T.A. Morrison Co. Inc.

Sound Ratings
Series 1000 / 1000 SW / 1500 / 1500 SW

Sound Ratings PDF document (33 KB)
Get Acrobat Reader

Note: Tested dampers are “Flanged to Duct” type.

NOISE CRITERIA RATINGS

NC ratings published below, for use with NC curves (ASHRAE 1993 Fundamentals Handbook: Chapter 7). NC curves define limits that the octave-band spectrum of a noise source must not exceed to achieve a level of occupant acceptance.

Noise Criteria (NC) ratings were determined by subtracting 10dB
(room effect) from the Sound Power Levels.
When comparing NC numbers with those supplied by other damper manufacturers,
ensure that only 10dB for room effect has been subtracted. Further subtraction
of another 10dB for room attenuation will result in false field readings.

ROOM CRITERIA RATINGS

RC ratings published below for use with RC curves (ASHRAE 1993 Fundamentals Handbook: Chapter 7). RC curves, for specifying design level in terms of a balanced spectrum shape, are designed especially for establishing H-VAC system design goals.