Field Measurement of Noise Reduction between Spaces.

The present ASTM procedure for field measurement of the noise reduction between spaces is time consuming and costly because it requires numerous measurements in order to compute the noise isolation class (NIC), particularly when separate measurements must be made at multiple microphone positions to obtain adequate spatial averaging. The purpose of the present investigation is to explore the relationships between NIC values based on <FRACTION><NUM>1</NUM><DEN>3</DEN></FRACTION>-oct band data and more easily obtained ratings of isolation based on either octave band data or on A-weighted or C-weighted sound level data. A large number of curves of <FRACTION><NUM>1</NUM><DEN>3</DEN></FRACTION>-oct band noise reduction versns frequency were calculated from data on transmission loss of partitions, assumed room geometry, assumed values for the source sound power spectrum, and assumed values for the sound absorption in the source and receive rooms. For each of these <FRACTION><NUM>1</NUM><DEN>3</DEN></FRACTION>-oct band noise reduction curves, the following quantities were calculated and compared: NIC rating, Ia rating (<FRACTION><NUM>1</NUM><DEN>3</DEN></FRACTION>-oct band data), Ia rating (octave band data), the A-weighted sound level difference, and the difference between the C-weighted level in the source room and the A-weighted level in the receive room. [ABSTRACT FROM AUTHOR]