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

# Fans - Noise Power Generation

## The sound generated by a fan depends on the motor power, the volume capacity, the static pressure increase and the discharged volume.

The empiric expressions below can be used to indicate generated Sound Power Level from fans.

Note! - Exact Sound Power Levels should be obtained from manufacturers data.

### Sound Power Level - SI-units

LN = 67 + 10 log(S) + 10 log(p)                              (1a)
LN = 40 + 10 log(Q)+ 20 log(p)
(1b)
LN = 94 + 20 log(S) - 10 log(Q)
(1c)

where

LN = sound power level from fan (dB)

S = rated motor power  (kW)

p = fan static pressure  (Pa, N/m2)

Q = volume discharged (m3/s)

Download and print Fan - Generated Sound Power vs. Volume Flow and Static Pressure chart

### Sound Power Frequencies

Sound power level in the octaves can be calculated by adding the values below to the sound power level calculated in the expressions or diagram above.

Fans - Noise Power Decibels to add (dB)
Fan Type

Octave (Hz)

631252505001000200040008000
Centrifugal fan, backward-curved blades -4 -6 -9 -11 -13 -16 -19 -22
Centrifugal fan, forward-curved blades -2 -6 -13 -18 -19 -22 -25 -30
Centrifugal fan, straight radial blades -3 -5 -7 -7 -8 -11 -16 -18
Axial fan -7 -9 -7 -7 -8 -11 -16 -18

### Sound Power Level - Imperial units

LN = 90 + 10 log(s) + 10 log(h)                         (2a)
LN = 55 + 10 log(q) + 20 log(h)
(2b)
LN = 125 + 20 log(s) - 10 log(q)
(2c)

where

s = rated motor power (hp)
h = fan static head (inch water gauge)
q = volume discharged (ft3/min)

### Maximum Discharge Velocity from Fans for Quiet Operations

The discharge velocity from fans should be kept within certain limits to avoid noisy operations.

Fans - Maximum Discharge Velocities (m/s)
ApplicationSupply SystemExhaust
System
Sound studios, churches, libraries 4 - 5 5 - 7
Cinemas, theaters, ballrooms 5 - 7 6 - 8
Restaurants, offices, hotels, shops 6 - 8 7 - 9
• 1 m/s = 3.6 km/h = 196.85 ft/min = 2.237 mph

### ACMA Certified Sound Levels

Fans - Certified Sound-Power Levels (dB)
Octave Band (Hz)Fan 1Fan 2Fan 3Fan 4
63 117 113 120 101
125 118 116 113 98
250 109 111 111 107
500 106 106 107 120
1000 103 103 103 116
2000 97 98 98 114
4000 94 95 93 109
8000 92 92 88 105

## Related Topics

• ### Acoustics

Room acoustics and acoustic properties. decibel A, B and C calculations. Noise Rating (NR) curves. Sound transmission through walls. Calculate sound pressure, sound intensity and sound attenuation.
• ### Noise and Attenuation

Noise is usually defined as unwanted sound - noise, noise generation, silencers and attenuation in HVAC systems.

## Related Documents

• ### Fan AMCA Classification

Fan classification established by AMCA.
• ### Fans - Efficiency and Power Consumption

Power consumption and typical efficiencies of fans
• ### Noise from Machines - Enclosures and Sound Pressure Level Reductions

Barriers and enclosures to reduce noise sound pressure levels from machines.
• ### Noise generated by Fans - Blade Pass Frequency (BPF)

TheBlade Pass Frequency noise generated by a fan can be very intense and varies with the number of blades and the rotation velocity.
• ### Noise generated in Air Ducts

Estimate noise generated by air flow in ducts.
• ### Noise generated in Blade Dampers

Sound power noise generated by blade dampers in ventilation systems.
• ### Octave Band Frequencies

The octave and the 1/3 octave band frequencies.
• ### Sound - Ls - Exposure Level

The EPA Sound Exposure Level - Ls - describes the noise from a variable source.
• ### Sound Power

Sound power from sources like fans, jet engines, cars, humans and more.

## Search

Search is the most efficient way to navigate the Engineering ToolBox.

## Engineering ToolBox - SketchUp Extension - Online 3D modeling!

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with older versions of the amazing SketchUp Make and the newer "up to date" SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp Make/Pro from the Extension Warehouse !

We don't collect information from our users. More about

We use a third-party to provide monetization technologies for our site. You can review their privacy and cookie policy here.

You can change your privacy settings by clicking the following button: .

## Citation

• The Engineering ToolBox (2003). Fans - Noise Power Generation. [online] Available at: https://www.engineeringtoolbox.com/fan-noise-d_61.html [Accessed Day Month Year].

Modify the access date according your visit.

8.21.8

.