This app shows of the new audio recording and play and filters on audio introduced in iOS 8. This application is created using swift and developed for iOS 8. This app shows off some of the new classes added in AVFoundation. You can see the demo for the app here and see tutorials for this app here on my blog http://www.jawadrashid.com/category/mobile/tutorials/swift-udacity-series/
Basically this app first records the audio from iOS device using AVAudioRecorder. Once the audio is recorded it is saved to the device.
Next, once the audio is saved then i play the audio back using AVAudioPlayer. I have added 4 different filters which you can apply on the audio file before playing it back. Using rate in AVAudioPlayer i slow down and speed up the audio.
The next 2 filters uses AVAudioEngine and first it creates a AVAudioPlayerNode which is capable of playing an audio file. This is the input for the audio engine. The file created from the first recording is used in audio player node. The output from this stage goes to AVAudioTimeUnitPitch node which can apply a transformation on the audio. In this case i have used the pitch and increased up the pitch to create the effect of chipmunk voice or decreased the pitch to make it sound like Darth Vader. The output from this node finally goes to the output node which is the speakers in this case.