Modulation techniquesRM & AM

Live ElectronicsDigital Signal Proccessing (DSP)

• To modulate is to impress a modulator signal on a carrier signal

• The modulator might be an sine wave and the carrier might be the sound of an instrument.

• Carrier. The signal that’s being modulated.• Modulator. The signal that modulates the

carrier signal.

Lytteeksempler Ring modulasjon

– KarlHeinz Stockhausen: Mantra 0:00 – throughout, Piano, Crotales

– Arne Nordheim: Distance0:00 -, Synth Bells

Side bands

• Carrier and Modulator are multiplied– Carrier fc

– Modulator fm

– Lower Side Band (LSB): fc – fm

– Upper Side Band (USB): fc + fm

Frequencyfc fc + fmfc - fm

Lytteeksempler Ring modulasjon

– Black Sabbath: Paranoid1:24 - 1:46, Guitar

– Miles Davis at Filmore West: Spanish Key0:00 -, E.pianohttps://www.youtube.com/watch?v=YUxIOFPg0MI

Amplitude modulation

• Nine Inch Nails: The Wretched 0:00 - 5:24, Drums (Noise Snare)

• When modulator is a hearable signal and the carrier a sine wave, output is similar to ring modulation except that the carrier frequency can also be heard.

Amplitude modulation (2)

• Carrier fc

• Modulator fm

• Three hearable tones: carrier, difference and sum• fc

• fc – fm

• fc + fm

Amplitude modulation (3)

• Modulasjon med lavere frekvens enn 20 Hz vil høres i tidsdomenet (ikke klang/timbre) som variasjon i lydnivå, tremolo.

• Modulasjon med frekvenser mellom 20-70 Hz introduserer en ”røffhet”, grovhet i lydsignalet.

• Modulasjon med høyere frekvenser høres som distinkte, unike komponenter (LSB (low side band) carrier og USB (upper side band)

Referanser

• Roads, Curtis (1996) The computer music tutorial. P. 215-224 https://books.google.no/books?id=nZ-TetwzVcIC&lpg=PP1&dq=computer%20music%20tutorial&hl=no&pg=PP1#v=onepage&q=computer%20music%20tutorial&f=false

• Ring Modulation, Frequency Modulation and Amplitude Modulation in Ableton Live 9 Suite http://www.youtube.com/watch?v=e0B3mXQ5rpw