This document provides an introduction and overview of acoustics and noise control for mechanical systems. It defines basic acoustical terms like amplitude, frequency, and quality of sound. It discusses indoor noise criteria curves and recommendations for limiting noise from air handling systems, roof-top units, terminal boxes, chillers, and pumps through strategies like isolation, attenuation, duct lining, and space planning.
21. Sound Power vs. Sound Pressure Total Radiated Heat/Time (BTU/hr) ~ Sound Power Heat converts to temperature based Sound power converts to pressure based on distance and heat conductance based on distance and sound of room surfaces. absorption of room surfaces. Room Temperature ~ Sound Pressure Level This is why we specify noise levels in terms of Sound Power.
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006 Conversational speech - ~60 dBA Typical Office - ~65-70 dBA Design a typical office to 45-50 dBA
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006 Frequency well-correlated to sensation of pitch
Guide to Mechanical System Acoustical Design June 6, 2006 Compare Male & Female Voices Piano Lowest A = 28 Hz Middle C = 256 Hz Highest C = 4096 Hz
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006 AHU Sound from duct in ceiling plenum – Unit in MER in adjacent room
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006 Same sound spectra shown on an RC curve. Note that the RC level is lower, because it is the average of the preferred speech frequencies (250 Hz – 2000 Hz) and the descriptor identifies the quality of the sound spectra.
Guide to Mechanical System Acoustical Design June 6, 2006 RC Mark II is a tool used for
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006 Correlation with Loudness Speech Interference Annoyance Hearing Loss (High frequency sounds more damaging)
Guide to Mechanical System Acoustical Design June 6, 2006 31.5 -39 63 -26 125 -16 250 -9 500 -3 1000 0 2000 +1 4000 +1 8000 -1
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006
A – Vibration inducted structure-borne noise B – Supply system ductborne noise C – Supply system low-frequency break-out noise D – Return ductborne noise E – Radiated noise path through the wall Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006
Based on studies commissioned by ASHRAE TC 2.6 conducted at the NRC, National Research of Canada Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006
Guide to Mechanical System Acoustical Design June 6, 2006