The associated Xcode project implements an iOS and macOS SwiftUI app that employs AVAudioEngine to play pure audio tones for various waveform types and frequencies by sampling mathematical functions. Frequency tones can be saved to WAV files of various durations, using AVFoundation to write audio sample buffers.
Learn more about how to play and save frequency tones from our in-depth blog post.
Frequencies are selected smoothly and continuously from a slider, entered directly with keyboard into a text field, or selected from a table of note buttons labelled A0 to B8, in the standard piano keyboard and grouped in octave 0 to octave 8.
Frequencies are in the range 20 Hz to a maximum determined by the current sample rate, that is usually 22050 Hz. Increment frequencies with stepper control increments of 1000.0, 100.0, 10.0, 1.0, 0.1, 0.01, 0.001, or use the x ½ and x 2 buttons to halve and double.
Waveform types are:
- Sine
- Square
- Square Fourier
- Triangle
- Triangle Fourier
- Sawtooth
- Sawtooth Fourier
The Fourier alternatives are smooth truncated Fourier series approximations to their counterparts with the same prefix, creating tones of a milder type.