Room acoustics and acoustic properties - decibel A, B and C - Noise Rating (NR) curves, sound transmission, sound pressure, sound intensity and sound attenuation

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The disruption of sound pressure waves and reduction of noise is called attenuation - Sound Pressure Level Calculator

Acceptable noise - dB A - level at some locations

Procedure for acoustic noise calculation of ventilation systems

The logarithmic decibel scale is convenient calculating sound power levels for two or more sound sources

Shift in hearing threshold for men and women

Speed and attenuation of sound at varous frequencies and air humidities

Sound power level generated in blade dampers

The fan Blade Pass Frequency noise can be very intense - and varies with number of blades and rotation velocity

Noise can be reduced by reactive , diffuser type, active and/or dissipative silencers

Comparing Noise Criteria - Noise Criterion (NC, NCB, RNC), Noise Rating (NR) and dB(A)

Daily noise dose when exposed in periods with different noise levels

Decibel is a logarithmic unit used to describe the ratio of a signal level - like power or intensity to a reference level

Sound pressure sensed by the human ear - dB(A), dB(B) or dB(C) frequency filters

Room attenuation depends on location of source and receiver - and the room constant

The change in frequency of sound due to relative motion between source and listener

The noise level should not exceed certain values to protect public health and welfare

Noise or sound generated by a fan depends on the motor power, volume capacity, static pressure and discharged volume

Human activities like walking, running, dancing - and operating machines can induce floor vibrations

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Speed of sound in gases

A doubling of the distance from a noise source will reduce the sound pressure level with 6 decibel

EPA has defined an A-weighted sound level day and night equivalent for a 24 hour period

Equivalent Sound Level - L eq - quantifies the noise environment to a single value of sound level for any desired duration

Sound Exposure Level - L s - describes the noise from a variable source

Reducing machines noise levels

Maximum A-weighted sound levels allowed by OSHA

Maximum recommended sound pressure levels in rooms with activities like kindergartens, auditoriums, libraries, cinemas and more ...

Noise Criterion - NC - level is a standard describing relative loudness of a space with a range of frequencies

An online Noise Criterion - NC - Calculator

Exposure to noise should be controlled so that the exposure is less than a max combination of exposure level and duration

Calculate road traffic noise levels

Noise generated form air flow in ducts

An online Noise Rating - NR - Calculator

Note frequencies

An introduction to the Noise Rating - NR - Curve developed by the International Organization for Standardization (ISO)

Octave and 1/3 octave band frequencies

Outdoor ambient sound level (dBA) in rural and urban business and industrial environments with or without limited traffic

Noise measurement system for continuous or ambient noise in indoor environments

An online Preferred Noise Criterion - PNC - calculator

The transmission of sound through and around outdoor barriers - the Fresnel Number

Sound and noise in a room reach the receiver as direct and reverberant sound

Outdoor propagation of sound - distance and attenuation

Room Criteria - RC - measuring background noise in a building over frequencies ranging 16 Hz to 4000 Hz

The NIOSH noise Recommended Exposure Limit - REL - for occupational noise

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 typical rooms

Room size - absorption characteristics and attenuation in direct sound fields

Room sound absorption and absorption coefficients for common materials like plaster walls, brickwork, plywood panels etc...

Approximate speech interference levels

An introduction to the nature of sound - frequency, wavelength and octave

Estimation of sound attenuation when ducts are split to terminals

Sound attenuation from main duct to branch ducts

Noise attenuation in duct elbows are caused by reflected sound

Some low frequency noise transferred from main duct to end terminals is reflected back to main duct

Attenuation of sound in unlined sheet-metal ducts

Sound attenuation in rectangular straight, lined, sheet metal ducts

Sound intensity is the acoustic power of sound per unit area

Introduction to decibel, sound power, sound intensity and sound pressure

Convert between sound level, sound pressure and sound intensity

Sound Power Level from common sources like fans, jet engines, cars, humans and more ..

Sound Pressure is the force of sound on a surface area perpendicular to the direction of sound

Estimating sound transmission from ducts to surrounding rooms

Sound attenuation in building elements like massive concrete walls or floors

Noise and sound transmitted through duct walls, through floors or through ceilings

Changing sound pressure level and subjective human perception

Use of telephone in noisy areas - satisfactory, difficult and impossible noise levels

An online Speed of Sound calculator

Calculate velocity of sound - sonic velocity - in gases, fluids or solids

Velocity of sound in air at temperatures from -40 to 1000oC (-40 to 1500oF) at standard atmospheric pressure - Imperial and SI Units

Velcocity of sound in some common fluids - like water, glycerol, kerosene ...

Velocity of sound in common solids and metals - aluminum, brass, concrete and ...

Velocity of sound in water at temperatures ranging 32 - 212oF (0 - 100oC) - Imperial and SI units

Required voice levels at distance