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

Sound Intensity, Power and Pressure Levels

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

Sponsored Links

The Decibel

Decibel is a logarithmic unit used to describe ratios of physical values like - like power, sound pressure, voltage, intensity and more.

The decibel can be expressed as:

L = 10 log (S / Sref)                                        (1)

where 

L = signal level (dB)

S = signal (signal unit)

Sref = signal reference (signal unit) 

Sound Power Level

Sound power is the energy rate - the energy of sound per unit of time (J/s, W in SI-units) from a sound source.

Sound power can more practically be expressed in a logarithmic scale named Sound Power Level as the ratio of sound power to the sound power at the threshold of hearing - 10-12 W: 

LN = 10 log (N / Nref)                                   (2)

where 

LN = Sound Power Level (decibel , dB)

N = sound power (W)

Nref = reference sound power (10-12 W)

  • The lowest sound power persons with excellent hearing can discern is about 10-12 W -  defined as 0 dB in the decibel scale
  • The loudest sound power generally possible to encounter is that of a jet aircraft with a sound power of 105 W - 170 dB

Sound Intensity Level

Sound intensity is the ratio acoustic or sound power to area. The SI-unit for Sound Intensity is W/m2

The Sound Intensity Level can be expressed as: 

LI = 10 log (I / Iref)                                (3)

where 

LI = sound intensity level (dB)

I = sound intensity (W/m2)

Iref = 10-12 - reference sound intensity (W/m2

Sound Pressure Level

The sound pressure is the force (N) of a sound on a surface area (m2) perpendicular to the direction of the sound. The SI-unit for the Sound Pressure is N/m2 or Pa.

The Sound Pressure Level in decibel can be expressed as

Lp = 10 log (p2 / pref2)

    = 10 log (p / pref)2 

    = 20 log (p / pref)                                  (4)

where

Lp = sound pressure level (dB)

p = sound pressure (Pa)

pref = 2 10-5 - reference sound pressure (Pa)

  • If the pressure is doubled the sound pressure level is increased with 6 dB (20 log (2))
Sponsored Links

Related Topics

Related Documents

Tag Search

  • en: sound, noise, decibel, power, pressure, intensity
Sponsored Links

Search the Engineering ToolBox

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

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 the amazing, fun and free SketchUp Make and SketchUp Pro .Add the Engineering ToolBox extension to your SketchUp from the SketchUp Pro Sketchup Extension Warehouse!

Translate this page to
About the Engineering ToolBox!

Citation

This page can be cited as

  • Engineering ToolBox, (2003). Sound Intensity, Power and Pressure Levels. [online] Available at: https://www.engineeringtoolbox.com/sound-power-intensity-pressure-d_57.html [Accessed Day Mo. Year].

Modify access date.

Customize Ads in the ToolBox

Make ads more useful in Google Ad Settings .

. .

close

3D Engineering ToolBox - draw and model technical applications! 2D Engineering ToolBox - create and share online diagram drawing templates! Engineering ToolBox Apps - mobile online and offline engineering applications!

Scientific Online Calculator

Scientific Calculator

11 16

Sponsored Links
.