Sound Waves  

Some introductory technical background concerning the nature of sound

Speed of Sound

Sound Waves and their properties

Sound Wave Calculator

Speed of Sound

In general the actual value of the speed of sound in a gas depends on the nature of the gas, its temperature and its pressure.  In the case of music, assuming the audience and players are warm and breathing, we can assume the gas concerned is air.  The approximate value of the speed of sound in a concert hall is 340 m/s (you can find the actual value for the speed of sound in dry air, at any temperature, using the calculator below).  If the air is humid the speed of sound is slightly increased (because water vapour is less dense than air).  And in case you were wondering - the photo shows a transonic F/A-18 Hornet approaching the speed of sound.

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Sound Waves and their Properties

Sound which we hear at a concert propagates in the air as a complex combination of simple pressure waves which consist of alternating high pressure and low pressure regions in the air.  Like all waves, sound waves have a characteristic frequency (the rate at which the pressure at a particular point changes from high pressure to low pressure and back again) and a corresponding wavelength (the distance from one wave crest to the next).  These two parameters are inversely related via the speed of sound according to the simple expression:

wavelength = (speed of sound) / frequency

We see from this that the higher the frequency, the shorter the wavelength and vice versa.  The equation lets us work out one parameter if we know the other, providing we know the speed of sound.  The calculator below will give you the wavelength at your chosen air temperature for any frequency you enter into the 'Frequency' box..

Using internationally agreed units of measurements, we measure wavelength in metres (m), the speed of sound in metres per second (m/s) and frequency in Hertz (Hz).  The Hertz, if you haven't met it, is simply the modern name for the old "cycles per second" and honours the name of Heinrich Hertz, the man who in 1888 demonstrated radio waves for the first time.  Actually, you will have met the Hertz in millions (MHz) if you have ever tuned an FM radio.

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Calculator for Speed of Sound in Air, Frequency and Wavelength

NOTE:  The calculator uses Javascript and your browser may have detected this and displayed a banner at the top of the screen concerning active content.  If so, to use the calculator you need to click the banner and follow the links to allow blocked content to be used.

The speed of sound depends on air temperature - the warmer it is, the faster sound travels.  In the calculator below you can find the speed of sound at any air temperature, and also the wavelength of a sound wave for any given frequency at the chosen temperature.

To use the calculator, enter the air temperature in oC and then enter a frequency (if you don't know where to start, try 440 Hz which is concert A).  The other values will then be calculated and displayed when you either press the "Tab" key or click anywhere else on the page.

Air Temperature   oC

Speed of sound   m/sec    = ft/sec    = mph
 

Frequency     Hz

Wavelength   m      = ft

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