Noise and Sound in HVAC Systems

Calculate noise, sound and silencers in HVAC systems

Acoustic Calculation of Ventilation Systems

A procedure for acoustic calculation of noise in ventilation systems

Blade Dampers and Noise Generation

Noise generated in blade dampers

Blade Pass Frequency - BPF

The noise level intensity varies with type of fan

Calculate Decibel

The logarithmic decibel scale is convenient when calculating resulting sound power levels and sound pressure levels for two or more sound or noise sources.

Classification of Noise Reduction Silencers

Noise can be eliminated with reactive silencers, diffuser type silencers, active silencers and/or dissipative silencers

Decibel

Decibel is a logarithmic unit used to describe the ratio of the signal level - power, sound pressure, voltage, intensity, etc.

Decibel A, B and C

The sound pressure is not equally sensed by the human ear at different frequencies. This can be compensated with the dB(A), dB(B) or dB(C) filters

Directivity Coefficient and Sound Attenuation 

The attenuation in a room depends on the receiver and source location. 

Effects of Low-Frequency Noise and Vibration on People

Physiological effects of low-frequency noise and vibration

Fans and Sound Power Generation

The Sound Power Level from fans depends on the motor power and the capacity of the fan - the static pressure and/or the discharged volume. 

NR - Noise Rating Curves

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

Online Attenuation Calculator

Calculate the attenuation in decibels in an outdoor free field

Online Noise Criterion - NC - Calculator

An online Noise Criterion - NC - Calculator

Online Noise Rating - NR - Calculator

An online Noise Rating - NR - Calculator

Online Sound Level Calculator

Convert between sound level, sound pressure and sound intensity

Outdoor Ambient Sound Levels in Decibel

Outdoor ambient sound level in different rural and urban business and industrial environments with or without limited traffic.

Propagation of Sound Indoors

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

Propagation of Sound Outdoors

Outdoor propagation of sound - distance and attenuation. 

Propagation of Sound Outdoors and Partial Barriers

The transmission of sound through and around outdoor barriers. 

Room Absorption Characteristics

Mean absorption coefficients and reverberation times for some typical rooms.

Room Acoustics Calculator

An online acoustic calculator for estimating the reverberation time and designing the acoustics of rooms

Sound Absorption Coefficients for some common Materials

Sound absorption coefficients for some common materials as plaster walls, brickwork, plywood panels etc.

Sound Attenuation - Duct split to Terminals

Estimation of sound attenuation when ducts are split to terminals

Sound Attenuation - Main Ducts to Branches

Sound attenuation for main ducts to branches.

Sound Attenuation due to End Reflection

Some of the low frequency noise transferred to the end terminals in a ventilation system, reflects back to the duct.

Sound Attenuation in Duct Elbows

Attenuation in duct elbows is caused by reflected sound. It is only in big ducts and at high frequencies the attenuation is considerable.

Sound Attenuation in Unlined Sheet-Metal Ducts

Attenuation of sound in unlined sheet-metal ducts

Sound Attenuation of Lined Sheet-Metal Ducts

Sound attenuation in rectangular straight, lined, sheet metal ducts.

Sound Frequency, Wavelength and Octave

An introduction to the nature of sound with frequency, wavelength and octaves.

Sound Intensity

The sound intensity level is the acoustic power of a sound per unit of area in relation to a fixed reference.

Sound Power

The definition of Sound Power Level and the Sound Power from some common sources as fans, jet engines, cars, humans ....

Sound Power, Intensity and Pressure

An introduction to decibel, sound power, sound intensity and sound pressure

Sound Pressure

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

Sound Pressure - Recommended Levels in Rooms

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

Sound Transmission through Duct Walls

Estimating sound transmission from a duct to the surrounding room.

Sound Transmissions through Flanking Paths

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

Speed of Sound Calculator

An online Speed of Sound calculator for air

Speed of Sound Formulas

Calculation formulas for velocity of sound in gas, fluid or solid

Speed of Sound in some common Liquids

Velocity of sound in common fluids as water, glycerol, kerosene ...

Speed of Sound in some common Solids

Velocity of sound in some common solids as aluminum, brass, concrete and ...

Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

Web The Engineering ToolBox