Using Audacity

Audacity is a free, multi-track audio editing and recording program. It is available for Windows, MacOS and Linux, but with a workaround it can also be run on a Chromebook (see below). To download the program, please click here. 

Note- PhysicsScotland takes no responsibility for the functionalilty or security of any programs or extensions. It is up to the user to decide on any installations to their own devices. 

In Physics, Audacity allows sound waves to be analysed to measure frequencies, amplitudes and periods of waves. It can also be used to investigation sound interference and noise cancellation technologies. 

Using Audacity on a Chromebook

In order to run Audacity on a Chromebook, as it cannot run on the computer directly, it is neccessary to remotely access the program through an extension to the Chrome Browser. 

To access the Extension please Click Here whilst using the Chrome Browser. 

Once installed, the program can be found in the 'Extensions' Menu of the Chrome Browser.

To pin it to the toolbar, go to ‘three dots’ at top right of Chrome, then ‘more tools’ then ‘extensions’. Then toggle the ‘blue dot’ for Audacity to ‘on’ and it should appear on your toolbar as shown below:-

To acess Audacity, click the audacity symbol, then in the pop-up window, click ‘Full Screen’. Audacity should now open on your Chromebook. If it does not, follow the troubleshooting instructions below.

Troubleshooting Audacity on a Chromebook

If you are taken to this screen:- 

Scroll down to Audacity and click on it. On the new popup window, again click on Audacity (at the top left) and it should take you to Audacity:-

Using Audacity to generate a basic Tone

On the Audacity toolbar, select ‘Generate’, then ‘Tone’ :-

From this window, you can now create waves of different frequency and amplitude.

When a tone is generated, the screen will most likely look like this, with the waves too close together to see:-

In order to see the waves, press ‘ctrl+1’ until the waves can be seen:-

To zoom back out, press ‘ctrl+3’. 

Measuring Period and Frequency

To start cacluating the Period or Frequency of a signal, a section of the wave needs to be selected. To improve the accuracy of the data, it is best to select multiple waves and find the Period and Frequency by the following method. 

To select a secion of the wave,  ‘left click and drag’ to make a selection, aiming to start and end exactly a whole number of waves apart: 

At the bottom-left of the window, click ‘length’ dot and the time covered by the section will be shown: 

By dividing this number by the number of full waves selected, the Period (T) of the wave can be found, and from which the Frequency can be found. This can then be compared to the value you set initially. 

In this example, 0.011s for 5 full waves gives a period of 2.2x10-3s, which using one of the wave equations (T = 1/f) gives an ‘experimental’ frequency of 454 Hz, close to the set value of 440 Hz.

Simulating Noise Cancelling Technology

In noise cancelling technology, an identical copy of a soundwave is inverted and layered over the original sound, this cause 'destructive interference' and the sound volume to be greatly (if not entirely) reduced. 

To simulate Noise Cancellation, the first step is to generate a tone of Frequency 450 Hz and amplitude of 0.5. Again zoom in to see the wave clearly:

Next, go to ‘Edit’ then click on ‘duplicate’ to copy the wave exactly to a new track: 

If played, the two waves will overlap ‘constructively’ and the sound will be louder. 

To invert one wave, left click on the control box on the left of the wave so that the whole wave becomes highlighted. Then click ‘Effect’ then ‘invert’ from the drop down menu. The wave should now look like this:-

If played, the two waves will overlap ‘destructively’ and no sound will be heard, the ‘noise’ has been cancelled out.

This can also be done with any audio file, so music etc. can be completely cancelled out. 

If the volume of the second wave is reduced (using the slider in the control box), the sound will become louder as the noise is no longer completely cancelled.