The disruption of sound pressures waves which reduces the noise is called attenuation - Sound Pressure Level Calculator
Acceptable noise - dBA - levels at some locations
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
Eliminating noise with reactive silencers - diffuser type silencers - active silencers and/or dissipative silencers
Comparing Noise Criteria - Noise Criterion (NC), Noise Rating (NR) and dB(A)
Daily noise dose level when exposed in periods with different noise levels
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
Change in frequency of a sound due to relative motion between source and listener
Air flow and noise generated in ducts
Air flow and noise generated in ducts
The noise level should not exceed values protecting public health and welfare
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
Frequency limits for octave bands and 1/3-Octave bands
For every doubling of the distance from the noise source, the sound pressure levels - Lp, will be reduced by 6 decibels
The EPA has defined an A-weighted sound level day and night equivalent for a 24 hour period
Equivalent Sound Level - Leq - quantifies the noise environment as a single value of sound level for any desired duration
Sound Exposure Level - Ls - describes noise from a varied source
Reducing machines sound level
Maximum A-weighted sound levels allowed by OSHA
For a given noise spectrum, the NC rating can be obtained by plotting its octave band levels on the set of NC curves
An introduction to Noise Rating - NR - curves, developed by the International Organization for Standardization (ISO) - NR diagram
Noise exposure should be controlled so that exposure is less than the combination of exposure level and duration
Online calculating of road traffic noise levels for non-complex situations
Calculate the attenuation in decibels in an outdoor free field
An online Noise Criterion - NC - Calculator
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
A noise measurement system for continuous or ambient noise in indoor environments proposed by Leo Beranek in 1971
An online Preferred Noise Criterion - PNC - Calculator
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
Room Criteria - RC - measures the background noise in a building over the frequency range 16 Hz to 4000 Hz
The NIOSH noise Recommended Exposure Limit - REL - for occupational noise
The Sound Reverberation Time indicates the time it takes until the sound pressure level in a room is decreased with 60 dB
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
Room size, absorption characteristics and attenuation in direct sound fields
Approximate speech interference levels
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
An online Speed of Sound calculator
Calculation formulas for velocity of sound in gases, fluids or solids
Speed of sound in some common gases
Velocity of sound in common fluids as water, glycerol, kerosene ...
Velocity of sound in some common solids as aluminum, brass, concrete and ...
Changing sound pressure level and the subjective effect on human perception
Using telephones in noisy areas - satisfactory, difficult and impossible noise levels
The voice level at various distances