Musical signal processing with labview  (Page 5/6)

Modulation synthesis

• Amplitude Modulation (AM) Mathematics -- Amplitude modulation (AM) creates interesting special effects when applied to music and speech signals.The mathematics of the modulation property of the Fourier transform are presented as the basis for understanding the AM effect, and several audio demonstrations illustrate the AM effect when applied to simple signals (sinusoids)and speech signals. The audio demonstration is implemented by a LabVIEW VI using an event structure as the basis for real-time interactive parameter control.
• Pitch Shifter with Single-Sideband AM -- Pitch shifting makes an interesting special effect, especially when applied to a speech signal.Single-sideband amplitude modulation (SSB-AM) is presented as a method to shift the spectrum of a source signal in the same way as basic AM, but with cancellation of one sideband to eliminate the "dual voice" sound ofconventional AM. Pre-filtering of the source signal to avoid aliasing is also discussed.
• Mini-Project: Ring Modulation and Pitch Shifting -- Create a LabVIEW VI to experiment with ring modulation (also called amplitude modulation, or AM), anddevelop a LabVIEW VI to shift the pitch of a speech signal using the single-sideband modulation technique.
• Frequency Modulation (FM) Mathematics -- Frequency modulation (FM) in the audio frequency range can create very rich spectra from only two sinusoidal oscillators,and the spectra can easily be made to evolve with time. The mathematics of FM synthesis is developed, and the spectral characteristics of the FM equation are discussed. Audio demonstrations as implemented by LabVIEW VIs illustratethe relationships between the three fundamental FM synthesis parameters (carrier frequency, modulation frequency, modulation index) and the synthesized spectra.
• Frequency Modulation (FM) Techniques in LabVIEW -- Frequency modulation synthesis (FM synthesis) creates a rich spectrum using only two sinusoidal oscillators.Implementing the basic FM synthesis equation in LabVIEW requires a special technique in order to make one oscillator vary the phase function of the other oscillator. In this module, learn how to implement the basic FM equation,and also hear an audio demonstration of the equation in action.
• Chowning FM Synthesis Instruments in LabVIEW -- John Chowning pioneered frequency modulation (FM) synthesis in the 1970s, and demonstrated how the techniquecould simulate a diversity of instruments such as brass, woodwinds, and percussion. FM synthesis produces rich spectra from only two sinusoidal oscillators, and more interesting sounds can be produced by using atime-varying modulation index to alter the effective bandwidth and sideband amplitudes over time.A LabVIEW VI is developed to implement the sound of a clarinet, and the VI can be easily modified to simulate the sounds of many other instruments.
• Mini-Project: Chowning FM Synthesis Instruments -- Implement several different Chowning FM instruments (bell, wood drum, brass, clarinet, and bassoon) andcompare them to the sounds of physical instruments. Develop code to model the Chowning algorithms as LabVIEW "virtual musical instruments" (VMIs) to be "played" by a MIDI file within MIDI JamSession .