Vibrato
Description
The vibrato effect is
created by periodically varying the pitch. The adjustable parameters are
magnitude and rate of the frequency variation. This effect is created using
principles of the Doppler effect. The Doppler effect, as it applies to this
application, states that variation in pitch is due to variation in distance
from the sound source. This variation in distance is simulated by implementing
a delay, periodically varying the delay time, and completely attenuating the
dry signal. When the delay time is increasing, the pitch is lowered. When the
delay time is decreasing, the pitch is raised.
Graphic Depiction
Effect Formula
|
y[n] = x[n-m] |
|
x[n-m] = delayed
input signal |
|
y[n] = output
signal |
|
m = length of
delay in samples |
|
m = sr * maxDelay
* [1/2 sin(ft) + 1/2] |
|
sr = sampling rate
(Hz) |
|
maxDelay = maximum
delay time (sec) |
|
f = oscillator
frequency (Hz) |
|
t = time (sec) |
Source Code
(.csd files can be viewed with Notepad or any text
editor)
Example Audio Clips
|
Clip1, unprocessed |
|
|
Clip1, vibrato added at t
= 3 sec |
|
|
Clip2, unprocessed |
|
|
Clip2, vibrato added at t
= 3 sec |
|
|
Clip3, unprocessed |
|
|
Clip1, vibrato frequency
increased linearly |
References
Lehman, Scott
(1996). Effects Explained. Harmony Central. Retrieved 6/04 from
http://www.harmony-central.com/Effects/effects-explained.html
Mikelson, Hans
(2000). Modeling a multieffects processor in Csound. In Boulanger,
Richard (2000), The Csound book (pp 575-594). Cambridge, MA: MIT Press.
Schindler,
Allan. (1998). Eastman Csound tutorial.
Eastman School of Music. Retrieved 6/04 from
http://www.esm.rochester.edu/onlinedocs/allan.cs/
Vercoe, Barry.
(1992). The public Csound reference manual, version 4.16. MIT Press. Retrieved 6/04 from http://www.lakewoodsound.com/csound/hypertext/manual.htm
Zolzer, Udo.
(2002). Digital audio effects. West Sussex, England: Baffins Lane..