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

This is an AMP page - Open full page! for all features.

• the most efficient way to navigate the Engineering ToolBox!

# Sound - Doppler Effect

Sponsored Links

The change in frequency of sound due to relative motion between a source and a listener is called the Doppler Effect.

The observed sound frequency for a listener can be expressed as

fr = fs (c + vr) / (c + vs)                                 (1)

where

fr = frequency observed by the receiver (1/s, Hz)

fs = frequency emitted from the source (1/s, Hz)

c = speed of sound (m/s)

vr = velocity of the receiver relative to the medium - positive if the receiver is moving towards the source(m/s)

vs = velocity of the source relative to the medium - positive if the source is moving away from the receiver (m/s)

### Example - A Train passing a Bell

A train with speed 200 km/h (55.6 m/s) passes a bell with sound frequency 1000 Hz. With an air temperature of 20 oC the speed of sound is 343 m/s.

The frequency observed by a passenger in the train before passing the bell can be calculated as

fr = (1000 Hz)((343 m/s) + (55.6 m/s)) / ((343 m/s) + (0 m/s))

= 1162 Hz

The frequency observed by the passenger in the train after passing the bell can be calculated as

fr = (1000 Hz) ((343 m/s) + (- 55.6 m/s)) / ((343 m/s) + (0 m/s))

= 838 Hz

### Doppler Effect Calculator

Calculate the observed frequency with the calculator below:

Sponsored Links

## Related Topics

### • Acoustics

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

## Related Documents

### Air - Speed of Sound vs. Temperature

Speed of sound in air at standard atmospheric pressure with temperatures ranging -40 to 1000 °C (-40 to 1500 °F) - Imperial and SI Units.

### Decibel A, B and C

Sound pressure filters that compensates for the hearing sensed by the human ear.

### Fluid Flowmeters - Comparing Types

An introduction to the different types of fluid flowmeters - Orifices, Venturies, Nozzles, Rotameters, Pitot Tubes, Calorimetrics, Turbine, Vortex, Electromagnetic, Doppler, Ultrasonic, Thermal, Coriolis.

### Notes, Octaves and Frequencies

Frequencies vs. notes and octaves.

### Sound Power

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

### Speed of Sound - Online Calculator

A free online speed of sound calculator.

### Ultrasonic Doppler and Time of Flight Velocity and Volume Flow Meters

An basic introduction to the ultrasonic Doppler and Time of Flight Flow Meters.

Sponsored Links

## Search Engineering ToolBox

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

## Privacy

We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.