Noise and Attenuation
Noise is usually defined as unwanted sound - noise, noise generation, silencers and attenuation in HVAC systems.
Change in Duct Area and Noise Attenuation
Sound attenuation vs. change in duct size.
Logarithmic unit used to describe ratios of signal levels - like power or intensity - to a reference level.
Decibel A, B and C
Sound pressure filters that compensates for the hearing sensed by the human ear.
Fans - generated Noise Power
The sound generated by a fan depends on the motor power, the volume capacity, the static pressure increase and the discharged volume.
Human activities like walking, running and dancing - and operating machines - can introduce floor vibrations due to resonance.
Human Effects when Exposed to Low-Frequency Noise or Vibration
Physiological effects from low-frequency noise or vibrations.
Lined Sheet-Metal Ducts - Sound Attenuation
Noise attenuation in rectangular straight, lined, sheet metal ducts.
Maximum Sound Pressure Levels in Rooms
Maximum recommended sound pressure levels in rooms like kindergartens, auditoriums, libraries, cinemas and more.
Noise Attenuation in Chambers
Chamber sound attenuation.
Noise Attenuation in Rotary Heat Exchanges
Sound attenuation vs. frequency in rotating heat exchangers.
Noise generated by Fans - Blade Pass Frequency (BPF)
TheBlade Pass Frequency noise generated by a fan can be very intense and varies with the number of blades and the rotation velocity.
Noise generated in Air Ducts
Estimate noise generated by air flow in ducts.
Noise generated in Blade Dampers
Sound power noise generated by blade dampers in ventilation systems.
Noise Rating (NR) - Free Online Calculator
An online Noise Rating (NR) calculator.
NR - the Noise Rating Curve
The Noise Rating (NR) Curve used to determine acceptable indoor environments for hearing preservation, speech communication and annoyance.
Outdoor Ambient Sound Pressure Levels
Outdoor ambient sound pressure levels (dBA) in rural and urban business and industrial environments with or without limited traffic.
Propagation of Outdoor Sound - Partial Barriers
The transmission of outdoor sound through and around barriers - the Fresnel Number.
Propagation of Sound Indoors - the Room Constant
In a room the sound or noise will reach the receiver as direct and reverberant sound.
Propagation of Sound Outdoors - Attenuation vs. Distance
The propagation of outdoors sound vs. distance and attenuation.
Seawater - Attenuation of Sound
Attenuation of sound in seawater vs. temperature and frequency.
Signals - Adding Decibels
The logarithmic decibel scale is convenient when adding signal values like sound power, pressure and others from two or more sources.
Sound - Attenuation and Speed vs. Sound Frequency and Air Humidity
The speed and attenuation of sound in moist air varies with sound frequency and air humidity.
Sound - Attenuation and the Directivity Coefficient
The attenuation in a room depends on the location of the sound source and the receiver - and the room constant.
Sound - Frequency, Wavelength and Octave
An introduction to the nature of sound with frequencies, wave-lengths and octaves.
Sound - Room Absorption Characteristics
Mean absorption coefficients and reverberation times in typical rooms.
Sound - Room Absorption Coefficients
Room sound absorption and absorption coefficients for common materials like plaster walls, brickwork, plywood panels and more.
Sound Attenuation - Duct split to Terminals
Estimating sound attenuation where ducts splits to terminals.
Sound Attenuation - Main Duct to Branch Ducts
Sound attenuation from main ducts to branch ducts.
Sound Attenuation in Duct Elbows
Noise attenuation in duct elbows by reflected sound.
Sound Attenuation in Ducts due to End Reflection
Low frequency noise transferred from main duct to end terminals is reflected back to main duct.
Acoustic power of sound per unit area.
Sound Intensity, Power and Pressure Levels
Introduction to decibel, sound power, intensity and pressure.
Sound Level - Online Calculator
Calculate sound level, pressure and intensity.
Sound power from sources like fans, jet engines, cars, humans and more.
Sound Pressure is the force of sound on a surface perpendicular to the propagation of sound.
Sound Transmission through Duct Walls
Sound transmission from ducts to surrounding rooms.
Sound Transmission through Flanking Paths
Sound transmitted through duct walls, floors and ceilings.
Sound Transmission through Massive Walls or Floors
Sound transmission and attenuation in building elements like massive concrete walls or floors.
Unlined Sheet-Metal Ducts - Sound Attenuation
Noise attenuation in unlined sheet-metal ducts.
Ventilation Systems - Acoustic Calculation Procedure
Acoustic noise calculation procedure HVAC systems.
Ventilation Systems - Classification of Noise Reduction Silencers
Noise in a ventilation system can be reduced by reactive, diffuser type, active and/or dissipative silencers.