oriented along said vertical axis and being separated from said first enclosure defining means by said acoustical means;
• means for mounting said sheet material on one end of said second enclosure defining means separated from said acoustical means;
• first means for detecting the pressure gradient within said second enclosure defining means;
• second means for detecting the pressure gradient above said sheet material mounting means, wherein each of said first and second pressure gradient detecting means comprises a pair of oppositely facing microphones disposed along a line approximately parallel to said vertical axis and separated by a predetermined distance;
• means for monitoring said first and second means and for responsively producing an output signal indicative of transmission loss through said mounted sheet material;
• wherein said monitoring means is connected to each pair of microphones of each of said first and second pressure gradient detecting means and includes means for differentiating the detection signal from the microphones in each pair and means for outputting a signal indicative of an integration of each differentiated signal.