Archive for the ‘Audio’ Category

Exercise 3b – Sound with Processing

Saturday, October 11th, 2008

Task 2: MP3-Player

The task was about creating a little MP3 player which is able to play mp3 and display the amplitude graphically. I added a few extra features so that for example the filename of the current track and its time are shown. The graph’s color and stroke weight are also dynamically changing.

View Applet / Source The mp3-file used in this example may take some time to load (0.9 MB).

Task 3: MIDI-Player

This applet plays a MIDI file and enables the user to pause the file. With the keys 1 to 9 you can also generate basic sounds.

View Applet / Source

Midi replay doesn’t yet work due to some problems with the paths. :-(

Task 4: Fourier Analysis

This is an extension to the simple MP3 player from Task 1. This one shows not only the amplitude, it displays also the frequencies by FFT (Fast Fourier transform).

View Applet / Source The mp3-file used in this example may take some time to load (0.9 MB).

Exercise 3a – Audacity

Saturday, September 27th, 2008

Audacity is free, open source software for recording and editing sounds. 

Task 1: Removing noise

Noise removal with AudacityTo use Audacity’s Noise Removal effect, you start by selecting a few seconds of noise. Then go to Effect -> Noise Removal… and click Get Noise Profile. The dialog closes and you return to your file. Select the whole track and again, open the Noise Removal dialog. This time you can chose the degree and you can perform some fine-tuning.

When you are happy with the result, click Remove Noise and voilà, your noise is gone.

In my example I also applied another effect called Normalize in order to boost the volume a little bit.

Example Before (strong background noise): mixed.mp3 – Before

After noise removal: mixed. mp3 – After

Task 2: Experimenting with Bit Rates

Definition Bit Rate (

In digital multimediabit rate often refers to the number of bits used per unit of playback time to represent a continuous medium such as audio or video after source coding (data compression). The size of a multimedia file in bytes is the product of the bit rate (in bit/s) and the length of the recording (in seconds), divided by eight. In case of streaming multimedia, this bit rate measure is the goodput that is required to avoid interrupts. … 

Audio (MP3)

Examples beispiel.mp3 – 16 Bit beispiel.mp3 – 16 Bit beispiel.mp3 – 128 Bit beispiel.mp3 – 128 Bit beispiel.mp3 – 192 Bit beispiel.mp3 – 192 Bit

Task 3: Podcast

For this task, I tried to overlay the songs “Put Your Hands Up For Detroit” and “Let Me Think About It” by Fedde Le Grand in Audacity. Here is what I did: 1. File -> Open … “Put Your Hands Up For Detroit.mp3″ 2. Go to Project -> Import Audio… and select the second song ”Let Me Think About It.mp3″. 3. Adjust Tempo by selecting a track and going to Effect -> Tempo… This changes the tempo without changing the pitch, so your song won’t sound like Mickey Mouse. It may take some trial and error until you get the right tempo. 4. With the aid of the Time Shift Tool you can easily move the tracks until they match. The Envelope Tool can be used to create a nice fade in and fade out effect. Result: Due to legal issues I’m not allowed to publish the result here. If you’ve got further questions, just leave a comment or contact me.