Noise is usually defined as unwanted sound - noise, noise generation, silencers and attenuation in HVAC systems
A procedure for acoustic noise calculation of ventilation systems
The logarithmic decibel scale is convenient calculating sound power levels and sound pressure levels for two or more sound sources
Noise generated in blade dampers
The fan Blade Pass Frequency noise can be very intense - vary with number of blades and rotation velocity
Noise attenuation in chambers
Eliminating noise with reactive silencers - diffuser type silencers - active silencers and/or dissipative silencers
Decibel is a logarithmic unit used to describe the ratio of the signal level - power, sound pressure, voltage, intensity, etc.
Sound pressure is not equally sensed by human ear at different frequencies - compensated with dB(A), dB(B) or dB(C) filters
The attenuation in a room depends on the location of the source and the receiver, and the room constant
Air flow and noise generated in ducts
Physiological effects of low-frequency noise and vibration
Sound Power Level from a fan depends on motor power, capacity, static pressure and discharged volume
Human activities like walking, running, dancing and operating machines can induce high levels of vibration in floors
An introduction to Noise Rating - NR - curves, developed by the International Organization for Standardization (ISO) - NR diagram
Changing duct size and noise attenuation
Calculate the attenuation in decibels in an outdoor free field
An online Noise Rating - NR - Calculator
Convert between sound level, sound pressure and sound intensity
Outdoor ambient sound level (dBA) in rural and urban business and industrial environments with or without limited traffic
Sound and noise in a room will reach the receiver as direct and reverberant sound.
Outdoor propagation of sound - distance and attenuation
The transmission of sound through and around outdoor barriers - Fresnel Number
Mean absorption coefficients and reverberation times for some typical rooms.
An online acoustic calculator for estimating the reverberation time and designing the acoustics of rooms
Sound attenuation in rotating heat exchangers
Sound absorption coefficients for some common materials as plaster walls, brickwork, plywood panels etc...
Estimation of sound attenuation when ducts are split to terminals
Sound attenuation for main ducts to branches
Some of the low frequency noise transferred to the end terminals in a ventilation system, reflects back to the duct.
Noise attenuation in a duct elbow is caused by reflected sound. It is only in larger ducts and at higher frequencies the attenuation is considerable
Attenuation of sound in unlined sheet-metal ducts
Sound attenuation in rectangular straight, lined, sheet metal ducts
An introduction to the nature of sound - frequency, wavelength and octaves
The sound intensity level is the acoustic power of a sound per unit of area in relation to a fixed reference
Sound Power Level and the Sound Power from some common sources as fans, jet engines, cars, humans and more ..
An introduction to decibel, sound power, sound intensity and sound pressure
Sound Pressure is the force of sound on a surface area perpendicular to the direction of the sound
Maximum recommended sound pressure levels in rooms with activities as kindergartens, auditoriums, libraries, cinemas and more ...
Sound and noise transmission through massive walls or floors - concrete or similar
Estimating sound transmission from ducts to surrounding rooms
Noise and sound transmitted through duct walls, through floors or through ceilings