Noise is usually defined as unwanted sound - noise, noise generation, silencers and attenuation in HVAC systems
Seawater and attenuation of sound
Logarithmic unit used to describe ratios of signal levels - like power or intensity - to a reference level.
Sound pressure filters compensating for hearing sensed by the human ear.
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.
Physiological effects from low-frequency noise and vibrations
Maximum recommended sound pressure levels in rooms like kindergartens, auditoriums, libraries, cinemas and more.
Chamber noise attenuation
Noise attenuation in rotating heat exchangers
Changing duct size and nosie attenuation
TheBlade Pass Frequency noise generated by a fan can be very intense and varies with the number of blades and the rotation velocity.
Estimate noise generated by air flow in ducts.
Sound power noise generated by blade dampers in ventilation systems.
An online Noise Rating (NR) calculator.
The Noise Rating (NR) Curve used to determine acceptable indoor environments for hearing preservation, speech communication and annoyance.
Outdoor ambient sound pressure levels (dBA) in rural and urban business and industrial environments with or without limited traffic.
The transmission of outdoor sound through and around barriers - the Fresnel Number.
In a room the sound or noise will reach the receiver as direct and reverberant sound.
The propagation of outdoors sound vs. distance and attenuation.
The logarithmic decibel scale is convenient when adding values for signals like sound power, pressure and more from two or more sources.
The speed and attenuation of sound in moist air varies with sound frequency and air humidity.
The attenuation in a room depends on the location of the sound source and the receiver - and the room constant.
An introduction to the nature of sound with frequencies, wave-lengths and octaves.
Mean absorption coefficients and reverberation times in typical rooms.
Room sound absorption and absorption coefficients for common materials like plaster walls, brickwork, plywood panels and more.
Estimating sound attenuation where ducts splits to terminals.
Sound attenuation from main ducts to branch ducts.
Noise attenuation in duct elbows by reflected sound.
Low frequency noise transferred from main duct to end terminals is reflected back to main duct.
Attenuation in unlined sheet-metal ducts
Sound attenuation in rectangular straight, lined, sheet metal ducts
Acoustic power of sound per unit area.
Introduction to decibel, sound power, intensity and pressure.
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 from ducts to surrounding rooms.
Sound transmitted through duct walls, floors and ceilings.
Sound transmission and attenuation in building elements like massive concrete walls or floors.
Acoustic noise calculation procedure HVAC systems.
Noise in a ventilation system can be reduced by reactive, diffuser type, active and/or dissipative silencers.