Assignment #5: Modulated Short Delay Effects

Hi, I'm Lameez from Cape Town, South Africa. This week I have chosen to demonstrate two of the three types of modulated short delay effects (flanger, phaser, chorus). I will describe how those two function and what they are best used for, I will include description of the Delay Time, LFO, Feedback and Dry/Wet sections.

Before we begin it's important to understand the basic concepts of delay. Delay is time delay between input and output. Signals can be described as Dry or Wet. A dry signal is one without delay and a wet signal is one with delay. How much of the wet signal goes back into the effect is known as feedback. 

There are several audio effects based on short delay, delay being the amount of time delay between the input and output. A comb filter are short delays of the same signal that result in a series of notches throughout the frequency spectrum  These Modulated short delays are the idea of putting the comb filter into motion e.g. putting motion into a static sound. 

The effects making up the modulated short delays are flangers, phasers and choruses. The two I have chosen to focus on in this lesson are Flangers and Phasers. 

Flanger: comb filter or slight delay put in motion. This adds a changing short delay of a signal to itself. It's a comb filter moving under the control of a LFO (Low Frequency Oscillator). It's a strict comb filter with even notches across the spectrum.

Let's try and see this on a spectrogram and spectrograph. Introducing the white noise with a 0.10 ms delay

Increasing delay with a flanger, with the LFO off / not in motion, note the change in patterns when changing to 0.89 ms delay then 1.55 ms

Now let's see the change with the LFO on, you will see motion added (as there is only picture no video it can be seen as the introduction of colour or additional waves or peaks in the spectrograph...

...and waves in the spectrograph below)

Flangers gives it a swirly outer worldly vibe to the audio. It is usually done differently in the left and right speaker and gives a back and forth studio presence.

Phaser: deep notches in motion. This effect is also modulated by a LFO so the effect is similar to flanging. It sounds much like a flanger giving a swirly stereo effect. They're a series of notches that move differently in the left and right speaker. This splits the signal in two, one goes through an all-pass filter altering the phase of the signal. When the two signals mix, a series of notches are formed. Unlike the flanger, the phaser's notches are not even across the spectrum.

Let's see the effects. First, introducing the white noise

Now introducing the phaser, notice the notice the notches aren't evenly space as they were with the comb filter or flanger (flanger looked just like the comb filter)

Adjusting the frequency, moves differently to the comb filter i.e. no new / higher notches

With the phaser the number of notches can be changed and...

...how they are related to each other can also be adjusted

With the phaser we have more control over where we are going to emphasise.

Now let's see what it looks like when we put in motion i.e. introduction of colour or additional waves or peaks in the spectrograph and waves  / shapes in the spectrograph below

So like the flanger, there is a series of notches put in motion that are different in left and right, but it is not a comb filter despite basically the same sound. It is great for guitars and anything overwhelming in the mix. The phaser can notch out a portion of the frequency range to possibly leave room for other instruments to be introduced in the mix or make something sound wider by adjusting the sound in the left and right channel.

Chorus: Multiple detuned copies. Choruses are multiple signals delayed and their pitch modulated by an LFO. The signals are then mixed to create a chorus effect. I won't go into detail on this, as it is not required for the assignment. I have just included for completeness sake.

That's my lesson for today, I hope I covered everything as required. The subject matter was completely new to me so I hope I relayed what I have learned correctly. Please let me know if anything is missing. Thank you for taking the time to review my work. As always, I look forward to hearing your feedback.

References:Introduction to Music Production Video Lectures and Course Wiki:https://share.coursera.org/wiki/index.php/Musicproduction:Main#Delays